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Products => Test Equipment => Topic started by: BravoV on November 01, 2011, 06:57:59 am

Title: Tektronix 2465B oscilloscope teardown
Post by: BravoV on November 01, 2011, 06:57:59 am
(https://www.eevblog.com/forum/index.php?action=dlattach;topic=5397.0;attach=16685;image)


Acquired recently this scope at local tech surplus store,  and even its quite old now, still, it should be pretty good piece of equipment. Among peers & friends here, we called this Jim's scope cause Jim Williams (in memoriam) used it too at his personal bench table.

I have another similar thread, but its for asking some details -> https://www.eevblog.com/forum/index.php?topic=5258.0 (https://www.eevblog.com/forum/index.php?topic=5258.0) , and decided to post the teardown photos in this new thread instead of there.

Here we go, teardown and preliminary inspection, since I'm going to recap the whole scope and took shots for documentation and component inventory purposes.


The whole bundle, with the top pouch, front cover and a single Tektronix P6136 350Mhz probe. Every thing is nicely preserved by previous owner, I was told it was previously used in clean r&d lab at a big consumer electronic factory.


Click to enlarge the pictures.
(https://www.eevblog.com/forum/index.php?action=dlattach;topic=5397.0;attach=16687;image)


With front panel facing down, and main cover detached, the rear, top and left sides view. Top and left are covered by aluminium plates, these are HV and power sections.
(https://www.eevblog.com/forum/index.php?action=dlattach;topic=5397.0;attach=16689;image)


With top cover opened. Wait !! It looks so empty and spacious ? Is that it ? No folks, these are just the crt tube and the main power supply only. The middle module has two separate pcbs, which are linear and switching part placed side by side isolated by a thick metal plate. Both supply the power for the whole scope. I guess they opted to place these noisy parts crt & psu in the middle isolated room to reduce hf noise.
(https://www.eevblog.com/forum/index.php?action=dlattach;topic=5397.0;attach=16691;image)


The bottom and the right sides view, still standing vertically at it's face, look at the view, now we're talking.  :)
Bottom part is the main board for all analog stuffs there, while the left board is for the logic, cpu and control. What interesting about this view is, the big main board is using through hole components, while at the control board is using smd. Probably this was designed and made during the transitional period from through hole component to smd style.
(https://www.eevblog.com/forum/index.php?action=dlattach;topic=5397.0;attach=16693;image)


The main A1 board, handles all analog stuffs here. The middle black zigzag stick is connected from the main power switch at the rear to the front panel power button. All components are using through hole style.
(https://www.eevblog.com/forum/index.php?action=dlattach;topic=5397.0;attach=16695;image)


The A5 logic & control board, made it portrait view for better detail, almost all are using SMD components.
(https://www.eevblog.com/forum/index.php?action=dlattach;topic=5397.0;attach=16697;image)


The left side view without the metal cover, high voltage crt power supply and the horizontal & vertical control board at the middle.
(https://www.eevblog.com/forum/index.php?action=dlattach;topic=5397.0;attach=16699;image)


The power supply linear part and the main rectifier at the left side, while with switching part at the other side encased inside aluminium box. Few classic and popular to-220 linear regulator ICs are bolted at the bottom with thermal pad like LM 317, 7805.
(https://www.eevblog.com/forum/index.php?action=dlattach;topic=5397.0;attach=16701;image)


The rear cooling fan without it's holding metal bracket, very noisy and it will be replaced with new & better fan. Also it's cables termination will be replaced with small 2 pins ordinary fan connectors for easy detaching it for cleaning and maintenance in the future, instead of permanently soldering them directly at the terminal (see inset).
Another interesting finding is the fan's date code 9605, it has the latest date compared to other components throughout the scope, looks like its 1996 or later made. Anyone know what year Tektronix stopped releasing the 24xx model ?
(https://www.eevblog.com/forum/index.php?action=dlattach;topic=5397.0;attach=16703;image)


Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on November 01, 2011, 07:02:52 am
The Tek hybrid U800 IC part no 155-0241-02, that is really hard to find for the replacement but easily gets killed caused by overheating. This poor little ic is handling the whole horizontal part of the scope, and when powered on, it is very-very hot that almost burned my finger when touching the ic black body. The cooling path for heat dissipation is only through that metal tab at the IC, and goes through that tiny front bolt and rings as it's main heatsink, while the other bolt at the back is doing nothing for cooling, it just for holding this ic.  >:( 
Also its working at +87 volt and currently I'm still thinking on how to cool this IC better, maybe by attaching a small heatsink directly at that metal tab instead using heatsink at it's black body, but its not easy task because that bolt and the ic metal tab are not ground, they're -5 volt instead, damn !  :-\

(https://www.eevblog.com/forum/index.php?action=dlattach;topic=5397.0;attach=16705;image)


Another corner, rusty nut, guess its time to replace it before it starting to eat through the bolt.  :-[ Also the bnc connection for the 4th channel and the 3rd at the background.

(https://www.eevblog.com/forum/index.php?action=dlattach;topic=5397.0;attach=16707;image)


Same here, worry once the nut disintegrated by the rust, it will be become loosed by the heatsink tension, and finally cracked and burst or spread into small metal pieces across the board. Bad, really bad news if this happened.  >:(

(https://www.eevblog.com/forum/index.php?action=dlattach;topic=5397.0;attach=16709;image)


Interesting spot, looks like that tiny inductor coil is hand made.  ;D  Definitely HF area, just too scared and afraid to touch or bump anything around here.  :o

(https://www.eevblog.com/forum/index.php?action=dlattach;topic=5397.0;attach=16711;image)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: EEVblog on November 01, 2011, 08:52:44 am
Awesome teardown, thanks for sharing!

Dave.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on November 02, 2011, 02:34:14 am
My pleasure Dave, glad you like it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Wartex on November 03, 2011, 03:33:49 am
Buy RAM chip heatsinks on eBay and use thermal epoxy to glue them right to the IC
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on November 04, 2011, 04:32:39 am
Buy RAM chip heatsinks on eBay and use thermal epoxy to glue them right to the IC

Thanks, yes, I have few of them made from pure copper, its just I'm not quite happy since they're too small and also by cooling that U800 ic's substrate black body is not very effective compared to putting the heatsink directly at the metal tab.

Pics of the ram chip sinks on the ic, they're not permanently applied yet.
(https://www.eevblog.com/forum/index.php?action=dlattach;topic=5397.0;attach=16757;image)


Other angle, as you can see, the front bolt and nut are useless, they're not touching any of the ic's body for cooling purpose, and whats the point of holding the IC when its already soldered at the pcb. I suspect originally these two bolts were designed to hold a custom shape heatsink for this scorching hot ic, looks like they never made it.   :-\
(https://www.eevblog.com/forum/index.php?action=dlattach;topic=5397.0;attach=16759;image)


The vent holes at the bottom of the scope, these are for air intake, and the U800 is positioned at the upper left rectangular shaped vent holes.
(https://www.eevblog.com/forum/index.php?action=dlattach;topic=5397.0;attach=16761;image)


Close up, the U800 is located right below here. From this vent holes position, its obvious that they're aware this location needs cooling, and should U800 have a proper heatsink, this is the right place for it.
(https://www.eevblog.com/forum/index.php?action=dlattach;topic=5397.0;attach=16763;image)


I've been thinking to make two pieces of heatsinks, illustrated by two rectangles, the blue one is for the body, will be secured by the left nut and a steel wire (yellow marking) across both nuts, no problem with the height clearance for the upper MC3346P ic since U800 is higher by about few milimeters, this blue heatsink should not have any problem here. While the other heatsink (red rectangle) will be applied directly at the ic's metal tab  and secured by the right nut, this one is definitely better in dissipating the heat than the blue one. Clearance is pretty tight here, and must be precisely made, may be its time to visit local cnc shop, two options, either make it shorter or with the fat "L" shaped to avoid the bottom left vertically positioned ic.  Those few resistors and diodes in front of the metal tab are about 2 millimeters lower than the metal tab, so the blue heatsink base won't touch them at all if its fastened properly at the right nut.
(https://www.eevblog.com/forum/index.php?action=dlattach;topic=5397.0;attach=16765;image)


Stay tune, I will be constantly update the progress here.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: rf-loop on November 04, 2011, 12:19:17 pm
Maybe you think that Tektronix EE's who design it are stupid?
They are not.

It works just perfect and thermal design is ok. There is NO any problem. Exept if someone take case off and use it without case. Also if FAN go bad it can go to thermal owerload.

I have study and inspect these oscilloscopes years (also I have no 3 pcs of these units in my lab for service and calibrate.

You can read Tektronix original full service and repair manual before you open oscilloscope if you design also power up it without case. It need use service enough airflow fan if need more time keep it running without case!

In the world you can find hundreds of defected Tektronix oscilloscopes just as burned hybrids and IC:s just becouse user do not care or "self learned service man" do not know how to handle these as professionals do who are specialised to make repair work with these nice scopes.

Before years they use different very expensive FAN in this scope but this version seems to be with this new fan what are in later manufactured units.

Before models have brushless hall controlled pulse driven motor what also have speed control as temperature change inside.

This airflow is calculated so that it is enough for cooling these circuits in full specified enviroment temperature range.
But it works only if scope have not much of dust inside and that air holes are open without dust.

U800 is very strong for high temperatures. It is also assembled to board just ok. Tektronix have long experience about use this circuit and if there is any big problem they have changed design after years of experience. This model is not one year design . 2465 models have been long time in production before your version and they have made many changes but U800 did not need make any changes for design. Not for circuit, not for mechanical and thermal design.
60 celsius is NOT hot. 90 celsius is not hot. 100 celsius is not hot. Also if uou know semi free air cooled chip. Thermal resistance between silicon and case is so that in free or small pressure air flow case temperature and silicon temperature have not big difference.

When case is closed and airflow work normally it keep it fully inside accepted temperature area.

If not believe you can put thermal sensor over chip and close case. Temp is more low than in free air temp.
same for these some maybe more sensitive hybrids.

Always if do example calibration  do it with service fan! Or do first adjustments what need open case and use service fan on the table. Then close case and let it warm half - one hour. Then continue these semiautomatic calibration steps.
Never touch any adjustments if have not needes test equipments. (and do not adjust these factory adjusted hand made looking coils without equipments and knowledge how to do.

In these units there are one problem Thiis NVRAM. They start be end of life.
Older version with separate soldered big lithium battery was more easy to handle.
If you loose this NVRAM data you loose all cal data and special data if scope have some options. (seems that you have not any options becous upside scope is nearly empty)

If you want change fan, kep special care its pressure/airflow data is perfect match. (it need know fan curve, noyt only free air volume. Best is change just same model. (littlebit can reduce noise if do floating assembly with thin and soft silicone isolating.
(this old model fan was more silent becouse there was no bearings noise connected directly to aluminium case.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: slburris on November 06, 2011, 03:33:51 am
I'd be less concerned about the U800 chip and more concerned about the 4 tantalum
surface mount capacitors on the A5 board.  They are known to leak with corrosive electrolyte
over time and can absolutely destroy the A5 board.

There's another thread on the forum about the A5 board, or you can look at this repair
guide someone put together:

http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf (http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf)

Scott
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: rf-loop on November 06, 2011, 01:27:46 pm
I'd be less concerned about the U800 chip and more concerned about the 4 tantalum
surface mount capacitors on the A5 board.
  They are known to leak with corrosive electrolyte
over time and can absolutely destroy the A5 board.


Also this issue is (maybe) related to manufacturing version (and  also where it have made).
If any suspect about possible leakage or fail. They need immediately take away, clean board and change new components.

And inside power unit are some famous weak electrolytics.

And also concern about this (mostly DALLAS) NVRAM. (this is designed lifetime!) Before they use EEROM and also RAM+Separate extremely good Lithium battery. (but reducing lifetime and costs...it is...what it is.)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: wkb on November 18, 2011, 06:26:46 pm
This week I had the case off my 2465CTS.  In some aspects it is quite similar to the B version in this thread, but for example the digital controller PCB (wow... an 68B08, nice, I grew up with 6800 and 6809 ;-) is through-hole and not SMD.

It was suffering from a rattling fan, which had an interesting cause: it had been stored (at work) on its side on some shelf.  And apparantly some fat-fisted colleague of mine had dumped it on its side hard enough to push the handle lever into the case.  This caused to whole case to dent and slightly deform. >:( The aluminium of the case is really quite soft.  End result was that the fan (mine has a "rodent wheel" style fan) just touched the plastic back of the scope. Which rattled.  Sigh..

Interesting (...) side effect was that the outer shell would not slide off the frame.  I had to "crowbar" the  side of the case somewhat to get it off.  Once it was off, I could hammer (yes.. I had to use a hammer to fix a scope..) the dent out, which made the case slide back easily onto the frame.
 
Oh.. And I had to fit a new 10Mc Xtal on the digital controller PCB.  That got stuck behind the dented case and broke off.  ::)

Ah well, it is back to its glorious self again.  I got it years ago (for free, can't complain there!)

Wilko
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: larry42 on November 19, 2011, 10:18:27 pm
Maybe you think that Tektronix EE's who design it are stupid?
They are not.

It works just perfect and thermal design is ok. There is NO any problem. Exept if someone take case off and use it without case. Also if FAN go bad it can go to thermal owerload.

Well I've seen quite a few Service Notes for HP equipment, with small upgrades and improvements. Perhaps all the perfect engineers worked at Tek  ;)

And yes MTTF goes down with temperature, so if the chip is seriously hot, I would *consider* adding a heatsink, or a small extra fan, though with the caveat of thinking how the whole airflow though the system is arranged.

Good points on the fan replacement though.


Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on November 20, 2011, 09:09:17 am
Maybe you think that Tektronix EE's who design it are stupid?
They are not.

It works just perfect and thermal design is ok. There is NO any problem. Exept if someone take case off and use it without case. Also if FAN go bad it can go to thermal owerload.

Who is calling those Tek EEs stupid ? Suggesting you to read again since I believe English isn't your native by looking at your respond here, and I guess you're somehow a tek fanatic aren't you ? :D

I was just questioning why those bolts are there at the 1st place ? They're not even grounded to aid the thermal dissipation, and also why mechanically secure the ic which already soldered at the board ? If you have better explanation, I will glad to hear that.


I have study and inspect these oscilloscopes years (also I have no 3 pcs of these units in my lab for service and calibrate.

You can read Tektronix original full service and repair manual before you open oscilloscope if you design also power up it without case. It need use service enough airflow fan if need more time keep it running without case!

In the world you can find hundreds of defected Tektronix oscilloscopes just as burned hybrids and IC:s just becouse user do not care or "self learned service man" do not know how to handle these as professionals do who are specialised to make repair work with these nice scopes.

I had the user and tech manual both printed in A3 paper "BEFORE" I got this scope, was that your personal experience back there in the past ? ;)


60 celsius is NOT hot. 90 celsius is not hot. 100 celsius is not hot.

Don't know how to comment on this one, just recommend you to read many more semiconductor's datasheet on their max temp junction, and the effect of silicon's life when exposed at high temp like close to 100C, definitely is not good for their life.


When case is closed and airflow work normally it keep it fully inside accepted temperature area.

No argument here, the cooling effect will be only effective if with closed case, thats why those air vents are made for.


If not believe you can put thermal sensor over chip and close case. Temp is more low than in free air temp.
same for these some maybe more sensitive hybrids.

Surface temp will never be lower than ambient temp if using air cooling at "a non evaporating surface", its the basic law of thermodynamic, not sure where did you learn yours.


And also concern about this (mostly DALLAS) NVRAM. (this is designed lifetime!) Before they use EEROM and also RAM+Separate extremely good Lithium battery. (but reducing lifetime and costs...it is...what it is.)

This nvram is already in the work list, it will be desoldered and I will put a socket there to aid future replacement.

Oh yeah, don't worry, once pulled, the calibration data will be backed up 1st. ;)


I'd be less concerned about the U800 chip and more concerned about the 4 tantalum
surface mount capacitors on the A5 board.  They are known to leak with corrosive electrolyte
over time and can absolutely destroy the A5 board.

There's another thread on the forum about the A5 board, or you can look at this repair
guide someone put together:

http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf (http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf)

Scott

Thanks Scott, yeah, already have that excellent document since the 1st day I got this scope. ;)

About this particular A5 model, its an early smd version which isn't plaque by the leaking caps like other late version, already got the confirmation at the TekScope yahoo group, but those caps will be checked too.


This week I had the case off my 2465CTS.  In some aspects it is quite similar to the B version in this thread, but for example the digital controller PCB (wow... an 68B08, nice, I grew up with 6800 and 6809 ;-) is through-hole and not SMD.

It was suffering from a rattling fan, which had an interesting cause: it had been stored (at work) on its side on some shelf.  And apparantly some fat-fisted colleague of mine had dumped it on its side hard enough to push the handle lever into the case.  This caused to whole case to dent and slightly deform. >:( The aluminium of the case is really quite soft.  End result was that the fan (mine has a "rodent wheel" style fan) just touched the plastic back of the scope. Which rattled.  Sigh..

Interesting (...) side effect was that the outer shell would not slide off the frame.  I had to "crowbar" the  side of the case somewhat to get it off.  Once it was off, I could hammer (yes.. I had to use a hammer to fix a scope..) the dent out, which made the case slide back easily onto the frame.
 
Oh.. And I had to fit a new 10Mc Xtal on the digital controller PCB.  That got stuck behind the dented case and broke off.  ::)

Ah well, it is back to its glorious self again.  I got it years ago (for free, can't complain there!)

Wilko

Bummer  :( , that poor thing, glad it works.



And yes MTTF goes down with temperature, so if the chip is seriously hot, I would *consider* adding a heatsink, or a small extra fan, though with the caveat of thinking how the whole airflow though the system is arranged.

Good points on the fan replacement though.

The whole airflow paths are quite clear from above pics, and the only exhaust is at the rear and the intakes are those vent holes scattered across the body which show those parts need fresh air.

Yep, replacing the fan is already in the list and will be using good fan like Sanyo Denki or similar.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: rf-loop on November 20, 2011, 10:35:47 am

If not believe you can put thermal sensor over chip and close case. Temp is more low than in free air temp.
same for these some maybe more sensitive hybrids.

Surface temp will never be lower than ambient temp if using air cooling at "a non evaporating surface", its the basic law of thermodynamic, not sure where did you learn yours.


There are so many misunderstoods in many places  becouse my poor english. I do not correct all, but this one I want try clarify what I mean (and it is extremely trivial case, only language is problem)

(of course there are three pathway for thermal power)

From silicon to out there is some thermal "resistance" between silicon and case outer surfaces including also pins.

If handle now only from case surface to air and leave these radiation and conducting away.

If case is open. There are only free air free convection what "flush" surface.
If case is closed and fan running. There is forced airflow directly to this componet surface. Amount of moving air is totally different and it moves more thermal power.  With case closed this component temperature is more low than with case open if there is not forced convection. This is reason why Tektronix rules that there need use service fan if use scope without case.
Of course becouse there is thermal resistance between case and silicon it also means that thermal current change means more thermal difference between surface and silicon if there is same thermal power generated.
If there is lower thermal current from case to enviroment then thermal difference between case surface and silicon is smaller (and hotter).
I have think these are so basic things that everyone can understand these without long explanation.

I have seen thermally damaged Tektronix hybrids. Sometimes reason is bad service man who forged scope runn without case and bottom down to table or even so that bottom of scope is upside but it is not very easy damaged. If fan stops there are no protection! And this is danger case. If case is closed as normally and fan fails. It may very easy overheat hybrids becouse there are anly low convection and radiation and conducting is not enough for cooling if it run long time. After hours there is very hot inside scope and some critical components may fail thermally.

Lack of thermal overheat protection is bad design.  How much it cost to watch fan or airflow (or temperature) nearly nothing if compare it to original price of this scope..

I have repaired these scopes and also years ago I have make many examinations about some design (and modifications) points inside these scopes for special use. Also this thermal question was one. And finally after many measurements and inspections I finally think, no need add heatsinks. (long time ago I was concerned just this same)
Yes it is true that component reliability littlebit go down if compare 60 celsius or nearly 100 celsisus.
But then need also remember what is product lifetime.  I have seen some this model what have >60000 hours and still working. 
Where are most common problems in these scopes (if keep out bad service damages).
(Fan (specially this older fan type), electrolytics, some resistors and diodes and capacitors specially in HV part and also input attenuators (mostly user mistakes but if unit have been in product testing and drived with computer there may also be worn attenuator unit). In older manufactured unit have different fan, it was very silent but also very fragile and hard work to change, and expensive!)
Units what I have in my lab have around 1500 - 4000hours.

If this scope need use in special enviroment then its thermal things need arrange different.
It need sometimes arrange separated closed inside air circulation and then  heat exchanger to outer cooling. (example in some explosive enviroment or if there is heavy dust or some other situation what is common example in military some other use)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on November 23, 2011, 03:29:26 am
rf-loop

Thanks for the reminder, definitely will have a big house fan blowing at that the A1 board when running without the case, also usually it was never turned on more than 15 minutes when without it for brief checking and measuring like I did last time at the J119 header.

About the environment, don't worry, it will be used 99.99% of it's time at my bench table.

Btw, since I don't have enough time to work on this yet, any clue where to look for for my read out cursors posistion problem ? I mentioned this at my other thread here -> https://www.eevblog.com/forum/index.php?topic=5258.0 (https://www.eevblog.com/forum/index.php?topic=5258.0) , currently I suspect the problem probably near the DAC ic and it's surrounding passive components at the A5 board.

About backing up the nvram, any suggestions or other tips ? My plan is to pull that dallas ic, do a backup externally and put it back but with ic socket installed. About the battery inside the nvram, I guess nothing we can do about it, its just a matter of waiting untill the internal battery ran out of power and have a replacement ready with the restored data.  :-\

If you have better solution, I'd love to hear that.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: rf-loop on November 23, 2011, 06:07:33 am
It looks that scope need service calibration.
If do adjustments it need follow _exactly_ Tektronix service manual. There are not words without meaning (even if it feels stupid..).

Also it need follow exatly this adjustment and calibration steps in the order what is  prescribed in manual, this order is important and manual tell what steps can do individually (there are not many these steps. First you start power unit voltages and reference adjustment and CRT itself adjustments (linearity etc things) and if then change these agen, oh well...do full service cal agen. So, follow manual, do not jump over any thing exept if manual tell specially that it can do, in other case it is prohibited..  (This manual need read so that what can do can clearly read on manual and if there do not read some thing is accepted then it is prohibited - just opposite than many other books - example law.)
Do NOT separate adjustments without knowing exactly if it interfere somewhere to some other thing (only some things can separately adjust without calibration procedure. Cursors need adjust inside cal procedure and in given order of steps.
What tell me that it need adj and cal. Cursosrs looks like fully out of order.  How is measurement accuracy?


How is this: "The power on message is "DIAGNSTIC. PUSH A/B TRIG TO EXIT", is this normal ?"

This is not normal!
This message tell that something is wrong (some rare cases it can do this once and reason may be "unknown" and in this situation it also can reset). 
Normally it do not appear without reason! If this appear, it can continue to normal scope  pushing a/b trig but now user  know that something is maybe wrong and it also need read as: "do not trust measurements before problem solved."

(exept if someone do manually "bad start" example keeping some button pressed during start up prosedure.)

But in older 2465  (B models with new SMD  HW I do not know)  it can also appear if oscilloscope shut down procedure fails (it may happend example if some capacitor is bad in this clever power unit and there is not enough power to run normal shut down procedure after switch off or loose mains electric...  This power up and power down "logic" can find in service manual. More serious case it may mean corrupted calibration or error in some circuit.

Becouse (in one your picture) cursors location is really bad it may tell that some calibration thing is not ok. (btw. now you have adjusted readings location without service calibration procedures - remember, they maybe now adjusted wrong and after (or better tell inside) service cal procedure you may need adjust also this agen).

Service cal must NOT START before sure that there is available all signals what need and just as they need be!
What ever step in procedure fails it can not continue AND id can not take back. There is no any "oops do not - take back" button after started cal prosedure (example vertical block) it need go from start to end and every step need just perfect cal signal from calibration generator and every step need adjust perfect becouse without this some other step may fail and it need do agen as long as it pass. (there is not "jump over" posibility -- oh yes there is is and result is what ever, maybe your cursors are from failed cal procedure if someone have not know what he is doing. Also in some things (some minor details) this manual is not very clear. 

Note also. Always before full calibration need inspect power unit voltages AND ripple. They need be well inside limits what service manual tell.  Selftest system give information what is wrong (what test number fails) but it do not know all. It do not know example if calibration data is wrong after some have done bad calibration.
This power up hours littlebit give feel that someone have reset system. If someone have done this, what other things he have done with oscilloscope in service mode.



Title: Re: Tektronix 2465B oscilloscope teardown
Post by: blueflash on November 23, 2011, 01:55:37 pm
Although the U800 post is some days ago here my solution, which is similar to Yours but I used a bigger Heatsink with a hole for the screw to avoid electrical contact. Bevor mounting the heat sink with normal super glue I isolated the screw with a plastic tube.

Also I have a question if You would be so kind to tell me if I'm right.
When I got my Tek2465A I wondered about the missing illumination. So I decided to open the front panel where I expected the bulbs - but I found nothing (see last picture). Shouldn't there be the illumination lights?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: rf-loop on November 23, 2011, 03:53:09 pm
There need be illumination lamp board together with light distribution clear (partially painted) plastic. Also these lamps are very special small soldered lamps. On the main board is lamp driving  circuit. (also it is designed just like perfectionists do)

You have not service manual? If I remember right there is also full explanation about this light system.

Someone have take this light module. Sometimes peoples have get scopes where are missing hybrids..  (do not connect not compatible lamps to connector on the main board, it is possible destroy this lamp driver circuit and then in worst case you need change one IC on the main board)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: blueflash on November 23, 2011, 04:09:29 pm
Yes I got a service manual, but the part with the illumination is not illustrated so good. So I thought it is better to ask some knowing guys about it  :)

Am I right when I suppose that the red marked connector is the supply connector for the illumination?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on November 24, 2011, 03:21:16 am
It looks that scope need service calibration.
If do adjustments it need follow _exactly_ Tektronix service manual. There are not words without meaning (even if it feels stupid..).
That is what I'm afraid of, cause I don't have enough supporting tools to do that, while sending it to certified calibrator is not an option since its way too expensive, the cost of certification might be more than a new 200Mhz china made digital scope.  :'(
While the price of this thing I bought is less than $300.


How is measurement accuracy?

So far I only tested with against the Tek 2901 time mark generator and these are the results :

(https://www.eevblog.com/forum/index.php?action=dlattach;topic=5574.0;attach=17237;image)
(https://www.eevblog.com/forum/index.php?action=dlattach;topic=5574.0;attach=17239;image)

(btw. now you have adjusted readings location without service calibration procedures - remember, they maybe now adjusted wrong and after (or better tell inside) service cal procedure you may need adjust also this agen).
Nope, checked with service manual, the adjustment I've made at R2918 to fix the readout vertical position is not part of the calibration procedure that will be stored as calibration data, check again your service manual.

For sure I will not touch or start any calibration until I have the adequate supporting tools to do that and aware that this must be followed step by step exactly as the manual instructed. Btw the service manual it self has flaw as pointed one of the member at tekscope group that there is an additional steps to be done to complete it.

Since you said you've done many calibrations on these scope before, what kind of tools you have there to help your job ?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on November 24, 2011, 03:28:36 am
Although the U800 post is some days ago here my solution, which is similar to Yours but I used a bigger Heatsink with a hole for the screw to avoid electrical contact. Bevor mounting the heat sink with normal super glue I isolated the screw with a plastic tube.

Thanks for sharing that, nice to see how other 2465x owner cooled their U800.

Also I have a question if You would be so kind to tell me if I'm right.
When I got my Tek2465A I wondered about the missing illumination. So I decided to open the front panel where I expected the bulbs - but I found nothing (see last picture). Shouldn't there be the illumination lights?

Yes I got a service manual, but the part with the illumination is not illustrated so good. So I thought it is better to ask some knowing guys about it  :)

Am I right when I suppose that the red marked connector is the supply connector for the illumination?

Although I haven't look into my front panel at the illumination part as yours, I believe yours are gone, sorry to hear that.  :-\

Looks like the previous owner pulled it out, anyway, there are few ebay seller are offering this part for few dollars.

Attached below of my cable connection at J181 connector and the picture from the service manual, apparently yours are missing the 11,12 and 15 parts.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: rf-loop on November 24, 2011, 06:32:47 am


(btw. now you have adjusted readings location without service calibration procedures - remember, they maybe now adjusted wrong and after (or better tell inside) service cal procedure you may need adjust also this agen).
Nope, checked with service manual, the adjustment I've made at R2918 to fix the readout vertical position is not part of the calibration procedure that will be stored as calibration data, check again your service manual.


My thinking was: Now if you do full service calibration it may affect some things and maybe also these readings position slightly change and need maybe also agen adjust.  All adjustements are not directly related each others but it is better to follow service cal steps in order so work is more easy and do not need go back agen. But of course something can adjust.
But I see one your picture and readings was extremely bad position before your adjustments. How they have changed? This kind of change is not normal exept some component fail or someone have done bad adjustments.
How are vertical cursors and horizontal cursors if you measure some exactly known signal. Also how horizontal cursors accuracy if measure things together with B timebase.
Cursors horizontal accuracy is best in -4 to +4div from centerline. If visually signal trace is in good accuracy and if cursors display enough accurate it do not of course need any cal.  In normal use this check is enough.

If need real  calibration/ calibration with data (and traceable)  then all need measure accurate and write values to record and if need (limits breaks) then do full cal and agen do cal check data record. Normal user do not have this.

-------

I have tektronix calibration generators. Example CG5011 and CG5001.  Then also fast rising pulse generator tektronix 284. And of course oscilloscope(s) what can use inside cal procedure. (it need external and good analog oscilloscope or so good digital oscilloscope what I have never own. It can not do with Hantek, Owon, and of course nothing with Rigol) 
And other tools. Also enough reliable DVM for reference adjustments.  But this level and timing calibration signals is most important. Then specially timebase(s) calibration need this external oscilloscope. There is nice adjustment method inside this 2465 FW)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: blueflash on November 24, 2011, 10:40:14 am
Thanks for the reply, that confirms my speculation about the missing illu.

Btw, if someone has problems with the eproms on the digital board loosing their "mind" - I read them out and can share the files if needed. I guess they are different for the models 2465/2465A/2465B (my model is 2465A). 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on November 25, 2011, 03:51:39 am
Thanks for the reply, that confirms my speculation about the missing illu.

Btw, if someone has problems with the eproms on the digital board loosing their "mind" - I read them out and can share the files if needed. I guess they are different for the models 2465/2465A/2465B (my model is 2465A).

No problemo, my pleasure and if you need other angles shot to compare with mine on other parts that you suspect that they're missing or tampered, just ask, I will try my best, got tons of close up shots here. ;)

Interesting offer, I take it although mine is 2465B, who knows someday I will need it even I'm pretty sure they're different.

Btw, is that 2465A has the same A5 board as mine that has the Dallas nvram ? or its using the older model with external lithium battery ?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: blueflash on November 25, 2011, 11:18:42 am
Seems to be the older model with lithium battery.

Find attached the binaries of the EPROMs in the hope that it will help somebody someday. I heard sometimes that EPROMS may loose their memory after 10 or more years - especialy if they work at higher temperature. So I deicided to save the EPROMs of my devices.

 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: slburris on December 20, 2011, 06:06:57 pm
Note that there's a lot of Tektronix firmware archived here:

ftp://ftp.bluefeathertech.com/electronics/testgear/Tektronix/firmware

Scott
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on December 21, 2011, 07:33:49 am
Scott, thanks for that links and bookmarked, definitely a precious resources if my old scope hoarding nerves get excited again.  ;D
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: slburris on December 21, 2011, 04:54:21 pm
Oh, I forgot this other site for firmware (and manuals):

http://www.ko4bb.com/manuals/index.php?dir=04 (http://www.ko4bb.com/manuals/index.php?dir=04))_ROM_Images_and_Drivers

Lots of good people trying to keep old test equipment alive by
archiving firmware images against eventual bitrot.

Scott
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on December 24, 2011, 06:57:47 pm
Oh, I forgot this other site for firmware (and manuals):

http://www.ko4bb.com/manuals/index.php?dir=04 (http://www.ko4bb.com/manuals/index.php?dir=04))_ROM_Images_and_Drivers

Lots of good people trying to keep old test equipment alive by
archiving firmware images against eventual bitrot.

Scott

Yeah, I have that bookmarked already, good site it is,  thanks, personally I'm very grateful for these old resources maintained by these people all this time.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: m1gry on January 27, 2012, 12:31:42 am
I've just bought a 2465A from Ebay  ;D. I've had my eye on this model scope for a while as I'm interested in the high bandwidth. It came with 2 off P6139A 500MHz Tek scope probes. I've never used this particular scope before, so I was interested to test it out. Everything appears to work OK, diagnostics pass, and it shows 4000+hrs and 800+ on/off cycles. Serial is B0106XX. I have no idea how old it is.

There are a few quirks: the A/B timebase switch is a bit "woolly" (possibly because it has been used a lot!). If I select GND and change volts per div, the trace moves around, but is the same "offset" for 50/5/0.5, but different to  10/1/0.1, and different again to 20/2/0.2. Not a showstopper but could be an annoyance during use. At the two higher sweep settings 5 & 10ns the timing cursors are about 10% wrong, but appear OK at slower sweep speeds. I hope that this might be a calibration issue.

Also if the READOUT INTENSITY pot is moved any small distance away from centre, the trace gets very bright and unfocussed. Again not a showstopper, but it needs careful adjustment and I can't beleive that Tek designed it that way. The main INTENSITY also seems a bit agressive, but can be turned right down and the traces are sharp and clean.

Comments welcome (and I think this is my first posting to EEVBLOG  :)

--Gary
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on January 27, 2012, 06:29:21 am
Gary, 1st of all, welcome to the forum ! ;)

Congratulation on the scope, hope you got it with a good price, also its really nice it came with two high speed probes, cause this probes thingy is really important.

I've seen lots of people hunting old high speed analog scope without realizing the importance of having a good probes to work with, otherwise it will be come useless like using those China made crappy one with it.

Looking at your problems, I guess its time for another 24xx teardown thread of yours ? Especially on cleaning and fixing the mechanical switch, it should be interesting to observe.  :D
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: butmach on March 31, 2013, 06:54:32 pm
Hello everyone, this is my first post to EEVBLOG  :-BROKE

digging thru the forum, I have found a post from BravoV.
Did you manage to backup externally the DS1225 (or someone else did ?).

My calibration data in 2467B got lost during desoldering of this pesky chip. I tried to secure them ... but the worst-case scenario that I always feared fulfilled.

I do not have the whole reference equipment. I have calibrated CAL01 thru CAL08.

But the CAL09 procedure for parametric measurment is not passable for me ... I got only LIMIT messages !, can be that there is a malfunction somewhere in AB sweep or AB gates (PAL), but before unsoldering of DS1225 everything worked fine.

My question is: do you know what part could cause exceeding the LIMIT's in the CAL09 procedure.
Could you please send me your NVRAM dump as a file, I will programm a blank device in an external programmer and look if the "diagnostic push a/b trig ..." disapears.

I'd be happy to any answer :)
P.S. Also I need to do something with the cooling off U800, I think there is a factory fitting error, IMHO there should be no shims between the IC a PCB, U800 should adhere directly to the PCB.
After I get done with calibration, I will add additional heatsink.

Pawel
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: hepcat on March 31, 2013, 09:05:17 pm
<snip>
P.S. Also I need to do something with the cooling off U800, I think there is a factory fitting error, IMHO there should be no shims between the IC a PCB, U800 should adhere directly to the PCB.
After I get done with calibration, I will add additional heatsink.




There are three things that were done to the U800 chip on my refurbished 2467B:  1. The chip was de-soldered from the board and a machined pin socket installed.  2.  A small heat sink was attached to the metal tab.  3.  The hold-down nut on the opposite side from the tab/ heat sink was removed.  This is to remove bending stress on the chip.

Regards,


Jason
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: grenert on March 31, 2013, 09:37:17 pm
QService in Greece sells these NVRAM chips pre-loaded with standard calibration data:
http://www.qservice.tv/vpasp/shopexd.asp?id=1252&bc=no (http://www.qservice.tv/vpasp/shopexd.asp?id=1252&bc=no)

Perhaps they can sell/give you the data for your scope.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on April 02, 2013, 01:33:59 am
@Pawel (butmach),

Welcome to the forum on your 1st post.

Really sorry to hear you've lost the cal RAM  :'( , also my mistake on our earlier offline message, I misread your scope model, I thought its 2465B instead of 2467B, really sad to hear this happened at the best portable analog scope ever made.  |O

Not sure if both are compatible, although I doubt it, attached below zipped of two copies of NVRAM from two different calibrated Tek 2465Bs just in case you feel adventurous. Also too bad our resident Tek expert here Alan (w2aew) has 2467, not the "B" version.  :-\

Maybe as above grenert's advise to contact QService for the nvram image if you still unable to solve the problem.

Also I would like to hear from you how you're going to cool the pesky U800, please share few photos once you've done it.


@Jason (hepcat)

Thanks for the info, sounds very interesting.  :-+

Do you have any photo shoots on how mod was done at the U800 ? Really appreciate it if you could share it here, I'm very interested and pretty sure other U800 owners too.  ;)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: hepcat on April 02, 2013, 02:02:08 am
<snip>
@Jason (hepcat)

Thanks for the info, sounds very interesting.  :-+

Do you have any photo shoots on how mod was done at the U800 ? Really appreciate it if you could share it here, I'm very interested and pretty sure other U800 owners too.  ;)



The attached photo was sent to me by the person I bought my scope from.  If I remember correctly, it's from a 2465B.

Regards,


Jason
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on April 02, 2013, 11:10:34 am
Jason, interesting mod, as my thought and described at my earlier posts when I saw the nuts and bolts, its simply a design flaw, thanks a lot for sharing that photo.  :-+
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on April 05, 2013, 09:54:24 am
Sad news, a failed to attempt to find the better replacement for the pesky Dallas DS1225Y BBSRAM, cause the F-RAM Ramtron FM1608-120 is not compatible. It was an impulse purchase thru a friend visiting abroad without checking the detail 1st, and also I was mis-leaded by info gathered from the Tektronix's Yahoo mailing list.  |O

The reason is the DS1225Y needs the Chip Enable (CE) pin to be enabled only "once" for multiple read/write operations, while the F-RAM needs the CE to be toggled at every address change and latched at CE 's edge.

What a waste, another addition into the components bin labeled "It will be useful .. someday".  :palm:
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: butmach on April 05, 2013, 07:22:45 pm
In my 2467B all functionality is restored  :-DMM, as before the disaster, thanx very much, my old humble scope is reincarnated.
Next NVRAM loss will never happen again ... now I have a backup :)
I have also tested NVRAM dump from a 2445B, (provided by an attentive and helpful ham radio operator), it is also working perfect.
I have tested the calibration to 50MHz, the error of measurement is from 1 ... 3% on readouts (dT, d1/T, dV), im very lucky.
Now I'm waiting for a TG501 to test the scope in full range and if it will be necessary I will perform a calibration.

Pity it did not work with F-RAM Ramtron FM1608, almost bought them  :(
I ordered the M48z08 ZeroPower STMicroelectronics SRAM, but there is not any greater advantage over DS1225 - are more readily available.

If I make the additional cooling for the U800 I will of course attach a few photos.

Regards,
Pawel
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on April 06, 2013, 09:07:36 am
Pawel, congratulation on reviving back your 2467B  :-+, so you did use 2465B SRAM image or others ?

Also thanks for the photoshoots of that weird BBSRAM module using the EPSON chip, especially with that weird battery's position  :o, whats the part no of that thing ? Never saw such strange chip.

About the F-RAM, I've decided to use another version that doesn't need to toggle the CE pin for read/write, its FM28V020 F-RAM, and since its 256K bit, planned to use it with the 2 extra address pins on dip-switch, so it can be manually switched between 4 of those 64K banks. Hopefully it will work flawlessly, the chip is on it's way direct from Cypress Semi.

Btw, that IC pin sockets inspired me to do the same for my U800 chip, that method will provide plenty of space underneath the IC body for a custom copper block heatsink.  :-+

Cause the best heat dissipation path is through the metal body part straight under the chip's die. Shot of U800's bottom view, pardon the texts, made this pic while ago to someone else on precautions when handling this damn chip.  >:(
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: butmach on April 06, 2013, 08:52:14 pm
I'm using the 2445B image, because the measuring errors are satisfactory for me without calibration. Your images also operate normally, but the calibration data does not  match to my hardware - error of measurement is 15...20% in my scope.

I don't know the part no of this BBSRAM, originated from an old RICOH photocopying machine, was located on main control board PWB no. A1535112. The EPSON chip is a 256K-BIT SRAM with Extremely Low Standby Current. It's like a Dallas DS1225 without cover and with larger battery :). Address lines A13, A14 are grounded and disconected from scopes board. Did not work properly as they were connected.

I am curious how it goes with FM28V020. It's hard to get !

You are right with the heat dissipation path, but there will be a lot of work to disassemble the main board from scope.

My additional cooling is already fitted, some photos are attached below. Before attaching the heatsink I gave some silicone thermal grease between the chip and the heatsink. It works very well. The temperature without the housing is about 42...45 degrees Celsius. With housing it will be even lower due to the forced cooling by the fan ^-^

Regards,
Pawel
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on April 07, 2013, 01:42:50 pm
I'm using the 2445B image, because the measuring errors are satisfactory for me without calibration. Your images also operate normally, but the calibration data does not  match to my hardware - error of measurement is 15...20% in my scope.

Looks like all analog Tek 24xxB scope's SRAM image are compatible each other, never expected that, great finding.  :-+


I don't know the part no of this BBSRAM, originated from an old RICOH photocopying machine, was located on main control board PWB no. A1535112. The EPSON chip is a 256K-BIT SRAM with Extremely Low Standby Current. It's like a Dallas DS1225 without cover and with larger battery :). Address lines A13, A14 are grounded and disconected from scopes board. Did not work properly as they were connected.

Yeah, I was curious when seeing the pin 1 & 26 mod job, no wonder.

About this BBSRAM at Tek 24x5B scope, an interesting finding, if you check the scope schematic, the pin 1 and 26 are connected, while at the BBSRAM DS1225Y chip, those are NC pins.  :-//

Probably they were reserving that A13 & A14 lines for optional expansion when the scope was designed back then. Your problem with that grounded 2 extra unused address lines is confirming that, both pins are supposed to be pulled high or as in no connections as DS1225Y does, pulling both down definitely will confuse the CPU.


I am curious how it goes with FM28V020. It's hard to get !

Yeah, its hard to find, since this F-RAM is not as common as other like EEPROM, just a warning, never buy these kind of rare memory type from Chinese online store like at ebay or aliexpress, trust me, 99.99% are fake.

Ordered my FM28V020 directly at Cypress Semi's online store, even though not that cheap @$21.69 a pop :(, they're providing "free" shipping, so its worth compared to buying the pesky battery based DS1225-AD (DS1225Y replacement) through Maxim's distributors ranging about $17 to $20 price range but with crazy s/h charge.  >:(

Btw, I've been reading intensely the 256K FM28V020 F-RAM datasheet and comparing with DS1225Y lately, and so far it is quite promising. With the 4 times bigger capacity, I'm going to route the two extra unused address lines into a dip switch with 2 positions, so basically I could manually switch between the 4 x 64K memory space, enough for experimenting with different calibration values, or easy hacking/tweaking around the SRAM's content if needed  >:D.

For physical compatibility, since FM28V020 is SOIC 28, its obvious I need a custom breakout PCB for SOIC 28 to DIP 28 and with a dip switch placed at the PCB.

Btw, thanks for the U800 heat sinking photos.  :-+
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: grumpydoc on April 07, 2013, 01:52:43 pm
Quote
Looks like all analog Tek 24xxB scope's SRAM image are compatible each other, never expected that, great finding.

The 2445 and 2465 are pretty much the same 'scope so it's not that surprising.

A while ago there was an ebay seller in the 'states who was changing component values in 2445 front ends (to be the same as the 2465) to increase bandwidth and selling them (de-badged) as 2465's. As far as I can discern from the posts on the TekScopes mail list this doesn't quite turn a 2445 into a 2465 as there are differences in the PCBs and I think some of the inductors at least are fabricated from PCB traces.

Needless to say the mailing list's opinion of the seller was rather low!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on July 25, 2013, 06:29:58 am
Got few PMs lately asking how I copied this scope's cal data from the battery backed up SRAM Dallas DS1225Y, all read from old chip & write to fresh chip was using the cheap MiniPro TL866 Universal Programmer as reviewed by Dave.

Btw, the DS1225 is officially supported by this programmer, check the list your self here, just ignore the Chinese characters at the beginning and scroll down to Dallas section -> http://www.autoelectric.cn/minipro/MiniProSupportList.txt (http://www.autoelectric.cn/minipro/MiniProSupportList.txt)

Edit : Quote from above link on supported Dallas chips :

[ DALLAS ]     19 PCS

DS1220 (RW)                DS1220 (TEST)            DS1225 (RW)            DS1225 (TEST)               
DS1230AB (RW)            DS1230AB (TEST)        DS1230W (RW)           DS1230W (TEST)             
DS1230Y (RW)              DS1230Y (TEST)          DS1245AB                   DS1245W                     
DS1245Y                      DS1249AB                    DS1249W                    DS1249Y                     
DS1250AB                    DS1250W                     DS1250Y       
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Stonent on July 25, 2013, 06:55:51 am
I'd be reasonably sure that 1996 fan was a replacement.  They wouldn't be using Dallas chips with a 1989 date code in a 1996 scope.  A lot of old Sun workstations use similar Dallas chips to hold the MAC address and configuration data and it is fairly common for those to have died with an FF:FF:FF:FF:FF:FF MAC address.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on July 25, 2013, 10:34:27 am
I'd be reasonably sure that 1996 fan was a replacement.  They wouldn't be using Dallas chips with a 1989 date code in a 1996 scope.  A lot of old Sun workstations use similar Dallas chips to hold the MAC address and configuration data and it is fairly common for those to have died with an FF:FF:FF:FF:FF:FF MAC address.

First I thought that too, but there are many other chips in there that have date code 1993, also I got a confirmation from an experienced Tek expert that this fan type is the original fan that came with similar 246x scope.

Btw, that 1989 Dallas chip is still kicking and working fine, intentionally put it back in there after I secured it's content just to see how long will it last.  >:D

Picture of that DS1225Y replacement with the cal data already copied into it DS1225AD, purchased from Digikey few months ago.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: PM33AUD on December 15, 2013, 05:06:05 am
Hello!

Figured I'd first try reviving this thread instead of starting a new one so info is consolidated.

I am hunting down a fan for my 2445B here... it is the same model as in this teardown.  It is a quite nice fan... aluminum frame and all.  Finding an 80x80x20mm fan is a bit of a tall order when looking for one that is of high specification.

Any leads?  It doesn't appear a 25mm thick fan will fit properly without modifying the airfoil (or whatever this is called).  Sanyo Denki makes some nice models with high life - I have a 9S0812F401 here but it is 25mm thick.

Thanks!
Phil
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 05, 2014, 01:49:04 am
80x80x20, on mouser:

http://www.mouser.com/Search/ProductDetail.aspx?R=AD0812HB-C70-LFvirtualkey66400000virtualkey664-D8020HB-12VLF (http://www.mouser.com/Search/ProductDetail.aspx?R=AD0812HB-C70-LFvirtualkey66400000virtualkey664-D8020HB-12VLF)

I bought that one and it should be here tomorrow or the next day.  I'll report back if it fits ok or not.

(clue: I was looking on ebay for a fan for the 2400(a/b) series and someone had this very fan pictured as an 'exact replacement'.  I searched on that model # and lo and behold, mouser had it!  if mouser carries it, its probably not a cheap POS fan).
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 06, 2014, 07:28:08 am
got my mouser order today.  I can confirm that that fan is an exact size replacement.  I have not turn it on or compared it to the old one, but size wise, its 100% exact.

fyi
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on March 06, 2014, 07:35:25 am
Even though chances of getting it wrong is quite low just for the simple DC fan replacement, suggesting to measure the working voltage & current of the old fan before installing the new one, and then re-measure again at the new one once installed, just an extra precaution on this little piece of good scope.

Great  :-+ , looking forward to see the process of your 2465B getting "the rejuvenation".   8)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 06, 2014, 07:42:40 am
good point about the voltage.  I just assumed 12v.  fortunately, I guessed right and both fans are marked as 12v.

fitting it to the scope was fine.

I did forget to make note of which way the old fan was facing.  I would assume it blows out but if anyone can confirm, that would be appreciated.  (it would not make sense to blow IN, but it never hurts to be sure).

the new fan is rated a slightly higher current draw but not by much.  the old fan has more blades, but I'm not going to worry about that.  I'm sure that its not going to be that critical.  certainly better than the dusty old one that was in there.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on March 06, 2014, 07:47:23 am
Confirmed, its blowing out.

At the 1st post of this thread, there is a picture of mine which is the original came from Tek factory untouched when it was shot, although its not very clear, you can see faintly the two arrows showing the rotation and air direction on the top of the fan.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 06, 2014, 08:04:54 am
thanks!

I should have noticed the label on your photo; that's enough to know which way the wind should blow ;)

all the parts from mouser and digikey came, but I'm still waiting on the chip programmer.  I'll probably replace some of the caps, replace the fan and put it back together to make sure I didn't 'go backwards' (do damage in my refurb effort).  I like doing incremental changes, anyway, so that if things don't work, you have some idea which thing you did between working and not-working.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 08, 2014, 01:56:15 am
bought a new friend for my 2465b:

(http://farm8.staticflickr.com/7348/13000931353_aba2a50e48_o.jpg)

(the scope cart, not the scope.  already had that scope from a purchase last year).

this cart was made for 2400 series and that's what will eventually go there.

went to my local shop, found this cart in decent shape (dirty as hell but not banged up) and just had to take it home with me ;)

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on March 08, 2014, 02:07:58 am
Nice score, now I'm so jealous.  :'(

How much did you pay for that ?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 08, 2014, 02:32:21 am
the cart was marked at $75, but I got it for 10% off when I talked nice to the salesman ;)

scope was $90 plus $25 shipping, about 2 years ago.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 09, 2014, 04:06:31 am
well, I replaced the 4 smd caps and the fan, then put it back together to do a quick check.

I don't think I like this fan ;(  its not at all quiet!  the original fan had more blades and maybe that helped keep it somewhat lower noise.  this one from mouser is not what anyone would call 'quiet'.  it works, I guess, and I think I'll have to live with it for now, but I don't suggest this model, really.  oh well.

next step for me, replacing the dallas module (not really looking forward to unsoldering it, to be honest.)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on March 09, 2014, 04:24:31 am
replacing the dallas module (not really looking forward to unsoldering it, to be honest.)
I'm afraid you just can not escape from that.  >:D

Please, post your original Dallas's content here once you backed it up.


Btw ...

(https://www.eevblog.com/forum/testgear/you're-going-to-be-so-jealous-of-my-workplace/?action=dlattach;attach=84396;image)

... c'mon, more photos please.  >:D
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 09, 2014, 08:11:36 am
here we go...

(http://farm3.staticflickr.com/2209/13028277734_88cf205fec_o.jpg)

dallas is removed with the help of hakko 808.  a few pins gave some trouble so I skipped them, did the rest and went back to the trouble ones with a soldering iron, some fresh solder and then re-attack with hakko 808.  no traces seemed to have gotton harmed.

the new dallas chip is there and a surplus gold pin socket, as well.  next step is to copy data over using that '$50 programmer' from china.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 09, 2014, 09:17:02 am
success!

(http://farm4.staticflickr.com/3317/13029010943_2fce723f9b_o.jpg)

the minipro copied the dallas chip just fine to the new digikey-supplied fresh chip.

I just bought another 10-20 years of cal data ;)  and the next guy does not have to unsolder that crazy chip.

firmware upload:

http://www.netstuff.org/tektronix_2465b/ds1225_firmware_linuxworks/ (http://www.netstuff.org/tektronix_2465b/ds1225_firmware_linuxworks/)

the .BIN file is the rom image and the .md5.txt file is the unix 'md5sum command checksum output (not needed for the chip programmer, but only used if you want to verify the file came thru ok on your download).

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on March 09, 2014, 06:21:58 pm
Bryan, good to hear it went smoothly, the cheap minipro just works for the 1st time without any problem here too.

I just bought another 10-20 years of cal data ;)  and the next guy does not have to unsolder that crazy chip.

With a refresh on the power supply caps + good luck, I pretty confident that the whole scope it self will last for another >10 years, especially yours was made in 1992, imo its still in very young age compared to others that were made in 80s and still working fine today.

Have you check it's power on hours and cycle counts ? Really curious to see yours.

Btw, thanks for RAM image file.  :-+
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: echen1024 on March 09, 2014, 06:30:53 pm
@Linux-works

That's really quite a clean scope. Not like some of the Israeli "boat anchors" or "totally harmonically distorted" equipment.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 09, 2014, 06:57:40 pm
I see that ebay site in israel that sells stuff in truly throw-away-and-don't-look-back condition ;)  what a funny thing to see how abused gear can be and they still want to sell it.  too weird!

this scope has some dings on the plastic front bezel (which I'm on the lookout for, to replace) but other than that its fairly clean and inside was no rust on any of the screws or nuts, like victor's had.  I bought this from a san diego seller and I suspect it spent its life in calif, so there would be little to no rust.

I'll check the power-on hours, but its not trustable since you can zero that out easily enough.

wish I could find a good clean front cover and also the top vinyl pouch; those didn't come with my scope and I'm on the lookout for a bargain on any of those.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: echen1024 on March 09, 2014, 07:15:01 pm
eBay auction: #231098193016

The description is just beautiful:

This unit powers up but not working,after powering the item up you see nothing on the display the display completely DAMAGED but when you press all the buttons you hear beep. it is mainly for part or repair,What you see in the pictures is exactly what you going to receive, if you have any questions please contact us.11819

"You see nothing on the display" Well really now? It's been damn smashed out!
 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 09, 2014, 07:17:33 pm
"that meter kept lying to me, so I just punched his friggin face out!"

lol

maybe the main board was still good and worth that price.

but *I* wouldnt' trust it! 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: jonpaul on March 09, 2014, 07:21:04 pm
Hello all, my first post, great teardown and good work on the NVRAM.
I have 2465B, 2467B, both need NVRAM, but I am NOT good with digital stuff, and getting on in years,  loosing the ability to do the very fine work you folks can do!

I would be interested to buy or swap for a few of these parts if someone can make them, prefer the one with the external lithium battery.

Happy to furnish the serial numbers and exact NVRAM part numbers in my units.

I have a lot of TEK and HP units, manuals and some parts for swap.

Kind Regards,


Jon
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on March 10, 2014, 02:02:33 am
Jon, welcome to the forum.

About fresh NVRAM chip + content sourcing, I guess linux-works can easily help you out since he is US too, its pretty straight forward and pretty quick to copy/write into a fresh DS1225 chip.

Its just I'm curious why you need that ? Cause every NVRAM image is unique since it has that particular scope's calibration values, and imo can not be used to other as it will cause your scope out of calibration.

If you've lost the NVRAM, you need to buy new Dallas DS1225AD and replace the old one, and send the scope to the calibration service to have a proper cal values in it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: casinada on March 10, 2014, 03:11:19 am
Jon,
Probably if you say where you live, some Tek Fan /Blog Member might be in your neighborhood and willing to help you.
I was able to calibrate my 2465BDM starting from a downloaded NVRAM from the KO4BB web site, programming a new NVRAM and calibrate most of the settings with the equipment I have. I'm not a calibration site by any means but willing to help if you're in my neck of the woods (Tucson, AZ)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 10, 2014, 03:17:01 am
I don't have any new pics (nothing really exciting to photo) but I finally did replace the caps in the lvps.

I hate getting that board set out!  on my scope, its very hard to wiggle that board pair out of the metal; its wedged in there very tightly.  I don't like how tek designed this part; they could have used slides or rails to vertically align the boards and things could have slid in a LOT easier than they do.

if you remove the power IEC socket and pull off its wires/clips you can get more room for your fingers to pull off the 120/240v switch wires.  that was identified as one of the harder things to do when removing these boards.

I didn't replace every cap there; but I did replace the big silver ones and a few others.  I don't notice any change in the scope but at least I know I have fresh caps in the critical places.

I read on one lvps upgrade that if you find 2 100uf caps, you want to keep them exactly 100uf (for some reason).  I replaced those with exact values but using new caps, just for good measure.

it took a good 2 hours to do the power supply boards.  kept scratching my head on how to remove that board pair and not break anything.  putting it back in was just as hard.  something must have been bent since I had to flex the rear metal chassis (near the fan) to create clearance for the metal and plastic standoffs.

anyway, it seems done now.  I'd like to get it professionally calibrated but at least its rejuvinated.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 10, 2014, 03:18:14 am
jon is in my general area, so I'll contact him offline and see what we can do.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on March 10, 2014, 03:22:23 am
I was able to calibrate my 2465BDM starting from a downloaded NVRAM from the KO4BB web site, programming a new NVRAM and calibrate most of the settings with the equipment I have. I'm not a calibration site by any means but willing to help if you're in my neck of the woods (Tucson, AZ)

Any chance you could share how you do that in details ? What sort of equipments do you have there ?

As cheap cal service is basically none at where I live, I will be content even for a poor man cal process that yields only with a "good enough" result.  :'(


anyway, it seems done now.  I'd like to get it professionally calibrated but at least its rejuvinated.

Really curious on the upcoming result, is there any chance you can pre-arrange with the calibrator, that you can get the detail on how much that thing has drifted from the current cal ? This question also for Casinada for your DIY cal as well.

If yours doesn't drifted too much, with the recent components refresh, I guess it will be in cal for many years ahead as the references in side are cooked well enough and wont drift anymore.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: casinada on March 10, 2014, 05:08:28 am
I posted some pictures on the Yahoo TekScopes group last september:
https://groups.yahoo.com/neo/groups/TekScopes/photos/albums/1871970004
I used an arbitrary waveform generator that only goes so far in frequencies and I used a signal generator for the high frequencies. When you go trough the calibration procedures, if something is out of range it won't let you finish the calibration so you go back and forth until you get it right.
You need a good DMM to adjust some of the voltages.
I connected with a member of the Tektronix group that lives at a reasonable distance and had good equipment that we used to verify that my calibration was within specs. He has a leveled signal generator and frequency counters that are referenced to GPS. The Scope is not a precision instrument so is not that critical to have it calibrated by a Lab. If you can verify the amplitudes and frequencies are correct and it triggers properly
Then you should have a very usable instrument. You can spend as much time as you want trying to get it as perfect as you want. It can be lots of fun but then it can get tedious as some of the procedures are long. :)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: chksum3 on March 12, 2014, 02:31:18 pm
Congratulations to linux-works on your successful replacement of the 2465B's NV-SRAM.  I'm brand new to this Forum after having found a partially renovated 2465B on EBay. The offending caps had been replaced within the power supply and A5 board and a heat sink was fitted.  The DS1225Y was however not replaced... leaving that to me. I've followed the task of removing the chip, copying the calibration data from it, then writing the data to a new DS1225Y and re-seating it (via socket) to the A5 board.  Before opening the 2465B and removing the 1225Y, I went ahead and bought a new one (DS1225Y 200ns) from a local - SF Bay Area - supplier, Jameco Electronics, and a universal programmer (GQ-4X) off of EBay, which was supposed to read and write to the DS1225Y.  I thought it best to prove to myself that I could read and write to a new chip before getting involved in 2465B surgery.  Sad to say, I've been unable to read and write to the new chip (tried on 2 of them) with the GQ-4X programmer.  Reading that you were able to navigate these waters and successfully program and install a new chip has raised my spirits considerably.  Could you detail the exact programmer model number and the exact chip you used (the Y version, or AD, etc.).  I'd like to follow the path you've cut through the forest. Thank you!   -- Gary
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 12, 2014, 02:33:46 pm
if you can return the jameco part, you may want to do so.

I was advised by a 2465b repair guy that the jameco chips are old and not to be used or trusted.  what is the date code on your new chip?

I got mine at digikey (they seem to be out of stock right now) and my date code was 2012, so I know it was pretty fresh.

if you are in the bay area and need help programming the chip, let me know and we could meet to do the copy.  but you may want to buy the chip from mouser or digikey if your date code is not recent enough.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: chksum3 on March 12, 2014, 02:50:41 pm
Thank you for the information! I'll see about returning the chips to Jameco and will order a DS1225Y from digikey today.  I really appreciate your offer of reading the old and programming the new chip -- saves me having to find and buy a programmer that works.  Now, did you go with ordering a Y version or some other version of the DS1225? And, just for curiosity - what programmer model number did you use?  Once the new chip arrives from digikey I'll open the 2465b and desolder the old chip then get in touch with you for the read/write.  Thank you extremely! Re: date code on the jameco chips --> none present.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 12, 2014, 03:22:32 pm
I bought this programmer:

http://www.ebay.com/itm/321085130796 (http://www.ebay.com/itm/321085130796)

it arrived safely and quickly.

for the chip, this is the one I ordered but it seems to be out of stock right now:

DS1225AD-200IND+-ND

AD is a wider temperate range (I think) but nothing critical to the scope.  the 200 is the speed of the device and I used the same speed as the original chip.  not sure if going faster or slower would matter but I just matched the same chip speed.

mouser has one that is not AD but very close and that's probably also ok:

DS1225AB-200+

and those are in stock.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on March 12, 2014, 03:28:58 pm
Chksum3, welcome to the forum.

About the Dallas chip DS1225, only buy from big distributor as they constantly refreshes the stock, also Ds1225Y is discontinued, and can be replaced by DS1225AD. This newer version has an unique feature that it's internal battery is disconnected internally until you used it for the 1st time.

Suggesting not to buy those Ds1225 chip from surplus shop as they are mostly very old, and who knows how is the battery freshness inside, and it does not have the new battery disconnected until 1st use feature as newer AD/AB version. Just watch the date code the one that linux-works has, its still very fresh.

Regarding the tl866, lots of info here -> https://www.eevblog.com/forum/blog/eevblog-411-minipro-tl866-universal-programmer-review/ (https://www.eevblog.com/forum/blog/eevblog-411-minipro-tl866-universal-programmer-review/)

Hope this helps.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: chksum3 on March 12, 2014, 03:51:43 pm
Thanks to linux-works and BravoV for all the info!  I just placed an order for the DS1225 from DigiKey. They did have the DS1225Y-200 in stock! (part#: DS1225Y-200+-ND; IC NVSRAM 64KBIT 200NS 28EDIP). Price: $23.13.  I was about to return the programmer (GQ-4X) that failed to write to the jamco chips; I'll hold off for a few days as the problem may not have been with the programmer. Again, many thanks for helping me out of the NVSRAM ditch.  -- Gary
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 12, 2014, 04:00:55 pm
jameco is usually ok.  they are not a surplus shop, they are like a mouser, but just smaller and not as common or as cheap to order from.  they go way back to the 70's when they were 'james electronics', so they are not new to the business.  but on this part, they may have old stock and for battery based things, that's not good.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: chksum3 on March 14, 2014, 11:46:20 pm
I'm happy to report that I just received a new DS1225Y-200+ NVSRAM from digikey, plugged it into the GQ-4X USB Universal Programmer (under Windows Vista), and got a clean write and subsequent read of linux-works' 2465B calibration .bin file image. This verifies that two DS1225Y-200 chips purchased from Jameco were not functional, and that my GQ-RX programmer works just fine.  The next step is to take my nicely functioning 2465B, de-solder the aging DS1225Y, take that image, write it to the new chip, and install it - via socket - into the scope.  Thank you again to linux-works and BravoV for all your help! 

PS - In word of explanation: I decided to first buy the "Y" version rather than the "AD" version of the DS1225 given the initially frustrating attempts to write to the Jameco chips.  I understand the "AD" chip would have a freshness guarantee, so to speak, given its first turn on would be at first write, but ... I decided to limit variables and take small steps by installing an exact replacement type.  Now, once the .bin image is safely tucked away and the new "Y" is in, the process can be easily repeated with an "AD" version years down the line.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 15, 2014, 12:06:55 am
interesting how the jameco chip just would not work.  what was the date code on that one?

glad you got it sorted out.  sounds like you are on your way.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: chksum3 on March 15, 2014, 01:08:01 am
I'm not sure how to read the date code.  Here are the numbers associated with the two non-functioning Jameco chips:

NON-PIN SIDE --> Both chips: 1207C 386017
PIN SIDE         --> Both chips: DS1218  1102D1

Here are the numbers associated with the one functioning Digikey chip:

NON-PIN SIDE --> 1334D5 391308
PIN SIDE         --> DS1218  1314D1 113AT 

Are there dates coded here?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 15, 2014, 02:21:43 am
I'm pretty sure the 1207 is a date code (year 2012, not very old at all).

ds1218 though?  should be ds1225, no??

1334 is also a date code, and that would be 2013, very fresh chip.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: chksum3 on March 15, 2014, 03:32:06 am
I did a little Googling and found that a DS1218 is the CMOS circuit within the DS1225 that monitors power input to it (or not) and switches the battery on when appropriate to provide power to the SRAM module - converting it to a nonvolatile package.  That is, nonvolatile until the battery eventually dies.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 15, 2014, 03:34:16 am
ah!  now I know what you are referring to.  'pin side' meaning BELLY side of the chip (lol).  yes, I see that on mine, too.  the 8pin dip embedded (potted) inside the chip.

ignore that.  that chip is not the one you care about.  the whole module date (the top of the module, pins facing away from you) is the date code you care about.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on March 15, 2014, 04:18:26 am
Gary, good to hear you've solved the problem. The Digikey's one looks very fresh, date code 1334, thats 2013 week 34, manufactured about last Aug 2013. This chip even in use will last > 10 years. Mine pulled from the 2465B with date code manufactured in 1989 (25 years  :o) is still working fine when I tested few months ago. 

Meanwhile the two from Jameco are not that old either, made around Feb 2012 (date code : 1207), curious why they're broken ? Assuming these are never used chips.

How much these Jameco DS1225 cost you ? If its too cheap, afraid they're knock off/fake ones like those sold at Aliexpress, some are even selling them at $2 with free shipping.

Btw, since you're using linux-works's SRAM image now, which carries unique calibration settings, have you measure it with some references to see if the cal is out way too much ?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: chksum3 on March 15, 2014, 06:04:04 am
Thank you, but I've solved only the reading / writing to a new DS1225 to date.  I used linux-works' SRAM image as a test of the functionality of the new DS1225 and universal programmer -- I was able to get the image in and read it back out.  I haven't yet opened the 2465B, so I haven't yet gotten my hands on the SRAM image contained in my scope.  Once I gather a few more details, I'll dive in, hopefully be able to extract the chip without damaging traces, etc.  Only then will I read the data, program the new DS1225 and reinsert it via a socket.  In other words, there is a long way yet to go. 

Part of my preparation has been to review your terrific tear-down documentation from Nov. 2011.  My plan is to investigate any potential road-blocks in removing the A5 board, then determine whether my solder - desolder station will be sufficient to the task, and if so, what temperature settings and what kind of solder should be used in seating the new socket.  In other words, I plan to go slowly and try not to screw anything up! I've fixed a few things in the past (my ICOM R7000 receiver for example), but the complexity of the 2465B is another level altogether. <gulp>  Oh... you asked about the Jameco chip price -- they were ~$11.00.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: chksum3 on March 15, 2014, 04:57:40 pm
Well, I awoke and just couldn't hold back any longer.  The 2465B was opened and the DS1225Y chip was desoldered, read, re-read, inspected, and photographed. Its date-stamp is 9404D3, which I believe is April 1994 (?). The new DS1225Y was then written to and verified, then inserted into the scope.  Everything was reattached, screwed down, re-cased, and plugged in.  The switch was thrown and behold - the 2465B started up normally and functions perfectly.  Hurray! Again thank you for providing such clear instructions out here!  I'll work on uploading the calibration .bin file.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on March 15, 2014, 05:06:26 pm
Congratulation, well done.  :-+

Btw, if its not troubling you too much, please the photo of your A5 digital board, and also the zipped file of your SRAM image if you don't mind, and attach it here in this thread as another Tek 2465B references.

Hopefully it will be useful someday for other 2465B owners.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: chksum3 on March 15, 2014, 05:28:13 pm
Thanks. OK, I've attached an image of the reinstalled A5 board and a zipped copy of the .bin file now safely written to the new DS1225Y-200.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 15, 2014, 05:34:59 pm
if you did not change out those 4 smd lytic caps, you will want to.  those are on the 'must change out' list.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on March 15, 2014, 05:36:12 pm
Thanks !  :-+

Wow, I noticed there are 3 dark spots that look like scorched badly, the damages caused by the leaked caps is really nasty.  ???

Btw, your firmware there at the EPROM labeled 160-5877-02, any chance you can read and post here too ? Really curious as mine (see the 1st post) is 160-5877-01.

My TL866 reader/writer just can not handle this rom type which is D27011.  :-//
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: chksum3 on March 15, 2014, 05:49:02 pm
I bought this scope on EBay from - rcatechalert_guy - as having been refurbished as follows: "The LV power supply filters (Capacitors) replaced with units with better specifications; The A5 control board SMD capacitors were replaced and potted.  Do you see evidence that this was not done?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 15, 2014, 05:51:26 pm
I agree, there are LOTS of black areas there!  what the heck is going on??  some exploded parts?

looks like someone also touched some of the red wima caps with a soldering iron? ;)

if you can get some close-ups of the dark areas of that board, that would be useful. 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: chksum3 on March 15, 2014, 05:52:37 pm
The areas that look like scorch marks are actually a resin of some sort. I'm assuming that this was done to protect against any future capacitor leakage damage, but I can't see through the stuff.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 15, 2014, 05:53:08 pm
I bought this scope on EBay from - rcatechalert_guy - as having been refurbished as follows: "The LV power supply filters (Capacitors) replaced with units with better specifications; The A5 control board SMD capacitors were replaced and potted.  Do you see evidence that this was not done?

please do get us some closer photos.  if you want, I could help take some photos (if you are bay-area based).

I was very close to buying from that very person and I read his write-ups on ebay.  if that is 'potting', then I'm a monkey's uncle....

nothing should be 'potted'.  this is an SMD board and there are proper smd parts that should fit there.

I hope he did not butcher your board!

and if he did service on this board, why on earth did he not replace the dallas module?

this does not look good, I have to say ;(

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 15, 2014, 05:54:38 pm
The areas that look like scorch marks are actually a resin of some sort. I'm assuming that this was done to protect against any future capacitor leakage damage, but I can't see through the stuff.

that's not a typical repair procedure that I'm aware of.  you replace the bad caps, you clean the board and solder new ones there.  I used polymer caps so there can't ever be leaking again.  I can give you the part #'s from mouser if you want.

having work done on a board like that would make me quite uneasy about what else was done, and HOW well it was done.  yikes!

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: chksum3 on March 15, 2014, 06:04:30 pm
Here's a closeup of the resin covered areas.  Yes, I was disappointed to see the work up close and personal. On the other hand, the scope appears to be functioning well and, as they say, the deal is done.  With all the resin (?) now present, my first reaction is to leave it alone and not try removing it. If the scope at sometime fails, I'll of course be forced into action. 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 15, 2014, 06:09:01 pm
I would also be concerned with any of that resin affecting the circuitry.  on high frequency layouts, capacitance and trace leakage can be an actual issue.  I don't know the a5 board well and maybe those things don't matter here (its not an analog input section or high z section) but it just looks real bad to me.

if I saw that in my scope, I'd return it and give the seller a super strong negative for being incompetant and claiming otherwise.  wow.  just wow.  maybe I'm over-reacting but I do not like the look of that one bit!

if it works, that's fine.  but it sure looks like a teenager hacked your scope and not a professional.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on March 15, 2014, 06:14:16 pm
Geezz Gary, I just downloaded your A5 board photo, and starred it for a while, must be really bad there. I slightly enhanced yours to show the dark spots, and compare with mine at the left side.

See the arrows I put there ? Also I'm very concern of the high precision 10 Mhz oscillator (blue box at the bottom), it seems like its so dark that I can't recognize it anymore.  :-//

Attached below the quite big sized picture I just made, suggesting to right click the thumb pic and view at other window for best resolution.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: chksum3 on March 15, 2014, 06:29:01 pm
Yep, the resin coating is ugly and inexplicable - I don't understand the need to have done this, unless there was leakage and damage then wire used in place of traces to reconnect the damage pathways, then resin to cover the whole thing.  Definitely a messy job at best. Why the 10Mhz oscillator is resin covered is another mystery.  Ugly, ugly, but appears to be functional.  I've decided to write the seller and ask what this is about.

Regarding the D27011 EPROM: my programmer also does not include that one on the list of supported chips.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 15, 2014, 06:37:44 pm
I would email that seller and have him explain himself.  his business seems to be fixing up old scopes and reselling them as refurbished units.

I don't want to make you feel bad, but I'm so glad I decided NOT to buy from this guy!  I had emailed him a few times and thought about buying one of his scopes, but I would have had some real issues with his repairs had I seen that in a scope I paid EXTRA for, for so-called expert repairs.

did you leave him feedback already?

I would try for a discount or even to return the unit.  its a disgrace.  sorry, but it is quite disgraceful given those pictures and the burn mark on the wima cap, too.

and to charge that much for the refurb scope and to NOT do the dallas module.  shameful.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on March 15, 2014, 06:40:30 pm
Another comparison photos yours vs mine, just in case you need it when "talking" with that seller. Hope it will ended well towards you, really, your A5 board looks scary to me.  ???


Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 15, 2014, 06:44:25 pm
hey victor, what camera are you using?  that's a REALLY sharp photo there!

I wonder what the burn marks are on the IDC (or is it IDT, I get those confused) connector.  just dirt or temperature issues?  victor's is quite clean and mine is also quite clean with no discoloration.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 15, 2014, 06:49:07 pm
now, I'm wondering if the seller used hot-air rework tools to try to remove the smd caps.  that might explain the burn marks (if they are actually that) on the plastic vertical pin idc/idt connector.

maybe he lifted traces when he did the repair, so maybe he had to run green wires and pot that.

you might also post this to the yahoo tekscopes group and get some opinions on this.

sharper shots would help, though.  if you can avoid using flash, put your cam on a tripod of some kind and set the self-timer to auto fire, you might be able to get some sharper, more telling shots.  I'd be happy to come by and take some decent SLR shots if you want.  this should really be documented so that people know what to expect from such a seller.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: GreyWoolfe on March 15, 2014, 08:47:22 pm
FWIW, it looks like he's trying to hide a bodged repair job |O.  If this is an smd board, there shouldn't be wires added.  If I couldn't get any satisfaction, as in returning it or getting a deep discount for the crappy repair job, I would see about getting a replacement board and keep that as an emergency spare if you have to fix the primary board.  Negative review and epic fail!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 15, 2014, 08:53:56 pm
just a thought: since the seller 'repairs' scopes regularly on ebay, I'd ask to swap this 'fixed' board with a totally stock unfuc^H^Hixed board.

then just do the usual things needed for a5 boards yourself.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: chksum3 on March 15, 2014, 09:16:28 pm
Hmmm. I've thought about this all day, and I agree that the seller really should be expected to replace this board with a functioning and professionally refurbished substitute.  After struggling with this for awhile, and reading your identical suggestion - I did write to him again and ask that he fulfill this compromise. I asked for a professionally refurbished substitute board, as that is what I paid for in the first place (as I have no experience replacing surface mount components), and as I believe he should be given the chance to make good on the work.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: casinada on March 15, 2014, 09:28:14 pm
 ;)Not to defend anybody, that looks like a sloppy job. My A5 board was very corroded and it really crumbled to pieces as I was desoldering components. I was afraid I was going to lose traces but in the end everything worked out. I had to use some wire wrap wire to recreate traces. I removed the cotton traces after I took the picture :(
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: GreyWoolfe on March 16, 2014, 02:18:51 am
Your work is much better than the so called "professional" refurb job.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 16, 2014, 02:48:20 am
Hmmm. I've thought about this all day, and I agree that the seller really should be expected to replace this board with a functioning and professionally refurbished substitute.  After struggling with this for awhile, and reading your identical suggestion - I did write to him again and ask that he fulfill this compromise. I asked for a professionally refurbished substitute board, as that is what I paid for in the first place (as I have no experience replacing surface mount components), and as I believe he should be given the chance to make good on the work.

or, to make it easier on him (and you, too!) get an UNTOUCHED board from him, that way you don't trade one problem of his for another of his.  if its stock tek, then you can do the smd cap work and you already have done the unsoldering, so you are good at it, now ;)

you also have a copy of your eeprom data.  that data belongs more to 'the scope' than the a5 board (folks, correct me if I'm wrong about that) and so I'd restore that data to the new a5 board and you'd be whole again.

in fact, you already have the data in your NEW chip, so just keep the new chip. send the old chip back on the old a5 board (with the socket; leave that in, of course) and when you get the new untouched a5 board, do the socket thing again and you're back to where you should have been.

hope he goes for it.  by asking him for a non-modified board, it actually should be appealing to him.  he gets his 'work done to it' board, which he seems to think is worth something and you get to start fresh and do your own work on that a5.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 16, 2014, 02:50:07 am
oh, and if he does offer you an untouched a5 board, I'll help you out with the smd cap removal.  not a problem.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: chksum3 on March 16, 2014, 03:08:36 am
I emailed the seller and got his reply: an offer to receive the scope back for my money back.  I suspect folks out here will disagree with my decision, but I declined that offer and will keep the scope, aesthetic warts and all.   I am definitely bothered by the Ferrari with a Chevy bumper metaphor, but will fix all of that by finding another A5 board to work on myself. That will enable me to play with removal and replacement of SMDs in addition to replacing the NVSRAM again, which I found much easier than I thought would be the case.  All in all, it's all a learning experience, and it's all good.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 16, 2014, 03:15:39 am
you paid a lot for that scope and I would worry about 'what else could he have done wrong, to it'.  so far, you see the a5 'patches'.  you should probably look deeper to see if anything else was done.

yes, shipping is not going to be cheap, but a fresh start on another scope could be liberating ;)  and very likely, you'll be able to find one that is a good $150 or more cheaper and that could help offset the cost in shipping.  it would be fair if you two split the shipping cost; so he pays shipping out and you pay shipping back to him.

just a suggestion.  once there is doubt about a repair guy, I would want no part of anything he touched.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on March 16, 2014, 06:38:16 pm
Gary, what ever the decision, its yours. Hopefully it will last long and really interested to hear how it performs once its properly calibrated.

At least look at the bright sides, thanks to your sharing, which are don't buy Dallas DS1225 chip from Jameco  ::), and approach with extra cautions should anyone "desperately" needs to deal with that seller in the future.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: chksum3 on March 29, 2014, 03:15:18 am
Dear BravoV and Linux-works (I don't know your names)... thought I'd let you know that I changed my mind about the 2465b with the "potted" A5 board and returned it to the seller for a refund. I found that it also had non-linearity issues and was clearly not a properly calibrated instrument.  I've now purchased another 2465b that has not (I hope) been "refurbished," so I can go ahead and make that a project for myself.  Thank you again for your good advice and your patience.

-- Gary
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on March 29, 2014, 03:54:55 am
that's good to hear, gary.

at least it was a learning experience for all involved ;)

/bryan
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: chksum3 on April 03, 2014, 06:56:42 pm
The saga continues... I've now returned and received a refund for the previously purchased 2465b with the "potted" A5 components, and I've now received another scope (at a much lower cost) that functions well, but does show damage to the A5 board from the well described leaking SMT capacitors.  I've included 2 close-up photos of the leakage/damage, which seems localized.  What do you folks think: is this easily repairable, or not?  I've not (yet) played with SMD devices, but I'm eager to learn and experiment. 

Also, I note that the NVSRAM chip was manufactured 3/1992. If I go ahead with repairs, I'll order another DS1225 from Digikey along with the other needed components for a refurbishment of the A5 and the low-voltage power supply, as also appears to be recommended.   Thanks in advance for any advice.

-- Gary
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: casinada on April 03, 2014, 09:45:06 pm
It is good that the scope works but that corrosion looks nasty. Try to neutralize the corrosion as soon as possible. Worst case scenario you'll have to rebuild traces with wire. As soon as you try to remove some of the components, things will disintegrate, look at my pictures a few posts back. :(  Good luck with the scope :)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on April 03, 2014, 10:27:47 pm
if it was my board, I'd use hot air and remove as many of the smd parts near the corrosion as I could.  then clean with alcohol and ohm out the traces to see if the solder pads are connected (to the right traces).

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: chksum3 on April 03, 2014, 11:59:02 pm
Thank you both.  I'll be ordering parts tomorrow, and will be practicing SMT techniques over the coming few days before diving in.  I'll photo document my progress also. 

Another question: Could changing out old power supply capacitors change scope characteristics such that a scope calibrated within the past few years could then fail to function because of retained NVSRAM calibration factors that were recorded at last calibration, when the older components were in place?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on April 04, 2014, 02:36:41 am
Another question: Could changing out old power supply capacitors change scope characteristics such that a scope calibrated within the past few years could then fail to function because of retained NVSRAM calibration factors that were recorded at last calibration, when the older components were in place?

Don't think just by replacing the old "decaying" cap in the psu will affect the scope's cal, especially if the new replacement improves the psu output quality as the specification compared to previous state.

Remember, the psu output (as long within specification), is not the reference point for the measurements mechanism in the scope.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on April 04, 2014, 02:49:03 am
Had an offline discussion with Kibi when he was repairing his Tek 2445 (Here (https://www.eevblog.com/forum/testgear/tektronix-2445-repair/)) that he had to lift the huge A1 board, the mounts & connections which is identical to 2465/B, and he shared few photos that I think will be useful if anyone plan to detach the A1 board, and I think this photo tips is valueable and never seen elsewhere even at the Yahoo Tek maillist.

Thanks and credit to Kibi for allowing me to share this photos here.  :-+

Quoting his tips & photos on detaching the A1 board :

1. Must unsolder the wires that go to the X and Y plates.

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=87803;image)


2. Now, I did not remove this PCB (HV) because it looked quite difficult to remove. The A1 PCB is easy to remove without taking this board out, but it's a bit more difficult to put the A1 back in because the pins don't line up nicely because of the A1 being at an angle when you put it back.

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=87805;image)


3. Don't forget where these coax cables go and their orientation, (take some pictures).

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=87807;image)


4. After removing the plastic front bezel, you must remove the strip of aluminium here to allow the front end BNC's to come out clear.

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=87809;image)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on April 04, 2014, 11:48:43 am


Thanks and credit to Kibi for allowing me to share this photos here.  :-+

Quoting his tips & photos on detaching the A1 board :

1. Must unsolder the wires that go to the X and Y plates.
[...]

Just a minor note - You don't have to unsolder these wires.  They lead to single pin connectors on the CRT neck.  You can pull them off the CRT through the slot in the shield (carefully!).
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on April 04, 2014, 01:35:23 pm
Just a minor note - You don't have to unsolder these wires.  They lead to single pin connectors on the CRT neck.  You can pull them off the CRT through the slot in the shield (carefully!).

Thanks for the tiny detail update, didn't know that.

So are you saying that 4 wires some how get joined together into single wire, and it is connected to this white board pointed by the red arrow at photo below ?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on April 04, 2014, 03:55:40 pm
The individual wires are not joined together.  Those "pins" sticking out of the shield are actually connectors.  You can pull on them, gently, to detach them.

I've attached a picture of what it looks like without the shield.  (It's a different type of wire, but I'm just trying to illustrate what I mean).  This is a 2465 CRT (#154-0850-01) and you can see the three pins from your picture.  There are 4 pins on the other side where it attaches to the A1 board.

The CRT pins are thin and delicate.  Avoid bending them as much as possible since you don't want to stress where it goes into the the metal-to-glass seal.

I've also attached a picture of the whole gun assembly.  I think it's an impressive piece of glass work.  Those little dots taped to the outside are magnets to tweak the beam position.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MeloMel on April 04, 2014, 05:59:16 pm
Awesome thread and comments! I have the 2445B and I suppose it's much the same internals and should be helpful since I'm planning on opening my case and cleaning it out a bit. It's not been used in years, and is displaying an error code "Test 05 fail 44" - Main Board Positive level too positive. I've posted a thread for it already

Mel
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on April 04, 2014, 06:16:31 pm
The individual wires are not joined together.  Those "pins" sticking out of the shield are actually connectors.  You can pull on them, gently, to detach them.

I've attached a picture of what it looks like without the shield.  (It's a different type of wire, but I'm just trying to illustrate what I mean).  This is a 2465 CRT (#154-0850-01) and you can see the three pins from your picture.  There are 4 pins on the other side where it attaches to the A1 board.

The CRT pins are thin and delicate.  Avoid bending them as much as possible since you don't want to stress where it goes into the the metal-to-glass seal.

I've also attached a picture of the whole gun assembly.  I think it's an impressive piece of glass work.  Those little dots taped to the outside are magnets to tweak the beam position.

Thanks, but after seeing the tube and those metal pins and also the fragile glass that is holding them, why suddenly I had the chill and goose bumps.  ???

Anyway, this will come into mind if I'm going to lift the A1 board as plan B.

To be honest, I prefer to de-solder those Horz & Vert wires, only 4 and not too difficult and much less risk than cracking those glass while pulling the wires, imo.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: casinada on April 04, 2014, 09:17:08 pm
Actually, if you need to take it apart is a good idea to disconnect and reconnect those pins as they tend to rust a little. So many problems can be fixed that way :)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on April 04, 2014, 10:05:02 pm
Actually, if you need to take it apart is a good idea to disconnect and reconnect those pins as they tend to rust a little. So many problems can be fixed that way :)
I'll second that.  When I got my 2465 the traces were intermittently jumping vertically.  I traced it to one of the deflection plate connectors.

It took a while to figure out.  The vertical plate pins on the A1 side pass *through* the CRT to the termination board on the other side.  I wasn't expecting that and I kept focusing on the vertical amp because I could see the output jumping.

I hate connectors.  It's always the connector.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on April 04, 2014, 10:11:39 pm
slightly OT: this is one reason (connectors suck) that I like wire-free builds as much as possible. 

on some pc's (mini-itx) you can have a full system with no cards (pci) and no wires at all.  the atx psu can be onboard, m-sata drives fit on m-sata connectors (the only connector you can't avoid other than RAM) and don't need power cables and everything else is soldered onboard.  for industrial use stuff, I try to remove as many wires and connectors as I can.

when I get old gear that has ic sockets, I also mistrust those, too.  cpu sockets seem ok but DIP sockets are often a failure point.  the old heathkit 'molex pins' sockets were the worst thing I've seen, for 'sockets'.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: chksum3 on April 05, 2014, 04:49:38 pm
re. 2565b A5 Board repair -->

I've now double checked the components on the A5 board here against the serial number of the scope (59877) and the service manual parts list to verify the board I have was not a swapped-out replaced board (different serial numbered boards used slightly different component values).  Everything checks out, i.e. this A5 is appropriate to the scope's serial number. 

I've also looked over the entire board under high magnification and have convinced myself that damage only extends from a leaking C2113 (10uF-35V electrolytic) to C2520 and C2222 (0.1uF-50V non-electrolytics). All other traces and components seem to have escaped damage. 

Before I can go ahead and order replacement components, I've got a very basic question for you all, as I am entirely new to SMDs and don't have a micrometer to do my own measurements.  From an earlier posting (here, or elsewhere - I don't remember) by H.Holden Oct. 2013, I plan to replace the four leak-prone cylindrical electrolytic units (C2011, C2331, C2113, C2965 - Panasonic FK SMD series devices) with tantalum SMDs instead.  I have no idea if there are preferable replacement types for C2520 and C2222 (the 0.1uF-50V) non-electrolytic capacitors.  Does anyone have the specifics re: sizes, manufacturers, etc. for these 6 components?  Thanks again...
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on April 06, 2014, 09:22:26 am
Gary, since you're going to clean it up 1st anyway, and you still don't know the extend of the damages at the traces and the cap's pads there.

Cause once all cleaned and damages are fully inventoried, there are chances they you may need to do some patch works to restore the cap's pads if they're heavily corroded, and "probably" it may need larger foot prints than the original ones, just a thought.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: chksum3 on April 06, 2014, 04:01:05 pm
Good point - I hadn't considered that! Thanks.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: chksum3 on April 10, 2014, 03:22:34 am
Progress report re: preparing to renovate my 2465B A5 board's SMT components: I just received a cheap, used Aoyue soldering tweezers station via eBay and tried it out on an old, discarded board populated with various SMDs.  It was surprisingly easy to desolder various components (all of which are significantly smaller than those populating the A5 board).  Resoldering, using a fine tip temperature controlled iron (also an inexpensive Aoyue unit), went just about as easily.  I've become a believer that SMD board repair is not a particularly difficult undertaking, provided the correct tools are at hand.  Many thanks to linux-works for his insight and suggestion to go with the tweezers.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on April 10, 2014, 03:27:42 am
I predict the tweezers are going to go up in price once people start to catch on to how useful those things can be.

I was watching a pace video that showed them removing large square smd chips with right-angle tweezer 'tips' and it was amazing to see how easy and fast it was!

one thing I am going to try, next time around, is this nozzle for hot air.  looks like just the thing for removing 2 lead devices:

(http://ecx.images-amazon.com/images/I/31dUmNR4mEL.jpg)

one nozzle is fixed and the other can move in or out, then you tighten the philips screw and do the hot air unsoldering.  I can't wait to try this attachment out ;)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: m1kta on April 10, 2014, 10:49:03 am
Seem to have lost the post to thread... ho hum apologies if this appears twice.

I have created photos and break down notes from my 2465CTS... slightly different model to what I have seen here and lot more packed inside.

http://m1kta-qrp.blogspot.co.uk/2014/04/oscilloscope-tektronix-2465cts.html (http://m1kta-qrp.blogspot.co.uk/2014/04/oscilloscope-tektronix-2465cts.html)

72

Dom
M1KTA
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: m1kta on April 10, 2014, 11:12:48 am
Images
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: KJDS on April 10, 2014, 02:00:23 pm
I picked up a 2465B today, which as it is in full working order isn't something I'm going to take apart, but have enjoyed seeing what's in there.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on April 10, 2014, 02:51:29 pm
I picked up a 2465B today, which as it is in full working order isn't something I'm going to take apart, but have enjoyed seeing what's in there.

If its still untouched from Tek factory, as least you need to do the A5 digital board to refresh the pesky Dallas bbsram that is holding the scope cal. , and definitely its already passed it's specified battery life.

Btw, just curious, you're well known here that have access or probably own many high end T&M gears and also selling them, which some beyond the reach of common hobbyists level, why still buy this "old clunker" ?  :o Sentimental value ? Anyway, welcome to the club.  >:D
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: KJDS on April 10, 2014, 03:49:47 pm
I picked up a 2465B today, which as it is in full working order isn't something I'm going to take apart, but have enjoyed seeing what's in there.

If its still untouched from Tek factory, as least you need to do the A5 digital board to refresh the pesky Dallas bbsram that is holding the scope cal. , and definitely its already passed it's specified battery life.

Btw, just curious, you're well known here that have access or probably own many high end T&M gears and also selling them, which some beyond the reach of common hobbyists level, why still buy this "old clunker" ?  :o Sentimental value ? Anyway, welcome to the club.  >:D

I bought it because it was the right price. I may need a fast scope soon, just bidding on some design work that may need a genuinely fast scope and the next fastest analogue scope I have is a 150MHz 2445. I do prefer analog scopes for looking at analog signals.

Thanks for the warning on the Dallas RAM.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: grumpydoc on April 10, 2014, 04:27:22 pm
The SMD caps on the A5 board in the 2465B are also notorious - probably should be replaced even if they look OK (see earlier in this thread).
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: m1kta on April 10, 2014, 04:30:47 pm
If its still untouched from Tek factory, as least you need to do the A5 digital board to refresh the pesky Dallas bbsram that is holding the scope cal. , and definitely its already passed it's specified battery life.
Does this effect ALL 2465 models?

Is this process documented/detailed anywhere?

Dom
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on April 10, 2014, 04:38:22 pm
not the base model or the A version, just the B version.

lots here on the 2465 series; you'll spend a bit of time searching thru it all, but its all explained here and on the yahoo tek-scopes group.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on April 10, 2014, 04:44:27 pm
The SMD caps on the A5 in the 2465B board are also notorious - probably should be replaced even if they look OK (see earlier in this thread).
+1, the well known problems for this Tektronix series which are the SRAM battery that is running out of juice, and the SMD electrolytic caps at the A5 board that leak like hell, this thread has a good example -> HERE (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg406487/#msg406487), or HERE (The damaged vs the good one) (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg406409/#msg406409) :o


Does this effect ALL 2465 models?

Is this process documented/detailed anywhere?

Dom
Dom, not sure about your 2465CTS, maybe you can share the photo of your A5 digital board about the caps and maybe its using the same Dallas DS1225Y too, not very sure my self.

On the Dallas, its a "Battery" Backed Static Ram (BBSRAM), and just read the datasheet yourself, it's specification on the battery life is maxed out only for 10 years. And if your 2465CTS also using it, its very likely already aged more than 10 years.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: casinada on April 10, 2014, 08:59:58 pm
On the B series probably above serial number 50000
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: guido on April 10, 2014, 10:39:02 pm
Does this effect ALL 2465 models?

A plain 2465 (no A or B) does not have SMD caps and no Dallas chip. Instead regular elco's and a very early kind of EEPROM (called EAROM).

I'm working on one. I've done a nearly full recap (elco's and X and Y caps), replaced two broken zeners and swapped the switches pannel. I'm now looking at a focus problem (found a broken pot, but there is more damage) and i need to get a new preamp module for one of the channels.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: m1kta on April 11, 2014, 10:31:40 am
The SMD caps on the A5 in the 2465B board are also notorious - probably should be replaced even if they look OK (see earlier in this thread).
+1, the well known problems for this Tektronix series which are the SRAM battery that is running out of juice, and the SMD electrolytic caps at the A5 board that leak like hell, this thread has a good example -> HERE (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg406487/#msg406487), or HERE (The damaged vs the good one) (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg406409/#msg406409) :o


Does this effect ALL 2465 models?

Is this process documented/detailed anywhere?

Dom
Dom, not sure about your 2465CTS, maybe you can share the photo of your A5 digital board about the caps and maybe its using the same Dallas DS1225Y too, not very sure my self.

On the Dallas, its a "Battery" Backed Static Ram (BBSRAM), and just read the datasheet yourself, it's specification on the battery life is maxed out only for 10 years. And if your 2465CTS also using it, its very likely already aged more than 10 years.

I'll drop a photo of the board here after lunch (about 3 hours from now).

The A5 logic and control board is the one the outside right of the scope looking from the front right?

Dom
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on April 11, 2014, 04:56:17 pm
I'll drop a photo of the board here after lunch (about 3 hours from now).

The A5 logic and control board is the one the outside right of the scope looking from the front right?

Dom
Yep, the long rectangle shaped board at the right side of the scope (front view), and if you see it closely, the board has almost all logic chips populated in it.

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=89134;image)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: casinada on April 11, 2014, 09:20:38 pm
It has SMD components => s/n > 50000
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on April 12, 2014, 02:55:30 am
I bought it because it was the right price. I may need a fast scope soon, just bidding on some design work that may need a genuinely fast scope and the next fastest analogue scope I have is a 150MHz 2445. I do prefer analog scopes for looking at analog signals.

Hey KJDS, I just visited your ebay shop and I can see you're also selling a 500 Mhz DSO.   :o

Understand its an old DSO, its just I'm very curious why your prefer using a 400 Mhz old analog scope than the one you already have in hand ?

Please, if its not too troublesome for you, share on the real world examples or any reasons even its subjective that at your design work, this old clunker is better than that DSO, maybe create another new thread for that ?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: m1kta on April 12, 2014, 07:10:18 am
I'll drop a photo of the board here after lunch (about 3 hours from now).

The A5 logic and control board is the one the outside right of the scope looking from the front right?

Dom
Yep, the long rectangle shaped board at the right side of the scope (front view), and if you see it closely, the board has almost all logic chips populated in it.

Sorry didn't mange it at lunch... mine does not look like that. All through hole, no SMD

All the boards look like have zero corrosion on them and almost pristine condition (bit of dust).

So looks like might not have anything more too do. Those caps 0.068uF.... I have 0.1uF close enough or do I need to stick wit the value?

Dom
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: KJDS on April 12, 2014, 07:24:33 am
I bought it because it was the right price. I may need a fast scope soon, just bidding on some design work that may need a genuinely fast scope and the next fastest analogue scope I have is a 150MHz 2445. I do prefer analog scopes for looking at analog signals.

Hey KJDS, I just visited your ebay shop and I can see you're also selling a 500 Mhz DSO.   :o

Understand its an old DSO, its just I'm very curious why your prefer using a 400 Mhz old analog scope than the one you already have in hand ?

Please, if its not too troublesome for you, share on the real world examples or any reasons even its subjective that at your design work, this old clunker is better than that DSO, maybe create another new thread for that ?

I just prefer living in an analog world. There's no more logical reason to it than my choice of cars.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SL4P on April 12, 2014, 07:35:04 am
Gotta say - even though it's a long time ago - these photos remind me why the 2465 series are still my favourite old school scope.  No question. Before I used a 2465, it was easy to lug around a 465B - and it was lighter!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: chksum3 on April 12, 2014, 11:58:11 pm
Progress report on repairing my 2465B with A5 board leak-damage from 2 of the 4 notorious electrolyic caps.  The 4 offending caps were removed with both a fine-tipped solder station and using a soldering tweezers.  Also, 3 of the small 0.1uf caps in the vicinity of the leaking electrolytics were also removed.  The electrolytics were replaced with tantalum types and the 0.1s with ceramics. 

I've attached two photos: 1) the pads and traces, one of which had decayed completely; a couple others were corroded but enough remained for resoldering.  After thorough cleaning, the damaged pad and trace were repaired with a small piece of adhesive backed copper foil I found at a local shop, and the new parts replaced.  The board was reinstalled and the second photo was taken. 

Oh, also the old Dallas NVSRAM was desoldered and read into a file, that file was then written to the new Dallas.  I decided to use a low-seat type gold plated machine pinned socket which offers a tight and secure fit without damaging the pins of the new Dallas. (I experimented first with the removed chip by installing it into the not yet soldered socket to see if pins bent, or if the pins stuck in the socket.  I was able to seat and to remove it without damaging anything, so I decided the wiper type socket wasn't needed.)  The socket was then soldered to the board and the newly written NVSRAM was socketed - again, without difficulty.

All in all - no surprises - all went well.  Very happily, the scope started, went through its routines normally and appears to be completely functional.  I am one happy guy, and very thankful to all of you for sharing your experiences and making it relatively easy for those of us down here on the learning curve.

Parts list for the repair:

DS1225Y-200+-ND 64Kbit 28EDIP chip (DigiKey part#: DS1225Y-200+-ND)
low-seated gold plated 28 machine-pin socket
C2011, C2965: 33uF 10v tantalum, size 2312, Vishay (DigiKey part#: 718-1075-1-ND)
C2113, C2331: 10uF 35v tantalum, size 2312, Vishay (DigiKey part#: 718-1052-1-ND)
C222, C2520, C2890: 0.1Uf 50v ceramic, size 1260, Kemet (DigiKey part#: 399-1250-1-ND)

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: GreyWoolfe on April 13, 2014, 12:13:19 pm
Congratulations on the repair job.  Enjoy the scope!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: m1kta on April 13, 2014, 05:01:23 pm
I have created photos and break down notes from my 2465CTS... slightly different model to what I have seen here and lot more packed inside.
http://m1kta-qrp.blogspot.co.uk/2014/04/oscilloscope-tektronix-2465cts.html (http://m1kta-qrp.blogspot.co.uk/2014/04/oscilloscope-tektronix-2465cts.html)

Tnx all for help... fixed and working again.

http://m1kta-qrp.blogspot.co.uk/2014/04/tekronix-2465cts-scope-fixed.html (http://m1kta-qrp.blogspot.co.uk/2014/04/tekronix-2465cts-scope-fixed.html)

72
Dom
M1KTA
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on April 13, 2014, 05:13:26 pm
@Gary, congratulations !  :clap: Looks really neat after the re-cap  :-+, I can see the traces are not too corroded. Great, at least you don't need to worry about loosing the calibration and since yours also made in 90s, hopefully it will last many years to come.

Btw, if I'm not mistaken these made in 90s or with serial no. > 50000 don't use the crap high voltage cap anymore like Dom's, but just suggesting to check it out.

The left section is the high voltage mains area, there are two red boxed caps pointed by the blue arrows. This type should not be a problem.

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=89407;image)


While bad example are like at older version which uses these well known transparent caps that will burst once aged.  :-\

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=89405;image)

Dom, permission to "steal" your photo if you don't mind.  :P



@Dom, congratulation too, glad to see it works now, great job you've done there.  :-+

Btw, your A5 board doesn't use the bbsram and not infected by those leaky smd electrolytic caps.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: chksum3 on April 13, 2014, 05:47:07 pm
Many thanks!  After a little breather, I'll open the cabinet again and begin work on the LV and HV sections. Although all is well, I gather it is best to be proactive and swap out all those older electrolytics before disaster strikes.  I'll be sure to look for those highly problematic caps in the HV area first - just in case they were still being used.  Best to all.   
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: m1kta on April 14, 2014, 05:51:09 am
Btw, if I'm not mistaken these made in 90s or with serial no. > 50000 don't use the crap high voltage cap anymore like Dom's, but just suggesting to check it out.

The left section is the high voltage mains area, in there there are two red boxed caps pointed by the blue arrows. This type should not be a problem.

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=89407;image)


While bad example are like at older version which uses these well known transparent caps that will burst once aged.  :-\

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=89405;image)

Dom, permission to "steal" your photo if you don't mind.  :P

No problem.

I replaced with same cap type but if fails again I'll know where to look.

72

Dom
M1KTA
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: m1kta on April 14, 2014, 09:43:36 am
.... if I'm not mistaken these made in 90s or with serial no. > 50000 don't use the crap high voltage cap anymore like Dom's, but just suggesting to check it out.
BTW everyone do not assume just because the serial number (front panel to the right under the 2nd channel input) is >50000 these capacitors are not used.... my serial is B050949, visually check them, mine had a HV black cover over the area so you have to take that off first.

Anyone got the CTS manual anywhere? I can use it as a regular scope (2+2 channel) but not worked out the CTS bit yet.... or found a PC to scope interface I can clone.

Dom
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on April 14, 2014, 04:57:37 pm
Anyone got the CTS manual anywhere? I can use it as a regular scope (2+2 channel) but not worked out the CTS bit yet.... or found a PC to scope interface I can clone.

Dom
Look around the net for the regular 2465 option 09 (counter timer/word recognizer) and option 10 (GPIB) manuals.  The CTS was just a specially priced bundle of those options plus some additional probes.  After a quick look I'm not seeing a free PDF of them, but you can search some more.

I have a 2465 with these options, but not bought as a CTS.  Before you go through the trouble of getting GPIB connectivity, be aware that the GPIB functionality is very limited (read the option 10 manual).  You can set and query things as you would from the front panel, but you can't do automatic measurements (e.g., Volts pk-pk) since the 2465 can't do them natively.  The only exception to this is that you have full control over the counter/timer unit so you can do those measurements remotely.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: m1kta on April 14, 2014, 05:07:35 pm
Tnx 72 Dom M1KTA
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: fpliuzzi on April 14, 2014, 06:07:24 pm
Here's the link to the "24X5A/2467 Options Service Manual". It contains service info for the following options.

01 (DMM)
05 (TV)
06 and 09 (CTT & WR)
10 (GPIB)

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCkQFjAA&url=http%3A%2F%2Fbitsavers.trailing-edge.com%2Fpdf%2Ftektronix%2Fscope%2F070-5857-00_24x5aOptions_Jun87.pdf&ei=nCFMU6DCI_bLsQSz64CwCQ&usg=AFQjCNE4Y_ZMzOg8JrgMinwOLnylrfTsIA&sig2=tzZ3mtsmt4uOkHgozdW3UQ&bvm=bv.64542518,d.cWc (http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCkQFjAA&url=http%3A%2F%2Fbitsavers.trailing-edge.com%2Fpdf%2Ftektronix%2Fscope%2F070-5857-00_24x5aOptions_Jun87.pdf&ei=nCFMU6DCI_bLsQSz64CwCQ&usg=AFQjCNE4Y_ZMzOg8JrgMinwOLnylrfTsIA&sig2=tzZ3mtsmt4uOkHgozdW3UQ&bvm=bv.64542518,d.cWc)

I also wanted this pdf file because my newly acquired TEK 2445 contains option 05. I received some replacement electrolytics and Y2 safety capacitors from Digi-Key this morning so I should have the 2445 on my bench soon. I just need to find two small replacement knobs for the intensity and focus controls.

Regards
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on April 14, 2014, 07:36:07 pm
Here's the link to the "24X5A/2467 Options Service Manual". It contains service info for the following options.
[...]
These are for the "A" version.  From the old catalog info I have, the CTS version is based on the plain 2465 (no A or B).

The "A" manuals may or may not be suitable; I don't know the internal subtleties of all the different models.

I have a printed copy of the "2445/2465 Option 06 and Option 09 Counter/Timer/Trigger and Word Recognizer Service Manual", pub #070-4632-00, so I can say the service manual is not the same.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: fpliuzzi on April 14, 2014, 08:11:56 pm
Thanks for the clarification.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: guido on April 14, 2014, 11:16:24 pm
I just need to find two small replacement knobs for the intensity and focus controls.

If you find a source, please let me know. I need four times 366-2041-0x.

I'm currently fighting the edge focus circuit. Found a 10nF cap that measured 25 ohms. Low enough to kill the pot when turned to 42V. Put in a new pot and swapped the cap. Now the opamp is not behaving.... Work in progress  :D
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mwilson on April 15, 2014, 08:13:06 pm
Thanks for everyone's great info about replacing the leaking caps and battery-backed RAM in the Tek scopes. I just picked up a nice 2467B and it works great but does have a small amount of black sludge around the capacitors on the A5 board. I'm going to embark on the project to replace those caps and put a fresh BBSRAM on the board, but I'm curious what the best way to clean the sludge off the board is. Should I try to clean before desoldering the caps so I don't "cook" the stuff onto the board, should I just get the caps out of the way then clean, etc. Is Isopropyl alcohol the right cleaning agent to use?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: chksum3 on April 15, 2014, 10:12:07 pm
Please wait for others to comment on this, as my experience is very limited.  I had success with first removing the offending components, then repeatedly cleaning with 99% isopropyl alcohol and Q-tips.  I next removed every trace of old solder I could on the pads with gentle use of solder wick, and then again alcohol re-cleaned everything in sight until, under magnification, all gunk was gone and no residue was seen on the just used Q-tip.

Regarding the purchase of the NVSRAM: as recommended by other people out here, consider ordering from DigiKey. I first ordered (twice) from a local company (Jameco) and found that my programmer could not successfully write to either of the devices.  The word is, other people have had similar experiences.

If it's not too difficult, please consider uploading a close-up photo of the board damage for all to see.
 
Have fun, and congratulations on your new 2467B!
 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: guido on April 15, 2014, 10:46:45 pm

A quick question for all the 2465 users here. One of the things i notice is that the brightness of the traces goes up if i switch on more channels. Doesn't matter which ones. So channel 1 on and then switch on 2; both become brighter. Switch on 3 and all three even more brighter. Ditto for the last one.

I'm wondering if this is a bug or a feature. It's normally the other way around with other scopes; switch more channels on and brightness goes down. Which is logical. So i'm wondering if this is over(?) compensation i'm seeing.

Thanks.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on April 16, 2014, 02:19:37 am
Thanks for everyone's great info about replacing the leaking caps and battery-backed RAM in the Tek scopes. I just picked up a nice 2467B and it works great but does have a small amount of black sludge around the capacitors on the A5 board. I'm going to embark on the project to replace those caps and put a fresh BBSRAM on the board, but I'm curious what the best way to clean the sludge off the board is. Should I try to clean before desoldering the caps so I don't "cook" the stuff onto the board, should I just get the caps out of the way then clean, etc. Is Isopropyl alcohol the right cleaning agent to use?

Congrats on the score, that beast you have there is probably the fastest portable analog scope ever made on earth.  :clap:

Yeah, de-solder 1st then clean, other wise worry the cap will still oozing out the nasty liquid while you clean it on board.  |O

Please, share some close up photos like before and after re-work, especially the affected area as it will be a good reference for others in the future.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mwilson on April 18, 2014, 12:47:56 am
.... if I'm not mistaken these made in 90s or with serial no. > 50000 don't use the crap high voltage cap anymore like Dom's, but just suggesting to check it out.
BTW everyone do not assume just because the serial number (front panel to the right under the 2nd channel input) is >50000 these capacitors are not used....

Confirmed. My scope is from late 1991, serial number B051767, and it has those transparent caps, not the red ones. Looks like getting that board out to replace the high voltage caps is more of an ordeal than getting the A5 board out for the other repairs. The transparent caps haven't burst yet but I should probably take care of those now before it does eventually happen. I'll grab pics for everyone as I go....
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on April 18, 2014, 04:11:21 am
I've read it somewhere that film cap with transparent case especially the old one, is plagued by that outer transparent plastic material it self, that it will dry out and crack once its aged enough.

The humidity from the air slowly sip into the structure through the micro cracks at thermal cycling, and water will slowly trapped/accumulated in the cap, and will create short circuit between the electrodes once its accumulated enough in there. Hence its common to see them burned/burst into flame and leaving charred mark everywhere.  |O

While the one like the opaque red case doesn't have this problem since it uses much better plastic material.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: iloveelectronics on May 01, 2014, 01:54:59 pm
I just joined the Tek 2465B club and got this unit from China last week. It seems to be functioning alright but BravoV told me to take a few inside pictures as mine looks like a Japanese made unit with a Sony/Tektronix badge on the back and a serial number that starts with "J3". I took it apart quickly and snapped a few pictures with my phone today, just before I had to leave the shop. I see some worrying images :(

Yes, I turned it on, before taking it apart:
(http://i.imgur.com/AvRuhKn.jpg)

There's a small blip near the second horizontal division with no signal (only on a couple of timebases):
(http://i.imgur.com/wU0J1QB.jpg)

Back side of the scope. You can see "Sony/Tektronix Corp. TOKYO, JAPAN":
(http://i.imgur.com/hZHGqN4.jpg)

Main board on the bottom. Apart from being a bit dusty, all seems to look good:
(http://i.imgur.com/H9iNZb6.jpg)

On the side:
(http://i.imgur.com/TWbuEJ3.jpg)

On the top, the CRT. Now this really doesn't look right :( That thing looks like a big piece of charcoal! Can anybody tell me what that thing is and what could have been going on here?
(http://i.imgur.com/tRUzyFc.jpg)

The power supply board. I haven't read this thread prior to taking this picture so I didn't know I needed to pay attention to the HV caps near the left side. From what I can see I've got those infamous transparent ones. Will have to take a closer look the next time.
(http://i.imgur.com/wxMYB1E.jpg)

Right side of the A5 board:
(http://i.imgur.com/ILaSGTA.jpg)

Left side of the A5 board. Again, I didn't read this thread so didn't know about the leaky caps area. I only reviewed the photo after I've taken it and I was shocked to see the corrosion and the completely missing electrolytic caps!!
(http://i.imgur.com/xPl6ZRx.jpg)

Here's an enlarged view:
(http://i.imgur.com/eUQS6DN.jpg)

I didn't expect to see what I saw as the unit was working while I tested it. What are those missing caps used for? And that charred part near the CRT?

Any help would be highly highly appreciated in restoring this unit. Thanks!


Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on May 01, 2014, 02:11:28 pm
missing caps!  wow ;(

amazing it even works.  I guess those caps are not mandatory but they are surely not OPTIONAL, either ;)

one thing that you lucked out on, and I'm jealous of: you have probe power sockets!!  I paid nearly $100 for a 1101 power supply just to give me probe power LEMO sockets.   with those, (5,15,-15v) you can power fet probes and stuff like that.  pretty cool and I have not seen one (photos) with probe power jacks before.  to me, that's worth $50 to $100 more just for that.

I used these parts, from mouser, for the caps:

647-PCF1C330MCL1GS
647-PCX1V100MCL1GS

organic polymer caps, not 'lytics, so they should last forever (in theory).

check me on those part numbers, but I think those are correct.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: grumpydoc on May 01, 2014, 02:29:34 pm
Quote
That thing looks like a big piece of charcoal! Can anybody tell me what that thing is and what could have been going on here?
It's the coupling for the final anode connector - so that you don't have to disconnect the cup if changing a CRT.

They often get covered in carbon soot which gets electro-statically attracted to the high tension, that's the sootiest I've seen though.

Probably worth cleaning all that soot off with some IPA (take care, the anode potential is 14kV so not one to do with the 'scope powered up and if you pull it apart bear in mind that a CRT anode connector can bite even with the power off).
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SeanB on May 01, 2014, 03:11:16 pm
A quick clean up of that anode connector, a generous application of polishing on the plastic and a spritz of anti corona spray and that will do for a long time. The caps will need cleaning of the board, looking for the dead bugs inside the case and soldering of new ones onto the board. As well you might want to read out the RTC chip and get a replacement one for when that one dies.

When I was working for the SAAF I got a 2223, and after about 6 months the digital board died. Unplugged the power connector and used it as a plain analogue scope for another 3 months till it's cal cycle time was due, and then plugged the board back in and sent it off. Came back with a new digital board.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: KD0CAC John on May 01, 2014, 03:39:41 pm
Will have to use this thread to look for the next broken piece of gear for my bench ;)
Being that disability is my regular source of income , I look for dead gear for my bench & ham radio shack .
And the next benefit to broken gear , is having to learn how to fix .
I've been in many trades and at least half of those , or more , were hobbies and then wanting to build / repair my own toys .
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: iloveelectronics on May 02, 2014, 02:31:06 am
A few more pictures...

The fan (after some cleaning up). Curiously, like BravoV's unit, the date code (if that's what it is) indicates a 2004 date while everything else inside has 89/90 dates.
(http://i.imgur.com/C0iTqGw.jpg)

The probe power sockets (option 22):
(http://i.imgur.com/oibheAu.jpg)

Another look on the power supply board, with the black plastic shield on the left removed:
(http://i.imgur.com/aph7Bdr.jpg)

Some solder joints look like they have some corrosion going on but they are actually fine. It's just some sort of reflection in the photo. Unfortunately this unit has the HV caps with the transparent housing. This one in the picture still looks OK:
(http://i.imgur.com/fhi2n0K.jpg)

Not the other one though. It's already cracked open:
(http://i.imgur.com/QfCENDc.jpg)
(http://i.imgur.com/FVWHuPg.jpg)

And here's a close-up view of the leaky/missing caps area after initial cleanup:
(http://i.imgur.com/oDpKuCd.jpg)

I've tested continuity and the one with only half a pad left seems to have lost connection to the trace. Shouldn't be difficult to fix given the proximity. The other pads are fine--ish.

I was trying to see if I could get the power supply board out but have had no luck. Can someone tell me how I should go about doing that? Does it come out together with the other board attached to it?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on May 02, 2014, 02:42:12 am
the power supply board pair comes out as a pair.  loosen the rear screws since its physically tight and very hard to remove the way tek designed it.  I struggled a lot to get my board pair out.  its not meant to be taken out, so you -have- to loosen a few chassis screws to -create- clearance to remove the boards.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: iloveelectronics on May 02, 2014, 03:23:09 am
the power supply board pair comes out as a pair.  loosen the rear screws since its physically tight and very hard to remove the way tek designed it.  I struggled a lot to get my board pair out.  its not meant to be taken out, so you -have- to loosen a few chassis screws to -create- clearance to remove the boards.

Thanks a lot! Loosening up the rear panel helped. I've now taken the PS board out. Yet more pictures...

Better look on the crack opened HV cap:
(http://i.imgur.com/4t8tQWp.jpg)

I didn't see where this dangling connector go while I pulled out the board  |O It's coming from the TV option board. Does it connect to J305 in the second photo (the other PS board in the pair)?
(http://i.imgur.com/5PhXRZe.jpg)
(http://i.imgur.com/OPSnbpB.jpg)

Does anyone have the part numbers for those 2 HV caps handy, before I dig into the service manual? Thanks a lot for all the help given in this thread so far!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mwilson on May 02, 2014, 04:41:25 am
Does anyone have the part numbers for those 2 HV caps handy, before I dig into the service manual? Thanks a lot for all the help given in this thread so far!

Yep, I'm actually putting together a DigiKey order for repairing my 2467B right now. They carry those exact same caps, Kemet part number PME271M568MR30 (CAP FILM 0.068UF 275VAC RADIAL). I'm debating whether to replace with new ones of the same type that have proven to be dodgy or going for something different that should be compatible like Panasonic ECQ-U2A683ML.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on May 02, 2014, 09:47:23 am
Franky, thanks for sharing the photo shots, glad the corrosion caused by the leaked caps didn't do heavy damages there, and look like all traces still intact except for that half pad, btw great cleaning job you've done there.  :-+

Btw, this confirmed that these particular hv transparent film cap is cursed, in this thread alone already two proven cases, hope this will help others in the future as reference and replace them before bad thing happened.

I guess you have many home works to do for this beast, btw just remember, when powering the whole scope without the enclosure, make sure you have a big fan blowing the "whole" giant A1 board with the scope up side down position, so those unobtainium hybrid ICs get cooled properly.

Looking at your fan's date code, year 2004 ?  ??? Wow, if its the original fan came with the scope from the Japan factory, then your 2465B is definitely quite fresh imo.

Regarding your missing caps at A5 board, suggesting after you desoldered the old Dallas chip, install a good dip or sip socket for the new Dallas DS1225 chip, so it will be easy to backup & restore the calibration in the future.

Btw, spotted another missing cap at your A5 board at the right upper corner, besides the screw pointed by the red arrow. Also there are other A5 examples at this post -> Here (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg406401/#msg406401) for comparison.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: iloveelectronics on May 06, 2014, 09:48:41 am
Got a little bit of time today so decided to desolder the two 250V film caps on the power supply board. The one that still looks normal measures about 83nF, which is still within tolerance I guess. But the broken one measures only 170pF! I'm really surprised this scope was working despite the missing caps on the A5 board and this broken film cap!

BTW, thanks BrovoV, for spotting the other missing cap on the A5 board! I've ordered them now from Mouser (using the part numbers given by linux-works), and hopefully will receive them in a few days. The Dallas NVRAM is on backorder though so it looks like I will have to wait a couple of months :( Will certainly backup the data when I work on the A5 board though.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on May 06, 2014, 05:49:50 pm
Even at the normal one if you look closely at the clear plastic case, it is already has so many fine cracks at it's surface.

Btw, about the Dallas chip, actually you can start desoldering it now while you're working at A5 board, buy & solder a good quality DIP or twin SIP sockets at the pcb, and the most important is to back it up 1st using your TL866, and put it back while waiting for the new chip to arrive.

Remember, the lithium battery that is holding the scope's calibration in your Dallas BBSRAM chip is > 20 years old now (date code 90xx), imo its wise not to trust your luck on it for too long.  >:D
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: guido on May 07, 2014, 11:31:03 pm
(http://members.home.nl/baltusg/2465_3.jpg)

One more up and running :D

Fixed two zener diodes (reference supply protection and attenuator supply).
Replaced a broken 10nF cap in the HV section (and swapped a similar one), which 'shortened' one of the trimmer pots to gnd (40V to ground = broken trimmer).
Replaced the whole pots/switches pannel (cheaper than getting separate time/div and volt/div switches, which were bent).
Replaced a broken attenuator (did swap channels for test and verified that the relays were ok).
Replaced all elco's and X / Y Rifas in the PS section.

Got it quite cheap, so all in all a good outcome.

PS, no Dallas chip in these early models but an EEPROM (called EAROM). I've noted all the values, so in the future i might be able to replace it with a modern solution if it would fail.

I've read the temperature stories about the U800 chip. But i was also told it is not related to temperature, but because of outsourcing the manufacturing from tek to a third party. The original tek chips don't break. If that is true, i'm safe as it is a very early 2465 (Guernsey). It is also full of factory installed bodges (as in reworks).


A quick question for all the 2465 users here. One of the things i notice is that the brightness of the traces goes up if i switch on more channels. ........

I'm wondering if this is a bug or a feature. .............

Well, RTFM. A feature. It is just that mine is adjusting too much. Specially going from one to two channels. Minor thing.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on May 08, 2014, 03:08:35 am
I've read the temperature stories about the U800 chip. But i was also told it is not related to temperature, but because of outsourcing the manufacturing from tek to a third party. The original tek chips don't break. If that is true, i'm safe as it is a very early 2465 (Guernsey). It is also full of factory installed bodges (as in reworks).

Well, my U800 chip was almost too hot to touch by fingers at the black ic body even there was a big fan blowing strong wind on it.

Yes, it was outsourced to Maxim IC after Tek decided not to produce it anymore, as far as I know, there are two versions of this U800 chip (TEK part no 155 0241 02) , photo of both attached below.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: w2aew on May 08, 2014, 02:57:34 pm
I've read the temperature stories about the U800 chip. But i was also told it is not related to temperature, but because of outsourcing the manufacturing from tek to a third party. The original tek chips don't break. If that is true, i'm safe as it is a very early 2465 (Guernsey). It is also full of factory installed bodges (as in reworks).

Well, my U800 chip was almost too hot to touch by fingers at the black ic body even there was a big fan blowing strong wind on it.

Yes, it was outsourced to Maxim IC after Tek decided not to produce it anymore, as far as I know, there are two versions of this U800 chip (TEK part no 155 0241 02) , photo of both attached below.

Well, not really outsource.  Tektronix had its own internal IC fab - called the Integrated Circuits Operation (ICO).  Tek sold ICO to Maxim in 1994.  It is still co-located on the Tektronix campus in Beaverton.  So, the name changed, but the fab remained the same. 

At the same time, Tektronix sold half-interest in their hybrids design and manufacturing group to Maxim, which formed the group known as MaxTek.  Several years ago, Tektronix bought out Maxim's interest in MaxTek, returning this group to be wholly owned by Tektronix.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: e-pirate on May 08, 2014, 04:44:54 pm
Hi folks!
A couple weeks ago I was lucky to get myself Tektronix 2467B. It's a end of 91 unit, produced in Japan by Tektronix-Sony (and seems to arrive somewhere from Japan because I found some papers with handwritten Japanese hieroglyphs inside pouch at the top of it). It's in a perfect visual condition and actually looks like a new device. TEST5 shows something under 2000 work-hours and about 900 power-on cycles, I'm not sure if I can trust this. But when I got into unit I was not able to find even a single tiny mark of dust on any of PCBs or parts, the only place that had just minor signs of dust is _original_ NIDEC fan, that is actually all most silent. Nothing soldered/repaired there. But dude, that sold it to me replaced A5 electrolytic caps and told me that the PCB is fine, and yes, it's virgin looking board without any signs of leakage. Besides, unit have active probe PSU option installed. I've had some time playing with this scope and seems that it work fine, all controls work as expected, all channels seem to be working fine to. So, meet another member in a 24xx club :)
But after reading this thread from the first page I came to conclusion that I still have some things to take care about.
Seems that I should start with A5 board (it is all SMD sure) and replace this pesky Dallas SRAM IC and then caps. Should I replace both electrolytic caps (I wish to replace them with solid state polymeric SMD caps) and this black one I don't know what type are they, seems that I've seen photos of them leaking to.
After I'm done with A5 board, I will go and check for HV and LV board and then recap A1 board.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on May 09, 2014, 01:14:13 am
Well, not really outsource.  Tektronix had its own internal IC fab - called the Integrated Circuits Operation (ICO).  Tek sold ICO to Maxim in 1994.  It is still co-located on the Tektronix campus in Beaverton.  So, the name changed, but the fab remained the same. 

At the same time, Tektronix sold half-interest in their hybrids design and manufacturing group to Maxim, which formed the group known as MaxTek.  Several years ago, Tektronix bought out Maxim's interest in MaxTek, returning this group to be wholly owned by Tektronix.
Straight from the horse's mouth, thanks Alan for clarifying this.  :-+

About the popular myth surrounding the Tek's hybrid ICs, is it true the chip design is gone caused by fire at MaxTek in the past ?

Alan, really wish if someday Tek will release the design of these hybrid IC's design, maybe begging contacting the PR dept about this possibilities ? Its like the good gesture in the past where Tek released all old scope's documentations to public legally.  :-+

There was an attempt to design the U800 ic replacement with discrete components like this -> Tektronix 2465/2467 series U800 IC replacement design (http://www.davmar.org/TE/Tek2465/lafay.html) created by Thomas Lafay, but if Tek released the hybrid IC schematic design, that will be like breathing a new life for these great 246x analog scope series.  :clap:

Please consider it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on May 09, 2014, 01:16:38 am
Seems that I should start with A5 board (it is all SMD sure) and replace this pesky Dallas SRAM IC and then caps. Should I replace both electrolytic caps (I wish to replace them with solid state polymeric SMD caps) and this black one I don't know what type are they, seems that I've seen photos of them leaking to.
After I'm done with A5 board, I will go and check for HV and LV board and then recap A1 board.

The black rectangle box cap are tantalum, the ones that are affected are using common rounded smd electrolytic cap. Maybe a photo of your A5 will clarify that better.

Btw, congratulation on the score, really a great condition you got there.  :-+
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: e-pirate on May 09, 2014, 08:31:22 am
The black rectangle box cap are tantalum, the ones that are affected are using common rounded smd electrolytic cap. Maybe a photo of your A5 will clarify that better.
Well, unfortunately, I'm half a thousand kilometers away from my scope and I have no idea when I will return back. That what I'm doing now is preparing my road map for the feature, so I can do thins faster on the scope.
I always thought that tantalum caps are always enclosed in yellow plastic and black ones are just regular electrolytic of different type, but I wasn't right in that case. BTW, what does symbol "2" in a circle on the original black rectangle cap means? Kind of package size or value tolerance?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: e-pirate on May 09, 2014, 05:56:03 pm
Actually, after googling a little bit and searching through SM a found that this a just regular general purposes tantalum 15 uF 25V 20% caps. And symbol "2" in circle is just a Vishay Sprague logo, nothing exciting here :(
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: guido on May 09, 2014, 10:11:55 pm

Had a go at U800; better safe than sorry.

I've had a look in my spare parts and found a heatsink that screws right onto one of the screws from U800. Used the one connected to the metal of it obviously. It is not as big as the examples in this thread, but i guess it is better than nothing.

It is from a 7A13 plugin; a beefy TO18 heatsink which has a screw mounting hole on the top. Fits like a glove. There is a bit less space than normal, as there are bodges around U800 which are not present in a more modern 2465  :P

Sorry, no picture. The battery of the camera is dead.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on May 10, 2014, 01:10:00 pm
Actually, after googling a little bit and searching through SM a found that this a just regular general purposes tantalum 15 uF 25V 20% caps. And symbol "2" in circle is just a Vishay Sprague logo, nothing exciting here :(
Yep, but they don't leak overtime and I think they should be pretty reliable.

Btw, for newly acquired 246x scope, suggesting to check these system voltage rails first at the J119 header when opening it for the 1st time.

Remember, get a big fan blowing the whole A1 board while its turned on without the enclosure to cool down those unobtainium hybrid ICs.

Of course ideally these rails should be measured with another scope instead of just ordinary DMM to see if the ripples are up to the specification.

The J119 header location and the voltages specification & tolerances required by the scope to work properly, quoted from Tektronix 2465B service manual.

(https://www.eevblog.com/forum/testgear/2467-no-power/?action=dlattach;attach=58502;image)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: e-pirate on May 10, 2014, 08:20:42 pm
Yep, but they don't leak overtime and I think they should be pretty reliable.
Btw, for newly acquired 246x scope, suggesting to check these system voltage rails first at the J119 header when opening it for the 1st time.
Remember, get a big fan blowing the whole A1 board while its turned on without the enclosure to cool down those unobtainium hybrid ICs.
Of course ideally these rails should be measured with another scope instead of just ordinary DMM to see if the ripples are up to the specification.
The J119 header location and the voltages specification & tolerances required by the scope to work properly, quoted from Tektronix 2465B service manual.
Well, after reading this particular tantalum caps datasheet I came to conclusion that there is no need to change them. They have no lifetime parameter specified at all, so, probably, as they intact, I will live them. But I'm going to replace aluminum "wet" electrolytic caps on A5 with solid state polymeric "dry" caps. The have longer lifetime, lower ESR and have nothing lo leak out. And I have to replace this pesky Dallas SRAM chip, but that's no so easy to get a fresh one here in Moscow and I have to get a good programmer before.
Concerning rails you told me about: I have another scope (just a cheepy chines Hantek DSO) and a DMM, so, I will take a look on this. Anyway, I'm going to completely recap the unit to make it stay alive for another couple decades, I hope. But I will need help and advices, just cause I had never my hands on anything complected like this scope before.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: e-pirate on May 11, 2014, 04:10:48 pm
Everybody, who's going to replace DS1225 SRAM chip should take a look at Dr. Hugo Holden's document, concerning this procedure and possible chip replacement with FRAM and DRAM. Defiantly worth looking at http://www.worldphaco.com/uploads/TEKTRONIX_2465b_OSCILLOSCOPE_CALIBRATION___REPOWERING_THE_DS1225.pdf (http://www.worldphaco.com/uploads/TEKTRONIX_2465b_OSCILLOSCOPE_CALIBRATION___REPOWERING_THE_DS1225.pdf)!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on May 11, 2014, 05:02:35 pm
Thanks for that document !  :-+

Yep, I bought few FRAM chips last year hoping I can throw away the DS-1225 (posted HERE (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg213270/#msg213270)), and the problem I have is my MiniPro TL866 universal programmer can not copy the SRAM content into this FM1608-120, since it has non standard CE signaling, so currently I'm stuck with this Dallas chip.  :'(
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on May 11, 2014, 05:11:09 pm
Everybody, who's going to replace DS1225 SRAM chip should take a look at Dr. Hugo Holden's document, concerning this procedure and possible chip replacement with FRAM and DRAM. Defiantly worth looking at http://www.worldphaco.com/uploads/TEKTRONIX_2465b_OSCILLOSCOPE_CALIBRATION___REPOWERING_THE_DS1225.pdf (http://www.worldphaco.com/uploads/TEKTRONIX_2465b_OSCILLOSCOPE_CALIBRATION___REPOWERING_THE_DS1225.pdf)!

Great article. Thanks for sharing. Too bad the TL866 can not write to the FM-1608 though
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SeanB on May 11, 2014, 05:42:33 pm
Turn off ID check and tell it it is a DS1225 and it probably will write to it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on May 11, 2014, 05:51:14 pm
Turn off ID check and tell it it is a DS1225 and it probably will write to it.

Nope, it won't work, the problem is this FRAM needs the /CE (Chip Enable) line to be strobed at "EVERY" write or address change, while DS1225 is just like ordinary SRAM which only needs the /CE line to be pulled down "ONCE".

The reason for strobing at the CE on every write is because of the nature how FRAM works, this action will latch the new address and preparing the "pre-charge" while CE is HIGH which is needed for FRAM ferroelectric cell operation, CMIIW.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: e-pirate on May 11, 2014, 06:26:35 pm
Well, probably the STK12C68 is a way to go? As mentioned in document above, you'll need a special PCB and a couple of spares to make it work, but I don't think it's a real problem. Having this chip instead of DS1225 you will have 106 cycles. According to it's way of operation, I'm pretty sure it's equivalent to power on count of the scope.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: e-pirate on May 13, 2014, 07:39:37 pm
Hi, folks.
During my conversation with mr. Hugo he told me that it's a good idea to have another fresh lithium battery in parallel with the old flattering one in old DS1225 desoldered from dcopes before they go to the reader. The trouble is that when the battery is almost flat, it will still hold data in SRAM and the whole thing will continue to work, but when DS1225 get into the reader, some of them MAY draw small current from its pins and that may lead to voltage drop and accidentally blank DS1225.
All information concerning paralleling the battery is in document.
As I'm currently facing the same problem, I will desolder DS1225 and will try to parallel the older battery with a fresh one before plugging it to a reader. I'm going to order the Wellon VP-390 programmer and try to read it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: iloveelectronics on May 15, 2014, 07:25:10 am
Just to give a quick update. I reinstalled the missing caps on the A5 boards, replaced the film caps on the power supply board and finally also desoldered the DS1225 and backed up the data on it. I had to get myself a Hakko 808 to desolder the chip as my other cheaper Chinese desoldering gun wasn't working very well. Made a few burn marks on the board :( Turned out it was merely clogged but its tip never tins properly so it's time to replace it anyway.

A new DS1225AD-200IND+ just arrived today (much sooner than I expected) so as soon as I get a bit of time I will copy the data and insert it into the newly soldered socket on the A5.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on May 15, 2014, 07:53:37 am
Hey Franky, please take few photos if you had a chance, also the cal data zipped and attach it here as well, might be useful someday for someone, who knows.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: iloveelectronics on May 15, 2014, 09:36:51 am
Hey Franky, please take few photos if you had a chance, also the cal data zipped and attach it here as well, might be useful someday for someone, who knows.

I will take some pictures the next time I open up the case.

I just had a go with the new DS1225 but failed :( I'm using the MiniPRO TL866CS programmer. I thought being a brand new chip it would be all empty with all "00" or "FF" but when I read it there was already something in it, is that normal? I tried programming it a few times with the binary file I saved from the old chip but it simply didn't work...
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on May 15, 2014, 09:54:37 am
Thats weird, my experiences with DS1225 either the old one and new were without any problem at all using the minipro I purchased from you.  :-+

Heck, I even still use the old one, while the new DS1225 which already has the cal data copied into it is in the storage, just curious how long the old one will survive.  >:D

Where did you buy that DS1225 ? Read few posts back, there was a similar problem with new "old" stock of DS1225 bought from a surplus shop if I'm not mistaken, and problem solved by using the new DS1225 from authorized distributor.

Fyi, mine was purchased directly from Digikey with quite fresh date code, whats yours ?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: iloveelectronics on May 15, 2014, 10:16:06 am
Thats weird, my experiences with DS1225 either the old one and new were without any problem at all using the minipro I purchased from you.  :-+

Heck, I even still use the old one, while the new DS1225 which already has the cal data copied into it is in the storage, just curious how long the old one will survive.  >:D

Where did you buy that DS1225 ? Read few posts back, there was a similar problem with new "old" stock of DS1225 bought from a surplus shop if I'm not mistaken, and problem solved by using the new DS1225 from authorized distributor.

Fyi, mine was purchased directly from Digikey with quite fresh date code, whats yours ?

I bought mine from Mouser. Date code is 1415 so it should be about as fresh as it gets.

I read Dr. Holden's article about replacing the Dallas chip with other alternatives and saw that he had success with your RAMTRON FM1608 with the GQ-4X programmer so I also went and got myself one of those (haven't got the FM1608 yet though). I just tried using this programmer on the new DS1225 chip but still had no luck. This programmer allows me to set writing speed and it seems to be able to go a little bit further with slower speed but still no more than 3 lines of binaries max :( I wonder if I got a bad chip? Or did I miss any steps?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: iloveelectronics on May 15, 2014, 10:44:23 am
I just tested it some more and it looks like I can't write a "0" to the least significant bit of the high byte in each word. I can fill the chip with 10, 11, 12...1F, 30, 31, 32...3F, etc. but can't write 2x or 4x etc.  :palm:
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: e-pirate on May 15, 2014, 01:26:16 pm
Mr. Hugo suggests to use FM16W08 as it a newer version of FM1608 and capable of more read-write cycles. Bat it's not a direct replacement is it 4 banks of 8K x 8.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: e-pirate on May 15, 2014, 01:29:46 pm
I just tested it some more and it looks like I can't write a "0" to the least significant bit of the high byte in each word. I can fill the chip with 10, 11, 12...1F, 30, 31, 32...3F, etc. but can't write 2x or 4x etc.  :palm:
BTW, did you checked old DS1225  for a multiple read sequence? It's not mentioned in document, but mr. Hugo told me that results MAY be different with data "fading" away more and more after each read attempt.
How old is your original DS1225 is?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: iloveelectronics on May 15, 2014, 01:50:03 pm
BTW, did you checked old DS1225  for a multiple read sequence? It's not mentioned in document, but mr. Hugo told me that results MAY be different with data "fading" away more and more after each read attempt.
How old is your original DS1225 is?

No, I didn't try that. Perhaps I will try that when I open the case up again. My old DS1225Y has a 1990 date code, so it's 24 years of age already...
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: chksum3 on May 20, 2014, 11:33:56 pm
Regarding your problem writing to a newly purchased DS1225: I had the same experience with a DS1225Y-200 purchased from a local supplier (Jameco) despite its having a recent date stamp.  Per advice given here, I bought another chip from Digikey - that one could be read and written to flawlessly. 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: e-pirate on May 21, 2014, 09:41:15 am
Regarding your problem writing to a newly purchased DS1225: I had the same experience with a DS1225Y-200 purchased from a local supplier (Jameco) despite its having a recent date stamp.  Per advice given here, I bought another chip from Digikey - that one could be read and written to flawlessly.
Could you provide us a photo of this two chips sitting one next to another?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: iloveelectronics on May 21, 2014, 10:04:18 am
I just replaced my DS1225Y with a Ramtron FM1608, and it works! Well, I've only tried some basic signals but everything is looking fine, just like it was with the 24-year-old DS1225Y :) I wrote the data onto the FM1608 using a GQ-4X programmer. The MiniPro TL866CS doesn't seem to be compatible with this chip.

Attached is the BIN file I saved from the DS1225Y chip in case anyone finds a use for it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on May 21, 2014, 10:23:28 am
Sigh ... Don't feel like to buy GQ-4X programmer just to program this fram, I guess I'm stuck with my TL866 and 3 pcs of unused FM1608s.  :'(

Btw, thanks for the cal ram image.  :-+
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: iloveelectronics on May 21, 2014, 10:35:34 am
Sigh ... Don't feel like to buy GQ-4X programmer just to program this fram, I guess I'm stuck with my TL866 and 3 pcs of unused FM1608s.  :'(

Btw, thanks for the cal ram image.  :-+

If you don't mind mailing the chip back and forth I can help you write your data onto it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on June 29, 2014, 10:08:22 pm
Well I think I toasted the calibration data on my Dallas.  Not sure what went wrong, but when reading it using my TL866 I just get values of 00 from Address 00000  to 0007F0 and 00 from address 001000 to 0017F0.  :( :(

When pulling off the Dallas one of the pins bent and crossed with another, so i am wondering if this somehow reset the stored values. Waiting for a 28 pin socket from Digikey before I see what error messages come up on the scope. Perhaps nothing is wrong and that is indeed my calibration data but I doubt it.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: e-pirate on July 01, 2014, 10:09:48 am
Good news, folks!
Yesterday I succeed on reading an dying cause of it respectable age DS1225Y from my TEK 2467B. As Mr. Hugo Holden noticed in his article, that this NVRAMs may get corrupted while reading attempt in programmer because of some programmer may sunk current from ICs pins, this may finish off already discharged heroic lithium battery inside DS1225 (mine is actually produces in mid 91, so it at least 23 years old with only 10 years guarantee data storage). I decided not to relay on chance and do a surgery for my DS1225Y and shunt it's internal battery with external fresh one before putting it to programmer. I spend some unpleasant hours desoldering it from A5 board, primary because if tiny traces and sucker back-kick. After DS1225 was desoldered, I replaced it with gold plated socket with round contacts and started the main act. Using Dremel with very small grinding bits I dig into compound on the bottom side of the DS1225 to reach DS1218 pin 7 shat is connected to internal battery positive terminal. Then, I tin going to install a standard CR2032 battery socket, salvaged from an old mother board. As I'm going to replace DS1225 with Ramtron 16W08 or STK12C08 (I got both, see what will do better), I decided to temporary stick socket on the top of DS1225 with a dual side sticky tape and then solder positive terminal to pin 7 of DS1218 and negative to pin 14 of DS1225. After battery was installed and wires soldered, I put DS1225 back again to see if it still holds calibration data. My scope booted without any warnings and EXERCISE 5 showed correct power hours and cycles. So, I put DS1225 to my new Wellon VP-390 programmer and successfully read data from it. Then, I just removed the battery and put DS1225 back again. I have no idea how to safely place external battery on A5 board, but now, as I have a dump, I don't really care.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on July 07, 2014, 11:41:18 pm
You description of the failure reading the Dallas NVRAMs after desoldering them from the board match what I experienced doing the same procedure on my 2440 which had a pair of DS1230 memories.  My programmer would not work with the 20+ year old memories but did with the EEPROM based replacements that I used.

While testing to determine the problem, I believe I inadvertently overwrote the NVRAMs destroying the calibration data but the 2440 series external calibration is trivial compared to that of the 2465B series so I just did that after installing sockets and the new memories.  If I had been working on a 2465B, I would have been more careful and persevered.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on July 08, 2014, 01:25:47 am
You description of the failure reading the Dallas NVRAMs after desoldering them from the board match what I experienced doing the same procedure on my 2440 which had a pair of DS1230 memories.  My programmer would not work with the 20+ year old memories but did with the EEPROM based replacements that I used.

While testing to determine the problem, I believe I inadvertently overwrote the NVRAMs destroying the calibration data but the 2440 series external calibration is trivial compared to that of the 2465B series so I just did that after installing sockets and the new memories.  If I had been working on a 2465B, I would have been more careful and persevered.

What is strange is where one would expect a value in the address bank there is just 00's. It's almost as if the programmer couldn't read the value and substituted 00.

 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on July 08, 2014, 02:16:19 am
What I saw was very similar if not identical.  It was like one or more of the address lines was causing the reads to be all 00 or all FF but reads from other addresses were good.

My hypothesis based on other information is that the control IC itself relies on the backup battery voltage being above a certain level or it fails to pass the chip select signal through.  Apparently at some point, the backup battery voltage gets low enough that while the SRAM contents are not immediately lost, the device cannot be accessed under any conditions even though external power is applied.

In this particular case, only some addresses were locked out for whatever reason because the backup batter voltage was just on the threshold before chip select would be completely disabled.

If I had been working on a 2465b or similar where the calibration is tedious, I would have been more careful and certainly tried accessing the backup battery directly so the calibration data could be read out.  I wonder if raising or lowering the temperature would have been enough to access the data.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on July 08, 2014, 04:56:25 am

If I had been working on a 2465b or similar where the calibration is tedious, I would have been more careful and certainly tried accessing the backup battery directly so the calibration data could be read out.  I wonder if raising or lowering the temperature would have been enough to access the data.

Well putting the chip back in the scope and it will not work, so I suppose what you suggest could be possible. Nothing would hurt to put it in the oven or freezer for a bit and retry. Since it's likely a loss cause i could always try and de-pot the area around the battery and add a replacement one in parallel and try and read it again. Never know, just might.

Some interesting reads on the Dallas 1225 and hacks.

http://www.google.ca/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CB4QFjAA&url=http%3A%2F%2Fwww.worldphaco.com%2Fuploads%2FTEKTRONIX_2465b_OSCILLOSCOPE_CALIBRATION___REPOWERING_THE_DS1225.pdf&ei=mHm7U92SG8G7oQT6-IHADA&usg=AFQjCNGFqXCfi2ArgRR6vCgu3btbZ-9B0Q&sig2=6BETUqeTL4Vv2wFvieI1rQ&bvm=bv.70138588,d.cGU (http://www.google.ca/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CB4QFjAA&url=http%3A%2F%2Fwww.worldphaco.com%2Fuploads%2FTEKTRONIX_2465b_OSCILLOSCOPE_CALIBRATION___REPOWERING_THE_DS1225.pdf&ei=mHm7U92SG8G7oQT6-IHADA&usg=AFQjCNGFqXCfi2ArgRR6vCgu3btbZ-9B0Q&sig2=6BETUqeTL4Vv2wFvieI1rQ&bvm=bv.70138588,d.cGU)

 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Mr Simpleton on July 08, 2014, 07:57:53 am
So for those with a lost memory and a non-working 2465B, could the scope use "generic" cal data?
I.e. how poor would the scope behave if one used cal data from an other working 2465??
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on July 08, 2014, 08:22:57 pm
Tried the Dallas hack in the link I uploaded and added a external battery to the Dallas. The old one read 2.64v, unfortunately no luck in reading it on the programer, same issue. Just returns 00 in the addresses that should contain data. Oh well....
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on July 08, 2014, 08:25:10 pm
So for those with a lost memory and a non-working 2465B, could the scope use "generic" cal data?
I.e. how poor would the scope behave if one used cal data from an other working 2465??

I have a TG501 time mark generator and it is pretty much bang on with the Rigol so pretty comfortable it is within calibration. Will try it on the 2565B with a generic "cal data" and see how far out it is.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on July 08, 2014, 09:16:43 pm
So for those with a lost memory and a non-working 2465B, could the scope use "generic" cal data?
I.e. how poor would the scope behave if one used cal data from an other working 2465??

The horizontal, vertical, and other calibrations will be wrong but it should otherwise work.  I do not know if it would be any better than just clearing the calibration memory and operating the oscilloscope anyway.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: casinada on July 12, 2014, 05:46:59 am
I lost the cal data from the Dallas Chip. I downloaded the backups available from the ko4bb repository as a starting point, programmed the data on to a fresh DS1225 and then calibrated my 2465BDM using different generators, signal sources, power supplies, multimeters until I was satisfied with the results.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on July 12, 2014, 06:25:23 am
Pretty much what I am faced with doing. Have myself a TG501 so that's half the battle. The rest I think I can do with my HP 50Mhz frequency generator, checking the outputs with a accurate DMM to test the amplitudes.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: richhas on August 02, 2014, 08:18:36 pm
Ok... Just received a 2464B and disrobed it for an initial inspection of A5 and the Main Board - having read this thread over several times.

I expected the worst wrt the A5 EC issues but think I'm pleasantly surprised - but I'm not an expert and thus my query here.

Both boards look super clean to me and I don't see any EC junk on A5. The thing that caught my eye have been the date codes. I thought that these units ceased production in '92-ish but I'm seeing date codes of '94, '95, and even a '97. Does anyone know how late these Beaverton units were produced? Or maybe these are replacement boards produced later than end-of-production. Could it be that Tek fixed the A5 EC issues late in the production?

In any case, it would great to get opinions from the experts here. Did I get lucky? Should I go ahead and replace the A5 caps? I'm going to heat sink U800 and socket/replace the damned Dallas ram - also update the LV/HV caps if needed.

This unit had 9330 hours spread over 1340 power cycles - approx on for 7 hours at a time. Makes some sense in a work environment - not too much cold start stress I hope.

The quality and experience from you guys has been super educational.

THANK YOU,

Rich
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on August 02, 2014, 09:40:49 pm
My notes say that the 2465B and 2467B were available from 1989 through 1996.

I suspect the U800 failures were more related to stress caused by the poor mounting than heat.

I believe the later oscilloscopes did not suffer from leaking surface mount aluminum electrolytic capacitors.  If that is the case, then I would not risk of damage to the oscilloscope while changing them unnecessarily.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: richhas on August 02, 2014, 11:04:56 pm
Thanks David... BTW the serial# is B065301.

I just went into the PS cage and many of the caps and other parts are marked '94 and some '95. The inspection sticker on the LV PS says mid '95.

Those transparent plastic covered caps on the PS pcb seem to not be cracked or such. Would your advise be the same - if is not broken, then...?

Best,

Rich
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Electro Fan on August 02, 2014, 11:25:24 pm
Kind of a big SWAG but...

If you took all the Tek 24XX and 22XX scopes manufactured between 1990-1995 that were subsequently humanely treated:
- used (turned on) a few hours per day (20 years x 4 hours per day x 250 business days per year = 20,000 hours)
- maintained in a decent environment (temperature, humidity, etc.)
- operated with proper respect

What percent of these humanely treated Tek scopes would make it to 2015 without needing any parts (other than a battery) replaced?

What percent would make it to 2020 without needing any parts replaced?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: richhas on August 02, 2014, 11:50:56 pm
No expert here but my guess is the cap plague with these EC lowered the average a great deal - amplified by the great tolerances tek tended to design in only served to hide problems until too much damage was done to pcbs... But just an old guy's guess.

Best,

Rich
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on August 03, 2014, 01:37:38 am
I think it was only the early surface mount aluminum electrolytic capacitors which had this problem in the 2465 series and it was not capacitor plague.  I suspect it had to do with washing after soldering where the capacitors or the capacitor seals were sensitive to halogenated solvents.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on August 03, 2014, 03:27:36 am
What percent of these humanely treated Tek scopes would make it to 2015 without needing any parts (other than a battery) replaced?

What percent would make it to 2020 without needing any parts replaced?

"In the year, twenty-five twenty-five
if tek is still alive
if agilent can survive
they may find..."


Title: Re: Tektronix 2465B oscilloscope teardown
Post by: richhas on August 03, 2014, 06:54:29 am
Very good!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on August 03, 2014, 07:36:48 am
Rich, great score you got there !  :clap:

About the A5 board's electrolytic caps, have agree if I were you I will be facing the same hesitation too.

But, assuming you're very confident that you won't break the board while replacing them, I would say just replace them with best cap that is available now, just to have a good sleep knowingly they will not leak out any time soon, also those old SMD caps are made in early 90s, which already more than a decade old.

Still, its your call.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on August 03, 2014, 01:26:55 pm
You could ask over on the TekScopes@yahoogroups.com email list or search the archive.  Someone there undoubtedly knows if the late 2465B series suffered from the surface mount capacitor problem.

I know of more than one instance now where someone changed all of the capacitors in one of these oscilloscopes and ended up breaking it.

Also, their is an error in the board layout diagram for the power supply which has two capacitors swapped so if you follow the service manual, it will short out the power supply.  It is a good idea to take notes and maybe photos as you go along.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on August 03, 2014, 01:36:45 pm
He is going to take out the whole big A5 board from the scope to desolder the big Dallas chip anyway, and solder the dip socket for new bbsram chip.

Imo, this task alone not a brief soldering job, and that will be the good opportunity to replace those caps at the board.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on August 09, 2014, 06:10:20 pm
I guess most of the Tek 24x5 owners are aware of the U800 chip vulnerability, just browsed Tek yahoo group pictures gallery and noticed this interesting pictures of A1 board captured using FLIR camera.

These pictures should speak for it self. Just remember to blow the whole A1 board with a strong fan when you're working without the enclosure, especially near the U800 chip.

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=105009;image)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: iDevice on August 09, 2014, 06:53:03 pm
That raises a question I wanted to post and forgot to.
A few weeks ago, I scored a mint 2445B with only 270 hours.
The only problem I could find was a failure of the beam finder switch that remained in the activated state.
It was fixed by cleaning.
But while the scope was open I left it running to check if everything was ok, obviously with a fan directed on U800.
And after about 15m, U800 was still cold.
So I stopped the fan a few minutes and U800 was still at about 30°C.
After about half an hour, I could still hold my finger on it and it felt just warm, I didn't think to take a real temp measure though.

So I'm wondering if there are different versions of U800, (based on IC dates, scope was build in '94) or if the legendary U800 meltdown only happen with certain settings ?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on August 09, 2014, 07:04:31 pm
So I'm wondering if there are different versions of U800, (based on IC dates, scope was build in '94) or if the legendary U800 meltdown only happen with certain settings ?
As far as I'm aware, currently only 2 versions, one made by Tek, another one from Maxim , posted both photos -> post #185 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg440178/#msg440178) while ago.

Whats yours ?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: iDevice on August 09, 2014, 07:26:36 pm
I have the Tek labeled version.
Probably one of the last since they sold the factory to Maxim in '94, as it seems.

I'm waiting for a new DS1225, so I will open it again in a week or two.
This time I will take some shots with my TIC.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on August 09, 2014, 07:44:19 pm
This time I will take some shots with my TIC.

 :-+ , sounds great, looking forward to see further details at the temperature in A1 board, thanks !
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: guido on August 24, 2014, 11:20:59 pm

Had to calibrate the vertical after repairing the 2465. It got a new attenuator. As i don't have a PG506, i looked in the partsbin and found an AD CMOS switch. Put in on a pcb with a 555 and presto, a "chopper". Used a fluke calibrator to generate the DC voltages (20mV to 10V range) and managed to calibrate vertical and trigger. Not much of a circuit, but you need a decent calibrator to begin with  :D

(http://members.home.nl/baltusg/chopper_case.jpg)

The 20mV signal and source on a 2430A:

(http://members.home.nl/baltusg/chopper_scope.jpg)

And since it was open (you need to calibrate the markers with pots), i also took a picture of my wannabee U800 cooler:

(http://members.home.nl/baltusg/u800.jpg)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on August 25, 2014, 05:09:54 am
Before I got a PG506, I managed to generate the calibration voltages using a stepped attenuator but I know of others that had good results using analog switches.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on August 25, 2014, 08:20:02 am
Does the vertical calibration have to be a 1khz square wave of varying amplitude like the PG506 or can it be a DC voltage. I know there is many cheap very accurate voltage references like a Ref5050 from TI .05% accuracy and 2.55 ppm/Celsius temp coefficient http://www.ti.com/product/REF5050/description (http://www.ti.com/product/REF5050/description) that one could feed into a LTC1043 to divide/multiply to meet the required voltages. May need a couple different reference voltages to feed into the divider.  Suppose would need a buffer ie LTC1050
https://www.eevblog.com/forum/projects/should-the-ltc1043-voltage-divider-circuit-be-buffered/msg461531/#msg461531 (https://www.eevblog.com/forum/projects/should-the-ltc1043-voltage-divider-circuit-be-buffered/msg461531/#msg461531)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on August 25, 2014, 01:28:12 pm
I really should be a chopped square wave in order to reduce the effects of thermal drift and seven different voltages from 20 millivolts to 10 volts are needed.  Calibration of the automatic measurements absolutely requires a square wave.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on August 25, 2014, 09:41:58 pm
I do have a HP81161 pulse generator that I could use. Can output a 1khz square wave at 50% duty cycle and vary the amplitude to match the required calibration volatages for the 2465b. Only issue is I am not sure how accurate it is any longer. The performance checks for AC amplitude fall within the specs according to the measurements with my Uni-T multimeter. But can i really really on such a  cheap measuring instrument to confirm the HP outputs, especially on a a AC output.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on August 25, 2014, 10:41:15 pm
There are two different easy ways to handle the calibration in that case.

An RMS reading voltmeter may be used in which case the peak to peak value is twice the RMS value.  A good meter will get you into the accuracy range necessary to calibrate an oscilloscope which is not a precision instrument for voltage measurements anyway.

Alternatively an average responding AC voltmeter may be used with a correction factor.  For square waves, it will read 11% high.  This is usually a better option because average responding meters are usually both faster and more accurate than RMS responding meters.

When I do this I use both as a sanity check.  All of my good meters handle 1 kHz square waves with no problem.

One thing to beware of though when doing the above is that the duty cycle needs to be 50% or at least known so a correction factor can be applied.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on August 26, 2014, 01:14:51 am
The multimeter I have is a UTI-61E, below is a pic of the AC specs. I thought crest factor also had to be taken into consideration. Either way you are right, splitting hairs. Will compare the output of the HP to the  multimeter and on my Rigol1052e. The Tek is only rated for 2% vertical accuracy so I am probably well in the ballpark. Although it would be nice to have a calibrated 34401a. :D

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on August 26, 2014, 02:04:52 am
I thought crest factor also had to be taken into consideration.

The crest factor for a square wave is 1 so it is not a consideration.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: calin on August 26, 2014, 03:18:54 am
I also need to do a vertical cal on my 2465 and of course no PG506 .. I do have a nice working FG 504 very stable and nice, a 51/2 digit Fluke  multimeter and some scopes to compare ... but I am scratching a bit my head at how the vertical calibration signal should look like.


So it is clear, the calibration signal should be a 1kHz  square with 50% duty with the following values, 0.5V, 0.2V, 0.1V, 50mV, 20mV, 1V and 10V. Now here is what is not clear:


1) Are these voltages in 50 ohm or in high impedance ? I think is HiZ.
2) Yes voltages are peak-to-peak, are they 0 to 0.5V for or AC  +/- 2.5V ? I think they are 0 to +0.5 but better check first before I do something stoopid :)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on August 26, 2014, 04:47:29 am
And since it was open (you need to calibrate the markers with pots), i also took a picture of my wannabee U800 cooler:

(http://members.home.nl/baltusg/u800.jpg)

Guido, that heatsink looks like a stacked coins to me.  ;D
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on August 26, 2014, 05:13:21 am
So it is clear, the calibration signal should be a 1kHz  square with 50% duty with the following values, 0.5V, 0.2V, 0.1V, 50mV, 20mV, 1V and 10V.

I wish if there is an easy and relatively cheap to build such circuit, any experienced or experts want to contribute on the circuit schematic ?

Don't need to be high precision right ? <5% accuracy is enough maybe ?  :-//
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on August 26, 2014, 06:38:22 am

1) Are these voltages in 50 ohm or in high impedance ? I think is HiZ.
2) Yes voltages are peak-to-peak, are they 0 to 0.5V for or AC  +/- 2.5V ? I think they are 0 to +0.5 but better check first before I do something stoopid :)

Good question. I assumed they are 50 ohm impedance. Thea manual states the testing procedure switches to 50 ohm impedance in Cal 01, I just assume this carried over to Cal 02 (Vertical).

Upon entering CAL 01, the Input Coupling is
automatically set to 50 Q DC and the 50 Q OVERLOAD
protection is disabled. Before starting the procedure,
make sure any 50 Q OVERLOAD condition
has been cleared.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on August 26, 2014, 05:03:45 pm
I also need to do a vertical cal on my 2465 and of course no PG506 .. I do have a nice working FG 504 very stable and nice, a 51/2 digit Fluke  multimeter and some scopes to compare ... but I am scratching a bit my head at how the vertical calibration signal should look like.

...

1) Are these voltages in 50 ohm or in high impedance ? I think is HiZ.

What matters is the peak to peak voltage at the oscilloscope's vertical input with or without termination.

Quote
2) Yes voltages are peak-to-peak, are they 0 to 0.5V for or AC  +/- 2.5V ? I think they are 0 to +0.5 but better check first before I do something stoopid :)

Only the peak to peak value matters as long as the waveform can be positioned on the CRT.  The PG506 for instance generates square waves from 0 to +x volts in calibrated amplitude mode.

Calibration of the 2465 cursors and any automatic measurements might require 0 to +x versus AC though.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on August 26, 2014, 05:07:44 pm
Good question. I assumed they are 50 ohm impedance. Thea manual states the testing procedure switches to 50 ohm impedance in Cal 01, I just assume this carried over to Cal 02 (Vertical).

It cannot always be 50 ohms because a PG506 will not generate 10 volts into a 50 ohm load.

Another reason it cannot be 50 ohms is that then the calibration amplitude would depend on the accuracy of the 50 ohm termination value.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mwilson on August 26, 2014, 07:50:01 pm
Good question. I assumed they are 50 ohm impedance. Thea manual states the testing procedure switches to 50 ohm impedance in Cal 01, I just assume this carried over to Cal 02 (Vertical).

It cannot always be 50 ohms because a PG506 will not generate 10 volts into a 50 ohm load.

Another reason it cannot be 50 ohms is that then the calibration amplitude would depend on the accuracy of the 50 ohm termination value.

Yep... also, to remove any remaining doubt, the PG 506 calibration procedure calls for calibrating its standard amplitude DC voltage ranges with an exact 1 megaohm load (within 0.1%).
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: calin on August 26, 2014, 08:10:27 pm
Perfect thanks guys. Looks like I am not a total noob and I've been reading right :).  1kHz square, 50% duty, 0 to +X DC voltages into HiZ it is.  I will use the FG 504 and my trusty Fluke meter to measure RMS and try a vertical cal on my scope.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: guido on August 26, 2014, 11:22:48 pm
Guido, that heatsink looks like a stacked coins to me.  ;D

It is out of a 7A13 actually.

So it is clear, the calibration signal should be a 1kHz  square with 50% duty with the following values, 0.5V, 0.2V, 0.1V, 50mV, 20mV, 1V and 10V.

I wish if there is an easy and relatively cheap to build such circuit, any experienced or experts want to contribute on the circuit schematic ?

Don't need to be high precision right ? <5% accuracy is enough maybe ?  :-//

Take a 10V reference chip, make the voltages with some precision dividers and use such a cmos analog switch to chop it up. Driven by a 555 or function generator. Maybe use a low offset opamp after the dividers or switch as buffer. I used a 6.8nF cap on the output to stop overshoot. You might check this with a good scope for a good value for your switch/coax cable.

Check the PG506 manual for the precision requirements...

I wonder if a normal function generator will work at the low voltages. What i looked at, some had offset figure specifcations of +/- 10mV... You might need to use a high voltage square as output and divide using precision resistors. See if you can get the 20mV nicely on the screen of a good scope.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on August 26, 2014, 11:30:47 pm
Good question. I assumed they are 50 ohm impedance. Thea manual states the testing procedure switches to 50 ohm impedance in Cal 01, I just assume this carried over to Cal 02 (Vertical).

It cannot always be 50 ohms because a PG506 will not generate 10 volts into a 50 ohm load.

Another reason it cannot be 50 ohms is that then the calibration amplitude would depend on the accuracy of the 50 ohm termination value.

What would my best option be for attempting to calibrate with my HP8116a. It as far as I know can only output the stated output voltages at 50 Ohm.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: calin on August 27, 2014, 12:25:21 am
The HP can output into HiZ ... just the voltage seen by the scope will be double. But then if you measure RMS with a mutimeter that is the same as seen by the scope . Of course if you have a square wave with 50% RMS value for 5V pk to pk is 2.5 .  Same is my FG504 .. 50 ohm.  At 1Khz reflections on the line are not something to worry too much about i think. Yeah many FG-s cannot go that low .. you don't need precision resistors .. just precision dividing any resistor of the right value and a multiturn pot/trimmer will do as ong as you have a good rms meter and a comparision scope you are set.  We are not looking for ultra high precision and low tempco here .. if is stable for 5 mins until the cal step is done is good enough i guess
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on August 27, 2014, 01:53:27 am
The HP can output into HiZ ... just the voltage seen by the scope will be double. But then if you measure RMS with a mutimeter that is the same as seen by the scope . Of course if you have a square wave with 50% RMS value for 5V pk to pk is 2.5 .  Same is my FG504 .. 50 ohm.  At 1Khz reflections on the line are not something to worry too much about i think. Yeah many FG-s cannot go that low .. you don't need precision resistors .. just precision dividing any resistor of the right value and a multiturn pot/trimmer will do as ong as you have a good rms meter and a comparision scope you are set.  We are not looking for ultra high precision and low tempco here .. if is stable for 5 mins until the cal step is done is good enough i guess

Right, double checked the HPmanual and that is what it suggests, double the output. I just wish I had a calibrated DMM to double check the output from the HP. 2.5v output reads 4.99v or 5.12 depending on the number of divisions on the scope. Odd in itself and may be a problem with my Rigol.

If I did not have the HP I would look at some precision reference voltage chips and use a couple LTC 1043 chips, supposedly very good , very accurate voltage divider, multipliers.  Page 8 of the datasheet

http://www.linear.com/product/LTC1043 (http://www.linear.com/product/LTC1043)

One or two reference voltages and a couple LTC1043's and you could come up with all the required voltages needed Just wondering what circuit one could use to chop it into 1khz without any appreciable noise or loss.



 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on August 27, 2014, 02:57:15 pm
It cannot always be 50 ohms because a PG506 will not generate 10 volts into a 50 ohm load.

Another reason it cannot be 50 ohms is that then the calibration amplitude would depend on the accuracy of the 50 ohm termination value.

What would my best option be for attempting to calibrate with my HP8116a. It as far as I know can only output the stated output voltages at 50 Ohm.

The way I did it with a function generator at low voltages was to use a stepped attenuator and 50 ohm termination while measuring the peak to peak voltage at the oscilloscope vertical input.  At high voltages the stepped attenuator and termination are not needed.

When dealing with voltages lower than can be accurately measured with an AC voltmeter, the stepped attenuator may be calibrated at a higher level and then the voltage can be measured at the input to the attenuator.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on August 27, 2014, 05:02:44 pm
Hmm, just got me thinking, could I not before the calibration procedure compare a precision DC voltage reference and the HP outputs on Channel 1 and 2 of the scope. Note the difference if any between the two and then subsequently adjust the HP outputs during the calibration standards. For example if the difference between the precision 1v dc and the HP 1v 1Khz AC is +10mv on the scope then when actually calibrating set the HP output for 90mv.

Or just don't worry about it and rely on the accuracy of my Uni61E to test the HP output. Thinking the scope comparison method may be more accurate in determining the output accuracy of the HP.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on August 27, 2014, 06:07:28 pm
Using two channels of the oscilloscope to make the comparison will not work because the offset and gain calibration of the two channels is independent.  One of the reasons to do the calibration is to match them as closely as possible.

There is an old technique which does exactly what you are proposing using one oscilloscope channel and it could be used to calibrate a signal generator.  It involves using a "differential comparator" which adds a precision offset voltage to the signal to be measured.  The offset voltage is adjusted to bring two different vertical levels into alignment and the difference represents the difference in voltage between those two signal levels.

The old Tektronix 7A13 does exactly this to 4 significant digits and with a resolution down to 1 millivolt although better resolution is available if an external voltmeter is used to measure the comparison voltage.

This is also known as a slide-back measurement.  I would have gone this route if I had lacked a modern AC voltmeter which could accurately measure low frequency square waves.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on August 27, 2014, 10:38:11 pm
Thanks David;

I did a Google search on Slide back measurements did not find much info. Any additional details you could share would be appreciated.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on August 28, 2014, 12:04:19 am
There is not much online about it.

Tektronix used and described the procedure in a couple of their service manuals where it was used for instrument calibration.

I suspect there is a detailed article about it in one of the TekScope publications but I have never seen an index of them to know where to look.  The 7A13 was first produced in 1969 so that would be the time period to search. 

There were earlier differential comparators as well and the operating manuals for them may describe how they can be used to make slide-back measurements.

The term also shows up in some old NIST publications.

Update: I did a search and found articles in November 1972 TekScope and January/Feburary 1973 TekScope but they are part 2 and 3 so there is an earlier one which I do not have.  They do not discuss the 7A13 differential comparator specifically but part 2 mentions slide-back measurement:

Let's see how we go about making a differential comparator measurement.  First, we establish a reference position on our display by grounding both inputs.  Then selecting the appropriate input (positive voltage source to the + INPUT, negative voltage source to the - INPUT), we switch the other input to the comparison voltage (Vc).  Next, the comparison voltage is adjusted until the trace "slides back" to the reference position.  What have we accomplished?  Using the "difference" principle we have introduced a "common-mode" condition in the form of the comparison voltage; that is, the comparison input voltage now equals the signal input.  We see that we now have the ability to measure any potential whether it be DC, complex in nature, or a combination of both - such as a complex wave superimposed on a DC potential.  Thus, we have an extremely versatile measuring tool.

The reason you would do this instead of reading the voltage directly off of the oscilloscope is increased precision and accuracy.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on August 28, 2014, 05:04:41 am
Let's see how we go about making a differential comparator measurement.  First, we establish a reference position on our display by grounding both inputs.  Then selecting the appropriate input (positive voltage source to the + INPUT, negative voltage source to the - INPUT), we switch the other input to the comparison voltage (Vc).  Next, the comparison voltage is adjusted until the trace "slides back" to the reference position.  What have we accomplished?  Using the "difference" principle we have introduced a "common-mode" condition in the form of the comparison voltage; that is, the comparison input voltage now equals the signal input.  We see that we now have the ability to measure any potential whether it be DC, complex in nature, or a combination of both - such as a complex wave superimposed on a DC potential.  Thus, we have an extremely versatile measuring tool.

Hi David:

Looks like to perform the differential comparator measurement as above  a differential probe is needed?.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on August 28, 2014, 01:43:53 pm
Looks like to perform the differential comparator measurement as above  a differential probe is needed?.

A differential comparator is a type of differential amplifier and may be used in place of a differential probe.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on August 29, 2014, 05:01:28 am
Well looked up on differential amplifiers and I am sure there is a way but way beyond me I am afraid, especially the complexity of one of the signals being AC. Ran my Rigol 1052E and a Tek 2465A side by side and compared the outputs of the HP, for the most part the Tek and the Rigol were very close in all the measurements. Under 1v outputs only a few mv difference between the two and 10's of mv above 2v. Where there was a large discrepancy was at the 10v range where the Rigol was almost .2v out compared to the tek. I think there may be a issue with the Rigol. The Rigol varies a fair bit in measurement depending on the vertical scale selected.

So in short I think the output accuracy of the HP is ok, at least for my hobbyist purposes to calibrate my 2465B.   
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on August 29, 2014, 02:44:54 pm
Well looked up on differential amplifiers and I am sure there is a way but way beyond me I am afraid, especially the complexity of one of the signals being AC.

Differential comparator slide-back measurements are one of those techniques which have been lost in time.  They are especially useful for measuring complex AC signals but as you observe, it would help to see how it is done in action and I know of no good examples showing this.

When first did oscilloscope calibration, I used an AC voltmeter to measure the peak to peak signal values instead of making a slide-back measurement which would have taken longer.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Phaedrus on September 04, 2014, 05:00:08 pm
I finally found the time to open up my 2465A I bought a couple months back. I was actually quite surprised; the date codes run up to middle of 1986. According to Wikipedia this model wasn't offered until 1987. So I think I might have gotten one of the first production batches.  :-+

All the electrolytics look good visually, but there's probably been some degradation anyway. I'm going to look into replacing them. Also probably stick a San Ace fan in there. How would you test to see if the U800 is having any issues?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on September 04, 2014, 05:58:23 pm
How would you test to see if the U800 is having any issues?

If U800 is having problems then it should be apparent on the display with horizontal drift or gain changes.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: e-pirate on September 10, 2014, 10:33:29 am
Hi, folks.
Some time ago I started my work on replacing NVSRAM (the DS1225) in my Tek2467B and ended with a success replacement with SIMTEK STK12C68. The STK12C68 is a fast SRAM with EEPROM and a schematics to store/restore data to/from EEPROM on power failure condition. It combines both infinity read/write cycles of SRAM and 100-year data retention in EEPROM without need of any external power (and that solves battery problem). As data stored to EEPROM only at power-off condition, this specs simply make STK12C68 lifetime grater then scope's.
The original idea belongs to Mr. Hugo Holden, who consulted me during my work. His fears goes to store operation, hi told me that hi was able to reproduce condition at witch scope failed to boot and data in  STK12C68 corrupted after very fast unit switch on-off cycles. However, with my STK12C68 I was not able to reproduce that behavior in unit. I did a series of unit power no-off-on-off as fast, as I was able to kick power button and then varying time delays. But that didn't convince no me, neither Mr. Holden. So, he suggested another test that I performed: I powered STK12C68 from a function generator, varying both duty cycle (10%-90% for square wave) and frequency from 0 to a couple hundred Hertz (that will never happen in real life) and even under that test contents of STK12C68 remained intact. So, this NVSRAM confirmed it usability. It work perfect in my scope: everything stored correctly, front panel and all settings stored/restored during reboot perfectly. Even after power button kick test.
The IC requires an external cap to store energy for power off EEPROM store cycle. I use the smallest recommended value: 68 uF tantalum, bypassed by 0.1 ceramic one. Besides, I use 0.1 ceramic to bypass the IC itself and 10K resister between pin 27 and VCC as recommended in datasheet. Previously I replaced DS1225 with a round pin socket. My current "adapter" is just a wire soldered STK12C68 to two raws of pins inserted to socket and some caps and resister soldered to all this mess and covered by a tape so it will not short to cover. But that work grate for testing.
P.S. The programmer I use for all my memory operations is Vellon VP-380. And I did a quick test reading an aged DS1225 (mine is '91 production code) without external parallel battery - and I can confirm that this universal programmer can read this old NVSRAM secure without corrupting contents.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on September 10, 2014, 03:44:22 pm
I had good results replacing the two DS1230 embedded lithium battery NVSRAMs in my 2440 with EEPROM based STK16C88s.  The STK16C88 has the advantage over the STK12C68 of not requiring an external capacitor so they were drop in replacements.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: e-pirate on September 11, 2014, 05:45:11 am
The STK12C88 is, probably, superior to STK12C68 in terms of external elements and cause it 4 times STK12C68 size, so using just a some jumpers we can get 4 storage banks. Yah, that grate! But unfortunately, I have no available this ICs on easy :(
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: iDevice on September 11, 2014, 09:04:12 pm
I have no available this ICs on easy :(
Really ?
http://www.ebay.com/sch/i.html?_mPrRngCbx=1&_nkw=stk16c88 (http://www.ebay.com/sch/i.html?_mPrRngCbx=1&_nkw=stk16c88)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on September 12, 2014, 02:59:32 am
It looks like Cypress is discontinuing their EEPROM based NVSRAMs.  They still list them but their distributors do not have them available anymore and Cypress does not sell them directly.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: miguelvp on September 12, 2014, 03:09:21 am
And if you don't trust eBay:

http://octopart.com/partsearch#!?q=STK16C88 (http://octopart.com/partsearch#!?q=STK16C88)
http://www.findchips.com/search/STK16C88 (http://www.findchips.com/search/STK16C88)

Maybe is because you typed STK12C88 instead and that would have found nothing.

Edit: in any event, not a lot of stock left and some that have stock don't list the price. My bad, if you click on the part they show the price at the distributors site
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: e-pirate on September 12, 2014, 04:28:21 am
There are STK16C88 available at my favorite semiconductor store, but they cost 1200 RUR a piece, where STK12C68 cost 220 RUR. Should I get more expensive part only to save a cheapy cap and a couple of resistors.. nop. And unfortunately, delivery prices to Russia are almost always unreasonable, at least from EU and US. But thats a different sad story :(
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on September 29, 2014, 05:06:54 pm
It looks like Cypress is discontinuing their EEPROM based NVSRAMs.  They still list them but their distributors do not have them available anymore and Cypress does not sell them directly.

I was wrong about this.  Cypress is discontinuing EEPROM based NVSRAMs in DIP packages or at least the commercial ones in favor of surface mount packages including SOIC.  They use different part numbers for the surface mount packages because they all require an external capacitor so they are not direct replacements for JEDEC SRAMs but with a surface mount package, a DIP sized module could be produced which includes the capacitor.  Most are 3.3 volt or lower but some are 5.0 volt.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Mr Simpleton on November 12, 2014, 10:47:56 pm
Having replaced the leaking caps, cleaned the A5 board it was the big time to remove the Dallas RAM. Everything worked like charm, and I put in a quality socket for easy replacement.
Now having a new Dallas chip, I started of playing with my old ALL-07A programmer, and to my surprise it could not read/verify this chip. Odd... everytime I do access this new chip I do get a new checksum.
Lucklily the old RAM still works and sits in my "scope".

Reading about misfortunes with MiniPro programmers, what would be the way to go?? Batronix seems to have a low-cost programmer just slightly 2x the price of the MiniPro...

I am tempted to put some glue logic around an Arduino and have a one-off construction for this project. Would be fun, but not sure I have the time. Clock is ticking in my old Dallas chip  :scared:
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Precipice on November 12, 2014, 10:57:50 pm
Now having a new Dallas chip, I started of playing with my old ALL-07A programmer, and to my surprise it could not read/verify this chip. Odd... everytime I do access this new chip I do get a new checksum.

There's not an RTC in there, is there? (Sorry, checking back in this thread, I couldn't see which Dallas chip you were wrangling).
Even if not, it might be worth saving a few dumps, and seeing if there's anything interesting going on.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on November 12, 2014, 11:38:48 pm
Now having a new Dallas chip, I started of playing with my old ALL-07A programmer, and to my surprise it could not read/verify this chip. Odd... everytime I do access this new chip I do get a new checksum.

Lucklily the old RAM still works and sits in my "scope".

I had the same problem reading the Dallas NVRAMs in my old programmer which should have worked and did with the replacement memories.  I never tracked down the cause.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Mr Simpleton on November 12, 2014, 11:55:43 pm
@David
What did you end up doing then?? Give up and calibrate or managed to transfer the data to a new chip? If so what type of programmer?

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on November 13, 2014, 02:18:10 am
@David
What did you end up doing then?? Give up and calibrate or managed to transfer the data to a new chip? If so what type of programmer?

It was with a 2440 oscilloscope which has a much less onerous external calibration procedure than the 2465B so I just recalibrated it.  If it had been a 2465B, then I would have bought another inexpensive programmer that was specified to work with the NVRAMs, built something, or contacted someone with the right kind of programmer.

What was weird is that my programmer worked with the replacement parts which used a different technology but not the Dallas NVRAM parts.


Title: Re: Tektronix 2465B oscilloscope teardown
Post by: nctnico on November 13, 2014, 02:44:24 am
Probably due to solder on the pins. That doesn't go well with ZIF sockets. If you solder the original NVRAM into a socket with turned pins then you'll see the programmer reads it just fine.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on November 13, 2014, 03:54:17 am
I cannot say that is impossible however the pins were cleaned of solder and flux and the same behavior occurred with both NVRAMs.  It looked like one of the lower address lines was not being latched properly and each complete read produced slightly different results.

The programmer was ISA based but running on a considerably newer system which had an ISA bus so I suspect there was a timing issue.  The newer NVRAMs were considerably faster, 45ns versus 120ns, and worked fine.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Mr Simpleton on November 13, 2014, 01:37:31 pm
The programmer I was using, listed the 1225 as supported, and still nothing. My take is there is a speed issue. Think the simplest thing would be for me to build a duplicator.
Use a address counter some glue logic and two 28 pin sockets. Make sure that the WR-pin is strapped to high to secure no write on source. Should be simple. Only thing is I will not have the data saved on file. Never mind...
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on November 13, 2014, 04:12:54 pm
The programmer I was using, listed the 1225 as supported, and still nothing. My take is there is a speed issue. Think the simplest thing would be for me to build a duplicator.
Use a address counter some glue logic and two 28 pin sockets. Make sure that the WR-pin is strapped to high to secure no write on source. Should be simple. Only thing is I will not have the data saved on file. Never mind...

Enough people have reported problems reading old Dallas NVRAMs that there may be something else going on.  One hypothesis I have read is that the heat of soldering interacts with the module in some way to cause problems.  Maybe this only occurs when the lithium cell voltage is low.

To me this suggests that cooling or heating the NVRAM before using it in the programmer might allow recovery of the data.

I also know that there is an issue where if the internal battery backup voltage is low enough, the internal logic which protects the memory from invalid writes fails.  The data is retained in this case but the memory becomes inaccessible even with external power applied.  I do not know how this would cause problems with a programmer trying to read the contents though when the memory still works in the original circuit.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Mr Simpleton on November 13, 2014, 08:10:07 pm
What puzzles me is that my programmer (supporting 1225) failed on a brand new chip... just wanted to verify programmer operation before plug in my precious old chip!

The only thing I can come up with, except for a faulty chip, is that there are timing issues, programmer acting too fast some signals.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Howardlong on November 13, 2014, 10:07:20 pm
I sold a 2465BCT on ebay about five years ago, as I also had a TDS2024B at the time and couldn't justify having both: I was doing paid-for work in software only at the time. I sold it for pretty much the same as what I'd paid for it eight or nine years earlier.

I've regretted getting rid of that 2465 ever since. So a couple of weeks ago I picked up a 2467B with the CT option, for about thes same price as I'd paid and sold my 2465 for. I so love these scopes, it's been like catching up with a long lost friend.

Unfortunately I've been so spoilt by DSOs in the intervening period, I had to refer to w2aew on tips for using the delayed/dual timebase, I'd almost completely forgotten how to configure this on a 2465/7. Ten minutes of w2aew video beat trying to make sense of the written manuals. It's my go-to scope now, in pole position right next to an Agilent 54831D on the bench.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tymm on December 23, 2014, 03:38:00 am
Hi,

Wondering if anyone has attempted to hand-copy cal constants using the "Calibration RAM Examine" thingie in the exercisers (or has at least verified that they are stored as shown in the RAM)...

Here's the blurb (from page 6-17 of the service manual):

Code: [Select]
CALIBRATION RAM EXAMINE (Exerciser 02). This routine allows the operator to examine the contents of 256 decimal locations, 00 (Hex) through FF (Hex), in RAM. When entered, the Exerciser displays the contents of RAM location 00 (Hex) on the top line of the CRT display. One hundred and seventy calibration constants reside between addresses 01 (Hex) and AA (Hex). Calibration constants residing between 01 (Hex) and 6E (Hex) should have odd parity as explained below. The remaining locations may be of either parity. The readout display line has the following format:
AA DDDD P
The format is defined as follows:
"DDDD" is the 14-bit word stored at that location (13 bits of data and one parity bit).
"P" is a parity indicator for the data word: X indicates even parity; blank is odd parity.
Pushing the upper or lower TRIGGER MODE switch will increment or decrement the RAM address by 16 (10 Hex) respectively. Similarly, pushing the upper or lower TRIGGER SOURCE switch will increment or decrement the address by 1 respectively.

-- looks like it's time to replace the NVRAM on mine soon and hoping that a hand copy of the cal data might give a backup in case something happens during the procedure (I'm a little leery due to past experiences with data loss when moving Dallas NVRAMs from board to board; in that case I think one of the boards had residual voltage on the + rail & it was probably more user fail than IC fail... but still makes me hesitate).

best case would seem to be that those 340 bytes are just stored on the NVRAM starting at address 1 - and that if one takes a blank NVRAM and writes only those bytes, that nothing else will be required to make the scope happy (e.g. no other checksums or other data required for the scope to see that it's calibrated and work properly).
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: auato on December 23, 2014, 02:58:58 pm
Hi all.... instead I have this fault and unfortunatley I am not able to read the CRT anymore (the only evidence available is the internal self test @power-up which probably jams on test 05)

http://youtu.be/WNzYjhgLwis (http://youtu.be/WNzYjhgLwis)

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mikeselectricstuff on December 23, 2014, 03:25:17 pm
What puzzles me is that my programmer (supporting 1225) failed on a brand new chip... just wanted to verify programmer operation before plug in my precious old chip!

The only thing I can come up with, except for a faulty chip, is that there are timing issues, programmer acting too fast some signals.
I have a vague recollection that some NVRs have some sort of "factory seal" to maximise shelf life, and are activated by a special command to wake them up - could this be it?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: c4757p on December 23, 2014, 03:30:00 pm
The 1225 has this (they call it a "freshness seal" in the current datasheet (http://datasheets.maximintegrated.com/en/ds/DS1225AB-DS1225AD.pdf), which makes it sound rather like food...), but it's activated simply by the first application of power.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: peter-h on December 27, 2014, 10:04:09 pm
I have just read most of this thread, and I apologise if I have misunderstood something, but I have a 2465B (400MHz) on which all the illumination (except the CRT graticule variable illum) has just "gone funny".

Initially it all went blank when I turned on the scope today.

So e.g. I can't tell if ch1 is on

AC
GND
DC
GND
50 ohm DC

Then after about 1hr all the lights lit up, but ALL of them so I couldn't tell which of the options were selected :)

When I moved one of the buttons, it all sorted itself out and now seems to work.

I have had this scope for about 7 years and it has been perfect.

What is the likely cause? It looks like it might be temperature dependent.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: sparkybg on January 04, 2015, 12:31:16 pm
Hi,

Wondering if anyone has attempted to hand-copy cal constants using the "Calibration RAM Examine" thingie in the exercisers (or has at least verified that they are stored as shown in the RAM)...

-- looks like it's time to replace the NVRAM on mine soon and hoping that a hand copy of the cal data might give a backup in case something happens during the procedure (I'm a little leery due to past experiences with data loss when moving Dallas NVRAMs from board to board; in that case I think one of the boards had residual voltage on the + rail & it was probably more user fail than IC fail... but still makes me hesitate).

best case would seem to be that those 340 bytes are just stored on the NVRAM starting at address 1 - and that if one takes a blank NVRAM and writes only those bytes, that nothing else will be required to make the scope happy (e.g. no other checksums or other data required for the scope to see that it's calibrated and work properly).

I am planning a full recap of my 2445B next week. The parts are on their way from Farnell, and I also ordered FM18W08 to put on the A5 board. The dallas NVRAM still works on my unit, but I suspect it is a matter of time for it to fail. The date code of most of the chips inside is 1991, so I suspect my unit manufacturing date is not far from this. The serial is B062263. I bought it from one the "famous" Israeli ebay shops with readout problem. The problem was the well known cap leak on A5 which I repaired some time ago. Some 74HC chips were gone. Now I will do full restorarion and replace the DAC chip also, because I suspect it has a leakage path under it on the PCB.

Anyway, I've got EasyPro 90B programmer which has both Dallas 1225 and 1608/1808 chips in it's device list and I hope everything will be OK with programming. I will back-up the calibration data with the exercise you mentioned and the will try to find out where is it in the NVRAM.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on January 05, 2015, 11:12:39 pm
This one is for BravoV. I have the same vertical geometry problem you had [the words are too low to read]
You said that you adjusted the  vertical readout trimpot.
 I cant find this "vertical readout trimpot" in the schematics or troubleshooting. I cant even find those words in a 2445B or 2465B service manual.
Could you tell me what R number you adjusted? :)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on January 06, 2015, 11:06:54 am
This one is for BravoV. I have the same vertical geometry problem you had [the words are too low to read]
You said that you adjusted the  vertical readout trimpot.
 I cant find this "vertical readout trimpot" in the schematics or troubleshooting. I cant even find those words in a 2445B or 2465B service manual.
Could you tell me what R number you adjusted? :)

Malch, remember, I'm NOT the expert on this problem, and "maybe" my method is not the right way to fix this problem. So proceed with your own risk.

My suggestion, read the service manual, and understand what these 2 pots do. Also use a sharpie/marker to mark the current position at the pot, so if you suspect you screwed up  ??? while adjusting these pots, you can turn it back to the previous position.

The attached photo shots below should speak for it self where to find the pot, sorry, I forgot which one  :-//, but definitely one of these two, again, read and understand what are their purpose 1st before adjusting it.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on January 06, 2015, 03:37:23 pm
I just received my 2445B, Its like new. The serial number is B064xxx , so I will have to change the caps in A5 and check the rest.
The Dallas has a 1990 date. It was last calibrated in Oct 2001.
I have the downloaded manual . I looked for many hours and could not find that fault mentioned.

So thank you very much for the info. I would not have found it as there are 8 possible trim pots.  :-+

P.S. Why does everybody hide their serial numbers?
 Got the failure prone .068uf caps.
Found the manual page for screen centering. page 5-22 CAL 07
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: linux-works on January 06, 2015, 03:40:46 pm
OT: but suppose someone sees your serial and makes a fake report to some police dept that your unit was stolen.

you just posted your unit with your serial number.  its now up to you to prove you did not steal it.

why even get into that mess?  why allow bad people to try to screw you over?

so, many of us avoid it by not posting the serial's.  no reason to give serials on gear away, anyway.  what gain (to anyone) would there be?  I've already listed at least one danger.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on January 06, 2015, 04:07:21 pm
Wondering if anyone has attempted to hand-copy cal constants using the "Calibration RAM Examine" thingie in the exercisers (or has at least verified that they are stored as shown in the RAM)...
I did this with my 2465, but I took a more lazy approach.  I took a video of the screen while flipping through all the memory locations.

The 2465 has an EAROM which hasn't gone bad (maybe yet), but now I have all the cal values if it does.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tymm on January 06, 2015, 07:50:07 pm
Cool -- though do you know whether the constants can just be copied into a new IC and have it work?

I've copied down the data from mine - and think there's a good chance it would work just straightforward... though I can see lots of ways that it could be more complicated (cal data stored at an offset address in the NVRAM, secondary checksums, etc).

Looking forward to hearing from sparkybg; will probably just go ahead with mine and test whether things match if there's no confirmation by the time I'm ready to go.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on January 06, 2015, 08:29:43 pm
Cool -- though do you know whether the constants can just be copied into a new IC and have it work?
No, I don't know.   I'm assuming it's accurately reporting the word at each location.  I'll have to test reprogramming in battle.

Living on the edge?  Maybe.  But I haven't heard any tales yet of the EAROMs going bad, and I don't use the scope enough to invest the time to fix what might not be a problem.

Another thing I've done on other equipment is to use an exercise routine to cycle through NVRAM and clip on a logic analyzer to capture the bytes.  Then you *know* whether or not you have all the cal data.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on January 06, 2015, 09:24:23 pm
Watch out you dont squash or bend the two little stiff wires going to the middle of the CRT
 while trying to get the psu cards out. :P
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: sparkybg on January 09, 2015, 12:04:42 am
Done:
- Full recap of power supply - the immediate result is sharper display, better triggering, and (although I am not completely sure) faster "boot-up" after the scope is powered up. I've used Panasonic FR, low ESR Nichicon and low ESR Rubicon caps.
- Full refurbishment of A5 board. I replaced the DS1225Y NVRAM with FM18W08 FRAM. No problems whatsoever. I was able to read the contents of my original NVRAM and put them in the FRAM without any problem. The scope boots and works normally.

To do:
- Full recap of main board.
- Replacement of the only electrolytic cap in the CRT supply.
- Full calibration, if I find a place with all the equipment needed, or at least vertical calibration. All other is OK, but vertical is with 2-3%  lower amplitude than cursors say.

The calibration constants from exercise 2 are located at addresses 1E00 - 1FFF in the NVRAM. I don't know if they can be used with another dump. Maybe I will try just out of curiosity. Maybe I will able to tell which constants are for vertical calibration when I calibrate the vertical.

I will post some pictures of the process when all the tasks are done.

Update: I have just tried a 2465B S/N B05xxxx dump on my 2445B S/N B06xxxx with my original calibration constants. It works flawlessly! So, it is a good idea to backup your constats from exercise 2 before you do anything with the NVRAM chip. It can save you a calibration if something goes wrong when you try to read your NVRAM after desoldering.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on January 09, 2015, 05:16:37 am
The calibration constants from exercise 2 are located at addresses 1E00 - 1FFF in the NVRAM. I don't know if they can be used with another dump. Maybe I will try just out of curiosity. Maybe I will able to tell which constants are for vertical calibration when I calibrate the vertical.

Great info !  :-+ Please, keep us updated on your quest for calibration constants if you decided to decode it.

I will post some pictures of the process when all the tasks are done.

 :clap:
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tymm on January 09, 2015, 08:25:02 am
Update: I have just tried a 2465B S/N B05xxxx dump on my 2445B S/N B06xxxx with my original calibration constants. It works flawlessly! So, it is a good idea to backup your constats from exercise 2 before you do anything with the NVRAM chip. It can save you a calibration if something goes wrong when you try to read your NVRAM after desoldering.

Sweet -- thanks so much for testing it out and following up.  Really great to know that it works!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: sparkybg on January 09, 2015, 11:14:34 am
Just two pictures of FRAM mod for now. Enjoy.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: sparkybg on January 09, 2015, 01:30:26 pm

Malch, remember, I'm NOT the expert on this problem, and "maybe" my method is not the right way to fix this problem. So proceed with your own risk.

My suggestion, read the service manual, and understand what these 2 pots do. Also use a sharpie/marker to mark the current position at the pot, so if you suspect you screwed up  ??? while adjusting these pots, you can turn it back to the previous position.


Use these pots without any marking or so. It is pointless - they are only to center the readout vertically. They have nothing to do with the calibration, or cursors. Try them - you will see for yourself that only the readout (top and bottom text fields on the crt) will move. One of the few things in this scope that does not interfere with something else. Maybe only horizontal or vertical readout jitter will have to be readjusted, but again - you can do this also without affecting anything else.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on January 09, 2015, 02:27:56 pm
Thanks sparkyb. I am going to get at pin 7 today to add a battery to my Dallas. I,m thinking of staying with the Dallas with a big battery.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: sparkybg on January 09, 2015, 03:07:47 pm
The choice is yours of course.

But, from my point of view, the FRAM is much better solution. FM16W08 costs around 10EUR in Mouser Europe, than you need a SOIC28 to DIP28 PCB (maybe a dollar or so, from eBay for example), and you are done with this problem forever.

On the other side, no one has confirmed (nor can confirm) how long the external battery will last, considering it has a 20 years old battery connected in parallel with it. The desoldering of the old chip is the most hard work to do, and once it is done, you have completed 90% of the work anyway.

...well, I bought a ZD215 desoldering station recently, and desoldering of the old chip was a piece of cake with it. It was done in under 2 minutes with perfect result. The recapping of the PSU was also a pretty easy task using such instrument.

P.S.: Bear in mind that you absolutely HAVE to change the caps in the power supply, especially the polyester/polypropylene X/Y type ones. These are a ticking bomb waiting to explode. I had an older 2445 scope before and two of them exploded. Also, some of the electrolytic ones had 15 times bigger ESR compared to the the caps I replaced them with. You can leave the A1 board without recap, but the power supply and the A5 board are absolutely "must-do's" if you are planning to use your scope for some years.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Howardlong on January 09, 2015, 04:17:16 pm
My programmer wouldn't deal with the DS1225Y (a TL866A, it's listed, but it doesn't work), so I built my own.

It's been tested with both the DS1225Y and the RAMTRON FM18W08-SG (although only the bottom 8k bytes of the RAMTRON is used).

I built it with parts that I had in the lab, it's based on a PIC18F4550, and I breadboarded it. It's controlled from a TTL 3.3v level serial port. I used an FTDI TTL-232R-3V3, but a 5V one should work just as well. The device must be powered from 5V, it will detect a brown out and reset if the voltage falls below about 4.3V or so, this is to make sure that unexpected writes don't occur during power up/power down (control signals go Hi-Z and there are also pullups on /WE and /CE).

The NVRAM data is stored in the PIC's flash program area, so it remains in place after power down.

(http://i34.photobucket.com/albums/d123/photobucket391/P1000677_zpse17b1e65.jpg) (http://s34.photobucket.com/user/photobucket391/media/P1000677_zpse17b1e65.jpg.html)

Schematic attached (Eagle and PDF), and source code and .hex file for use MPLAB 8 IDE (compiler is XC8), although it should import into MPLAB X if that's what you prefer.

Here is how to use it:

Insert source NVRAM and power up...
Code: [Select]
1E: reset status

--- DS1225Y NVRAM copy programmer ---
Select:
  [R]ead NVRAM into PIC flash
  [V]erify NVRAM with PIC flash
  [W]rite PIC flash to NVRAM
  erase PIC [F]lash
  erase [N]VRAM
  [B]lank check PIC flash
  fill NVRAM with ran[D]om data
  fill PIC flash with rand[O]m data
  [P]rint NVRAM contents
  print PIC f[L]ash contents
  get [C]hecksums
> R

Erasing flash...
Reading 1F00
Read completed.
Verifying 1F00
Verify completed: success.

--- DS1225Y NVRAM copy programmer ---
Select:
  [R]ead NVRAM into PIC flash
  [V]erify NVRAM with PIC flash
  [W]rite PIC flash to NVRAM
  erase PIC [F]lash
  erase [N]VRAM
  [B]lank check PIC flash
  fill NVRAM with ran[D]om data
  fill PIC flash with rand[O]m data
  [P]rint NVRAM contents
  print PIC f[L]ash contents
  get [C]hecksums
> C
NVRAM checksum=0xF9AB
Flash checksum=0xF9AB

--- DS1225Y NVRAM copy programmer ---
Select:
  [R]ead NVRAM into PIC flash
  [V]erify NVRAM with PIC flash
  [W]rite PIC flash to NVRAM
  erase PIC [F]lash
  erase [N]VRAM
  [B]lank check PIC flash
  fill NVRAM with ran[D]om data
  fill PIC flash with rand[O]m data
  [P]rint NVRAM contents
  print PIC f[L]ash contents
  get [C]hecksums
>

Power down and insert new NVRAM chip, then power back up...
Code: [Select]
1E: reset status

--- DS1225Y NVRAM copy programmer ---
Select:
  [R]ead NVRAM into PIC flash
  [V]erify NVRAM with PIC flash
  [W]rite PIC flash to NVRAM
  erase PIC [F]lash
  erase [N]VRAM
  [B]lank check PIC flash
  fill NVRAM with ran[D]om data
  fill PIC flash with rand[O]m data
  [P]rint NVRAM contents
  print PIC f[L]ash contents
  get [C]hecksums
> W
Writing 1F00
Write completed.
Verifying 1F00
Verify completed: success.

--- DS1225Y NVRAM copy programmer ---
Select:
  [R]ead NVRAM into PIC flash
  [V]erify NVRAM with PIC flash
  [W]rite PIC flash to NVRAM
  erase PIC [F]lash
  erase [N]VRAM
  [B]lank check PIC flash
  fill NVRAM with ran[D]om data
  fill PIC flash with rand[O]m data
  [P]rint NVRAM contents
  print PIC f[L]ash contents
  get [C]hecksums
> C
NVRAM checksum=0xF9AB
Flash checksum=0xF9AB

--- DS1225Y NVRAM copy programmer ---
Select:
  [R]ead NVRAM into PIC flash
  [V]erify NVRAM with PIC flash
  [W]rite PIC flash to NVRAM
  erase PIC [F]lash
  erase [N]VRAM
  [B]lank check PIC flash
  fill NVRAM with ran[D]om data
  fill PIC flash with rand[O]m data
  [P]rint NVRAM contents
  print PIC f[L]ash contents
  get [C]hecksums
>

That's it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on January 09, 2015, 04:32:16 pm
I already have all the fram pieces in my watch at ebay.
I also found an earom on ebay [new] and a earom burner.$$

Removing the Dallas and soldering the socket has been done.
I dug in the epoxy and checked the Dallas battery voltage=3.45v.
So now I will copy the Dallas to my hard drive before anything else.

My idea is to add a laptop battery [connector and all] and disconnect the original battery.
If that fails or is impractable I still have the bin to burn to a new chip-Dallas or Fram.

Mouser is sending all the caps for A5 and the LVPS cards.
Two points.
 If I had to do all over again I would only buy a 24x5b with a lower serial number than 50,000 to get rid of the SMDs.
 I am replacing 3 of them, but there are still 20 to 40 of them left in the scope.[replaced the 4 axial ones too]

It is a pleasure working on this scope mostly because of the people on this thread.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: sparkybg on January 09, 2015, 06:02:26 pm
Make sure you get "W" FRAM. FM18W08 or FM16W08. These lasts 100 times longer (10E14 cycles) then devices without "W" (10E12 cycles).

I have not seen "W" devices on eBay. And, I prefer to buy from well known reseller (Farnell, Digikey, Mouser) than eBay.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on January 09, 2015, 07:31:22 pm
This pic is for anybody interested in the battery connection  under the epoxy. A strap is spot welded to a watch battery with one end going straight to pin 14.
I drilled two holes, one on each side so I could get my side cutters in to make the fatal cut.
I used a 1.2mm carbide router bit in a Dremel to do the cut.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: grumpydoc on January 09, 2015, 08:44:04 pm
Make sure you get "W" FRAM. FM18W08 or FM16W08. These lasts 100 times longer (10E14 cycles) then devices without "W" (10E12 cycles).

I have not seen "W" devices on eBay. And, I prefer to buy from well known reseller (Farnell, Digikey, Mouser) than eBay.

Are you sure - the cypress datasheets list the "W" types as "Wide voltage" - i.e 2.7 to 4.5V max. The Non "W" 5.5V max devices are rated for 4.5 to 5.5V Vcc max.

Both are rated for 1014 operations.

Or, in other words if you sequentially accessed every location in the device at maximum speed (130ns cycle time) it would take 130ns x 1014 x 32768/8 = 16k years to wear the device out.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on January 10, 2015, 02:30:57 am
@Howardlong

Thanks for sharing that !  :-+


.... 16k years to wear the device out.

Hmmm ... give it a really-really generous de-rating, say only 1% of 16K years = 160 years , ok, I'm content now.  :-DD
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: sparkybg on January 10, 2015, 02:56:57 am

Are you sure...
Yes, I am.

Both are rated for 1014 operations.
No, they aren't. Look again.

Here's FM1608 datasheet:
http://www.farnell.com/datasheets/82469.pdf (http://www.farnell.com/datasheets/82469.pdf)

And here is FM16W08 datasheet:
http://www.cypress.com/?docID=48242 (http://www.cypress.com/?docID=48242)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: grumpydoc on January 10, 2015, 10:23:05 am
No, they aren't. Look again.

Here's FM1608 datasheet:
http://www.farnell.com/datasheets/82469.pdf (http://www.farnell.com/datasheets/82469.pdf)

And here is FM16W08 datasheet:
http://www.cypress.com/?docID=48242 (http://www.cypress.com/?docID=48242)

Ah, I see your confusion

EDIT: I see mine as well - it's the newer FM1608B which is currently on the Cypress site - guess I missed that small part number change  :-\

You have compared the data sheet for a Ramtron part with the data sheet for a slightly different Cypress part and concluded that the difference in endurance is due to the slight change in part number - but failing to spot that there is at least one other difference between these parts.

The supply voltage on the FM1608 is 4.5 to 5.5V
The supply voltage on the FM16W08 is 2.7 to 5.5V

In fact if you look over all of the Cypress parts http://www.cypress.com/?id=4986&addcols=&parametric=html&filter_184=32Kb+x+8#parametric (http://www.cypress.com/?id=4986&addcols=&parametric=html&filter_184=32Kb+x+8#parametric) you will see that they are all specified as 1014 cycles, both the "W" and non "W" part numbers.

So in your example it was the manufacturer that made the difference between 1012 and 1014, however I suspect it is really process because the Ramtron data sheet is from 2007 and the Cypress one from 2014.

In fact there is a Ramtron FM16W08 which is wide supply voltage and 1014 cycles but the data sheet for that is quite recent as well (2012).

It's all moot anyway because Cypress acquired Ramtron last year.

So, yes, there are 32kx8 FRAMs with 1012 endurance and 32kx8 FRAMs with 1014 endurance, and buying the wide supply voltage FM16W08 should get you a part with the better endurance but the "W" in that part number does not denote the endurance, it denotes the extended supply voltage tolerance.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: sparkybg on January 10, 2015, 06:14:42 pm
Now, go to eBay, seek for "FM1608", and all the parts you will get will be Ramtron ones.

Then, do the same with "FM16W08", and you will again get some Ramtron devices.

Then, on the Cypress page, look for "FM1608", and you will get nothing. 16W08 is there.

So, in practice, buying FM1608 from eBay, you cannot know what exactly you are buying - a device with 10E14 or a device with 10E12 cycles. Buying 16W08 you are sure it is 10E14.

P.S: I would like to see that datasheet for 1608 with 10E14 rating. I cannot find it anywhere. Can you please give a link or upload it here?

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on January 10, 2015, 06:21:27 pm
On page 3 BravoV posted this
 "Sad news, a failed to attempt to find the better replacement for the pesky Dallas DS1225Y BBSRAM, cause the F-RAM Ramtron FM1608-120 is not compatible. It was an impulse purchase thru a friend visiting abroad without checking the detail 1st, and also I was mis-leaded by info gathered from the Tektronix's Yahoo mailing list"
How come his chips didnt work but yours does?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: sparkybg on January 10, 2015, 06:29:31 pm
On page 3 BravoV posted this
 "Sad news, a failed to attempt to find the better replacement for the pesky Dallas DS1225Y BBSRAM, cause the F-RAM Ramtron FM1608-120 is not compatible. It was an impulse purchase thru a friend visiting abroad without checking the detail 1st, and also I was mis-leaded by info gathered from the Tektronix's Yahoo mailing list"
How come his chips didnt work but yours does?

The only difference between FM1608 and DS1225Y is that the FM1608 needs an impulse on CS every time the address changes in order to latch it and put the data at this address on the output. The DS1225Y does not need this - it can run with continuous CS low, and every time the address changes, the data at this address is available at the output. This is called "fast reading" or something like this. But, the 2465B processor is not using a fast reads and every time it reads or writes from/to the NVRAM it generates an impulse on CS. That's why it works.

P.S: Here is a link to the document: http://www.worldphaco.com/uploads/TEKTRONIX_2465b_OSCILLOSCOPE_CALIBRATION___REPOWERING_THE_DS1225.pdf (http://www.worldphaco.com/uploads/TEKTRONIX_2465b_OSCILLOSCOPE_CALIBRATION___REPOWERING_THE_DS1225.pdf)

From my point of view, reading this document, the FM16W08 is the best possible replacement - it just needs an SOIC28-DIP28 PCB and nothing more. The STK12C68 is another one. The read/write cycles then will be equal to powering up/downs of the scope. With 1000000 store cycles and 100 years data retention, in practice this will last forever. Although it needs a PCB with some additional parts on it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on January 10, 2015, 06:37:31 pm
But it didnt work in BravoV's case. ?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: sparkybg on January 10, 2015, 06:42:40 pm
But it didnt work in BravoV's case. ?

I don't think Bravov ever tried it. This is stated on the datasheet as the only difference between classic SRAM ind this particular FRAM.

Anyway, let him tell us what was the case, but I can confirm it works - my scope is right next to me in this moment, and works flawlessly with FM18W08 on it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on January 10, 2015, 06:56:44 pm
Thats one of the reasons I spent time putting a new battery in my Dallas. It works good by the way. It is supposed to last 26 years. :)

edit: maybe 130 years.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: grumpydoc on January 10, 2015, 08:25:08 pm
Now, go to eBay, seek for "FM1608", and all the parts you will get will be Ramtron ones.

Then, do the same with "FM16W08", and you will again get some Ramtron devices.

Then, on the Cypress page, look for "FM1608", and you will get nothing. 16W08 is there.

So, in practice, buying FM1608 from eBay, you cannot know what exactly you are buying - a device with 10E14 or a device with 10E12 cycles. Buying 16W08 you are sure it is 10E14.
I'll agree with you as far as "from eBay, you cannot know what exactly you are buying"  :)

Quote
P.S: I would like to see that datasheet for 1608 with 10E14 rating. I cannot find it anywhere. Can you please give a link or upload it here?
Now I look it's a FM1608B http://www.cypress.com/?docID=48234 (http://www.cypress.com/?docID=48234), Cypress don't currently list an FM1608, as you say.

You are correct that the FM1608 is 1012 and you are correct that buying the FM16W08 will be a higher endurance part, just that the "W" does not mean higher endurance per-se.

In fact the plain FM1608 is obsolete and the FM1608B is supposed to be the replacement - so that's the normal supply range but 10E14 endurance part - there are some notes about the differences here http://www.cypress.com/?docID=47983 (http://www.cypress.com/?docID=47983), note that the new part is not better across the board - it has higher standby current requirements and under some conditions has lower data retention.

The other reason that you are correct in practice is that I can't see anywhere with an FM1608B in stock, whereas the FM16W08 does appear to be available.

Sorry - it's splitting hairs and for that I apologize - but you know how it is (http://www.xkcd.com/386/)  >:D (actually that's a bit unfair as you weren't really wrong)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: sparkybg on January 12, 2015, 12:32:29 am
Sorry - it's splitting hairs and for that I apologize - but you know how it is (http://www.xkcd.com/386/)  >:D (actually that's a bit unfair as you weren't really wrong)
There's nothing to apologize for. :)

I just finished the vertical and trigger calibration. Finaly my 2445b is in one piece. :) I had to do a calibration generator out of old board I constructed several years ago - it had a 10 bit DAC on it, with opamps after it to give the needed 10V for calibration. I just had to add a resistor divider network. Everything is calibrated perfectly now. :) I will attach some pictures of the entire process in a day or two.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: sparkybg on January 12, 2015, 07:20:40 am
Another aspect of F-RAM programming - my programmer have 1608, 1808 and 18L08 (which is older low voltage part now obsolete). When I select either 1608 and 1808, the programmer refuses to program and read the first byte (at address 0000). I suspect this is because of 10ms "power to first access" time of the 18W08. But when I select 18L08 everything is OK. So, again the "W" part gives you the flexibility of trying more different devices in your programming software, if some of them don't work. In my case, only the 18L08 worked as it should. My programmer is EasyPro 90B, and the list of devices it supports is not updated so often.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: sparkybg on January 18, 2015, 12:00:37 pm
OK, here we go. I've decided to go one by one, and check if everything is OK after each step.

First , the PSU.

Nothing special, really. There was clear signs of electrolyte leak from some of the caps. And well known issue with the X/Y transparent caps. I've replaced them with EPCOS units.
Bear in mind that there are 3 bipolar electrolytic capacitors on one of the PCBs. They must be replaced with the same type. The only caps I did not replace are these bi-polar ones.

I've replaced most of the caps with Panasonic FR low ESR/long life units. On the last pictures there is a small comparison between the old ones and the new ones. As you can see, the capacitance is there even on the leaked ones, but the ESR is several times (between 5 and 20) higher than on the new ones.

Also you can replace all the 180uF and 250uF with 330uf 50 or 63V. I've replaces the 180uF with 270, and 250uF with 330.

The immediate result of this was clearer traces.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: sparkybg on January 18, 2015, 12:13:09 pm
Next, the A5 board.

When I bought this scope, it had some issues with the readout. Because of the leaked caps there was pretty intense corrosion on the board. Unfortunately while removing some of the caps, the pads were heavily damaged. I had to replace some of the logic chips around the upper left part of the PCB. Well, I replaced the chips and caps back then, made a good bath with isopropyl alcohol, and all was OK.

There are some missing parts on the photo, but I forgot to take a picture before I started the restoration.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: sparkybg on January 18, 2015, 12:25:10 pm
Unfortunately this was not enough. Recently the front controls began to work strangely, and the horizontal deflection of the CRT was a bit lower. When I made some measurements, the DAC reference was way out of 2.5V, and I was not able to correct it with the trimmer. There was not any reaction when I rurned the trimmer. Clearly there was a problem with it, so I decided to make a full replacement of all parts around the leakage with signs of corrosion on their legs.

The width of traces on this board is unnecessarily low, and the consequence of this is easy corrosion breaks just next to the pads the trace is connected to. So pay extra attention around the pads for broken traces. This is why I had to rotate one of the resistors. I replaced the DAC with a new one from Analog Devices.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: sparkybg on January 18, 2015, 12:26:43 pm
And, here it is after the restoration. The replaced logic chips on the left are clearly visible.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: sparkybg on January 18, 2015, 12:42:33 pm
After I confirmed that everything works, I wanted to replace the DS1225Y NVRAM. It was a matter of time for it to fall out of specification and loose all the calibration data.
I bought a ZD-915 desoldering gun some time ago and desoldering ot the DS1225Y was pretty easy task using it. There was not any problem reading it with my EasyPro 90B programmer.

I bought a FM18W08 F-RAM and SOIC28 - DIP28 PCB. The process was easy. I leaved two terminals stated "NC" in DS1225Y's datasheet unconnected to A5 board, and connected them to the address lines next to them. This is visible on the pictures. I was able to write the data from DS1225 in the FM18W08 flawlessly, and everything worked.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: sparkybg on January 18, 2015, 12:54:52 pm
Next, full recap of A1 board, and heatsink mounting on the infamous U800.

1. You have have to desolder all the connections to back BNC connectors.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: sparkybg on January 18, 2015, 12:56:42 pm
2. you have to desolder all the connections to the CRT.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: sparkybg on January 18, 2015, 12:58:07 pm
3. Remove the front bezel, disconnect all the connectors to the front panel, and to the front controls (focus/brightness/etc.)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: sparkybg on January 18, 2015, 01:01:58 pm
4. Remove the A5 board and power supply. While doing this, pay extra attention not to touch and bend the CRT termination.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: sparkybg on January 18, 2015, 01:02:53 pm
5. Disconnect the connector to the HV power supply.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: sparkybg on January 18, 2015, 01:05:37 pm
6. Remove all the screws of the front BNC connectors, remove all the screws holding the A1 board to the frame. This will also detach the delay line case from the board. You will have to desolder the delay line from the board later.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: sparkybg on January 18, 2015, 01:16:51 pm
7. Remove the A1 board. You will have to pull the A1 board up to disconnect the connectors to the HV board, and next pull tha A1 board to the back of the scope to take it out. You will have to remove the small connector on the back which prevents you to pull the board up. You will have to push a delay line a bit to the front while doing this - the back BNC connectors prevents you to do it directly. Pay extra attention while removing the A1 board - there are several things you can bend or break while doing this. Pay extra attention to the focus/astig/brightness front panel connector while doing this. The back of the board needs to be pulled up and then back to remove theA1 board.

8. Once the A1 board is out, take a picture of the delay line connections, then desolder them. This is a bit tricky - you will need a pretty powerful soldering iron in order to desolder the outer mountings of the delay line. I desoldered them with the ZD-215 desoldering gun on 400C.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: sparkybg on January 18, 2015, 01:21:30 pm
9. The rest is more or less easy - just replace the caps. Again, with desoldering gun this is a piece of cake. I've replaced all the caps with Panasonic FR and Panasonic EB.

10. Put a good heatsink to U800 chip. I've used an FPGA heatsink for this. I bought it from Farnell.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: sparkybg on January 18, 2015, 01:22:41 pm
And, here it is, up and running again, with clear and bright traces and readout. It will last some more years for sure. :)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: sparkybg on January 18, 2015, 01:30:58 pm
11. I went through all the adjustment procedures I could, considering the equipment I have. The vertical calibration of my unit always was was out of specification, so I decided to correct this also. I had a mixed signal board I made some time ago with MCU, DAC and OPAMPs on it, able to give 10V peak to peak amplitude on it's output. I made a resistor network in order to have 10V, 5V, 2V, 1V, 500mV, 200mV, 100mV 50mV and 20mV out of it. I hooked my Agilent U1272A DMM to this in order to be able to correct the amplitude for best possible accuracy. I went through the vertical and trigger adjustment procedure, and finally my vertical cursors began to show exactly what they should show. Here's my setup.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on January 18, 2015, 09:24:47 pm
Finished my U800
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on January 25, 2015, 10:10:24 pm
Well all done. Moved the cal/nocal jumper to cal and fired it up.
The 10 v was out a little [9.98 v ] and I had to fiddle with the vertical jitter pot.
Ran test all and all passed.
What is the exerciser used for ? How do you know when it is finished? How do you stop it?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: sparkybg on January 26, 2015, 12:06:23 am
Well all done. Moved the cal/nocal jumper to cal and fired it up.
The 10 v was out a little [9.98 v ] and I had to fiddle with the vertical jitter pot.
Ran test all and all passed.
What is the exerciser used for ? How do you know when it is finished? How do you stop it?

Which exerciser? Calibration constants exerciser? If yes, on every step you have an address and the contents of this address. Just make a movie of the screen while you go from the lowest to the highest address. When you reach the highest address, it will turn back to the lowest. You can exit from exerciser at any time or any step you want.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mtdoc on January 26, 2015, 12:29:13 am
Finished my U800

Nice heatsink!  I hope it doesn't stick up far enough to touch the case though.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on January 26, 2015, 12:31:58 am
Measured twice cut once!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on January 26, 2015, 12:36:43 am
sparkybg When you press t,v and slope you get a menu of calibration,test and exercise routines that are in a loop.
When I started the exerciser nothing happened. Why in the world would I make a movie of it?
Besides I dont have a movie camera.
I can exit the exerciser any time I want if I knew how to. :)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: sparkybg on January 26, 2015, 11:34:17 am
The cal/no cal jumper doesn't have to be in "cal" position for the exercise and test routines.

1. Turn the scope on.
2. Pres V, T simultaneously and then "SLOPE". You will see "DIAGNOSTIC. PUSH A/B TRIG TO EXIT" on top of screen and "ALL 00" on bottom.
3. Using "MODE" buttons, scroll to "EXER 02".
4. Push upper trigger "COUPLING" button. You will see "00 xxxx" on top of the screen where "00" is the address and "xxxx" are hexadecimal number.
5. Using upper trigger "SOURCE" button scroll from address 00 to FF address and write down the numbers. It is much easier to make a movie of the screen while you are scrolling. Every decent phone with camera can do this.
6. When you are done, press lower trigger "COUPLING" to exit exercise, and then "A/B TRIG" if you want to exit from diagnostic mode.

All this is written in the service manual, and maybe operator's manual as well.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on February 02, 2015, 08:28:52 pm
This is the best series of posts on EEVBLOG! Very informative, and interesting. My 2467B is on it's way from NYC off ebay. Cannot read SN well, but looks to be starting 05, so probably has the Dallas. Cannot quite read what is showing on the CRT either, so unknown if it has error messages. Seller did not seem to really know much. I figured out from the fuzzy rear photo that it has Option 05 TV Sync Sep, Option 06 CTT, Option 11 Probe Power. Can't wait to get it, open it, and see what's up... leaning toward the big battery option for the Dallas.

Martin
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on February 02, 2015, 08:48:04 pm
BTW...

does anyone have, or know about Option 01E? it's the Reference signal input. It was only $200 to begin with. Sounds like mostly installing a BNC jack, but don't know.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on February 02, 2015, 09:01:38 pm
It's not in my option service manual. just 01 and 01B. :)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on February 02, 2015, 10:30:57 pm
Hi,

Thanks for the reply. Yes, it was offered. maybe 1E...  anyway, shown on the original datasheet for $200.00
It's just an External Reference Clock input.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on February 02, 2015, 10:34:06 pm
Wikipedia notes 01E is for joining two scopes with one sync pulse.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Howardlong on February 03, 2015, 12:44:46 am
This is the best series of posts on EEVBLOG! Very informative, and interesting. My 2467B is on it's way from NYC off ebay. Cannot read SN well, but looks to be starting 05, so probably has the Dallas. Cannot quite read what is showing on the CRT either, so unknown if it has error messages. Seller did not seem to really know much. I figured out from the fuzzy rear photo that it has Option 05 TV Sync Sep, Option 06 CTT, Option 11 Probe Power. Can't wait to get it, open it, and see what's up... leaning toward the big battery option for the Dallas.

Martin

To wet your whistle, here's a comparison vid I took a few days ago between a 2465B and 2467B http://m.youtube.com/watch?v=ZGi1Uw8l-ac (http://m.youtube.com/watch?v=ZGi1Uw8l-ac)

CTT is nice to have, the 2467B I have has it but my 2465B doesn't. You can still measure frequency without the CTT but it isn't as accurate and it takes some time (and usually reconfigures your scope at the same time). With the CTT you can have a continuously updating frequency display shown, but not without it.

They are beautiful scopes. I use mine daily, the immediacy of operation compared to DSOs makes them such a joy to use. But no, I can't do an I2C decode with it. ;-)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Kartman on February 03, 2015, 02:29:52 am
As usual, I'm late to the party! I haven't read the extensive posts here, so please forgive me if I'm repeating stuff you already know. I have a 2465 that had some problems a few years ago. It reported a earom failure. Turned out it was the electro for the -42V rail in the power supply. I went through and did an ESR test on all the caps on that board and all but one cap was ok. I disassembled the code and found where the earom was accessed. Shouldn't be too hard to poke in some code to use a modern spi eeprom. Since I found the root cause, I had no need to do any mods.
One problem I had recently is the power switch. This looks like a standard ITT shadow part that was common years ago. Does anyone know where to source these at a reasonable cost? As in around $10-20 USD? I've just put wires across the switch for the moment and power off by pulling the plug.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on February 03, 2015, 04:22:59 am
Hi Howard,

Nice video. We have a variety of very nice scopes at work Agilent, and Tek DSO's, but I prefer working with the analog scopes. we have a 2465B in our Faraday cage, and I was checking it out. Best analog scope we have. Pretty bright, but yes, you proved the 2467B is much brighter. My eyes are not that good anymore, so I need it! Glad I chose it over the standard CRT.

Martin
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on February 03, 2015, 04:30:38 am
Wikipedia notes 01E is for joining two scopes with one sync pulse.

Hi, checked Wiki, but only found this...

Oscilloscope Options

The important oscilloscope options are:

01 - Digital Multimeter

03 - Word Recognizer Probe Pod (P6407)

05 - Video Waveform Measurement System

06 - Counter/Timer/Trigger (CTT)

09 - Counter/Timer/Trigger (CTT) with Word Recognizer (WR)

10 - GPIB Interface

11 - Probe Power

1E - External Clock

22 - Two additional Probes

1R - Prep for rack mounting kit

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on February 03, 2015, 04:32:19 am
1E - External Clock
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on February 03, 2015, 04:34:34 am
Right.

But no mention of "joining 2 scopes together"....
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on February 03, 2015, 04:44:55 am
I'm sure there are numerous uses for a Ref Clock input, and yes, one could be referencing 2 scopes to one clock signal.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on February 03, 2015, 04:51:43 am
My first Google brought up the first three here.

https://www.google.ca/search?q=1E+-+External+Clock&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a&gfe_rd=cr&ei=G1DQVKKLGpLu-QOBuoC4DQ#newwindow=1&rls=org.mozilla:en-US:official&q=TEXTRONIX+OPTION+1E+-+External+Clock (https://www.google.ca/search?q=1E+-+External+Clock&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a&gfe_rd=cr&ei=G1DQVKKLGpLu-QOBuoC4DQ#newwindow=1&rls=org.mozilla:en-US:official&q=TEXTRONIX+OPTION+1E+-+External+Clock)

But then I found this on a brochure.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on February 03, 2015, 04:57:34 am
Kartman , I'm pretty sure you have tried this: S350  260-1849-00  DPDT 4A 250V   31918   NE15/F2U103EE   ITT SCHADOW INC

The  NE15/F2U103EE   comes up on all the military surplus sites. I suppose you tried them?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on February 03, 2015, 05:35:17 am
Attached scanned brochure of the original price list of the Tektronix 2400B Series as a reference, as it has all the options details.

PS : Not sure when it was printed, as there is no date there.  :-//

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=133968;image)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on February 03, 2015, 06:15:03 am
Yup that's where I got it from.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on February 03, 2015, 04:34:10 pm
That datasheet was the initial source of my original question.  Not much detail of the 1E option.
My real question is how to wire in a BNC to accomplish it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tymm on February 05, 2015, 04:04:50 am
As usual, I'm late to the party! I haven't read the extensive posts here, so please forgive me if I'm repeating stuff you already know. I have a 2465 that had some problems a few years ago. It reported a earom failure. Turned out it was the electro for the -42V rail in the power supply. I went through and did an ESR test on all the caps on that board and all but one cap was ok. I disassembled the code and found where the earom was accessed. Shouldn't be too hard to poke in some code to use a modern spi eeprom. Since I found the root cause, I had no need to do any mods.
One problem I had recently is the power switch. This looks like a standard ITT shadow part that was common years ago. Does anyone know where to source these at a reasonable cost? As in around $10-20 USD? I've just put wires across the switch for the moment and power off by pulling the plug.

Not sure if this is what you're asking about, but I was able to get a replacement switch cover (the flip dot like thing that goes over the switch) from Sphere Research a few years ago.  Don't remember the cost, but I think it was in that range.  They may also have the switches themselves.

http://www.sphere.bc.ca (http://www.sphere.bc.ca)

They're great.

In some cases I've found that I needed to email them when looking for a specific part that I couldn't find on their site, but they've always been super helpful and pleasant to deal with.

** edit ** oops reread original post; you are talking specifically about the switch itself.  Still would suggest checking Sphere.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on February 16, 2015, 04:40:20 am
The time out on the CRT brightness on my 2467B seems to be 30secs according to the screen. Is this normal? Pretty silly having to turn a knob every 30 secs to keep the display on!!!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: EV on February 16, 2015, 06:05:08 am
The time out on the CRT brightness on my 2467B seems to be 30secs according to the screen. Is this normal? Pretty silly having to turn a knob every 30 secs to keep the display on!!!

Is it same time if you adjust the trace darker?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on February 16, 2015, 04:01:23 pm
The time out is a normal feature I think on the 2467B, just not sure if 30 secs is the default, and if that can be changed. No, it makes no difference on the intensity setting, still 30 secs  countdown, no matter what. I'm sure it saves burns, but quite annoying!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Howardlong on February 16, 2015, 06:26:57 pm
The time out is a normal feature I think on the 2467B, just not sure if 30 secs is the default, and if that can be changed. No, it makes no difference on the intensity setting, still 30 secs  countdown, no matter what. I'm sure it saves burns, but quite annoying!
There are two timeouts, one to dimming and the other to "shutdown" (as far as I cans see this is just a sleep mode, the scope comes back immediately when you hit a button).

The first timeout to dimming on my example seems a little random, but ranges from about 75s to well over three minutes, I don't know the algorithm it uses, or maybe it's just age!

The second timer, to shutdown, is about 3 minutes.

I usually just hit Beam Find as the benign way to get the display back again, and while it's a minor irritation you do get used to it. I have the timer turned on permanently, it's the EXER 09 setting.

Here's an OCR'd copy of the manual that has the relevant sections https://onedrive.live.com/redir?resid=2EDA80327053C74D!22445&authkey=!ABOYAYHimQYnnAs&ithint=file%2cpdf
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on February 16, 2015, 11:21:03 pm
Thank You Howard!     :-+

I have been looking for this , but could not find! It's exactly what I need!

Martin
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on February 16, 2015, 11:33:51 pm
Howard,

Do you know much about the differential aging feature? I was certain the CRT had light burn spots, (could see them in a flooded screen) but after reading the manual section on differential aging it sounds like I am just getting less beam amplification in those areas. Does that sound right?

Martin
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Howardlong on February 19, 2015, 11:57:16 pm
Sorry, I am no expert, if Alan w2aew comes by I am sure he will be able to answer far better than I can.

What does happen is that the readout text ever so slightly dances around the CRT, a pixel or two horizontally and vertically, at certain times, and it is by design. Unless I'd read about it in the manual, I probably wouldn't have noticed it to think anything much about it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: w2aew on February 20, 2015, 11:04:57 pm
Sorry, I am no expert, if Alan w2aew comes by I am sure he will be able to answer far better than I can.

What does happen is that the readout text ever so slightly dances around the CRT, a pixel or two horizontally and vertically, at certain times, and it is by design. Unless I'd read about it in the manual, I probably wouldn't have noticed it to think anything much about it.

In my experience with the "non-B" 2467, and the 7104 mainframe that had the same microchannel plate CRT - the shutdown timer was most definitely proportional to the intensity that was dialed in.  It would range from less than 1 minute for high intensity settings, and more than 10 minutes when the intensity was dialed down to a somewhat dim value.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on February 21, 2015, 04:22:00 am
OK. so it was really, really messed up!!!

Display kept getting dimmer, and dimmer, and then got to the point that no matter what I did I could not get ANY display at all! I started worrying the CRT was failing, and died. But no! Did NOT adjust the CRT bias or touch anything in the CRT ckt. at all.

I checked all the PS DC voltages. Spot on. Then tried to adjust the DAC per the adjustment section in the svc man. It would not adjust to the 2.5 volt total range, and kept getting worse, and worse! Studied that bridge ckt. with the adjust pot, found R2013 10k COMPLETELY open. There was a small amount of electrolyte leakage from the caps, but this area looked perfect! No idea why that resistor would open!

So to my surprise this fixed not only all the brightness issues, but also many other problems that I was certain were going to require a complete CAL. NOT SO!!!  DAC adjusted just fine. Everything seems to be working now!!! Previously amplitude, and Freq measurements were pretty far off. I'm so pleased to get this baby runnin' like it should be. About $300 and a little troubleshooting. Yippeee!

Thank you all so much for your support, and guidance. Reassuring to get informative replies. Thanks!

Martin
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on February 21, 2015, 06:04:41 am
Good job Martin, your perseverance paid off.
Yep I often wonder why silly little things like a 10K resistor fails too.
Maybe its age or a crook one from new, probably why you ended up with it.

You learnt a lot and that will stand you in good stead to keep her running until you decide to get a new DSO.   ;)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on February 21, 2015, 06:45:11 am
Hi,

Thanks!

yeah, I use those DSO thingies at work sometimes, and I do have a Tek THS-720A here too, but I still prefer the analogs!!!
I guess you get so used to that warm green glow after so many years, that everything else seems cold by comparison :)

So fixing the 2467B was the good thing that happened today. The other thing that happened, was I found out I need an angiogram, maybe a stent, or even bypass surgery.
Maybe it's a really good thing... I might live to use the damn thing! :)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on February 21, 2015, 08:10:12 am
The other thing that happened, was I found out I need an angiogram, maybe a stent, or even bypass surgery.
Maybe it's a really good thing... I might live to use the damn thing! :)
Well at least the stress of the Tek has passed now.
But you need to know: old CRO's will do that to you.  :-DD

Good luck with the angiogram and stuff.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on February 21, 2015, 04:07:03 pm
Studied that bridge ckt. with the adjust pot, found R2013 10k COMPLETELY open. There was a small amount of electrolyte leakage from the caps, but this area looked perfect! No idea why that resistor would open!

Great to hear the happy ending.  :-+

Martin, any chance you haven't throw away that resistor, please, shoot a close up and post it here.

Who knows, probably this will help someone in the future.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on February 21, 2015, 04:20:15 pm
Yes, I saved it, and taking it to work to look under the microscope at it. I'll try to get some photos of that. The only thing I thought I noticed was a bit darker colorization of the red coating on top of the resistor. Maybe there was some electrolyte that seeped in, dried, and no evidence on the outside of the part. I'll try to get photos as is, and then scrape/pop the top off, see what's going on inside...

I have read at least one post on here, and elsewhere, that describe the symptoms of this problem exactly. I never saw any resolution of the problem posted/detailed.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on February 21, 2015, 04:37:34 pm

In the article by H. Holden, he found the adjust pot destroyed. R2013 is one resistor away from it...

http://www.worldphaco.com/uploads/TEKTRONIX_2465b_OSCILLOSCOPE_A5_BOARD_REPAIR.pdf (http://www.worldphaco.com/uploads/TEKTRONIX_2465b_OSCILLOSCOPE_A5_BOARD_REPAIR.pdf)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on February 23, 2015, 03:04:02 pm
R2013 is in the DAC adjust bridge. Problems in the DAC ckt. can cause a myriad of problems. I had what looked like calibration errors, and a CRT dimming problem that eventually worsened to the point of no display at all. There were also several error messages at boot before the CRT was no longer visible. When I tried to do the DAC adjust procedure, it would not adjust properly.

Here are some photos of what I found with R2013. When I cleaned the top with IPA, the coating easily flaked off in one area. Underneath the traces were corroded apart. The resistor appeared very normal on the outside mounted in the board. Hope this helps someone.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on February 24, 2015, 02:21:46 am
Martin, thanks for sharing those really nice macro shots of the dale smd resistor.  :clap:

I can't see clearly the resistor coating color as its quite dark, is it dark brown like below example shot of mine ?

The R2013 I have is the dark brown colored without any printed label on top of it.

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=138431;image)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on February 24, 2015, 02:52:09 am
Yes, I just looked at the board again. Those 3 resistors in a row
(ending in R2013) are darker, and do not have values printed on them. so really, there was no outward indication this part had failed at all. The creeping electrolyte went in, and left no trace on the outside. All those resistors need to be measured if you suspect a problem (no DAC adjust/out of range) in that vicinity.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on February 24, 2015, 03:04:16 am
Thanks, and your experience is an important lesson, that the cap's leaked electrolyte can affect the SMD's coating, not only pcb traces.

Noted !  :-+

Once the cap's electrolyte leaked, and even the surrounding resistors or other components that still look perfectly good, we will have to assume that they already corroded or starting to corrode the metal inside.  :palm:
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mskobier on February 28, 2015, 12:12:11 am
sparkybg,
    I have a 2445B I recently acquired that I am in the process of repairing (channel 1 trace dead). Once I get that sorted out, I plan on doing the capacitor change out on the PS and A5 boards (no indication of leakage at this time). Since I will already have the A5 board out, I plan on also removing the Dallas chip, and replacing it with the Fram FM16W08 chip and adapter board. I have made a video of the current EXER 02 settings (thanks for the idea Markl) since it is probable that I will loose the settings (25 year old battery). Back in mid Jan  in this thread you discussed doing some NVRAM programming using the FRAM chips, and I have been reading that info with much interest. I also have a programmer that will work with both the Dallas chips and the FRAM chips. I have already downloaded a copy of the bin file for a 2465B and have been examining the file structure and information contained in the file using the program that came with my programmer. Your posts back then showed the calibration info from the 2465B would work in a 2445B with the appropriate data modified. I have programmed a couple of chips in my day (20 years ago), but I am having some difficulty in understanding how the EXER 02 data correlates to the HEX data in the downloaded file. Is it possible that you could give me a brief explanation on how the two data sets compare. Thanks in advance for any assistance.

Mitch

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: sparkybg on February 28, 2015, 03:23:40 pm
sparkybg,
    I have a 2445B I recently acquired that I am in the process of repairing (channel 1 trace dead). Once I get that sorted out, I plan on doing the capacitor change out on the PS and A5 boards (no indication of leakage at this time). Since I will already have the A5 board out, I plan on also removing the Dallas chip, and replacing it with the Fram FM16W08 chip and adapter board. I have made a video of the current EXER 02 settings (thanks for the idea Markl) since it is probable that I will loose the settings (25 year old battery). Back in mid Jan  in this thread you discussed doing some NVRAM programming using the FRAM chips, and I have been reading that info with much interest. I also have a programmer that will work with both the Dallas chips and the FRAM chips. I have already downloaded a copy of the bin file for a 2465B and have been examining the file structure and information contained in the file using the program that came with my programmer. Your posts back then showed the calibration info from the 2465B would work in a 2445B with the appropriate data modified. I have programmed a couple of chips in my day (20 years ago), but I am having some difficulty in understanding how the EXER 02 data correlates to the HEX data in the downloaded file. Is it possible that you could give me a brief explanation on how the two data sets compare. Thanks in advance for any assistance.

Mitch

Here I already explained it:
The calibration constants from exercise 2 are located at addresses 1E00 - 1FFF in the NVRAM.

This means that if you see "12BC - 00" this means the word at address 00 is "12BC" hex. This is stored on chip at address 1E00. So on address 1E00 on the chip you will have 12 hex, than on address 1E01 you will have BC hex. Than, if you got "3456 - 01" on the screen, this is stored as 34 hex on address 1E02 and 56 hex on address 1E03. And so on...

My chip was nearly as old as yours, and in the last 6-7 years it maybe had less than a hour per month  working time. Hope for the best - maybe you will be able to read it and program it to the new chip flawlessly, just as I did.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on March 01, 2015, 09:01:09 pm
Wikipedia notes 01E is for joining two scopes with one sync pulse.

Hi, checked Wiki, but only found this...

Oscilloscope Options

The important oscilloscope options are:

01 - Digital Multimeter

03 - Word Recognizer Probe Pod (P6407)

05 - Video Waveform Measurement System

06 - Counter/Timer/Trigger (CTT)

09 - Counter/Timer/Trigger (CTT) with Word Recognizer (WR)

10 - GPIB Interface

11 - Probe Power

1E - External Clock

22 - Two additional Probes

1R - Prep for rack mounting kit


While you could connect the Ref Signal to 2 scopes, as was suggested, it's not going to do much for you.
The External Reference Option 1E only works if you have Option 06 CTT, or Option 09 CTT with Word Recognizer installed in the scope.
All it does is give you one more digit, 8, instead of 7 on the CTT display, and the accuracy is determined by the stability, and precision of your Reference signal. I took a couple shots with the EXT Ref signal, (in this case a GPSDO) and a Rubidium 15mHz source for the input, and also from a Gigatronics 12720A for the (spec limit) 150mHz signal as well. You can see the 8 digit display, and increased accuracy. Quite an easy Option to install, just a BNC, and a plug for the J5990 header. :-+ Unless you have a Pre B05xxxxx Scope, then you need to install a resistor per TimB 08/12/2015

Title: Tektronix 2445B oscilloscope
Post by: ronnie_murphy on March 01, 2015, 09:32:04 pm
I have a tek 2445B scope that has the dreaded test 05 44 error which says a voltage is too positive.  Question 1, is this the right to ask this question and if so where or how do I find that voltage so I can understand why it is to high.  I checked all the voltages on the J119 IC socket and found all were within spec.  Also what on the main PCB would cause such an error.   :)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on March 01, 2015, 09:58:53 pm
According to the trouble chart 05 44 fail, you need to check U500 pin28. if you are triggering on an input signal, or doing line triggering, you should have 425 mV there. Check that first.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mskobier on March 02, 2015, 01:21:43 am
sparkybg, I sent you a private message.

Mitch
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: siggi on March 02, 2015, 01:26:53 am

I have a tek 2445B scope that has the dreaded test 05 44 error which says a voltage is too positive.  Question 1, is this the right to ask this question and if so where or how do I find that voltage so I can understand why it is to high.  I checked all the voltages on the J119 IC socket and found all were within spec.  Also what on the main PCB would cause such an error.   :)

This is often due to trouble on he A5 board, in the DAC machinery. The most common fault is leakage from SMD capacitors on that board.
You may want to join the TekScopes yahoo forum, there are good resources there in the archives.


Sent from my iPad using Tapatalk
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on March 02, 2015, 01:52:52 am
I'd agree with that assessment, having seen what happens with problems from unseen corrosion in the DAC adjustment bridge circuitry.
The DAC sets up quite a few voltages, and mine had several problems all exhibiting at once, then the CRT display died altogether.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: ronnie_murphy on March 02, 2015, 05:47:24 am
Thanks for your quick response.   :-+
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Kartman on March 06, 2015, 07:09:24 am
Thanks for the responses. Stupid me didn't realise tektronix have the part numbers in the service manuals!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mskobier on March 08, 2015, 09:10:27 pm
Well, I went and did it now!  While waiting on components to arrive for the 2445B I found in the salvage yard a few weekends ago, I attended the Puyallup, WA hamfest/electronics swap yesterday. While I was there, I stumbled upon a guy that had two non working 2465's. One is a plain 2465, and the other is a 2456CTS. I was able to acquire them both for a very small sum of money. I purchased them mostly for parts, but I may end up repairing at least one of them. I plugged them in and ran a few tests. the first one has no trace, not even with the beam find button pressed. The second one does not have a trace either, but it does display a trace when I press the beam find. Various panel lights light up on both machines. The previous owner had removed the cases and lost the screws, but all the major parts are there. I figure I can find some 4-40 screws to put them back together again. Looks like a power supply recap on at least one of them, and we will see where the other leads me. Not that I need two more scopes, but I just could not pass them up.

The information I have found and things I have learned will be very useful for getting them back on line. So a big hearty thanks to everyone.

Mitch

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mskobier on March 12, 2015, 03:05:51 am
All,
  The repairs on my 2445B is progressing. The parts to repair the broken plastic nobs on the front arrived today. Got that all squared away, now just waiting on some electronic parts to make sure the A5 board doesn't take a dump on me while sorting out the channel 1 trace issue. Stillwaiting on the caps and a few other components to arrive.

I should have read more posts before ordering the replacement NVRAM chips. I had already ordered a couple of DS1225AD-200's and Ramtron FM1608 chips from a couple of sellers on -bay. Yes they were located in China before I read the post earlier in this thread about China sourced chips being counterfeit and not working, After I read the post, I ordered a DS1225AD-20o from Mouser. The china chips and the one from Mouser have arrived and been tested. I have access to two different programmers, a Sivava Willen and a TL866. None of the chips from china will program. The chip from Mouser works just fine with no problems at all. The DS1225 chips from china are dated 1317. So they should have been relatively fresh stock. Apparently not. The FM1608's would not program either. I have a couple of them coming from Mouser now too. In an effort not to kill my original programming, I have ordered the same programmer that sparkybg used. I had not planned on ordering the programmer, but a friend of mine has a 2465B that still has the original chip in it too. When I swap mine over, we are going to do his too. Hopefully the better programmer will work without any problems.

If anyone needs any front panel parts, knobs, shafts, indicators, etc, drop me a line. I'll see what I can do.

Later
Mitch
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: monz on March 13, 2015, 12:36:32 am
This pdf contains info on power supply rebuild and gives specific replacement part numbers for the input filter caps. Mine were cracked like this too. He used Vishay type KP339, digikey has them in stock part number BC2586-ND

http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf (http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mskobier on March 13, 2015, 12:51:57 am
Monz,
    Thanks for the reply. I had already found that article. It definitely is a good tutorial on repairing the power supply.


All, Im going to move my posting over to the Repair section under a different thread so I am not hijacking this one.

Thanks
Mitch
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on March 13, 2015, 01:13:35 am
All, Im going to move my posting over to the Repair section under a different thread so I am not hijacking this one.

Mitch, I was going to ask you to share all the repair photos here, and I don't have any problem at all if you post them all here rather to have these 24xxB related infos scatter around.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mskobier on March 14, 2015, 04:25:30 pm
With BravoV's gracious request, I will post the pictures in this thread. Unlike BravoV's teardown, mine should be fairly simple. However, there were a few mechanical repairs I had to make before I attack the electronic ones. Here are some pictures showing the main panel damage after I cleaned it up. Then the teardown showing the sub assembly damage, and finally how it looks now.

The case had a number of dents too. I was able to mostly straighten them out, but the two 2465's I picked up last weekend provided me a very nice case.

I replaced the entire potentiometer sub assembly. It was easier to just replace it than to unsolder and remove the potentiometers from the ribbon strip it was attached to. Less risk of damaging the ribbon

The last picture shows the three extension shafts. The one on the right is broken and should be about 1in (25mm) longer. The parts board I picked up provided the replacement shaft and missing knobs.

I also attached some pictures of the A5 board. Looks like either I have a little bit of leakage, or the ceramic capacitor next to the caps has already been replace and I'm seeing flux residue. Either way, I'll remove the cap, clean around it and replace. This will also be the time when I remove the Dallas chip, and hopefully be able to copy the calibration data file. I've also been having some fun finding the replacement tantalum caps to replace the electrolytic. The caps on my A5 board show 10uf 35v and 33uf at 35v. The manual specs them out as 15uf 25v and 45uf 25v. I'll probably go with what the latest manual calls for, 15uf and 45uf. However, finding the 45uf in a C size form factor has been interesting. Kemet doesn't seem to make one. Will have to try a different manufacturer.

Enjoy
Mitch

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SeanB on March 14, 2015, 04:49:49 pm
47uF is as close as you can get to 45uF, and will work. Nice job on the repair, I wish I could find one locally that is not either close to new price or just a stop short of the crusher.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mskobier on March 14, 2015, 04:59:14 pm
SeanB,
      Actually, it is a 47, the 45 was a typo. I can find them in D size all day, but C size to fit the board is more difficult. I literally found this scope in the crush pile at the local metal salvage yard. Along with a HP 45601A that works great and two frequency counters, a Fluke 7220A and a BK Precision 1856C. Both of the frequency counters work too, they just need a good calibration.

Also, here is a picture of the potentiometer board ribbon connector. I chose not to unsolder the broken pot, and just replace the entire sub assembly.

Mitch
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mskobier on March 14, 2015, 10:45:56 pm
SUCCESS!!!!
Today, I was able to remove the Dallas chip from my A5 board and read the calibration data to a file! Then I promptly wrote it to the new Dallas chip and everything worked fine. What a relief! The original chip in my 2445B has a date code of 9026. That is a 25 year old battery That was still working. Anyway, as soon as the caps and IC socket arrive, I'll put it all back together and start the channel 1 diagnostics. I was hesitant to spend a lot of time of fixing that issue until I was sure I would not loos the calibration info in the Dallas since I lack the necessary equipment to perform a recalibration.

On a side note, I was able to read the chip with both the MiniPro TL866 and the EasyPro 90B. One strange thing about using the 90B. I was doing some experiments when I first got it and the new Dallas chip. I would program one of the bin files I have downloaded, and it would say everything was programmed correctly. When I would run a verification of the data on the chip, it would have two errors. Always in location 000000 and 000040. So I read my original chip in both programmers, and the data came out exactly the same. I could program the chip with the TL866, and it would program perfectly. I could read the chip in the 90B, and it would be correct. Strange to say the least. Anyway, I have a couple of copies of the data on two different computers and burned to a CD, as well as programmed on the new Dallas chip. I will be programming it to one of the FM1608 chips for safe keeping too. I know it is probably overkill for a scope that is 25 years old, but I don't want to take any chances. Of course, if I had lost the cal data, I would have been forced to pick up even more test gear. Hummm.......

Mitch

Here is the calibration file from my 2445B if anyone wants it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on March 14, 2015, 11:06:28 pm
When I removed the Dallas chip I read and stored it.
Then I cut out the little battery and wired in a large battery. I read and stored that too.
I then compared the info between the first and second read with Beyond Compare.
In handling the chip so much to gain access to the battery some info was lost- about 10 lines.
After everything was done I burnt it to the first reading and it was successful.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: cutemonster on March 15, 2015, 09:10:03 am
I'm trying to replace Channel 1 BNC because it's loose and not usable.  Can you provide guide on how to replace it?
I have a 2465A.  Is the part easy to buy online?

thanks!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mskobier on March 15, 2015, 01:16:05 pm
cutemonster,
      I'm fairly new to tek scope repair myself. Been learning a lot. I think the BNC is part of the attenuator module. I also think you have to remove the module to get to the BNC. I have a module on order, it should be here in a few days. When it gets here, Ill take a look to see what it takes. I do not know if you have to remove the A1 board to get the module out. Maybe BravoV can weigh in and give you better guidance.

Mitch
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on March 15, 2015, 03:02:15 pm
cutemonster try https://www.eevblog.com/forum/repair/tektronix-2445-repair/ (https://www.eevblog.com/forum/repair/tektronix-2445-repair/)

Two thirds of the way down this thread is a 2445A teardown showing the BNC connectors.
A 2445A should be close to a 2465A
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: cutemonster on March 15, 2015, 05:56:17 pm
thanks mskobier and malch.
I will try to open up and check.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mskobier on March 19, 2015, 01:41:45 am
Time for another update.

I have been working with the different versions of the replacement NVRAM chips as discussed in this thread. Here is what I have learned. When programming the DS1225AD chip with the EasyPro90B (same one sparkybg used) I had a similar issue with not writing the 000000 location and the 0000040 location. Don't have an explanation as to why, just that the error was consistent and repeatable. I ended up using The MiniPro TL866 to program it. No issues using that programmer and the DS1225AD

When programming the Ramtron FM1608, I had no problems with the 90B. The TL866 does not have that chip in it device list, and I was unable to program it.

When programming the FM16W08 (SOIC) on the adapter board, I got the same error as described by sparkybg in his post from Jan 12 2015. I kept getting the error at location 000000. All the other locations programmed fine. When I would run the verify routine, everything except 00000 took the programming correctly. I finally selected the 18L08 from the device list, I could get it to program, but when I ran the verify routine, it showed that I had errors in all locations starting at 00002000, all the way to 000017FF. Then it dawned on me that those memory addresses were outside the addresses that the FM16W08 chip has. I told the programmer to only program from 000000 to 00001FF, and ran the programming routine again. Everything worked fine then and the error at location 00000 was corrected. I tried a couple of different bin files. Everything was correct, and repeatable.

Many thanks to sparkybg for his many contributions to this thread.

Here is a picture of the ram chips I have programmed so far. Remember, when I get mine finished a friend has a 2465A that need to have the NVRAM replaced before it looses its calibration. We'll probably start on that in a couple of weeks. I also have the two 2465's. They take a different set of chips, but what I am learning will hopefully help me repair those.

I'm still waiting for the Tantalum smd capacitors to arrive so I can replace the electrolytics. Hopefully they will be here in a couple of days.

Here's the chip picture.

Mitch

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: flynwill on March 20, 2015, 04:05:01 pm
Thanks for the responses. Stupid me didn't realise tektronix have the part numbers in the service manuals!
Did you manage to find a suitable replacement for your power switch?  The switch in my 2465B is failing as well (arcing, sticking and sometimes giving of that fine odor of burning phenolic).  There are still manufactures making that form-factor of switch, but I haven't had a chance to tear the unit down, and do the necessary measurement to find a replacement.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mskobier on March 20, 2015, 05:42:20 pm
Got another question that maybe someone else has encountered. In the process of removing the leaky A5 board capacitors, I discovered that the component values on my board are significantly different than what the latest version of the service manual states they should be. On my board, I have in the C2011 position, a 33uf @10v. The manual shows a 15uf @25v. In the C2113 and C2331 position, I have 10uf @35v and the manual calls for 47uf @25v. So, has someone replaced the caps with improper values, or is there a later rev to the service manual that has different values? The manuals I have are from 1989. My scope was manufactured sometime in 1990. I recall seeing some where a picture of a board with the same values I have. So I guess the question is, which values should I use? I am strongly leaning towards using the same values that are currently installed.

I removed all of the suspect items from my board today, cleaned it up and found one pad/trace had failed. It is location R2016. I was able to install a replacement resistor using the one good pad to anchor then solder bridge to the existing trace. Other than that, everything looks great, and is ready for parts as soon as the capacitor question is resolved. I'll post before and after pictures later.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mtdoc on March 20, 2015, 05:59:38 pm
 I have seen mentions on the Yahoo Classic Tek scopes group (https://groups.yahoo.com/neo/groups/TekScopes/conversations/messages) of errors in the service manual re caps.  I don't recall exactly which ones but I'm sure if you pose the question to that group you'll get a quick response. It is a very active group.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mskobier on March 20, 2015, 06:43:31 pm
Thanks for the reply. I am a member over on the Yahoo Tek group. I should have posted my question over there too.

Mitch
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on March 20, 2015, 07:12:19 pm
I changed the caps with the free 2465B service manual like so many others.
 I haven't run that scope very much, so It's not much of a test.
There must be lots of recapped scopes out there.
Have you measured the voltage across C2011?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mskobier on March 20, 2015, 08:40:59 pm
malch,
    No, I have not measured the voltage. Currently the board is on the bench. I planned on using at least the same voltage rating as is already there. It was the capacitance rating I was concerned about.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mskobier on March 22, 2015, 06:12:17 pm
Well, I've been a bit busy this morning. The caps I have been waiting for finally arrived yesterday afternoon. This morning I installed the replacement tantalums as well as a few .1uf ceramics. Everything went well. Here are a couple of pictures showing the replaced components. I did take before pictures of the bare pads, but they did not turn out well, so they don't get posted.

I also reinstalled the A5 board, and tested all four of the replacement chips. The first one was the replacement Dallas 1225AD , the second was a DIP FM1608 and the last two were FM16W08 on SOIC to DIP adapter boards. All four chips work just fine. The scope went through its startup routine and seemed to operate normally. So at this point, I am declaring the A5 board electrolytic replacement as well as the NVRAM replacement/upgrade to be a success.

I also pulled the power supply cover and saw that I have the problematic HV capacitors. Looks like I have a power supply cap replacement coming in the near future. I had hoped that mine was late enough that it had different caps. I visually inspected the HV caps, and they do not look bad at all. No indication from what I could see of near term failure. 

I also manually ran all of the self diagnostics. Its interesting in that the scope passed all test when I run the auto routine. I noticed that it cycles through each input channel. On all but channel 1, I get a bunch of little dots on the screen while the test of that particular channel is running. However, there are no dots on the screen when channel 1 routine runs. The display says it passed though.

Anyway, here are the pictures.

Mitch
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on March 23, 2015, 09:11:01 pm
Nice JOB!!!  :-+

Mine is not nearly as neat, and professional looking.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Howardlong on March 23, 2015, 09:59:59 pm
My 2467B is starting to show a few "signs", the CTT frequency counter for example is unreliable sometimes.

It serial number <50000, being lazy I am wondering if someone has an electrolytic cap BOM they'd care to share that they've used for one of these, or indeed a 2465B for serial <50000?

Many thanks!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mskobier on March 24, 2015, 12:45:38 am
Howard,
     From what I have read, the power supplies in these 24XX series scopes are pretty much the same. With that said, here is a link to another guys webpage where he has a list with a major suppliers parts numbers that may be what you are looking for. Hopefully this helps

http://bradthx.blogspot.com/2014/01/tektronix-2445b-capacitor-replacement.html (http://bradthx.blogspot.com/2014/01/tektronix-2445b-capacitor-replacement.html)

Mitch
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on March 24, 2015, 12:51:34 am
Howardlong I sent you a PM.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mskobier on March 24, 2015, 12:52:27 am
SoundTech-LG
     Thanks for the compliment. Fortunately, I only had one trace/pad that was damaged so it made it easy to replace the suspect parts. If you look closely at the first picture, the third component above the tantalum capacitors I installed, you will see the resistor is installed just a little to the right of where it should be. That was the component that has the trace that came off during desoldering. Fortunately, there was enough of the thin trace to make a solder connection to. I put a drop of superglue at the base of the capacitor after I was done soldering to ensure it was mechanically anchored to the board. Not much trace there to hold it on the right side.

Mitch
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mskobier on March 24, 2015, 01:02:26 am
All,
    Last night while I was looking for a service manual for my Tektronix 221 battery powered scope (works great, bad battery) I stumbled upon a Tektronix Scope WIKI page that lists lots of information about Tek scopes. You can select by series, then individual model numbers within the series. Once you select a particular model, it takes you to a page where they usually have a link to manuals for the model selected. Its not 100%, but I was able to find the service manual for the 221. This is the only place where I have found the manual free online. I had not seen this page referenced in any of the posts I have read on this group. Anyway, take a look and see if its of use to you. Here's the link.

http://w140.com/tekwiki/wiki/Main_Page#2000_Series_Scopes (http://w140.com/tekwiki/wiki/Main_Page#2000_Series_Scopes)

Mitch

 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on March 24, 2015, 01:24:15 am
Howardlong I sent you a PM.
I cant make the PM work. :(
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: miguelvp on March 24, 2015, 01:35:25 am
Howardlong I sent you a PM.
I cant make the PM work. :(

It works, but by default it doesn't save the messages you send, for that you have to go to the message settings:
https://www.eevblog.com/forum/pm/?sa=settings (https://www.eevblog.com/forum/pm/?sa=settings)
and check the "Save a copy of each personal message in my sent items by default." check box

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on March 24, 2015, 01:38:58 am
I did that but didnt log out.After logging back in I have sent messages now. Thanks for the tip.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mskobier on March 26, 2015, 03:19:21 am
All,
 I was given some guidance over on the Tek Scope Yahoo group on a test to run to see if the channel 1 trace is getting a position signal from the A5 board. Basically it was to check the signal at pin 17 on the channel 1 and 2 preamps. This pin receives position control from the A5 board and varies with the position control on the front. The voltages varies the same when I adjusted the vertical position controls for both channels. So with that said, it looks like the channel 1 preamp has an issue.

So, ignoring the fact I needed to go to bed, I removed the little shield over the solder connection on the channel 1 preamp, unsoldered the connection, then removed the nuts holding the preamp to the circuit board, installed the replacement preamp, and put it all back together. Plugged it in, and turned on the power. Low and behold, I now have a channel 1 trace! It moves with the position control and everything. I hooked it up to the internal cal post, which is supposed to measure .4volts, and the display said it was .43volts. Close enough for me tonight. Anyway, It appears that I now have all four channels working.

I still have to change out the power supply caps, but that can wait until a later date. Now I just need to learn all of the capabilities of this scope, and of course, I have the two 1465's to see if I can get back into service. The fun never ends.

Mitch
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Michaela Joy on March 27, 2015, 05:28:27 pm
Hi All,
This is my first post, so I thought I'd send best wishes to everyone here. :)

@BravoV: Awesome post! Thanks for the info here, and to everyone who contributed. I just purchased a used 2465B, and am looking forward to using it for my projects.
At some point, I will try the U800 modification.

Best,
:MJ
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on March 27, 2015, 06:26:42 pm
Michaela Joy  Boy are you going to have a lot of rewarding fun! This scope is one of the most pleasing . It has full schematics and other manuals. It is easy to work on. There are many fans to ask questions. and it is powerful- just ask w2aew.

Dont worry about what the Rigol fundamentalists say, they dont know quality when they see it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Michaela Joy on March 27, 2015, 07:35:16 pm
Quote
Dont worry about what the Rigol fundamentalists say, they dont know quality when they see it.

@malch: The truth is, the 2465B was a better deal than the new digital scopes are. I don't need storage or FFT / math functions, I just need to look at signals.
As long as it functions ok, I'll be happy. I have some inexpensive probes that I'll be using until I buy the "correct" probes. The "good" probes are expensive, but worth the price. Then, I'll do the U800 mod, just to be safe. :)

:MJ
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: flynwill on March 27, 2015, 09:51:18 pm
I bought a pair of these http://www.caltestelectronics.com/ctitem/20-probe-oscilloscope-passive-voltage/CT3133RA (http://www.caltestelectronics.com/ctitem/20-probe-oscilloscope-passive-voltage/CT3133RA)

to go with my 2465 (300 MHz model) and have not been unhappy with them.  They may not be quite as accurate as the Tektronix ones, but they seem just as robust, and have all the extra bits you need.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: DC912 on March 28, 2015, 04:24:45 pm
Question Re: Dallas Chip Replacement

I recently picked up a 2465B locally, serial BO57xxx.  The scope will only be used for hobby purposes, and I know nothing about programming an IC (and would prefer not to make this scope my first experiment in programming an IC).  As a preventative measure, does it make sense to buy a pre-programmed IC (e.g., from the seller in Greece) and replace the existing chip with the pre-programmed chip or would it be better to have someone copy the info from my chip info to a new chip? What functionality/calibration information of potential significance to a hobbyist, if any, is lost by replacing the Dallas chip with a new chip pre-programmed with "basic" settings? Thanks.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Michaela Joy on March 28, 2015, 04:49:21 pm
@flynwill: Thanks for the tip. I found this on eBay. http://www.ebay.com/itm/CT2841A-Passive-Voltage-Oscilloscope-Probe-/251895651922?pt=LH_DefaultDomain_0&hash=item3aa6269e52 (http://www.ebay.com/itm/CT2841A-Passive-Voltage-Oscilloscope-Probe-/251895651922?pt=LH_DefaultDomain_0&hash=item3aa6269e52)

I'm sure that there others like it. If you wish to grab it, please do. :)
:MJ
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 28, 2015, 06:01:16 pm
Question Re: Dallas Chip Replacement

I recently picked up a 2465B locally, serial BO57xxx.  The scope will only be used for hobby purposes, and I know nothing about programming an IC (and would prefer not to make this scope my first experiment in programming an IC).  As a preventative measure, does it make sense to buy a pre-programmed IC (e.g., from the seller in Greece) and replace the existing chip with the pre-programmed chip or would it be better to have someone copy the info from my chip info to a new chip? What functionality/calibration information of potential significance to a hobbyist, if any, is lost by replacing the Dallas chip with a new chip pre-programmed with "basic" settings? Thanks.

Your chip contains calibration information specific to your scope.  You want to have a copy of that, so get someone to do it for you if that's an option.

I don't know how bad the calibration would be with a generically programmed chip, if that's what you're asking.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mskobier on March 28, 2015, 06:32:41 pm
DC912,
       You can copy down the calibration constants for your scope found by running the EXER 02 routine. Then download a copy of a bin file for your model scope. Using a bin editor, replace the portions of the downloaded file with your calibration data, then your ready when you replace the DS1225Y. That should  but you a bit of confidence you won't loose your calibration data. It's actually pretty easy to do. I'm sure you can find someone near you that can assist with programming.g the replacement chip.

Mitch
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: DC912 on March 28, 2015, 07:53:20 pm
Great. Thanks much.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on March 31, 2015, 08:30:12 pm
Question Re: Dallas Chip Replacement

I recently picked up a 2465B locally, serial BO57xxx.  The scope will only be used for hobby purposes, and I know nothing about programming an IC (and would prefer not to make this scope my first experiment in programming an IC).  As a preventative measure, does it make sense to buy a pre-programmed IC (e.g., from the seller in Greece) and replace the existing chip with the pre-programmed chip or would it be better to have someone copy the info from my chip info to a new chip? What functionality/calibration information of potential significance to a hobbyist, if any, is lost by replacing the Dallas chip with a new chip pre-programmed with "basic" settings? Thanks.

bought one a them Greek Dallas chips... don't bother. ALL I got was ??????????????????????????????????????????????????

at the bottom of the display.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: c4757p on March 31, 2015, 08:33:49 pm
That means it doesn't like the cal data. Bad checksum? Contact them, tell them you got a shit chip.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mskobier on April 01, 2015, 01:47:13 am
SoundTech-LG
    Did you ever get the Greek Dallas chip working in your scope? Did you do a full calibration, or did you just program the chip with another scopes calibration data?

I'm loving my 2445B now that I have it up and running. Looks like I may need to do a vertical section calibration, but the horizontal is dead on. I fed a 175Mhz signal into the scope, and it auto measured it perfectly. It also is accurate at lower frequencies too. Still need to get some good Tek probes to go with it. I recently purchased a couple of P6138 probes off of _bay. They should be here any day. Then the real testing can begin.

Mitch
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Michaela Joy on April 01, 2015, 02:50:58 pm
I just received my 2465B yesterday. I noticed that one of the front panel buttons was stuck. I managed to unstick it with a little bit of contact cleaner spray.
The scope seems to work well, although I think it needs to be opened and the front panel switches need to be cleaned. Cosmetically, it's in great shape. All 4 traces come up and I can see waveforms on the screen. I don't have 400 MHz probes to test it fully. I do have some inexpensive scope probes that will work fine for anything upwards of 10 MHZ.

I have a friend who has worked on His own Tektronix scopes before. He also does a lot of radio / RF work, so, I'll see what signal generators He has that will go up to 400 MHZ.
Then, we'll open it together, clean it, and see how far off the calibration is.

All in all, I'm super happy. I feel like I bought a "diamond in the rough".

:MJ
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on April 01, 2015, 02:55:26 pm
It would be a good idea to follow along with post #1 and see some possible problems.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on April 02, 2015, 07:51:53 pm
the Greek Dallas is screwy for sure because if I load on any of the .BIN files previously uploaded from this 2465 Teardown topic, it works fine with the scope (although would still need a CAL of course). Yeah, I should at least get a refund for the programming part of that Dallas.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mskobier on April 02, 2015, 08:42:46 pm
the Greek Dallas is screwy for sure because if I load on any of the .BIN files previously uploaded from this 2465 Teardown topic, it works fine with the scope (although would still need a CAL of course). Yeah, I should at least get a refund for the programming part of that Dallas.

So, as you stated, it sounds like the chip is good, just bad programming. That's too bad that the Greek programming is faulty. I was looking at contacting them for a standard cal for my 2445B while I was performing other repairs and afraid that my original Dallas chip would go flat and become unreadable. Fortunately for me, that didn't become necessary. At least you have a good chip to copy your calibration into. Do you still have the original chip, and is it still readable?

Mitch
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on April 02, 2015, 09:32:14 pm
mskobier  Have you tried this? ftp://ftp.bluefeathertech.com/electronics/testgear/Tektronix/firmware/24x5/2445B/
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mskobier on April 03, 2015, 12:46:47 am
malch,
    Yes, I am aware of that particular file. I downloaded it when I was not sure I was going to be able to save my calibration data from the DS1225 that was in my scope. Once I was able to recover my cal data, it became a moot point. The questions I was asking SoundTech-LG was to determine if he was able to salvage his cal data, and if not how he went about calibrating his scope.

I do not have access to the Tek cal fixtures. I have been studying all that I can find trying to determine what types (square wave, sine wave), amplitudes, and frequencies (1khz) I would need. To perform a vertical amp calibration on my scope. I have a Tektronix SG280 function generator that goes to 20mhz and up to 20v p-p that I can use to generate the square wave signal necessary to do some of the calibration, and a Boonton 102D that goes to 520mhz and up to 3v I can use for some of the other signals. I do not think my scope needs a full calibration, as the frequency measurements are dead on. The voltage measurements are where I am having some issues. When using the internal cal fixture, it is supposed to be exactly .4v p-p square wave. My scope measures .415v p-p. Not bad, but just a little out of spec. When I try to measure a sine wave signal, then things get a bit more interesting. Having a known RF signal of a know amplitude, the scope reads quite a bit higher than I think it should. About twice the expected value.  I still have a lot to learn about the operation of the scope. Might just be operator error. I'll figure it out eventually.

Mitch
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on April 03, 2015, 02:18:16 am
...
When I try to measure a sine wave signal, then things get a bit more interesting. Having a known RF signal of a know amplitude, the scope reads quite a bit higher than I think it should. About twice the expected value.  I still have a lot to learn about the operation of the scope. Might just be operator error. I'll figure it out eventually.

Mitch
RF and other high frequency sources are typically terminated in 50 ohms.  If it's not terminated (or loaded with a very high impedance like the scope 1M input), the amplitude will be double.

Are you using the 50ohm input coupling?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mskobier on April 03, 2015, 03:54:37 am
MarkL,
   Thanks for the reply. I tried it in both the 1meg and 50ohm inputs. At the moment, I do not remember what the differences were, it was way late and I should have been asleep. The next time I will put a 50ohm termination feed through as well as having the scope in 50 ohms to see if that makes things look better. Like I said, I still have a lot to learn about this particular scope. I do have another scope I have had for many years, but it is not nearly as much scope as the 2445B.

Mitch
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on April 03, 2015, 04:22:32 am
Hi Mitch,

You wouldn't need both the external 50 ohm and internal 50 ohm termination.  If everything is working and you did that, you would get an amplitude that's too low.

But your test is a good one since maybe your scope's internal 50 ohm termination isn't working.  You could also see how the other channel behaves.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on April 03, 2015, 04:16:02 pm
I know my suggestions are sometimes off the wall, but they are search ideas.
Have you checked out w2aew's youtube  https://www.youtube.com/watch?v=SsoAe0kMYfc (https://www.youtube.com/watch?v=SsoAe0kMYfc)  for ideas?
 and post #244 to #264 ?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mskobier on April 03, 2015, 05:48:18 pm
MarkL,
      I got a chance to play with the scope some more this morning. I fed the output of a Boonton 103D signal generator (.125mhz to 175mhz) set at 10mhz to a T connector which went to two different oscilloscopes. The 2445B and my Kenwood CS-5170. I bought the CS-5170 new in about 1996 or so. So I have a high degree of confidence in its accuracy. I set the 2445B to 50 ohms coupling, and used a 50 ohm feed through termination on the CS-5170 and compared both displays. Both scopes read exactly the same (within a couple of decimal points) in both frequency and amplitude. These readings also agreed with the expected output of the signal generator. So it looks like at least for these simple tests that the scope is working as expected. One test down and many more to go.

malch,
    I had seen that youtube clip, but had not watched all of it. Good general information on how to cal a scope.

So, using the info from post#252, I need a 1khz 50% duty cycle square wave signal at 20mv, 50mv, 0.1v, 0.2v, 0.5v, 1v, 10v. My CFG280 function generator has the ability to do all of that with the exception of the precision p-p voltages. For that, I can use my Amprobe AM-530 to measure the output voltages in RMS and multiply by 2 to get the actual p-p voltage. I believe my AM-530 will go that low. The spec sheet states the lowest range is 0-400mv. Not sure I will be able to set the lowest voltage with the level of precision necessary. I may be able to use a stepped attenuator I have (Jarrod AV-50), set the output voltage to a range that the AM-530 can read reliably, and use the stepped attenuator to drop the final voltage to a level that is appropriate. Of course, at these low levels, every connection can have a significant effect on the final input voltage. The challenges never end!

Mitch
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on April 03, 2015, 07:00:46 pm
Unfortunately lost my CAL Data as I was placing the Dallas in the TL866. The external battery wire came unsoldered and touched another pin. Dallas is ok, just F'd the Data...  :palm:
I think I have all the gear together now to do the CAL. Just need to get up one morning and spend all day, and maybe the next twiddling it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on April 03, 2015, 07:16:06 pm
Be happy you're not doing a TDSXXX
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on April 04, 2015, 01:40:29 pm
MarkL,
      I got a chance to play with the scope some more this morning. I fed the output of a Boonton 103D signal generator (.125mhz to 175mhz) set at 10mhz to a T connector which went to two different oscilloscopes. The 2445B and my Kenwood CS-5170. I bought the CS-5170 new in about 1996 or so. So I have a high degree of confidence in its accuracy. I set the 2445B to 50 ohms coupling, and used a 50 ohm feed through termination on the CS-5170 and compared both displays. Both scopes read exactly the same (within a couple of decimal points) in both frequency and amplitude. These readings also agreed with the expected output of the signal generator. So it looks like at least for these simple tests that the scope is working as expected. One test down and many more to go.
If I understand your setup, you would actually have *two* 50 ohm terminators.  One in the Tek scope and one external on the other scope.  So that would be 25 ohms because they're in parallel.

I can't find a manual for it, but the 103D is undoubtedly a 50 ohm source and its output amplitude would be calibrated assuming a 50 ohm load.  So, it's not adding up that you're seeing exactly what you expect with 25 ohms loading.  And the two scopes are also in direct parallel with eachother, so they would always display the same amplitude whether they were terminated correctly or not (not counting effects from reflections).

I guess the 103D could also have its AGC pick-off at the RF output and it might compensate for a 25 ohm load, but I think that would be unusual.  Or maybe you've already calculated for 25 ohms and that's what you mean by "expected"?

Anyway, if still in question, there's a quick check for a bad terminator.  Just turn on the 50 ohm termination on the Tek scope and use a DMM to check for 50 ohms at the scope's input BNC.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mskobier on April 04, 2015, 02:46:03 pm
MarkL,
     You are correct in regards to the miss match. What I was trying to state is that the amplitudes and wave forms were the same on both scopes. Yes the amplitude was off, but I was trying to see if the 2445B responded the same as my CS-5170, which was the case. I'll round up a 50 ohm splitter and replace the  BNC T with it. Or just run the one 50 ohm termination and see what the scope shows. I'll have to pull down one of my Boonton 92C RF Millivolt Meters and measure the output so I have a good reference. I know the output meter on the 103D is not calibrated and is out by some amount. It was originally a 75 ohm unit. After inspecting the schematic, I discovered that the only difference between it and the 50 ohm version, is that it had a 50 ohm to 75 ohm unun in line with the output. I even have a new 50 ohm meter face that I need to install then do a cal on it.

Mitch

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Howardlong on April 04, 2015, 09:30:20 pm
About a week ago I started on recapping the low voltage regulator and inverter boards in my 2467B after a few anomalies started showing up.

I would like to draw people's attention to an error on the board layout sheet fig 10-13 in the Service Manual 070-6863-01 that has C1115 and C1132 transposed on the inverter board (250uF/20V vs 10uF/160V). This took several hours to figure out, and a few burnt out parts too.

It was only while probing the underside of the caps during the fifth or sixth iteration of the fault finding flowchart (which also uses low voltage PSUs to diagnose but showed no fault) that I noticed that there was 30V on the supposed 5v unreg cap. This was after I deliberately disabled the over current protection that kept kicking in to have the lower voltage cap splutter itself unceremoniously when full AC was applied.

The symptoms are that on the low voltage tests no faults show, but on full AC the over current protection kicks in two or three times each second.

It made a two hour job into a three day event.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Howardlong on April 04, 2015, 09:51:19 pm
Looking back on it, I am wondering how I'd have figured it out without disabling the overcurrent protection and blowing the cap. Must've gone over that board checking parts visually and electrically dozens of times now.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on April 04, 2015, 10:56:58 pm
MarkL,
     You are correct in regards to the miss match. What I was trying to state is that the amplitudes and wave forms were the same on both scopes. Yes the amplitude was off, but I was trying to see if the 2445B responded the same as my CS-5170, which was the case. I'll round up a 50 ohm splitter and replace the  BNC T with it. Or just run the one 50 ohm termination and see what the scope shows. I'll have to pull down one of my Boonton 92C RF Millivolt Meters and measure the output so I have a good reference. I know the output meter on the 103D is not calibrated and is out by some amount. It was originally a 75 ohm unit. After inspecting the schematic, I discovered that the only difference between it and the 50 ohm version, is that it had a 50 ohm to 75 ohm unun in line with the output. I even have a new 50 ohm meter face that I need to install then do a cal on it.

Mitch
Hi Mitch,

Sounds like the 103D needs a little work.

My only concern was from a couple of posts back when you said you had double the amplitude when you didn't expect it.  The first thing that pops into my mind when I hear that is an unterminated connection.

I would just double check your internal 50 ohm termination on your 2445 channels with a DMM to make sure they're ok.  You might not even need internal termination for your calibration procedure, but you'll want to know at some point if they're working or not.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on April 04, 2015, 11:30:24 pm
Howardlong This is my board layout. Is it the same as yours?
C1116 is at 8B at the bottom of A3 board and C1132 is at 7.5C
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Howardlong on April 05, 2015, 12:15:29 am
Yes. That has the same error.

If you change the caps one at a time without referring to the layout diagram it isn't a problem of course. However if, like me, you removed all the caps first and then repopulated them using the layout diagram, you'll have the same problem :-(

C1114 and C1115 are the same value and voltage rating, but show as different sizes on the layout diagram if you use that as your guide.

If you look a picture such as this one from http://bradthx.blogspot.co.uk/2014/01/tektronix-2445b-capacitor-replacement.html (http://bradthx.blogspot.co.uk/2014/01/tektronix-2445b-capacitor-replacement.html) before replacing the caps, you'll also see that C1114 and C1115 look different sizes if you use the layout diagram to identify them.

(http://1.bp.blogspot.com/-b1PXd_qaBbk/UtNsdQkls4I/AAAAAAAAAqg/w-6nWUNheKY/s1600/Tektronix_2445B_power_supply.jpg)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on April 05, 2015, 12:34:19 am
In this repair the "before" pic has C1114 and C1115 different, but the "after" pic he replaced them with the same.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on April 05, 2015, 02:35:11 am
OK I couldnt stand it anymore. I took my 2445B apart and this is what I found.

C1113 and C1116 are 180uf/40v
C1114 and C1132 are 250uf/20v
C1120 and C1130 are  10uf/100v
C1115 is 10uf/160v

C1132 and C1115 are flipped in the service manual.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mskobier on April 05, 2015, 06:35:18 am

[/quote]
Hi Mitch,

Sounds like the 103D needs a little work.

My only concern was from a couple of posts back when you said you had double the amplitude when you didn't expect it.  The first thing that pops into my mind when I hear that is an unterminated connection.

I would just double check your internal 50 ohm termination on your 2445 channels with a DMM to make sure they're ok.  You might not even need internal termination for your calibration procedure, but you'll want to know at some point if they're working or not.
[/quote]

MarkL,
     You read correctly. I did some more checking, and realized I was sending a 50 ohm RF sine wave (10mhz) signal into the 1meg ohm scope input. That had things all messed up. I did some more testing this morning with the function generator set to 1khz square wave, and sampling the output with my Amprobe AM530 DMM, (which is supposed to be a true RMS meter). This signal was fed into the scope set to 50 ohm coupling. I expected to see about twice on the scope display as what I was seeing on the DMM, which is roughly what I saw. Actually the scope reading was a bit more than twice the DMM reading. Both of my scopes read very close to each other, so I think the scope reading are good, but the DMM reading may not be as accurate as I would like. Now the frequency readout on the scope appears to be very accurate. Tomorrow, I'll verify the accuracy by feeding the output of a rubidium frequency standard I have. That frequency has been verified by a frequency counter calibrated against a GPS disciplined clock a friend has. I expect the scope to be dead on from what I have seen so far. As for the amplitude readings, I'm sure its something I am doing wrong. Just need to get my head out of where the sun doesn't shine and figure it out.

Yes, the 103D does need a bit of attention. It, the 102C, the 102D, as well as most of the other pieces of equipment I have around here. That's what happens when you play with old equipment. It may not be as fancy as the new stuff, but it does work, just needs a bit more TLC. Gives me something to do in my copious amounts of free time. Spent most of today re-plumbing the toilet in the guest bathroom to make the domestic supervisor happy. I'm getting way too old to be crawling around under the house for long hours. 

Mitch
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Howardlong on April 05, 2015, 07:25:09 am
OK I couldnt stand it anymore. I took my 2445B apart and this is what I found.

C1113 and C1116 are 180uf/40v
C1114 and C1132 are 250uf/20v
C1120 and C1130 are  10uf/100v
C1115 is 10uf/160v

C1132 and C1115 are flipped in the service manual.

While I am delighted that I am not completely crazy, I really was questioning myself at times because surely this must be a known error? Perhaps it is, but I have not been able to unearth any references to it. I am sorry, but at the same time very appreciative, that you went to that trouble, you have to do a fair bit of disassembly to expose those caps.

When it finally came to putting mine back together after a few days being dismantled and a nasty dose of man flu later, it took me about four attempts to reassemble it and not have any spare screws/brackets/shields left over! After all, I had only anticipated a couple of hours for this repair.

I would imagine then that this affects 2445B, 2455B, 2465B and 2467B, all of which share that same inverter board, although I searched online and couldn't find board layout diagrams specific to all those models, I only have the service manual (including layouts etc) for the 2465B and 2467B.

Thank you once again for confirming my sanity, it is appreciated.

Edit: I guess we should be clear that they are only flipped in the board layout diagram, fig 10-13. The schematic and BOM are correct.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on April 05, 2015, 07:47:05 am
OK I couldnt stand it anymore. I took my 2445B apart and this is what I found.

C1113 and C1116 are 180uf/40v
C1114 and C1132 are 250uf/20v
C1120 and C1130 are  10uf/100v
C1115 is 10uf/160v

C1132 and C1115 are flipped in the service manual.
I would imagine then that this affects 2445B, 2455B, 2465B and 2467B, all of which share that same inverter board, although I searched online and couldn't find board layout diagrams specific to all those models, I only have the service manual (including layouts etc) for the 2465B and 2467B.

Edit: I guess we should be clear that they are only flipped in the board layout diagram, fig 10-13. The schematic and BOM are correct.
Everybody take note, make a note and stick it to your scope. Ohh shit it rhymes.  :palm:
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on April 05, 2015, 01:49:07 pm
Going through the schematic now. So the parts layout fig 10-13 should be remarked C1132 to C1115 and C1115 to C1132.


mskobier has a proper 2445B service manual. It would be handy if that manual proved to be incorrect.

I changed the fan solder point to a feed-through connector with plugs and sockets, so I can remove either the fan or LVPS without a soldering iron.
I cut out the fan punched-in area that interferes with the LVPS cards, so the cards come out in a minute.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on April 05, 2015, 04:06:44 pm
MarkL,
     You read correctly. I did some more checking, and realized I was sending a 50 ohm RF sine wave (10mhz) signal into the 1meg ohm scope input. That had things all messed up. I did some more testing this morning with the function generator set to 1khz square wave, and sampling the output with my Amprobe AM530 DMM, (which is supposed to be a true RMS meter). This signal was fed into the scope set to 50 ohm coupling. I expected to see about twice on the scope display as what I was seeing on the DMM, which is roughly what I saw. Actually the scope reading was a bit more than twice the DMM reading. Both of my scopes read very close to each other, so I think the scope reading are good, but the DMM reading may not be as accurate as I would like.
...
I think you're right.  The Amprobe AM530 spec sheet says its frequency range is only to 400Hz and it's unclear if that's a 400Hz sine wave 3dB point or the meter is good for measuring some number of harmonics past 400Hz if you're working with 400Hz AC line current.  Since you're using it to measure 1kHz, you can be suspicious of whatever reading it's giving you.  You could try 50Hz and see if they agree more closely.

The scope is going to have a better frequency response than the meter, so the fact the scope is higher doesn't surprise me. 

The 2445 has a basic amplitude accuracy of +/-2% for a 4 to 5 division signal display, and goes to +/-3% with the 50 ohm coupling on.


EDIT:  Oops "sine wave", not "since wave"....
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mskobier on April 05, 2015, 04:08:48 pm
All,
  My scope is currently fully assembled, so I could not look at the inverter board. However, I did consult my 2445B manual (also covers 2455B) and saw the same component size mismatch as shown in previous posts. I also have a copy of the service manuals for the 2445 and the 2465. Those have the diagrams with the physical size correct, but positioned slightly different. According to all three manuals I have, the parts list C1114 and C1115 as the same value. When looking at the 2445 board layout, the physical size of both C1114 and C1115 are the same, with C1132 being physically smaller. According to what I see in my manuals, C1132 is supposed to be 10uf@160v, C1115 is supposed to be 250uf@20v.

Mitch
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mskobier on April 05, 2015, 04:15:05 pm
MarkL,
      I knew it was something simple. For some reason  I was thinking the Am-530 went to 400khz, not 400hz. That would explain the discrepancies I have been seeing. I can try a lower frequency, or better yet, get a DMM that can handle higher frequencies. Any reason to get more test gear!!!

I need to go review the posts in the forum on DMM's.

Mitch
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on April 05, 2015, 05:39:49 pm
MarkL,
      I knew it was something simple. For some reason  I was thinking the Am-530 went to 400khz, not 400hz. That would explain the discrepancies I have been seeing. I can try a lower frequency, or better yet, get a DMM that can handle higher frequencies. Any reason to get more test gear!!!

I need to go review the posts in the forum on DMM's.

Mitch
Most DMMs don't go very far in RMS frequency.  Some of the best top out at a few hundred kHz.  And even then, the accuracy can be quite poor at the upper end.

Then you start getting into the realm of RF power meters, which can sink a pile of money if you like to buy test equipment.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Howardlong on April 05, 2015, 07:07:31 pm
All,
  My scope is currently fully assembled, so I could not look at the inverter board. However, I did consult my 2445B manual (also covers 2455B) and saw the same component size mismatch as shown in previous posts. I also have a copy of the service manuals for the 2445 and the 2465. Those have the diagrams with the physical size correct, but positioned slightly different. According to all three manuals I have, the parts list C1114 and C1115 as the same value. When looking at the 2445 board layout, the physical size of both C1114 and C1115 are the same, with C1132 being physically smaller. According to what I see in my manuals, C1132 is supposed to be 10uf@160v, C1115 is supposed to be 250uf@20v.

Mitch

It may be that only the "B" versions are affected judging from your layouts.

As stated before, the BOM and schematics are correct. Here are annotated uncorrected and corrected versions of fig 10-13 from service manual 070-6863-01

Uncorrected:
(http://i34.photobucket.com/albums/d123/photobucket391/2465002_zps556npulp.png) (http://s34.photobucket.com/user/photobucket391/media/2465002_zps556npulp.png.html)

Corrected:
(http://i34.photobucket.com/albums/d123/photobucket391/2465001_zpsr2x7bbbi.png) (http://s34.photobucket.com/user/photobucket391/media/2465001_zpsr2x7bbbi.png.html)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: malch on April 05, 2015, 07:17:55 pm
Yup that last pic is how my caps are laid out.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: zze110 on April 20, 2015, 10:38:25 pm
So... my 2445 power supply is dead. (Almost identical to 2465).

I went through and replaced all the electrolytic caps... no good.   I made it somewhat through the flowchart but sorta dead ended.

10 > Power Supply Troubleshooting > Audible clicking when power is applied?  YES > Current limit or startup problem > Refer to inverter procedure > Go to 11.

11 > Inverter troubleshooting Procedure > Disconnect Fan > Does supply start? NO > Fuses F1101 and F1102 open NO > Remove comb filter P232 > Connect +5V load to J303 > Does supply start NO >  Remove comb filters P233 and P234> Does supply start? "click click click RF whine from A3 inverter board"  > Check for excessive loading by regulator board shorted pass transistor or regulator IC.


I started measuring some of the resistors on the A2 regulator board.  None seem to meet spec or even close   R1334, R1331, R1332, R1358, R1357, R1354, R1355, R1352, R1353.  Most are between 20 and 70% off of marked value on the parts.  Any idea what is going on here?  How can every part on the board test bad. About 10% of the parts I measured are within 1% and perfect.

Thanks for your help!!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Howardlong on April 21, 2015, 12:31:16 am
So just to confirm, with the three combs removed (not the three pin one), running on AC, and a dummy load on the 5V, all comb voltages look reasonable on the inverter board? I assume the whine isn't too loud either, it should be fairly quiet.

I'm not going to be much help on the regulator board, but man do I know that inverter board after finally finding that documentation error!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mskobier on April 21, 2015, 12:44:41 am
zze110,

Did you measure all of the voltages on J119 as specified in Table 5-1 on page 5-3 of the manual prior to removing the power supply, and if so, what were the values?

Was the power supply dead, or is it not currently working as a results of the capacitor replacement?

Did you change out the problem prone poly caps?

Did you lift one end of each resistor before you took the resistance measurement? If not, then there is probably nothing wrong with the resistors, and you are seeing more than just the one resistor you were trying to measure. Did all of the resistors measure lower in value than expected? If so, that's probably the reason.


Sorry for all the questions, but it really helps to know what you have or have not done.

Mitch
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: zze110 on April 21, 2015, 01:01:00 am
Did you measure all of the voltages on J119 as specified in Table 5-1 on page 5-3 of the manual prior to removing the power supply, and if so, what were the values?
+10V was 0V, +84V was 1.21V... after that I gave up taking measurements.

Was the power supply dead, or is it not currently working as a results of the capacitor replacement?
Identical behavior before and after cap replacement.  It will power up once in 10 tries, the rest of the time I get the 'click click click' and nothing happens

Did you change out the problem prone poly caps?
I replaced them in the high voltage section of the regulator board.  Skipped them on the inverter board. I am getting an lcr meter so I can test the remaining caps.  I don't have another scope so my options are limited to lcr tester and dmm.  I checked the large transistors and they seemed good


Did you lift one end of each resistor before you took the resistance measurement? If not, then there is probably nothing wrong with the resistors, and you are seeing more than just the one resistor you were trying to measure. Did all of the resistors measure lower in value than expected? If so, that's probably the reason.
No, that was dumb I guess.

Sorry for all the questions, but it really helps to know what you have or have not done.
Mitch


Not sure if the voltage was OK or not on the inverter board.  I'm a bit afraid to touch this thing while plugged into the wall.  I pulled all 3 combs and it did the coil whine sound.  Pretty loud to me but I am sensitive to those frequencies.

Tomorrow I am going to replace my EMI filter on the input (leads are in really poor shape) and run the load test again.  Maybe I can get some better measurements this time.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mskobier on April 21, 2015, 01:20:31 am
zze110,
   You said you pulled the comb's, but you never said that you hooked up the test load. Did you make up a test load and did you hook it up? The inverter board needs that load for the inverter to start as stated in the manual under the test load diagram. If not try that and see what happens.

Mitch
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: zze110 on April 21, 2015, 01:28:58 am
yes, I did connect the test load as specified on the previous page.  I'm going to repeat the whole thing tomorrow.  btw this is a 1xxxxxxxx serial # scope, channel islands built (not sure if that matters in any way).

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mskobier on April 21, 2015, 02:17:34 am
zze110,
     It should not matter where it was made. I have a 2445B, a 2465 and a 2465CTS. The 2445B works great, and I am working out the bugs on the other two. the 2465 is a B01xxxxx and the 2465CTS is a B02xxxxx, so I am working with a similar vintage to yours. I have a hard copy of the 2445 and 2465 manuals, as well as electronic versions for the 2445B and 2465B series scopes. if you need a scan of anything in particular from the manual, just drop me a PM and I will do what I can.

Mitch
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: zze110 on April 23, 2015, 11:13:04 pm
Small update. I set the power supply on my bench (ESD mat 8Mohm to ground) and it started up with all the combs installed.  Observed behavior:

Pulsing fan on startup, very slow to start.  Eventually reached full speed.  Could smell something burning on the board so I looked around a bit...

On the A3 board, R1071 has a nice black burned section through the middle.  I cut the power and measured the resistance, still perfect.
Connect to that is C1072 (one of the caps I replaced).  Slightly warm after 15 seconds but not hot.  According to the PCB marks I have the cap installed the right way around... going to have to check the pcb tomorrow.

R1073 & R1069 test good.  On the part of the schematic right next to those there is a label "+12.6V"  I measured 11.5V but it was bouncing around a lot.

So, tomorrow I guess I will check out the C1072 capacitor.  It isn't shorted and seems to increase in resistance showing it is charging with a meter... and it is installed correctly according to the board.  So something tells me the board has the wrong + mark OR the capacitor is defective and they labeled the wrong lead as negative.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Howardlong on April 23, 2015, 11:51:13 pm
As I remember, I had a similar concern over that resistor in my scope. Turns out if the supply is not under enough load, it will get quite sweaty, and mine discoloured as a result. Spent a while chasing my tail on that as a result, when in fact all was working. This bit of the circuit is used as a temporary load at startup, and if there's not a load across the supplies this is what takes the hit. The 3.3uF C1072 is quite a high working voltage, 350VDC, I assume you have that?

It's quite a design that inverter board that's for sure!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: zze110 on April 24, 2015, 12:23:59 am
Yes, I replaced C1072 with a panasonic 3.3uF 450VDC.  Having the circuit bake itself isn't what I'd call a good design but oh well...
I'll poke around a bit tomorrow with the 5V dc test load installed.  See if it still starts smoking.  I just need it to work long enough to do the real test  |O
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: zze110 on April 24, 2015, 11:06:05 pm
Got the supply working stable with the 5V dc load installed.  Started walking through the regulator troubleshooting guide.

TP201 measurement: 10.00V, perfect.
P232 Pin 1 @ 5V?: No, 5.87V, way out of spec.
Check +5Vd feedback by varying R1292: Feedback working?: No.  I measure -8.7VDC on P233 pin 1 regardless of potentiometer position. -> "Repair path through U1371C and U1040"

Not sure where to look next.  I guess i'll try to look at the circuits surrounding U1371C and U1040 for a bad part.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: schofield on May 26, 2015, 02:19:52 am
NOTE: This message has been deleted by the forum moderator Simon for being against the forum rules and/or at the discretion of the moderator as being in the best interests of the forum community and the nature of the thread.
If you believe this to be in error, please contact the moderator involved.
An optional additional explanation is:
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Ridgh on July 01, 2015, 12:48:37 am
Hello ALL!
I need - as far as I know - a major help and assistance:
I've bought 2 scopes: 2465A and 2465B. I've tested them prior purchasing for about half an hour and they worked perfect.
After a while, on the 2465B, I've observed that the trace and readout are dimming after approx. half hour up to disappearing completely. I found a friend that told me to change the capacitors on PSU and I did it.
The new capacitors are on specs, but maybe it was mentioned on this forum that 2 capacitors are interchanged on Layout. After this "incident", I got no trace or readout.
The 'scope does several tests (the 4 channels, and at ADD it remains stuck. After pressing A/B Trig, the panel lamps are working and responding, there are "clicks" when they should be (compared to the A version, but nothing appears on CRT. Just after several hours it is disconnected (5-24 hours), the beam appeared, without readout.
I understood that A5 PCB has a problem, and indeed I've found several leakages from electrolytic caps. There was a lot of "salt" on the solder, and as well a 10k resistor (0.1%) burnt. I exchange then with what I had on my lab and ordered new ones that are supposed to arrive within 2-3 days. All the voltages at J119 are good. The DAC shows me that I have inputs as they should be, the microprocessor pin 40 is high (it should be), and I have a good stable clock at pin 39. The DAC has normal measurements at pin 16 and 19.
The U800 is not too hot (approx. 50*C after 20 minutes).
These are the details so far. From time to time, (long time...) the 'scope has a beam, but it surf down the screen up to ~70%. It can be moved up or down, right and left. However, if I turn it off even for a second, I can see nothing again on screen.
The recall button works, I can recall the saved configurations. The beam finder doesn't work.
I'll be more than thankful if any of the members from this forum may help or get an idea for what I am supposed to look for further.
This is the summary, and I have no idea  what to do further...
Thanks in advance,
Ridgh 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on July 15, 2015, 05:46:55 pm
I have a printed copy of the "2445/2465 Option 06 and Option 09 Counter/Timer/Trigger and Word Recognizer Service Manual", pub #070-4632-00, so I can say the service manual is not the same.
Dredging up this old thread...

I've had several requests for this manual since the 2445/2465 (plain version) CTT WR service manual doesn't seem to be out there anywhere.  I've scanned in my copy and you can pick it up here if you're interested (no index or OCR):

  http://employees.org/~markl/Tektronix_2445_2465_Opt_06_09_CTT_WR_Service.pdf (http://employees.org/~markl/Tektronix_2445_2465_Opt_06_09_CTT_WR_Service.pdf)

I've also uploaded it to http://www.ko4bb.com (http://www.ko4bb.com).  I will delete the above copy once KO4BB publishes it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on July 19, 2015, 11:27:40 pm
Speaking of CTT...

I just now finally solved this on 2467B/2465B.

I got a CTT 87 error 78 message after having the TV/CTT option board out of my scope.
I swapped it with another board from another scope. Now both scopes had the same CTT error message.
I have been pulling hair trying to figure out what I blew up/ESD etc.

Nope... just hidden under the J101/J102 cables for the options board is another connector that connects to J104. :palm: In the case of TV options, it also connects to  J100, J103, J105, J109, but the error is generated off J104 not being connected.
You can't see this connection to the bottom edge of the option board, unless you peer down under the cables going through the main board hole!!!

Quite relieved to find this. Been playing around with this for months!
Something to be aware of if you remove the CTT or TV options board on 2465B's or 2467B's.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on July 27, 2015, 06:23:30 pm
Did the CRT replacement on one of the 2467B's. Pretty straightforward. Just be careful with the neck terminals. Quite fragile. Attaching the wires back on to the neck required a small flashlight. Hard to see in there at the mainboard. Threading the cables through the shield holes is critical for lead length, so take note as you remove them. I was able to find the CRT on ebay, which is a miracle in itself, but the fact that NO SCREEN BURNS was 100% true, was amazing. the original CRT had some, not real bad at all, very usable, and only noticeable under a full screen flooding. So now I have that one as a spare, just in case...
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: timb on August 11, 2015, 10:23:54 am
Hey guys, I got a 2465B (>B04xxx serial) back in January to fix up. I had taken it apart, cleaned it, checked caps, swapped the BBSRAM, etc.

Unfortunately, I had a bunch of other pressing projects come up so I didn't get the scope back together until last week. At least, it *seems* back together... I've got a mystery part that, for the life of me, I can't figure out where it goes. I've checked the exploded diagrams in the service manual with no luck.

Any ideas?

(http://images.tapatalk-cdn.com/15/08/11/67c5781ad2e8032b08a4bdafc37b6bb0.jpg)

(http://images.tapatalk-cdn.com/15/08/11/e7b5001cd6400c0c681adae378d0262e.jpg)


Sent from my Tablet
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: timb on August 11, 2015, 11:04:46 am
Annnnd nevermind. I found it in the 2465A Options Service manual, of all places... (http://img.timb.us/emoticon/ughh.gif)

(http://images.tapatalk-cdn.com/15/08/11/af5a71840cc872cc07755cf67aa89aa9.jpg)

(http://images.tapatalk-cdn.com/15/08/11/e9132a5d2421328472bfbc5bb5050926.jpg)

Oh, if anyone needs knobs, buttons or a replacement front panel board, let me know. The overlay on my unit was trashed and I scored a deal on an entire front panel assembly, so I've got parts!

(http://images.tapatalk-cdn.com/15/08/11/ef3544c4a1501b1dc5282adb3ed4ebcc.jpg)

(http://images.tapatalk-cdn.com/15/08/11/e7b61084692df23e22b76d8dd299d564.jpg)



Sent from my Tablet
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on August 11, 2015, 07:34:01 pm
knobs, shaft extenders, and pots. How much???
Title: Tektronix 2465B oscilloscope teardown
Post by: timb on August 12, 2015, 09:11:42 pm
knobs, shaft extenders, and pots. How much???

Send me a PM and we'll figure out something. Do you want the entire board, or just the pots? (The board 100% works and has been fully cleaned with DeoxIT.)


Sent from my Tablet
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on August 13, 2015, 04:31:08 pm
Sent the PM. not seeing responses... :-/O
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: timb on August 14, 2015, 12:16:29 am
Sorry, I've been tied up all day.  I'll get to it this evening! :)


Sent from my Smartphone
Title: Tektronix 2465B oscilloscope teardown
Post by: timb on August 14, 2015, 09:46:48 am
Sent the PM. not seeing responses... :-/O

Replied!

In other news, I got my 2465B back together tonight and it lives! Originally, I had put it back together on Saturday, but when I turned it on all I got was a flashing TRIG'D light. Turns out I had put the A20 (buffer board) ROM in backwards... Doh! Of course it was fried. Luckily, I had a dump of it! (Which was the entire reason it was taken out in the first place.)

Ordered some NOS M2732A's with a 1998 date code from a US seller that got here today. Programmed one, popped it in and everything seems to work! Hurray!

My unit is a 2465B-CT with a Pre-B049999 serial. I replaced the SRAM with FRAM, which works fine. Unfortunately I lost the cal data when trying to read the SRAM with my programmer while simultaneously keeping it powered. (These low serial units used a discrete battery and SRAM chip.)

Another issue I noticed is an error 06 02, which relates to the battery voltage. Obviously, since there's no battery installed there can't be any voltage to detect! The fix ended up being pretty easy:

Remove CR2770 and replace it with a 4.7K resistor, then add a jumper wire across the former battery + and - pads. The negative battery pad goes through a 10K resistor to ground; CR2770 connects the positive battery pad to the SRAM's VCC line.

Without the diode, +5VD flows through the new 4.7K resistor, which together with the existing 10K unit create a voltage divider. This feeds about 3.4V into the battery voltage detection op-amp.

Here's before and after schematics:

(http://images.tapatalk-cdn.com/15/08/14/1aacfc94a226b957226a51e1a1f2b645.jpg)
Before

(http://images.tapatalk-cdn.com/15/08/14/625d12c770f4ec8cc42a65dcd41ab761.jpg)
After

(http://images.tapatalk-cdn.com/15/08/14/0ce30c92a3a4121e2bf4123ddeb7dd0f.jpg)
The Mod

No more error 05 on startup! (I am getting CT TEST 81 FAIL 02 and 86 FAIL 02, but after having a look at the options service manual, these are related to calibration.)

Now, to figure out what I need to calibrate the unit...


Sent from my Tablet
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on August 14, 2015, 01:44:32 pm
Those Adafruit adapters are so nice to use...

The CTT Cal is pretty painless, as the manual mentions, set the sweep to 10nSec, V/div at 200mV, and then you need to supply a 1 Volt .5uSec pulse centered about 0 Volts (no offset), and triggered externally by the timing generator set for 1uSec markers. the onscreen prompts are fairly easy to follow. I am stating all this from memory,  :-/Oso excuse any errors, corrections to follow later, if any.
The CTT Options Service manual explains it...   oh here it is...
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: ehsmeng on August 14, 2015, 07:59:47 pm
Thanks a thousand times for this teardown. It just helped me fix a moving damaged 2465a.
Title: Tektronix 2465B oscilloscope teardown
Post by: timb on August 24, 2015, 09:58:53 pm
So, over the weekend I finally got my $80 eBay Calibration Special back together and working!

(http://images.tapatalk-cdn.com/15/08/24/4798250bcc691de6ff943d3978ce1b6d.jpg)

At some point this spring I picked up a TM 503 Power Module, PG 506 Cal Gen, TG 501 Time Mark Gen and SG 503 Leveled Sinewave Generator on eBay for $80. All the units had yearly cal stickers up to 2013. At first the units were behaving erratically, which turned out to be a power supply issue. $20 in capacitors and a new bridge rectifier in the power module solved that problem. After fully disassembling and cleaning all three units, I just needed to lube some switches, reseat all the ICs, replace some 74 Series logic and now everything works perfectly. Well, except the fast rise board in the PG 506; I broke one of the BNC connectors off the board when I over-torqued the nut. I'm trying to find a suitable pair of end launch BNC connectors to replace them with.

Anyway, it's amazing what you can find on eBay with a bit of patience and some luck. Hopefully I can get my scope calibrated this week, just waiting on some attenuators now.

(http://images.tapatalk-cdn.com/15/08/24/e41b631064e7ceac40e1972ad005ef68.jpg)

(http://images.tapatalk-cdn.com/15/08/24/6b3cb61730c8ad373b892c67edf67080.jpg)

Oh, I also modded the TM 503 a bit. It was a stock unit without the rear BNC/DB-50 option; but I found out the steel frame actually has the holes for the BNCs and cutout for the DB-50, they just put a cover plate on without the holes! So, I added BNC connectors, in case I need them, and also added an IEC power connector where the DB-50 would have gone. Since the built-in push-pull switch was wonky, I opted to replace it with a bog standard toggle switch in the hole that the hard-wired power cord formerly occupied. I'm really pleased with how it came out.

(http://images.tapatalk-cdn.com/15/08/24/41a6ca769685f5936c1d984b1225bb0e.jpg)


Sent from my Tablet
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: j ferguson on September 13, 2015, 10:38:11 pm
Has anyone here actually entered calibration data recorded from the scope Exer 02 display onto a generic NVRAM file ( to correct its calibration data for your scope) and successfully used the new chip?  Part of this question involves relating data addressing on the new file as shown on a typical hex editor. 

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: timb on October 07, 2015, 06:50:40 am
Anyone have the Digi-Key parts list handy for a power supply re-cap?


Sent from my Tablet
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mtdoc on October 08, 2015, 09:56:18 am
Anyone have the Digi-Key parts list handy for a power supply re-cap?


Sent from my Tablet

Here's the file posted to the Yahoo Tek scope forum. Mouser and Newark part no.s only though.

https://dl-web.dropbox.com/get/_2465LVPS_ReCap%2C%20A1%20recap-parts.xls?_subject_uid=315056499&w=AABBEwsyvXv8-MkXuvQXylKApXyus6nBmOsuJ0r-fgUkYw
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: timb on October 08, 2015, 09:57:05 am
Sweet, that'll work. Thanks!


Sent from my Tablet
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on October 10, 2015, 01:06:46 pm
Since this has turned into a thread about Tek 24XX scopes in general I figured I'd join the fray with my recently acquired 2465 DMS. It was a business write off and  I managed to get it for free.

I've used many Tek scopes in the past but I wasn't familiar with this series. Upon power up I was greeted with a screeching fan and an error code of CT Test 81 Fail 02. I solved the fan issue with some lube on the motor shaft.  I started searching the net for manuals and found them for the mainframe as well as the options. And stumbled upon the Tek Yahoo group and joined up.

One of the first things I learned with these 24XX scopes before doing any troubleshooting is to verify all the supply voltages (This is true with any old equipment but seems to be really emphasized with this series). I was lucky in this respect. All the supply voltages are in spec and no caps have been changed. But I know the day will come where I'll have to pull the supply and inverter boards and re-cap them. That won't be an easy task with this fully optioned 2465 DMS.

CT Test 81 Fail 02 is a calibration fail with the Counter/Trigger option. According to the manual a Tek PG 502 Pulse Generator and a Tek TG 501 Time Mark Generator are required for calibration. I'm just a hobbyist and I don't have this equipment. But I do have a Heathkit IG-4244 Oscilloscope Calibrator that is capable of generating a very precise 1 MHZ square wave. With the help of the Yahoo group, a BNC tee, a 2X attenuator, and a DC supply to insure proper offset the Buffer board accepted the signal and performed a successful cal and cleared the error. See 1 MHZ photo.

After clearing the CT fail the scope passed all kernel and confidence tests, at least for a while. It is now getting a BU Test F1 Fail 10 on an intermittent basis which is a buffer board EAROM checksum fail. I need to investigate this further but the consensus is leaning towards a bad EAROM chip. For now I'm bypassing the error and the mainframe and counter appear to be working properly. See BU fail photo.

The DMM option is a total train wreck. The DCV spec'ed accuracy is 0.03%. Not even close. Example: with my 1.000 VDC standard it reads 0.9886 V on autorange. If I go up one range it reads 1.000 V. The kernel/confidence tests do not check the DMM cal directly other than basic functions. The service manual states to perform a cal if you suspect an issue. I did do some extensive resistance checking of the input networks just in case something was fried and found nothing. Proper calibration of the DMM option requires a Fluke 5101 with calibration constants ranging from .19 V to 450 V. As I stated before I'm just a hobbyist and there is no way I'm going to be able to get a Fluke 5101. I don't really consider this function important anyway since I have a Fluke 87 and a Fluke 8021B that take care of my needs. See DMM1 and 2 photos.

The A5 Control Board in a 2465 is pin thru hole, not SMD as in 2465A and B. It is not as prone to damage from leaking caps as many have discovered with the SMD board. Also, the 2465 uses EAROM's to store it's cal data and doesn't require a battery. See A5 photo.

The DMM board swings over or can be completely removed to gain access to the buffer board and supply/invertor boards. See DMM board photos.

Thanks for reading. Input/comments always welcome.   

                 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: j ferguson on October 10, 2015, 08:00:53 pm
Has anyone here actually entered calibration data recorded from the scope Exer 02 display onto a generic NVRAM file ( to correct its calibration data for your scope) and successfully used the new chip?  Part of this question involves relating data addressing on the new file as shown on a typical hex editor.

Sparky was kind enough to share both a dump of the NVRAM on his 2445b and a video of the EXER (02) output taken from the screen prior to removal of the old Dallas NVRAM.  I stepped through the display a word at a time and copied down all 256 of the "words".  He was right, each word is comprised of two characters and the first one at 00h address in the EXER (02) sequence is written to 001Eh on the chip itself, second character to 001Fh and so forth. 

The data on his video and the data in the NVRAM dump starting at 001E agreed exactly.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: timb on October 11, 2015, 01:12:17 am
If anyone in the VA/NC area needs a scope cal, I've got a calibrated PG506, SG503 and TG501 to do it with. You just need to bring your scope over.

You know, I wonder if it would be possible to take the main A1 board out of a 2465X, put it in another scope, do the cal and then move the board and NVRAM back to the original scope. That should work, right? As all the analog stuff is there. If so, that could make it a lot easier for people without the equipment to get their unit calibrated, as you wouldn't need to ship the whole scope back and forth, just the main board. Hmmm.


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Title: Re: Tektronix 2465B oscilloscope teardown
Post by: soren on October 11, 2015, 01:58:41 am
You know, I wonder if it would be possible to take the main A1 board out of a 2465X, put it in another scope, do the cal and then move the board and NVRAM back to the original scope. That should work, right? As all the analog stuff is there. If so, that could make it a lot easier for people without the equipment to get their unit calibrated, as you wouldn't need to ship the whole scope back and forth, just the main board. Hmmm.

Calibration depends on the 10V trimmer in the power supply and the DAC reference trimmer on the A5 board.

Removing the A1 board is also rather fiddly.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: timb on October 11, 2015, 02:03:07 am
Ah yeah, forgot about the DAC reference. It's a shame a scope's calibration involves so many factors; it would have been cool if they could have made a "Calibration Module" that you could pull/swap out, sort of like the HP 3455A DVMs.


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Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on October 11, 2015, 06:50:53 am
...<snip>...  I managed to get it for free.

I hate you. LOL ...j/k  >:D

Congrats on the score.  :clap:  :-+
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on October 11, 2015, 01:28:21 pm
...<snip>...  I managed to get it for free.

I hate you. LOL ...j/k  >:D

Congrats on the score.  :clap:  :-+

Please don't hate me.   :-[   I was definitely in the right place at the right time.

But if I manage to find someone who has a Fluke 5101 AND they let me borrow it for a few hours THEN you can hate me.  :P
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on October 12, 2015, 01:29:25 am
If anyone in the VA/NC area needs a scope cal, I've got a calibrated PG506, SG503 and TG501 to do it with. You just need to bring your scope over.

You know, I wonder if it would be possible to take the main A1 board out of a 2465X, put it in another scope, do the cal and then move the board and NVRAM back to the original scope. That should work, right? As all the analog stuff is there. If so, that could make it a lot easier for people without the equipment to get their unit calibrated, as you wouldn't need to ship the whole scope back and forth, just the main board. Hmmm.


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The gains and electrode physical placement differences in each CRT will make that very questionable. At the very least H, and V gain, will quite likely need adjustment to compensate for each CRT. Most likely more.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: timb on October 12, 2015, 03:15:37 am
Anyone have the Digi-Key parts list handy for a power supply re-cap?


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Here's the file posted to the Yahoo Tek scope forum. Mouser and Newark part no.s only though.

https://dl-web.dropbox.com/get/_2465LVPS_ReCap%2C%20A1%20recap-parts.xls?_subject_uid=315056499&w=AABBEwsyvXv8-MkXuvQXylKApXyus6nBmOsuJ0r-fgUkYw

Link doesn’t work for me. Says I’m not logged in, despite being logged in.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mtdoc on October 12, 2015, 04:55:24 am
Anyone have the Digi-Key parts list handy for a power supply re-cap?


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Here's the file posted to the Yahoo Tek scope forum. Mouser and Newark part no.s only though.

https://dl-web.dropbox.com/get/_2465LVPS_ReCap%2C%20A1%20recap-parts.xls?_subject_uid=315056499&w=AABBEwsyvXv8-MkXuvQXylKApXyus6nBmOsuJ0r-fgUkYw (https://dl-web.dropbox.com/get/_2465LVPS_ReCap%2C%20A1%20recap-parts.xls?_subject_uid=315056499&w=AABBEwsyvXv8-MkXuvQXylKApXyus6nBmOsuJ0r-fgUkYw)

Link doesn’t work for me. Says I’m not logged in, despite being logged in.

That's weird. I'm new to DropBox. Let's try again. Try this:

https://www.dropbox.com/s/fvqo6oj8ktbm2pj/_2465lvps_recap%2C%20a1%20recap-parts.xls?dl=0 (https://www.dropbox.com/s/fvqo6oj8ktbm2pj/_2465lvps_recap%2C%20a1%20recap-parts.xls?dl=0)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on October 12, 2015, 05:02:31 am
Why not just zip it and attach here, it will be useful reference for others in the future, sorry , don't have dropbox account.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mtdoc on October 12, 2015, 05:13:16 am
Why not just zip it and attach here, it will be useful reference for others in the future, sorry , don't have dropbox account.

Well doh!  I didn't realize you could attach zip files here. Here it is:
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: timb on October 14, 2015, 07:32:00 pm
Thanks, I made an order with Digi-Key. Though, I screwed up one part! Instead of three 1uF caps I ordered 10uF! I looked at the schematic, and it appears they're used in the Op Amp feedback path that goes to the inverter feedback. (C1274, C1291 and C1292)

I'm wondering if it's okay to use them? Normally it's okay to increase a cap's size when it's just for filtering, but when it's for an op amp's feedback I'm just not sure.


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Title: Re: Tektronix 2465B oscilloscope teardown
Post by: timb on October 16, 2015, 08:14:14 pm
Hurf durf, disregard last post. Upon looking at the caps in question, they are bi-polar electrolytics. Which, thinking about it, makes the schematic make much more sense!

I happened to have two new 1uF Nichicon BP caps in my parts drawer (thanks to Radio Shack going belly up). They're axial instead of radial, but I made it work. I went ahead and replaced the two that belong to the 10V ref circuit and just put back the original 1uF cap that belongs to the +5D circuit, as it tested OK. I figure the reference is the most critical so I might as well refresh those caps.


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Title: Re: Tektronix 2465B oscilloscope teardown
Post by: timb on October 16, 2015, 09:39:59 pm
Hmm, okay, new problem! I just noticed that according to the schematic C1132 is a 10uF 160V part and C1115 is 250uF 20V; however, on my board with the original Tektronix caps, it's the opposite (according to the layout diagram).

As I removed the original caps, I wrote down the values on a printout of the layout, so that's how I put them back. I'm going to assume the layout sheet has the numbers wrong and what's labeled C1132 is actually C1115. I feel this is a safe assumption, but I wanted to double check before I make an ass-umption of myself. ;)

(http://images.tapatalk-cdn.com/15/10/16/e9ae2f8df5edb34d41167f2a36206cc7.jpg)

(http://images.tapatalk-cdn.com/15/10/16/60230d2015682d5c3fcd1270f3422118.jpg)

(http://images.tapatalk-cdn.com/15/10/16/a24be33a3b9ae0e42e35cf9aa8bd5c3c.jpg)


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Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on October 16, 2015, 10:42:02 pm
Follow the traces to see which one is connected to CR1132.  That has to be the higher voltage cap.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: timb on October 16, 2015, 10:43:30 pm
Unless CR1132 is marked wrong too! XD


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Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on October 16, 2015, 10:51:10 pm
Well, trace as much as you need to satisfy your uncertainty.

The same side of CR1132 also goes to P223, pin 5.

Conversely, the other capacitor in question goes to P234, pin 4, and also L1115.  And the other side is ground.  That should be an easy giveaway.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Howardlong on October 16, 2015, 10:59:23 pm
Errr.... https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg644951/?topicseen#msg644951 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg644951/?topicseen#msg644951)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: timb on October 17, 2015, 07:35:12 am
Well, there you go! Thanks! This thread has been going awhile and I've read the whole thing, must have just glossed over that at the time.

So, I reassembled the scope, turned it on and...it worked...sort of. The readout and trace is super crisp, all supply rails are tight, but the fan doesn't work anymore! After a bit of poking around I noticed the fan wire that goes from the PS to the feed through cap had come unsoldered. (Which I didn't notice since I'd put heat shrink over the connection.)

I fixed it, however I don't think it was the problem. The fan still doesn't work. I guess I've got to take the power supply apart again. *Sighs*

I figure it has to be the LM317 as I'm not getting any voltage on the fan wire. Unless there's something wrong with the solder connection between the wire and the board or the wire itself. You know, looking at the schematic again, maybe the wire is the issue. There's a 300 ohm resistor between +15V and the fan wire, so even if the LM317 was bad, I should be seeing *some* voltage there.


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Title: Tektronix 2465B oscilloscope teardown
Post by: timb on October 18, 2015, 06:51:20 am
I feel like I'm banging my head against a wall with this thing. Turns out the fan was a broken wire. No big deal, fix, reassemble and now something is seriously broken.

Upon power up, all the front panel lights come on and stay lit. No readout or trace, no relay clicks, nothing. All rails are slightly low, so something is seriously pulling power, but not enough to trip the current. +5VD is the worst, there's 300mV ripple in the shape of a triangle wave on it.

I used my HP current tracer probe, but nothing appears to be pulling any serious power on the digital board.

I'm getting a 1.25MHz clock on the MPU pin, but the IRQ pin is toggling at like 100ms, instead of the few microseconds listed in the troubleshooting chart. Could be the aforementioned ripple though.

I guess first step is to build a load for the PS and test the rails. If that checks out I guess I start tracing signals.

*Sighs*



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Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on October 18, 2015, 02:39:54 pm
I feel like I'm banging my head against a wall with this thing. Turns out the fan was a broken wire. No big deal, fix, reassemble and now something is seriously broken.

Upon power up, all the front panel lights come on and stay lit. No readout or trace, no relay clicks, nothing. All rails are slightly low, so something is seriously pulling power, but not enough to trip the current. +5VD is the worst, there's 300mV ripple in the shape of a triangle wave on it.

I used my HP current tracer probe, but nothing appears to be pulling any serious power on the digital board.

I'm getting a 1.25MHz clock on the MPU pin, but the IRQ pin is toggling at like 100ms, instead of the few microseconds listed in the troubleshooting chart. Could be the aforementioned ripple though.

I guess first step is to build a load for the PS and test the rails. If that checks out I guess I start tracing signals.

*Sighs*



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This is exactly why I am so lucky (Knock on wood) that the supply voltages on my 2465 DMS are (so far) in spec. You're not the first I've seen pull the supply and invertor boards and have the damn thing FUBAR upon reassembly. Those boards are apparently a PITA to get out on a typical 2465 without options. Mine has a DMM and C/T plus buffer board which makes it even more of a challenge. I feel for you. Hopefully you'll find the issue.   
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on October 18, 2015, 02:56:40 pm
The IRQ input should be 10us for every 3.3ms according to the flowchart.  A 1.25MHz processor couldn't possibly respond to an IRQ with a continuous period of only a few microseconds.

You could also take a look at the reset circuitry for the processor.  Iif you have instability on the +5V supply, it could be causing continuous resets.

But I would agree the 300mV ripple on the 5V supply is the main concern.
Title: Tektronix 2465B oscilloscope teardown
Post by: timb on October 18, 2015, 08:41:44 pm
The IRQ input should be 10us for every 3.3ms according to the flowchart.  A 1.25MHz processor couldn't possibly respond to an IRQ with a continuous period of only a few microseconds.

You could also take a look at the reset circuitry for the processor.  Iif you have instability on the +5V supply, it could be causing continuous resets.

But I would agree the 300mV ripple on the 5V supply is the main concern.

I couldn't remember the exact number, but yes 10uS is what it should be.

So, I read a thread on here where someone is having the same problem after a recap. His issue was a dead opto-isolator. I'm going to check mine tonight, but last night I tried varying the 10Vref pot; the voltage responded, as did all the rails *except* +5VD, which tells me it could be U1040. (Since the other rails are actively regulated.)

That 300mV sawtooth on 5VD could be the input to error amp U2 oscillating if U1040 isn't working, right?

Does anyone know what the substitute is for U1040? It's marked SOC123A in the schematic.

Edit: Parts list shows H11AX, which gives me 4N2X as well. I get the same when I search for SOC123A.  Seems like they're a family. Hmm, still in production too!


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Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on October 19, 2015, 01:28:22 am
I wouldn't blame U1040 just yet.  The frequency of the sawtooth might provide a clue.  Is it the switching frequency or something else?

Is the fan running now that you fixed the broken wire?

If things were working before you fixed the fan, go back a step.  Try disconnecting the fan or undo whatever you did, no matter how unrelated it may appear.

Can we get a screen shot of the ripple on +5VD?  Any ripple on the 10V ref?  How's the +15V unreg, which feeds the +10V ref circuit (and also the fan)?

Title: Tektronix 2465B oscilloscope teardown
Post by: timb on October 19, 2015, 07:45:58 am
Okay, I built a load and hooked it to the supply. I checked +-15V and both +5V rails, everything is in check. Less than 20mV ripple on the +5VD rail. I tested -5V and -8V, looks like they are sitting very low: -8V rail is sitting at -1.2V, -5V is sitting at -2.7V, but maybe I need to up the load resistors, because those rails were fine inside the scope last night, I think. I used 50 ohm on -8V, -5V and +5V; 100 ohm on +15V and -15V; 150 ohm on +42V; 2k on +87V; 2 ohm on +5VD.

To answer your question, I did try disconnecting the fan. One of the first things I tried!

Tonight I'll get a screen cap of the ripple on the 5VD rail.


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Title: Re: Tektronix 2465B oscilloscope teardown
Post by: timb on October 19, 2015, 09:41:57 pm
So, I'm about to start more testing, but I was reading the service manual earlier. Looks like the -5V rail relies on -8V, so one of them could be the problem. I'll check them inside the scope first.

The other thing I was thinking, what if the line up signal isn't getting through? That could hold the system in reset. Anyway, first thing's first, put the supply back in the scope and check the ripple again.


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Title: Tektronix 2465B oscilloscope teardown
Post by: timb on October 20, 2015, 07:00:30 am
Alright, so I changed all the 50 ohm resistors out with 100 ohm ones on my dummy load. Hooked it up and the supply was 100% in regulation. Put it back in the scope and it started right up. All rails are in spec and there's no visible ripple on +5VD (at least at 50mv/div).

This thing is gaslighting me!

Nearest I can figure is maybe one of cables that goes from A1 to the supply wasn't secure, though I swore I checked those.

I'll check deeper tonight, measure the ripple on all the rails. But yeah, there you go. Weird.

Edit: Oh, here's the load I made. Pretty simple and in the end worked great!

(http://images.tapatalk-cdn.com/15/10/20/7719c04181d0ccd53bc7ce6ce54c371d.jpg)

(http://images.tapatalk-cdn.com/15/10/20/5eb8e251c9403acd165da73bc46a8d20.jpg)


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Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on November 07, 2015, 06:10:21 pm
The DMM option is a total train wreck. The DCV spec'ed accuracy is 0.03%. Not even close. Example: with my 1.000 VDC standard it reads 0.9886 V on autorange. If I go up one range it reads 1.000 V. The kernel/confidence tests do not check the DMM cal directly other than basic functions. The service manual states to perform a cal if you suspect an issue. I did do some extensive resistance checking of the input networks just in case something was fried and found nothing. Proper calibration of the DMM option requires a Fluke 5101 with calibration constants ranging from .19 V to 450 V. As I stated before I'm just a hobbyist and there is no way I'm going to be able to get a Fluke 5101. I don't really consider this function important anyway since I have a Fluke 87 and a Fluke 8021B that take care of my needs.
         

For about $45 USD in assorted parts I was able to get most of the DMM option calibrated....

DCV: the calibration constants required are 0.19V, 1.90V, 19.00V, 190.0V, and 500V. I used an LM723 to generate a precise 19.00V and then cobbled together a voltage divider to set 0.19V and 1.90V. For 190.0V I used this little device:

http://www.amazon.com/gp/product/B010UGJF1I?psc=1&redirect=true&ref_=oh_aui_detailpage_o01_s00 (http://www.amazon.com/gp/product/B010UGJF1I?psc=1&redirect=true&ref_=oh_aui_detailpage_o01_s00)

There were concerns that this inverter would be very unstable and hard to set precisely at 190.0V but surprisingly it was very stable. The processor in the DMM accepted all the constants fed to it and the DCV function is now calibrated and accurate up to at least 190V. I haven't figured out a way to get an accurate 500V so that range wasn't calibrated but for now I'm very pleased with the results.

Hi-Ohms and Lo-Ohms. I ordered .1% resistors from Mouser and these ranges calibrated quickly with no issues.

I did some spot checking of ACV and it looks reasonably accurate as is. I have the required constants to perform a full calibration but it does require a precise calibrator. ACV requires the same voltages as the DCV but some at frequencies other than 60 HZ. No easy way to achieve that. The DCA and DCA were also left as is. Again that requires very accurate standards. I have other DMM's to measure ACV and current if needed. 

This 2465 is now about 98% done and will serve as my “swiss army knife” with it's combination scope, frequency counter, and DMM. It still has an EAROM checksum error in the buffer board upon power up that I haven't quite figured out but it doesn't appear that it affects anything once bypassed. So for now I'm leaving it as is.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on December 22, 2015, 06:09:13 pm
I just got a 2465BCT for Xmas! However, it needs to be fixed up. I fired it up and started running it through its paces. It appeared to be working ok. I had two 100Mhz probes in x10 mode connected to the calibration output running at around 6Mhz. When I switched them to x1, the vertical trace went large (as expected) then I heard a "pop" and the scope went dead after a few seconds. I opened it up and found that C1016 on the A21 board had exploded and that R1015 was seriously burned. The main fuse had popped as well.

C1016 and R1015 form an RC bridge across hot / neutral just before the CR1011 bridge. Some sort of surge must have been coupled from the high voltage side when the CRT vertical voltage jumped which took out C1016. That probably short circuited and took out R1015 and, in turn, the fuse. The question is how that coupling could have happened? I don't currently have a clue.

The maximum voltage on the calibration output is 0.4V, so there is nothing that I should be able to do with the probes that would cause a scope failure! I am sure that there is an underlying cause, but I don't know what it might be. Perhaps someone will have a suggestion.

I could not find any other damage and the boards all look very good in general. The scope actually ran for a few seconds after I heard the "pop" so hopefully the new damage is limited to C1016 and R1015. This is a B010xxx scope so it is an early BCT. There are no SMT parts at all which is wonderful. No Dallas chip to deal with either.

So, my first approach will be to 1) replace the bad parts, 2) recap the board and possibly replace some of the resistors identified by dehav7 and 3) replace R6190 with C6190 to install option 1E. I am currently pulling together a parts list for Mouser. I would also like to replace the soldered in Lithium battery. Does anyone have a suggestion on how to do this without losing calibration data? Can I socket that? I don't currently have the equipment to perform a calibration so I don't want to risk losing the calibration data.

So far, I have only done a partial tear down to find the immediate problem and to visually inspect (most of) the scope. Since all of the tear downs I have seen have been for 2465, 2465A and later model 2465B scopes with SMD parts, I will post pictures when I do a full tear down. I will also post the parts that I am using. So far that is

   C6190 - C412C223K1R5TA Kemet 0.022uF MLCC, 100V, 10%
   C1016 - ECQ-U2A683ML Panasonic 0.068uF Film, 250VAC
   R1015 - 291-36K-RC  Xicon, 36K 5% carbon film

I don't have the relevant schematics for the option 1E modification, so all I have is the value for C6190 but not the voltage rating or suggested type. Other caps in the area are 25V, 50V or 100V so I am going ceramic with 100V.

The project may move a bit slowly given the need to order (and wait for) parts and the time of year. There will probably be several cycles of that as I discover more parts that need to be replaced. I also don't want to pull some of the more difficult boards more than once, so when I have one of them out I will do everything possible before putting it back in. That could cause additional order / wait cycles.

In the meantime, I look forward to any and all suggestions that more experienced people may have. This is my first major scope tear down and refurbishing (although I did repair a 60's vintage scope in the very early '80s - threw it out about 15 years ago, shouldn't have done that). Worse, I have had to interrupt a tear down and rebuild of a Revox B215 to do this one!

So - wish me luck and let me know anything that might help!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on December 25, 2015, 11:34:18 am
I have created my parts list (attached). There may be a few errors because the service manual does not distinguish between radial vs axial, aluminum electrolytic vs. tantalum electrolytic (expect for one part) or polar vs. bi-polar. It also lists a single part as "ALUM" which I have interpreted as aluminum electrolytic, but perhaps it means bi-polar. I have taken my best guess by looking at the scope as much as possible and by reading other people's posts. I will update the list, as necessary, when I can compare individual items directly to the circuit boards. This is also a very early 2565B CT (serial number B010xxx). The actual board versions aren't in the service manual (some are -02 and the manual has -00 and -05 as the closest).

However, except for complete board differences (SMT vs. through-hole and the high voltage board) there do not appear to be any version differences that affect this list. I have ordered everything on the list except for the LTC-7PN battery (which is the exact part currently in the scope, so it is possible that has already been changed). I did include the fan board although that is probably not in the scope (just a single capacitor, so no big deal).

On additional consideration and taking into account other people's repairs, I am currently thinking that when I switched from x10 to x1 and the vertical size jumped that there was a minor current surge to handle the increased vertical deflection. The C1016 capacitor was probably very marginal and blew, shorting out. That would have stressed R1016, burning it due to excessive current (which would have then been directly across the main power supply at 132V) finally causing the main fuse to burn out. I have also discovered that C1018 - which is exactly the same type and value of part - is cracked. Since those two capacitors apparently tend to fail that may (with luck!) be the extent of the problem.

On the good news side, when I reported the situation to the vendor and said that I was planning on keeping the scope anyway, unasked the vendor refunded $50 of the purchase price. That has paid for most of the materials for a complete rebuild!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on December 25, 2015, 02:58:02 pm

So, my first approach will be to 1) replace the bad parts, 2) recap the board and possibly replace some of the resistors identified by dehav7 and 3) replace R6190 with C6190 to install option 1E. I am currently pulling together a parts list for Mouser. I would also like to replace the soldered in Lithium battery. Does anyone have a suggestion on how to do this without losing calibration data? Can I socket that? I don't currently have the equipment to perform a calibration so I don't want to risk losing the calibration data.


You have to bridge in the voltage while changing out the lithium battery or you will lose the calibration data. I forgot where I saw the procedure. If I find it I'll post the link. My older 2465 DMS has EAROM so no battery issues.

Looking forward to your teardown. So far I haven't had any power supply issues but I know that day will come where I'll have to recap to inverter and power supply boards. So far all the voltages are in spec.

One "gotcha" regarding the DMM option. The power up self checks do check some basic DMM functions but will NOT flag the  DMM calibration. The DMM option manual states to perform a calibration if you suspect it to be out of spec. That's exactly what I found out as I posted in this thread. If you find the same with yours I can give you some pointers on how to get a reasonable calibration cheaply  :-+     
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Gixy on December 25, 2015, 07:12:02 pm
To replace the battery, you can use a procedure described in the Yahoo Tek Group, well described in four pictures.
You can also use a bench PSU to back-up the battery while replacing it, but be careful not to have it grouded to earth because your soldering iron would then make a beautiful short when you solder the positive pin... In this case you can unplug your iron for the time of the soldering.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on December 26, 2015, 08:54:23 am

You have to bridge in the voltage while changing out the lithium battery or you will lose the calibration data. I forgot where I saw the procedure. If I find it I'll post the link. My older 2465 DMS has NVRAM so no battery issues.

Looking forward to your teardown. So far I haven't had any power supply issues but I know that day will come where I'll have to recap to inverter and power supply boards. So far all the voltages are in spec.

One "gotcha" regarding the DMM option. The power up self checks do check some basic DMM functions but will NOT flag the  DMM calibration. The DMM option manual states to perform a calibration if you suspect it to be out of spec. That's exactly what I found out as I posted in this thread. If you find the same with yours I can give you some pointers on how to get a reasonable calibration cheaply  :-+   

Thanks. This is a BCT which does not have the DMM, but does have the frequency counter. When choosing this unit, I had several priorities...

1. 2465B / 2457B - but preferably 2465B because the CRT is more easily replaced and is larger. I don't really need the CRT features of the 2467B. I wanted a 2465B because while it is far more than I need at the moment, but I can only afford to do this once so I want the most bang that I can get.

2. I wanted a unit without SMDs. Easier to maintain and appears to have a lot fewer service "updates" apparently due to Tektronix still trying to fine tune the SMD version. Also, no Dallas chip to deal with. Once the procedure is known, changing a battery is not a big deal.

3. I wanted a unit with the frequency counter because I need one. Option 09 gives 7 digits without an external time base and 8 digits with. Since my next purchase will be a GPSDO that is more than sufficient in terms of accuracy. Anything more than that - or even to match it - would be very expensive. So that narrows the field down to the BCT, BDM or BDV. Also, I have very limited space on my work bench and the integrated frequency counter helps there as well.

4. I already have a DMM of about the same accuracy as that provided by option 01. That accuracy is not much to write home about and increases the size of the scope. So while a BDM or BDV is ok, optimal is the BCT.

With this unit I hit all of my points exactly. It is an early model (s/n B010xxx), but there are no service updates listed for any s/n below B050000. There are some board variations, but those appear to more layout than anything else. So, while I paid more for it than I might have for a plain 2465B in the same shape, I think the cost difference was worthwhile. Certainly cheaper than buying a separate frequency counter. When it failed, the $50 rebate from the vendor paid for most of the parts which reduced the cost further (since I would have recapped it anyway - just not as soon).

I may need pointers on the tear down. I haven't taken out any board yet that requires desoldering. I have had the options out several times. There are two areas where it is a pain. First is the ribbon cable that tends to get pinched. It is hard to get that in right. The second is the two cables at the very end which go onto the same pins. It is not clear which cables go where. I figured that out because one of the pins goes to the resistor / capacitor that I will be changing for option 1E, but the manual is useless there.

The case and back were not the cleanest and had permanent marker, floor scum and sticker goo all over them. I have cleaned all of that of so the case looks nice now. I haven't had the front of the scope off yet, so it is still a bit grungy.

I may also need help identifying some parts. My part list was as accurate as I could make it, but I am sure that there will minor corrections (radial vs. axial / aluminum electrolytic vs. tantalum electrolytic / polar vs. bi-polar, etc.) which are not spelled out in the service manual. Also, I don't have the 24x5B / 2567B options service manual. I have been unable to find it online and am not willing to pay for what should be a free manual unless it is absolutely necessary. My understanding is that Tektronix made all of that information publically available.

Right now I am waiting on Mouser. The parts shipped on the 24th so they will probably sometime early next week.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on December 26, 2015, 09:04:59 am
To replace the battery, you can use a procedure described in the Yahoo Tek Group, well described in four pictures.
You can also use a bench PSU to back-up the battery while replacing it, but be careful not to have it grouded to earth because your soldering iron would then make a beautiful short when you solder the positive pin... In this case you can unplug your iron for the time of the soldering.

Thanks. That looks like an easy procedure - especially with the AAA battery case. It might be good to have a replacement for the capacitor on hand in case it gets damaged by removal. That will probably be the last thing I do. Having seen some other pictures of the battery, I suspect that it has been changed comparatively recently. Mine has the bright yellow label and is not the apparently older blackish version without a label. Also, the part number of mine exactly matches Mouser's part number.

I am trying to join the Yahoo Tekscopes group and the arc / arc2 groups as well. However, I refuse to get a Yahoo account - I keep fairly tight security policies and Yahoo doesn't need to know my phone number OR date of birth! The moderator may not accept an email subscription request so that avenue of knowledge may be blocked off (don't have a Google account either and only have a Microsoft account for downloading development tools). Otherwise, I have read everything else I have been able to find. This thread and the 1E thread (also on this board) have been very informative. I have read this thread once and will read it again while I am waiting.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on December 26, 2015, 02:01:34 pm


3. I wanted a unit with the frequency counter because I need one. Option 09 gives 7 digits without an external time base and 8 digits with. Since my next purchase will be a GPSDO that is more than sufficient in terms of accuracy. Anything more than that - or even to match it - would be very expensive. So that narrows the field down to the BCT, BDM or BDV. Also, I have very limited space on my work bench and the integrated frequency counter helps there as well.

Yep, Option 09 is definitely a nice feature and I use it all the time. But keep in mind that the frequency counter is only good out to 150Mhz which is odd when you consider that the bandwidth of the scope is double that.


Quote
I may need pointers on the tear down. I haven't taken out any board yet that requires desoldering. I have had the options out several times. There are two areas where it is a pain. First is the ribbon cable that tends to get pinched. It is hard to get that in right. The second is the two cables at the very end which go onto the same pins. It is not clear which cables go where. I figured that out because one of the pins goes to the resistor / capacitor that I will be changing for option 1E, but the manual is useless there.

I have yet to do a tear down too. And I have the additional DMM board across the top of the chassis. Luckily it swings to one side and can be removed.

I've also had issues locating all the service and operating manuals. I have the vanilla 2465 ops and service manual. I have the DMM service manual but no ops manual. And no options ops or service manual but I did find the 2465A options service manual and 2465B options ops manual but they are only good for some reference because of the changes TEK made over the years. 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on December 26, 2015, 04:34:34 pm

Yep, Option 09 is definitely a nice feature and I use it all the time. But keep in mind that the frequency counter is only good out to 150Mhz which is odd when you consider that the bandwidth of the scope is double that.

I have yet to do a tear down too. And I have the additional DMM board across the top of the chassis. Luckily it swings to one side and can be removed.

I've also had issues locating all the service and operating manuals. I have the vanilla 2465 ops and service manual. I have the DMM service manual but no ops manual. And no options ops or service manual but I did find the 2465A options service manual and 2465B options ops manual but they are only good for some reference because of the changes TEK made over the years.

For my near-term needs, 150Mhz is fine. Even a 60Mhz scope would have done. However, I only plan on buying an analog scope once and so I went with much more than I actually require at this time. That could change rapidly, so the 2465BCT is the best that I can do at this time.

I have the following PDF manuals...

   Tektronix 2465 Options 06 09 CTT WR Service
   Tektronix 2465A Options Service Manual
   Tektronix 2465B 070-6863-00 Service Manual
   Tektronix 2465B 070-6863-01 Service Manual
   Tektronix 2465B Operators Manual

I would like to find a PDF copy of the 24x5B / 22467B Options Service Manual. I think that the 2465A Options Service Manual will be pretty close. I don't think that there was much changed for the options. It has the GPIB, TV, CTT and DMM options in it.




Title: Re: Tektronix 2465B oscilloscope teardown
Post by: timb on December 27, 2015, 10:15:07 pm
It's good to 200MHz, not 150MHz.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on December 28, 2015, 01:37:15 am
It's good to 200MHz, not 150MHz.

I think that depends on whether it's a 2465, 2465A, 2465B. I have the Tek 1986 Product Catalog which describes the 2465 and, unless I'm reading it wrong, the counter option is good for 150Mhz. I don't have a signal source greater than 100Mhz so I can't test it. But it would make sense that it would increase in response since the 2465A B/W is 350Mhz and the 2465B is 400Mhz.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on December 28, 2015, 05:36:05 am
It's good to 200MHz, not 150MHz.

I think that depends on whether it's a 2465, 2465A, 2465B. I have the Tek 1986 Product Catalog which describes the 2465 and, unless I'm reading it wrong, the counter option is good for 150Mhz. I don't have a signal source greater than 100Mhz so I can't test it. But it would make sense that it would increase in response since the 2465A B/W is 350Mhz and the 2465B is 400Mhz.

I have a 2465B CT, so mine is probably good to 200Mhz. I don't actually have anything that describes that for a 2465B.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on December 28, 2015, 09:05:40 pm
The parts for refurbishing my 2465B CT have arrived!

Here are the first batch of pictures. These are all of the outside. The next batch will be the inside after I open it up.

I couldn't manage to embed the pictures, so I have attached them. Also .jpeg files are not allowed! WTF! And apparently only tiny files are allowed! So, one per post. Sigh.

Front of scope.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on December 28, 2015, 09:06:44 pm
2465B CT Outside pictures continued...

Back of scope.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on December 28, 2015, 09:53:06 pm
2465B CT Outside pictures continued...

Left side of scope.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on December 28, 2015, 09:56:58 pm
2465B CT Outside pictures continued...

Right side of scope.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on December 28, 2015, 10:00:56 pm
I couldn't manage to embed the pictures, so I have attached them. Also .jpeg files are not allowed! WTF! And apparently only tiny files are allowed! So, one per post. Sigh.


Your pictures are too big. Use a program such as "IrfanView". Resize images to 1920 x 1080. Save. Then you should be able to upload each pix in one post.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on December 28, 2015, 10:01:39 pm
2465B CT Outside pictures continued...

Top of scope.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: timb on December 28, 2015, 10:03:32 pm

I couldn't manage to embed the pictures, so I have attached them. Also .jpeg files are not allowed! WTF! And apparently only tiny files are allowed! So, one per post. Sigh.


Your pictures are too big. Use a program such as "IrfanView". Resize images to 1920 x 1080. Save. Then you should be able to upload each pix in one post.

Yeah. They need to be resized first. Or try something like www.imgur.com which should take care of resizing and give you (img) tags you can can copy and paste.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on December 28, 2015, 10:07:51 pm
2465B CT Outside pictures continued...

Bottom of scope.

P.S. I prefer to upload high resolution images. Extremely low resolution images such as 1920 x 1080 are annoying when you want to zoom in on the detail (which is something I do all the time and assume that other people do as well). I would rather not have compression used at all, but uploads are limited to 1M per file so a full resolution image of 25M or so doesn't work. I  should have done two per post, though.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: c4757p on December 28, 2015, 10:13:06 pm
P.S. I prefer to upload high resolution images. Extremely low resolution images such as 1920 x 1080 are annoying when you want to zoom in on the detail (which is something I do all the time and assume that other people do as well). I would rather not have compression used at all, but uploads are limited to 1M per file so a full resolution image of 25M or so doesn't work. I  should have done two per post, though.

Huh? Resolution is only useful when the actual image supports it. That picture is nowhere near sharp enough for a 5269x3573 resolution to be useful...did you even look at it? It's blurry! You're just wasting bandwidth and server space and annoying people on slow connections...

I size my photos based on the actual level of detail in the original. Works much better.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on December 28, 2015, 10:30:31 pm

I couldn't manage to embed the pictures, so I have attached them. Also .jpeg files are not allowed! WTF! And apparently only tiny files are allowed! So, one per post. Sigh.


Your pictures are too big. Use a program such as "IrfanView". Resize images to 1920 x 1080. Save. Then you should be able to upload each pix in one post.

Yeah. They need to be resized first. Or try something like www.imgur.com (http://www.imgur.com) which should take care of resizing and give you (img) tags you can can copy and paste.

Ok, if people really want small images, I'll see what I can do.

I tried www.imgur.com (http://www.imgur.com) and it didn't appear to work well for me. I am trying Ifranview - it resizes the images, but they are still 2.5M. Once I get it fixed I'll upload the images.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: grumpydoc on December 28, 2015, 11:09:02 pm
P.S. I prefer to upload high resolution images. Extremely low resolution images such as 1920 x 1080 are annoying when you want to zoom in on the detail (which is something I do all the time and assume that other people do as well). I would rather not have compression used at all, but uploads are limited to 1M per file so a full resolution image of 25M or so doesn't work. I  should have done two per post, though.

Huh? Resolution is only useful when the actual image supports it. That picture is nowhere near sharp enough for a 5269x3573 resolution to be useful...did you even look at it? It's blurry! You're just wasting bandwidth and server space and annoying people on slow connections...

I size my photos based on the actual level of detail in the original. Works much better.
It's blurry because the camera has focussed on the front of the knobs (the "var" is in focus on the three knobs) and there is little depth of field. The photo of the rear of the 'scope is actually quite sharp, not very exciting viewed at the actual pixel resolution though.

c4757p is absolutely correct - if you are going to post a huge image so that "people can zoom in" it is worth looking at it at the actual pixel resolution and making sure that there is detail to see.

Actually 1920x1080 is plenty big enough most of the time - I usually post something only a little larger such as 2400x1350 or 2400x1800 with a 1/4 size picture in the post linking to the larger pic if people want.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on December 28, 2015, 11:13:55 pm
2465B CT Outside pictures resized. I had to use GIMP to scale and compress, then I got imgur to work. I resized so that the maximum dimension was no larger than 1920 x 1080 at 96 dpi. Let me know if this is more appropriate.

Front       (http://i.imgur.com/vd0ObUY.jpg)
Back        (http://i.imgur.com/9XtlexQ.jpg)
Left Side   (http://i.imgur.com/9Bln0Fr.jpg)
Right Side  (http://i.imgur.com/tLynSpx.jpg)
Top         (http://i.imgur.com/LxYghO1.jpg)
Bottom      (http://i.imgur.com/S97ixzD.jpg)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on December 30, 2015, 06:05:46 pm
Here are the pictures for the inside of my 2465B CT, before removing any boards.

A1 Main Board               (http://i.imgur.com/ZxogM0F.jpg)
A5 Digital Control Board    (http://i.imgur.com/Tm0WPJ3.jpg)
A14 Dynamic Centering Board (http://i.imgur.com/LzfAM00.jpg)
A9 High Voltage Board       (http://i.imgur.com/8S5wmge.jpg)
Top Shield                  (http://i.imgur.com/10YSLTy.jpg)
Back                        (http://i.imgur.com/uFU5Rdc.jpg)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on December 30, 2015, 07:14:27 pm
Attached are the images for the options assembly tear down and refurbishing. Also, option 1E was installed. The "WR Out" photo shows the resistor (circled in red) that enables WR Out for the Word Recognizer Option. The "Option 1E" photo shows the resistor removed and a 0.22uF capacitor installed to enable Option 1E (disabling WR Out). Option 1E allows a reference frequency to be input to the scope increasing the frequency counter accuracy from 7 digits to 8 digits (+/- 1). Option 1E does NOT affect the scope's time base. The reference frequency is used to dynamically calibrate the CTT time base which is separate from the main scope time base. The WR Option will still function and trigger, but the trigger will no longer be available externally. There were only 5 electrolytic capacitors to be replaced, so this was a simple recapping.

Bottom Option Connection               (http://imgur.com/XmV2kKI.jpg)
WR Connector                           (http://imgur.com/2rZQHwg.jpg)
Options Assembly                       (http://imgur.com/8JO1YzQ.jpg)
A20 Buffer Board                       (http://imgur.com/4UiHBHt.jpg)
A23 GPIB Option 10 Board               (http://imgur.com/tfiszb4.jpg)
A27 Counter Timer Trigger Option Board (http://imgur.com/CIYBtxi.jpg)
Recapped CTT & GPIB Option Boards      (http://imgur.com/hGNB0Ym.jpg)
WR Out                                 (http://imgur.com/EgtokUo.jpg)
Option 1E                              (http://imgur.com/qukY0b7.jpg)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on January 01, 2016, 12:19:20 am
I am getting ready to remove the High Voltage board from my 2465B CT. I understand how to remove it, in general. However, there is one sticking point. The service manual says

   "Remove the high-voltage lead from the retainer cap"

Some of the terminology / parts are not clearly explained, but physical examination makes most of it clear. However, this is not clear. Assuming that this is the correct part

(http://imgur.com/JJl5Igs.jpg)

and, what is necessary, is removing the white plug from the black cap then I am not sure how that is done. The white plug turns freely inside of the black cap, but I have been unable to separate the two using reasonable force. Too much force and a back reaction could lead to damaging the small circuit board and CRT connections to the immediate left. Is there some trick to this, or is just especially difficult?

Thanks.


Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on January 01, 2016, 06:07:01 am
Tom Miller on the Yahoo Groups TekGroup confirmed that it just needed a bit more "pull".

That was all I needed and I have finished recapping the high voltage board (even if it was only one capacitor)! Hopefully, I got the CRT socket back on right. Apparently, any one of a dozen orientations would fit. Given wire length, probably no more than three in reality. I think that I did. Here is the after picture of the high voltage board. In spite of appearances, the metal standoff in the bottom right is not touching the replacement capacitor or even close for that matter. The original was a 100uF, 25V, 85c Sprague capacitor. The replacement is a 100uF, 50V, 85c Sprague capacitor. Slightly larger, but it fits.

(http://imgur.com/ATxA57U.jpg)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on January 01, 2016, 10:17:10 pm
Here is the photos of the A5 control board before and after recapping.

Before: (http://imgur.com/ksGlfoC.jpg)
After: (http://imgur.com/SMYdlv2.jpg)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: rafik on January 02, 2016, 02:09:37 am
Hello,

I am new in the forum am I find this blog very interesting.
I have searched about restoration of Tektronix 2465B PSU but I could find anything about it.
For this reason I write here, I hope not disturb. Well, at the present time, I am trying to repair the PSU of this wonderful scope but I could not more. I recap this stage and changed other parts but the PSU is now in a tick mode. Please someone could me help and explain why this happends and how could I go out of this mode? ....I do not know what to do... I hope you can help me with this...
Thank you in advance..
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on January 02, 2016, 04:00:40 am
Hello,

I am new in the forum am I find this blog very interesting.
I have searched about restoration of Tektronix 2465B PSU but I could find anything about it.
For this reason I write here, I hope not disturb. Well, at the present time, I am trying to repair the PSU of this wonderful scope but I could not more. I recap this stage and changed other parts but the PSU is now in a tick mode. Please someone could me help and explain why this happends and how could I go out of this mode? ....I do not know what to do... I hope you can help me with this...
Thank you in advance..
There's a good Tek pdf with a section on troubleshooting SMPS in this thread:
https://www.eevblog.com/forum/repair/repair-documents-and-links-sticky-me-please-mods/msg477909/#msg477909 (https://www.eevblog.com/forum/repair/repair-documents-and-links-sticky-me-please-mods/msg477909/#msg477909)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on January 02, 2016, 10:18:55 am
Hello,

I am new in the forum am I find this blog very interesting.
I have searched about restoration of Tektronix 2465B PSU but I could find anything about it.
For this reason I write here, I hope not disturb. Well, at the present time, I am trying to repair the PSU of this wonderful scope but I could not more. I recap this stage and changed other parts but the PSU is now in a tick mode. Please someone could me help and explain why this happends and how could I go out of this mode? ....I do not know what to do... I hope you can help me with this...
Thank you in advance..

Best thing you can do is download the service manuals. They are invaluable and the troubleshooting steps for the power supply are very good. Failing that join the Tektronix's group on yahoo. That's where the Tek experts/enthusiasts hang out.

https://groups.yahoo.com/neo/groups/TekScopes/info

I had a issue with a power supply on my 2465B and if it wasn't for the help on the group never would have figured out the problem. Aged and out of spec opto-isolator. Note if you recapped there is a error on the schematic and likely one of the caps was inserted backwards, can't remember which though.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on January 02, 2016, 09:49:13 pm
Hello,

I am new in the forum am I find this blog very interesting.
I have searched about restoration of Tektronix 2465B PSU but I could find anything about it.
For this reason I write here, I hope not disturb. Well, at the present time, I am trying to repair the PSU of this wonderful scope but I could not more. I recap this stage and changed other parts but the PSU is now in a tick mode. Please someone could me help and explain why this happends and how could I go out of this mode? ....I do not know what to do... I hope you can help me with this...
Thank you in advance..

Best thing you can do is download the service manuals. They are invaluable and the troubleshooting steps for the power supply are very good. Failing that join the Tektronix's group on yahoo. That's where the Tek experts/enthusiasts hang out.

https://groups.yahoo.com/neo/groups/TekScopes/info

I had a issue with a power supply on my 2465B and if it wasn't for the help on the group never would have figured out the problem. Aged and out of spec opto-isolator. Note if you recapped there is a error on the schematic and likely one of the caps was inserted backwards, can't remember which though.

The labels for C1115 and C1132 were reversed on the schematic.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on January 04, 2016, 03:22:15 am
Here is the tear down of the power supply section of my 2465B CT. I included the readout board because it was convenient to remove it to facilitate unsoldering the fan power cable.

A2A1 Regulator Board                           (http://imgur.com/Q4IExmF.jpg)
A3 Inverter Board                              (http://imgur.com/NDhX7cs.jpg)
A4 Readout Board                               (http://imgur.com/u9Y4gz5.jpg)
Inside Case with A3, A4 and A2A1 Removed       (http://imgur.com/5iqFqUF.jpg)
Shield Between A3 and A2A1                     (http://imgur.com/9CMemrA.jpg)
Back Panel Wiring                              (http://imgur.com/CnaaPG6.jpg)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on January 04, 2016, 03:36:55 am
Here is the damage, apparent bad components and recapping of the A3 Inverter board for my 2465B CT scope.

On the A2A1 Regulator board, C1016 RIFA capacitor has exploded. That has grunged up some of the nearby components, but does not appear to have done further damage. The C1018 RIFA capacitor has cracked open, but not exploded. Almost certainly non-functional. Resistors R1016 and R1018 have both been severely burned. They may or may not be functional. There are a couple of other resistors with dings and scratches which I will replace.

Additionally, on the A3 Inverter board there are three more RIFA capacitors and it can be seen that all three are cracked. They may still be working, but probably not for long. The A3 Inverter recap does not include those because I need to order replacements. It can also be seen looking at the bottom on the replaced capacitors that one looks like it was starting to leak, a second appears to have damage to the bottom (pre-leak?) and I am not at all sure if some of the rest are slightly bulging or not. They certainly aren't completely flat, but that may be a construction difference.

The only gotcha during replacement is the large axial capacitors. The leads are too short. I had to snip some lead from the original capacitors to extend the lead length. Also, even though these replacements have increased voltage ratings, increased capacitance or increased thermal rating and much better ESR, the replacements are generally smaller. In particular, the radial capacitor which was originally mounted on its side because it was too tall can now fit upright with no clearance issues.

A2A1 Regulator Board Damage                    (http://imgur.com/zuik04G.jpg)
A3 Inverter Board Bad RIFA 1                   (http://imgur.com/HF3CYoK.jpg)
A3 Inverter Board Bad RIFA 2                   (http://imgur.com/xwddyuR.jpg)
A3 Inverter Board Bad RIFA 3                   (http://imgur.com/OimaNkj.jpg)
A3 Inverter Board Replaced Capacitors          (http://imgur.com/LboLNmN.jpg)
A3 Recapped Inverter Board                     (http://imgur.com/pnUyrOJ.jpg)

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on January 04, 2016, 09:58:06 am
Here is the damage, apparent bad components and recapping of the A3 Inverter board for my 2465B CT scope.


Isn't the smell of those old leaky caps just lovely, mine had a horrible fishy oil smell.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: dan3460 on January 04, 2016, 04:46:16 pm
I repaired a 2465 a few months ago, and those square caps that exploded had exploded on mine too. They did have a weird smell, it could be the plastic they used or some of the components inside.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on January 06, 2016, 06:04:31 am
Here is the recap of the A2A1 Regulator board in my 2465B CT. This does not include replacing the bi-polar electrolytics or the damaged resistors. I am waiting on parts for those. As with the A4 Inverter board, when I get the missing parts, I will repost a final picture.

Regulator board (http://imgur.com/E1dyUP7.jpg)
Replaced capacitors (http://imgur.com/GlV9bub.jpg)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on January 06, 2016, 06:12:46 am


Replaced capacitors
 (http://imgur.com/GlV9bub.jpg)
You have hidden all the brand names.  :-// On purpose?
How many were faulty?
Care to list them for us?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SeanB on January 06, 2016, 07:30:54 am
RIFA, Nichicon, Sprague and Cornell Dublier is my guess.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on January 06, 2016, 07:44:42 am
RIFA, Nichicon, Sprague and Cornell Dublier is my guess.
Sure, but why guess?

We need this info for another thread Sean.
Can you correctly guess that one?  ;)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SeanB on January 06, 2016, 08:43:06 am
RIFa and Nichicon are easy, and the light blue Sprague are also a common sight. The grey are the guess, and from the age and colour.....
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on January 06, 2016, 09:57:17 pm
I will be happy to list the various brand names. I don't know which ones are faulty. This is a preventative recapping plus fixing known damage. I don't have an ESR meter, and my multimeter is flaky about testing capacitance - some times it works and sometimes not. No idea why.

Do you want the exact parts for this board only or for all boards that I have recapped? I haven't recapped the main board yet, but it is on my work table with the parts laid out.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on January 06, 2016, 10:21:27 pm


Replaced capacitors
 (http://imgur.com/GlV9bub.jpg)
You have hidden all the brand names.  :-// On purpose?
How many were faulty?
Care to list them for us?

There are 5 capacitors (gray), Tektronix part 290-0942-00, with the following on the label

   100uF
   0 - 25 VDC
   + (2) 672D +
   USA8814H - one, labeled with text top to bottom
   USA881 1H - four, labeled with text on side
   105 C

There are 2 capacitors (light blue), Tektronix part 290-0939-00, with the following on the label

   10uF
   0-100VDC
   (2) 672D
   USA8821H
   105C

There are 2 Nichicon capacitors (dark blue), Tektronix part 290-0943-02, with the following on the label

   VX(M)
   85c
   A8810
   nichicon
   47uF 25v

There are 2 RIFA capacitors (yellow and exploded), Tektronix part 282-1222-00, with the following on the label

   0.068uF X2 - top

   250V - SH - front
   565-1   LD2

   PME 271M - back
   40/085/56
   CW2

What do need them for? I have the complete parts list, with replacements that I have previously posted. There have been some updates as I have worked on each board. Do you need the updated list? I will be posting that later, but was going to wait until I have complete finished.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on January 07, 2016, 09:58:58 pm
I have knob problems with my 2465B CT scope. On the front panel, the two bottom halves of the VOLTS / DIV knobs have set screws that are stripped. Probably because somebody screwed them in far too tight. How do I get these off, and where can I get either a knob replacement or a set screw replacement (assuming I get them off without damaging the knobs)?

Additionally, two of the smaller knobs with a blank front (e.g. like the TRACE SEP knob) and two of the smaller knobs with a line on the front (e.g. like the POSITION knobs) have their internal "cap" broken. These are my fault because they were on so tight I had to pry them off with a screwdriver. Unlike the ones under the CRT, which came off with just finger pressure, all of the knobs on the main panel were stuck really badly. Where can I get a knob replacement for these?

These knobs are common to pretty much all of the 22xx and 24xx series, so I would think that they are out there somewhere.

Thanks.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on January 07, 2016, 10:11:21 pm
What do need them for? I have the complete parts list, with replacements that I have previously posted. There have been some updates as I have worked on each board. Do you need the updated list? I will be posting that later, but was going to wait until I have complete finished.
Only information for this thread:
https://www.eevblog.com/forum/projects/capacitor-quality/ (https://www.eevblog.com/forum/projects/capacitor-quality/)

I have knob problems with my 2465B CT scope. On the front panel, the two bottom halves of the VOLTS / DIV knobs have set screws that are stripped. Probably because somebody screwed them in far too tight. How do I get these off, and where can I get either a knob replacement or a set screw replacement (assuming I get them off without damaging the knobs)?

Additionally, two of the smaller knobs with a blank front (e.g. like the TRACE SEP knob) and two of the smaller knobs with a line on the front (e.g. like the POSITION knobs) have their internal "cap" broken. These are my fault because they were on so tight I had to pry them off with a screwdriver. Unlike the ones under the CRT, which came off with just finger pressure, all of the knobs on the main panel were stuck really badly. Where can I get a knob replacement for these?

These knobs are common to pretty much all of the 22xx and 24xx series, so I would think that they are out there somewhere.

Thanks.

http://www.sphere.bc.ca/ (http://www.sphere.bc.ca/)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on January 08, 2016, 11:35:39 am
I managed to drill the two offending knobs off using a Cobalt drill bit. Only minor damage to one shaft. Now, I just need to replace the bad knobs.

Otherwise, I have completed the recapping of the A1 Main board. Here are the photos...

Before Recapping (http://imgur.com/RACkcaZ.jpg)
After Recapping (http://imgur.com/3XtmjBF.jpg)
Replaced Capcitors (all Nichicon) (http://imgur.com/2jkLUrk.jpg)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: macboy on January 08, 2016, 03:18:48 pm
I have a 2465A, which has the digital board similar to the earlier 2465B serials, that is, with through hole components, and with the separate SRAM and battery, rather than a DS1225 module. My calibration data is intact but the battery is original, so I can assume that it will not be intact for too much longer.

The separate SRAM/battery is a mixed blessing: on one hand I can more easily desolder and replace just the 4 pin battery a 28 pin NVSRAM. On the other hand, I have no way to read out and save (or restore) the calibration data itself. After browsing the service manual, I got the idea to put the processor into the diagnostic NOP loop. It will cycle through all addresses on the address bus, with the intention of allowing the testing of address bus and decoding (chip selects). I thought that the data could be captured by using either a logic analyzer or by piggy-backing an NVRAM and supplying write pulses for each address so that it captures the data that the SRAM presents to the bus when it is addressed. One issue is that I don't have a logic analyzer. Does anyone have an opinion about either of these methods? Should I just replace the battery and cross my fingers that I'll never need to restore the data?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on January 08, 2016, 07:32:16 pm
You can replace the battery without losing calibration data. Essentially what you do is to solder in a temporary battery replacement, change the battery and then remove the replacement.

I don't remember where it is at, but there are a series of photos that show one fairly easy way to do that. If I remember correctly, the steps are

   1. Remove the capacitor just above the battery. That is C2470 on the 2465B.

   2. Take a AAA battery holder that holds three batteries and solder the wires in place of the C2470. Make sure to get the polarity right. This will keep your data alive. C2470 is not polarized, but you really don't want +3.75v going to ground!

   3. Remove and replace the battery.

   4. Unsolder the wires to the AAA batteries and solder C2470 back in.

There is another option, which I have not done yet, but am planning on with timb's assistance. That is to make some minor circuit modifications, replace the RAM with an FRAM and completely remove the battery.  Basically, you replace CR2770 with a 4.3k resistor, replace the battery with a link and replace the RAM with an FRAM. However, you need to copy the calibration data or do a full calibration (or, possibly both) so if you can't do that you are better off with the battery replacement.



I have a 2465A, which has the digital board similar to the earlier 2465B serials, that is, with through hole components, and with the separate SRAM and battery, rather than a DS1225 module. My calibration data is intact but the battery is original, so I can assume that it will not be intact for too much longer.

The separate SRAM/battery is a mixed blessing: on one hand I can more easily desolder and replace just the 4 pin battery a 28 pin NVSRAM. On the other hand, I have no way to read out and save (or restore) the calibration data itself. After browsing the service manual, I got the idea to put the processor into the diagnostic NOP loop. It will cycle through all addresses on the address bus, with the intention of allowing the testing of address bus and decoding (chip selects). I thought that the data could be captured by using either a logic analyzer or by piggy-backing an NVRAM and supplying write pulses for each address so that it captures the data that the SRAM presents to the bus when it is addressed. One issue is that I don't have a logic analyzer. Does anyone have an opinion about either of these methods? Should I just replace the battery and cross my fingers that I'll never need to restore the data?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on January 08, 2016, 09:08:41 pm
There is a diagnostic routine "Exerciser 02" which allows you to read out the 256 locations in the SRAM that contain the cal constants (service manual pg. 6-17).  You can take a video while you step through the locations so you have a record of them.

However, I'm not aware that anyone has ever gone from this display to re-creating the entries in the SRAM on an A or B series.  There was some discussion about it on the yahoo tekscopes list a month or two ago.

Your idea to let the processor loop through the locations sounds like it would work.  Instead of making your own capture memory, it might be easier to buy a cheap logic analyzer from ebay.  The memory cycle time of the processor is quite slow on the order of 800ns, so you wouldn't need anything extravagant.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on January 11, 2016, 06:13:20 am
I am nearing the end of recapping my 2465B CT. However, that still leaves modifications. One modification which many people have recommended is to put a heat sink on U800 because (at least on some machines) it gets pretty hot. That probably isn't necessary, but reducing heat can extend the lifespan of components. However, in looking at my U800, it appears as if it may already have a built-in heat sink. If that is the case then there probably isn't any need to add a second one. Some people have said that it gets so hot that it nearly burns them. Others have said that it only gets warm. Is it possible that there are two different versions, one with built-in heat sink and one without? Here are two pictures of my U800. The first is on the entire IC. The second is just of the bolt closest to the center of the A1 board. Notice that it has a thick slab of metal on the bottom that appears to be integrated with the IC. That sure looks like a heat sink to me.

Let me know what you think!

Entire U800 (http://imgur.com/VEpYWut.jpg)
U800 bolt only (http://imgur.com/qTzL41R.jpg)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Orange on January 11, 2016, 10:45:52 am
Tektronix had a change in their manufacturing process. At one point they closed their hybrid production plant, or it was sold to a subsidiary of Maxim.

When Maxim started to produce the U800 for Tek, the troubles were introduced. The bad chips are having the maxtek marking, and not the Tek marking on them.
There is a reliability report floating around on the internet with statistics on this chip, made by Maxim.

Basically what happens is the the die comes loose from the heat sink. if this happens, you will notice a gradual shift of the characters on the screen to the left on power on.
If this situation continues, eventually, the chip burns out....

In my scopes all U800 got an heat sink, despite the fact that they all were Tek branded. Be aware that the IC heat sink is a -5.2 volts

Added link to Maxim report https://www.maximintegrated.com/en/qa/reliability/general/RR-B2A.pdf (https://www.maximintegrated.com/en/qa/reliability/general/RR-B2A.pdf)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on January 11, 2016, 10:04:03 pm
Thanks.

Mine is a Tek part. My scope appears to have been manufactured in '88.


Tektronix had a change in their manufacturing process. At one point they closed their hybrid production plant, or it was sold to a subsidiary of Maxim.

When Maxim started to produce the U800 for Tek, the troubles were introduced. The bad chips are having the maxtek marking, and not the Tek marking on them.
There is a reliability report floating around on the internet with statistics on this chip, made by Maxim.

Basically what happens is the the die comes loose from the heat sink. if this happens, you will notice a gradual shift of the characters on the screen to the left on power on.
If this situation continues, eventually, the chip burns out....

In my scopes all U800 got an heat sink, despite the fact that they all were Tek branded. Be aware that the IC heat sink is a -5.2 volts

Added link to Maxim report https://www.maximintegrated.com/en/qa/reliability/general/RR-B2A.pdf (https://www.maximintegrated.com/en/qa/reliability/general/RR-B2A.pdf)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on January 14, 2016, 01:10:04 am
I thought I would share a quick bit of part supply information.

While I am waiting to order the rest of my parts for my 2465BCT, I was looking at other parts I may need to replace. In particular, I am could not tell by looking at them whether or not I need to replace the graticule illumination lamps. These are Tektronix part number 150-0057-01. I did not find an obvious source for these. I found a reference to Anchor Electronics, but they do not appear to have the part. After some research, I found that these are 5.0V 0.115A T-3/4 miniature lamps with wire leads with a very long life (40,000 hrs). They are type 7153AS15 and NSN 6240-00-183-0669.

Given all of that, I was able to find them at Mouser for just over $1 each. They are a 7153 lamp and Mouser has them, in stock, from two vendors (JKL and VCC). The Mouser part numbers are:  606-CM7153 and 560-7153. DigiKey also lists these same two vendors, but does not have them in stock. Newark lists another vendor (CML), but has a minimum order of 10 at $11.94 each. I have since found a few other locations, where sometimes they are in stock (usually not), but their pricing is always similar to Newark's. It looks like Mouser is the best source for these lamps.

EDIT: The Tektronix part has "AS15" added to it to indicate a closer tolerance on the brightness (+/-15% vs 25%). Mouser also has the 606-CM1753AS15 for about 50% more in cost. Mouser appears to have some typos in their listings. The CM7153AS15 listing erroneously says it is a T1-3/4 and the 560-7153 either has the listing wrong or the link to the datasheet wrong (I think it is the datasheet). My best guess is that any of them will do. If I order any, I will order the CM7153AS15 to stay closest to the original specification.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on January 23, 2016, 11:17:26 pm
FireDragon:
Typically the recommendation is to avoid recapping the mainboard. Can't recall the specific reasons why, think it had to do with issues of the multilayer PCB. in any event good job, did you notice any improvements in performance in recapping the main board.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on January 28, 2016, 01:16:38 am
FireDragon:
Typically the recommendation is to avoid recapping the mainboard. Can't recall the specific reasons why, think it had to do with issues of the multilayer PCB. in any event good job, did you notice any improvements in performance in recapping the main board.

I have just received the last set of parts (mostly) and hope to finish this next week. After that, I will make sure it is working (if not, then who knows?) and I need to get it calibrated. Timb has graciously offered to help with that, and with the final battery modification (he can read the data, replace the chip and program the old data). I also still have a couple of modifications that are waiting on parts, but those can be done later. I will update when I have something new.

Right now, even though I have the parts, I can't do anything until I finish repairing my daughter's laptop that failed. Just the hard disk, but it has been a nightmare getting the OS reinstalled. Windows 10 doesn't like it even though it satisfies all of the published requirements and passed the compatibility test.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MSO on January 31, 2016, 07:14:35 pm
Here is the damage, apparent bad components and recapping of the A3 Inverter board for my 2465B CT scope.

Additionally, on the A3 Inverter board there are three more RIFA capacitors and it can be seen that all three are cracked. They may still be working, but probably not for long. The A3 Inverter recap does not include those because I need to order replacements. It can also be seen looking at the bottom on the replaced capacitors that one looks like it was starting to leak, a second appears to have damage to the bottom (pre-leak?) and I am not at all sure if some of the rest are slightly bulging or not. They certainly aren't completely flat, but that may be a construction difference.

A3 Recapped Inverter Board                     (http://imgur.com/pnUyrOJ.jpg)

I've been following this thread for days now, including all the links to other information.  This is a great thread full of good information and populated with great posts.  Thanks to all of you who have contributed here.

FireDragon, it appears as though you may have fallen prey to a documentation error. Specifically, on the A3 inverter board, the documentation has the info for C1132 & C1115 reversed.  It may just be the picture you've provided, but it's worth checking it out.

See this post from HowardLong https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/475/ (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/475/) for complete information.

Again, I've been very impressed by the content and quality of this thread.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on January 31, 2016, 08:18:45 pm
Here is the damage, apparent bad components and recapping of the A3 Inverter board for my 2465B CT scope.

Additionally, on the A3 Inverter board there are three more RIFA capacitors and it can be seen that all three are cracked. They may still be working, but probably not for long. The A3 Inverter recap does not include those because I need to order replacements. It can also be seen looking at the bottom on the replaced capacitors that one looks like it was starting to leak, a second appears to have damage to the bottom (pre-leak?) and I am not at all sure if some of the rest are slightly bulging or not. They certainly aren't completely flat, but that may be a construction difference.

A3 Recapped Inverter Board                     (http://imgur.com/pnUyrOJ.jpg)

I've been following this thread for days now, including all the links to other information.  This is a great thread full of good information and populated with great posts.  Thanks to all of you who have contributed here.

FireDragon, it appears as though you may have fallen prey to a documentation error. Specifically, on the A3 inverter board, the documentation has the info for C1132 & C1115 reversed.  It may just be the picture you've provided, but it's worth checking it out.

See this post from HowardLong https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/475/ (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/475/) for complete information.

Again, I've been very impressed by the content and quality of this thread.
Welcome to the forum.

Well said and a good reminder for the documentation error, it's been mentioned several times over the years.
We look forward to your further contributions.  ;)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on February 04, 2016, 05:03:02 am
FireDragon, it appears as though you may have fallen prey to a documentation error. Specifically, on the A3 inverter board, the documentation has the info for C1132 & C1115 reversed.  It may just be the picture you've provided, but it's worth checking it out.

Thank you. I am fully aware of the documentation error. I replaced the capacitors that were ACTUALLY on the board, in the same locations. I only used the parts list to create the initial order (which is why a follow-up order was needed). That list has been updated and when everything is complete, I will post the final version. Along the way, I verified that the documentation was in error. My process was NOT "remove 'em all and then replace using documentation" - instead it was "remove, verify and replace one-by-one". In some cases where there were multiple capacitors all of the same values, I removed all of them (as long as the correct orientation was obvious, marked or otherwise determinable) and then replaced them.

I have been delayed making the final fixes. My daughter's laptop repair / upgrade was only complete yesterday, and everyone here has had the flu. We did get Windows 10 installed and I stripped out most of the spying, but will still need to do some work / research there.

I have started just this evening on the final fixes. I have now completed A3 and will do A2A1 in a couple of hours. I will (as usual) post the final pictures when that is completed. Then, on to the magic smoke test!

I am waiting on two LEMO (knockoff) connectors from China to add two probe power sockets. The holes are already drilled (except for the plastic back panel), wire routing is determined, I have the plug connectors for the A2A1 probe power pins, so once I get the LEMO connectors I am all set there.

I also need 2-pin, shielded wire-to-wire plug & socket connectors (smallish, around 1/4" x 1/2") so that I can add Option 1E using a switch to select either the WR Output or 1E Input options as needed. I have the switch, the shielded cable and know what changes to make, but I have been totally unable to find an appropriate shielded wire-to-wire connector. I need the connector so that I can disconnect the wires for board removal.

Does anyone have a suggestion?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on February 04, 2016, 11:21:11 am
I have replaced the remaining parts on the A3 and A2A1 board.

A3 Board: (http://imgur.com/dnDgjtd.jpg)
A2A1 Board: (http://imgur.com/UO8L01g.jpg)
Replaced parts on A2A1: (http://imgur.com/ttKuheh.jpg)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on February 04, 2016, 11:38:11 am
Damn .. what happened to those toasted resistors ?  :o

Are their resistances still within the printed values especially for those are not toasted ?

Btw, thanks for the contribution to this thread.  :-+
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on February 04, 2016, 11:45:23 am
Well, my 2465BCT  failed the smoke test! It didn't actually smoke, but it remained dead as a doornail. When I checked, the fuse was blown. I replaced the fuse and found that if I plug it in, but don't turn it on the fuse doesn't blow. When it off, I read 468k between neutral and hot. Since there is a 470k resistor across, that appears to be reasonable. If I turn it on, but leave it unplugged, I cannot tell if the bridge is bad. I get around 20k-40k in either direction, but it jumps around.

Someone has suggested that one of the MOVs appear to be swollen and so may have failed. However, I am not sure that they are MOVs. These are RT1010 and RT1016 and are "thermal resistors". They do not have the same value and so may not look the same. I can't tell by looking if they are bad or not. If they are bad, I am not sure that the replacement part would be. If either RT1010 or Rt1016 failed open then the fuse wouldn't have blown. If they failed short that would not have directly caused the fuse to blow, so they may be a red herring. But, they may still need to be replaced.

Is my most likely culprit the bridge? Since it fails as soon as power is applied, the failure should be fairly early in the circuit.

Let me know what you think.

Area with Rt1010 / Rt1016: (http://imgur.com/YXG7gNr.jpg)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on February 04, 2016, 11:54:39 am
Damn .. what happened to those toasted resistors ?  :o

Are their resistances still within the printed values especially for those are not toasted ?

R1018 reads 30.2 and is specified at 30, 5%, 0.5W. R1016 reads 68.8 and is specified at 68, 5%, 0.5W. So they are within specification! These (and a few others) tend to fail over time because they apparently run too close to their rating. All of the resistors that I replaced were replaced with 1W versions. Actually the same size or smaller than the originals. Some people replace them with 3W or even 5W versions, but that is probably overkill. Only R1016 and R1018 were replaced because of damage, the others were replaced preemptively. Some of those had been chipped, but that shouldn't be a serious problem.


Btw, thanks for the contribution to this thread.  :-+

You're welcome.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: electrongeek on February 04, 2016, 11:16:44 pm
RT1010 and RT1016 are negative temperature coefficient thermistors. They have a high resistance when cold to limit surge current when the unit is first turned on, then their resistance drops as they heat up to allow adequate current flow to the power supply. Perhaps one or both have failed shorted, or drop resistance too fast etc. If they allow too high an initial surge current, you certainly could blow the fuse.

Do they meet their cold specification?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on February 05, 2016, 05:48:40 am
RT1010 and RT1016 are negative temperature coefficient thermistors. They have a high resistance when cold to limit surge current when the unit is first turned on, then their resistance drops as they heat up to allow adequate current flow to the power supply. Perhaps one or both have failed shorted, or drop resistance too fast etc. If they allow too high an initial surge current, you certainly could blow the fuse.

Do they meet their cold specification?

Currently measuring things. One side of the bridge is shorted. I will replace that with a Visnay GBPC606-E4/51.  As far as RT1010 and RT1016, so far RT1016 appears to be around 7.8 at 20c - specification is 5 +/- 10%, so it may be a little high. RT1010 appears to be 10.5, specification is 7.5 +/- 10% so it may be a little high. However, without knowing the specification temperature, it is hard to judge. Being off by a single degree C would be enough to account for the differences. Even my estimate of 20C might be off a degree or two. Both respond to a can of (nearly empty) air with their resistance going up. Both surge suppressors E1001 / E1002 are good. I may replace those preemptively with Littlefuse's CG2230L.

I have not found a replacement for RT1010 / RT1016. Any suggestions?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on February 05, 2016, 08:58:12 am
I have discovered that both RT1010 and RT1016 were sourced from Ketema's Rodan division. That division was sold to Selas and renamed RTI Electronics. RT1016 has the manufacturer part number SG200-S. RTI still sells the SG200. The "S" was for "straight" leads. However, the current tolerance is 15% and not 10%. Otherwise, the part appears to be a dead match. That is Mouser part number 995-SG200 and is $1.33.

I have not found a direct match for RT1010. Its manufacturer part number is 75DJ7R5K-RO-220 which appears to be an older product. It is 7.5 ohm, 10% and 3.9%/C. The value of IMax is not given, but is 7A for RT1016 and so should be fairly close. These are used in opposite input legs of the power supply. However, the circuits are slightly different so the current flows will also be slightly different. The RT1016 has 3.3%/C and is curve "A". There is a curve "B" which is 3.9%, but it is only available for a 40 ohm part with much lower maximum current rating. The closest that I have found is SG64 (Mouser part 995-SG64, $3.62) which is 7 ohms, 15%, curve J (3.5%/C) and 10A for IMax. It may be acceptable. It may even be almost the same because RT1010 is larger than RT1016 which may be an indication of a higher IMax.

I have a query out to RTI to find the best modern match for RT1010 - they have several product lines and one of those may be better.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: electrongeek on February 05, 2016, 01:22:30 pm
I have no idea how NTC thermistors age or typically fail. Since at room temp they are close to their specified resistance, I'm kind of doubting that is your problem. I would keep looking for something else, but wouldn't hurt to replace them anyway I suppose.

I wonder if using a variac to bring voltage up more slowly while monitoring current with a clamp meter would be helpful? That might depend on how the switching power supply starts up, but might get you past the surge and you could at least tell if current draw was normal or not in the steady operating state.

Chip
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on February 05, 2016, 10:51:17 pm
I have no idea how NTC thermistors age or typically fail. Since at room temp they are close to their specified resistance, I'm kind of doubting that is your problem. I would keep looking for something else, but wouldn't hurt to replace them anyway I suppose.

I wonder if using a variac to bring voltage up more slowly while monitoring current with a clamp meter would be helpful? That might depend on how the switching power supply starts up, but might get you past the surge and you could at least tell if current draw was normal or not in the steady operating state.

Chip

The bridge has shorted and is almost certainly my problem. The NTC thermistors are used as surge limiters and do fail and do age. Mine are significantly out of specification. I am also preemptively replacing the surge suppressors.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on February 05, 2016, 10:53:04 pm
For those who might want (now or in the future) a replacement for the RT1010 thermal resistor, 75DJ7R5K-RO-220. This is 7.5 ohms, 10% 3.9%/Cpart. Contact

   Mehdi Samii
   mehdis@ametherm.com

at Ametherm. He is making a couple of free samples for me and stated that he is the contact for any future requests.

The RT1016 is SG200-S 5 ohm, 10% 7A and is still currently available. It is part SG200 (the -S means straight leads, kinked leads are now SG311). The Mouser part number is 995-SG200 for $1.33. It is also available at DigiKey.

These parts are used in many Tektronix products as surge limiters. They may not fail often, but do age. Mine haven't filed, but appear to be significantly out of specification.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MSO on February 06, 2016, 03:51:22 am
I've completed recapping the A3 and A2A1 boards on my 1995 era 2467B. I found only the C1101 on the A3 board actually leaking electrolytic and the RIFA capacitors (C1016 & C1018 on A2A1; C1020, C1052, C1051 on A3) with the gold tinged translucent cases showed mild crazing, but no actual breakage. All in all, everything was pretty clean.

Now I'm moving on to the A5 digital control board I intend to replace all the aluminum electrolytic capacitors (C2011, C2113, C2331, C2965) with new aluminum electrolytic caps.  Is it recommended to replace the tantalum caps as well?  I've ordered the replacements for the tantalums (C2010, C2350, C2420) as they were cheap enough, but I don't know if these are at all problematic.

The real challenge on the A5 board is replacing U2460, the DS1225Y-200 NVRAM with the built-in battery.  I've ordered a new chip and a socket and will perform a direct replacement.  My hope is that I'll be able to make a copy of the data in the old NVRAM and copy the data to the new NVRAM.  It seems that the chances of success doing this is pretty limited.

I've hand copied all of the calibration data (EXER 02) from the NVRAM so I have that information saved, but I don't know if it's necessary to save any/all other data from the NVRAM.  Perhaps the ROM information (EXER 04) should be saved as well?

If I'm unable to read the current NVRAM, I thought I'd read the new chip just to get a clean binary file that I would then edit to insert the calibration data or anything else I might need. The calibration data, as I read somewhere is this thread is located starting at address 1E00.  Now EXER 02 returns the calibration in the form of 16bit words instead of bytes. The 2467 uses the Motorola MC68B02P microprocessor so I assume it uses the Motorola convention for byte ordering.  The most significant byte is written at the lowest address followed by the least significant byte at the next address. Does anybody know if this is correct?

Any help here would certainly be appreciated.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on February 06, 2016, 06:18:57 am
The 2467 uses the Motorola MC68B02P microprocessor so I assume it uses the Motorola convention for byte ordering.  The most significant byte is written at the lowest address followed by the least significant byte at the next address. Does anybody know if this is correct?

The Motorola 68xx processors use the big endian byte ordering, so you are correct.

The tantalums are sealed, so they don't have the same failure modes as aluminum electrolytic capacitors. They do have their own failure modes, but generally they don't need to be replaced. Some people suggest measuring the ESR, but that is difficult to do without lifting one pin. Lifting a lot of pins unnecessarily just increases the risk of damage due to recapping. If you are going to lift one pin to measure, you might as well just replace it and be done with it. I would recommend leaving the tantalums alone unless you can trace a failure to one because the likelihood of failure is comparatively low.

The only things I have replaced (during a full recap) was all of the electrolytic capacitors, and some resistors on A1A2 which tend to fail due to overheating. I had two that were seriously burned (and two of my RIFA capacitors had exploded). I replaced the 0.5W resistors (and two 0.25) with 1W versions. Some people replace those with 3W or 5W versions, but 1W should be enough to prevent the problem and are the same size as the originals.

If your scope has failed, you might want to consider replacing more, but sometimes just the capacitors is enough. In my case, my scope had failed and the capacitors / resistors weren't enough. I found that the bridge was shorted, so I am replacing it, the surge suppressors and the two thermal resistors. Only the bridge is really necessary.

As far as the battery is concerned, I have a non-SMD version of the 2465BCT so I have an explicit battery. Even so, I plan on replacing the ROM with an FRAM. You can do something similar, but either way you need to save the calibration data. EXER 02 allows you to read the data, but doesn't do squat for putting it back. So you need to read out the data and then write the data to the replacement IC. That is a complicated process and I can't advise on that. There are people who have replaced their Dallas chips with an FRAM and a piggyback battery. You need to do some searching to make sure you fully understand what you are doing for that. If you can't read / write the data, then you need to do a full calibration. That takes specialty equipment.


Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on February 09, 2016, 05:38:34 am
My first posting!   Been following this thread for some months with interest, because it's one of the best.  I purchased a 2465B months ago with problems.   It worked great - except when it intermittently didn't.   Decided to keep and fix it because it was so clean inside and out with no physical damage.

Through this process I've learned that this scope is an electronic engineers dream.   That is; a manager puts together a team of engineers with free rein to design the best scope possible.   The result is; short of a signal trace memory, it includes just about every detail known to man at that time.   Consequently, it can be a dream for users - but a nightmare to fix when something goes wrong.   But at least it is designed to be repairable.

While searching for the cause of the signal trace going crazy, the first unrelated thing I replaced was the fan.   It was a bit noisy and I suspected it to be the original fan (Nidac, Mod. D08G-12th).   I replaced it with an NMB Technologies Corp. #3108NL-04W-B30-P00 which seemed to be a perfect match.

While confirming the fan polarities and air flow direction, I found the voltage at the fan feed through to be 6.7 volts.   This did not sound right as both the old and new fans were rated for 12 volts.   Further investigation revealed that they didn't simply just drive the fan with 12 volts when the scope was powered on - they put in a temperature sensing voltage controller, powered from the +15 volt power supply.   So when the shop and scope are cold, the fan will see a floor of 6.7 volts.   And as proven with hot air from a heat gun on the temperature sensor, the fan voltage increases - then decreases when blowing room temperature air.

Taking it a step further, with the scope back in its case on a clear bench with the front elevated a few inches by the carry handle, I turned it on.   Over time, I monitored the voltage through added leads extending out through the rear grille, and the exhaust temperature with a thermocouple in the exhaust port.   Over the course of an hour the exhaust T rose from 62 degrees F (shop T), to 83 deg. F where it stabilized.   That's a delta T of 21 deg. F.   The fan voltage increased from 6.7 to 9.7.   Therefore, I'm assuming that in a hotter environment the fan will see 12 or more volts.  A closer look at the new fan spec's found it's rated at 6-13.8 volts.   So from all this, I assumed the scopes cooling fan is working correctly.   Ok - - this is an elegant way to control the scopes temperature, but I question the value to cost trade off.

The other thing I found with the fan was that the sheet aluminum assembly that clamps the fan in place was a bit too tight.   It was deforming the fan spokes enough to cause a noise increase in the fan bearings.   looking at the original fan revealed that it's frame spokes were permanently deformed by the excess pressure on the center of the fan, rather than the outboard ears that were designed for mounting.   They were EE's not ME's :)   The old original fan now runs quieter on the bench with the mounting pressure removed.   To fix this, I tweaked one of the bends in the aluminum clamp, ever so slightly with long nose pliers, to remove most of the pressure on the fan.   it runs quieter now while still being firmly held in place.

More later
Old-E 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MSO on February 09, 2016, 07:32:00 am
Thanks for the tantalum info FireFragon, I'm from the firmware side of things, so my EE skills cause me more problems then they solve.

My scope was working, so my goal was to replace all the electrolytic caps before they ruined the boards.  I did replace all the electrolytic caps with new electrolytic caps rather than attempting to spec tantalum replacements. From what I could gather, the tantalums require a bit more knowledge of their usage than I possess, so I stuck with the 'lytics.

I looked at replacing the DS1225Y-200 chip with the FM1608 family, but decided to just put in a new socketed DS1225Y-200 instead. The device currently in use is over 20 years old and I figured that I could easily program another one ten years from now and be on my merry way.

You did set a bit of a high standard when you replaced all the 'lytics on the main board, though, and it seems foolish of me not to do the same thing.  Did you replace the main board caps with tantalums or did you use new electrolytics?

OLD-E, thanks for the fan info.  Mine fan is a bit noisy too and I was going to order  a new one as well.  With only size, voltage and current specs to draw upon, I didn't feel comfortable specifying a replacement. I'll follow your lead and then blame you if it doesn't work out. (I'm kidding!).

I did order a new MiniPro TL866A programmer from amazon, but I didn't pay enough attention; seems mine is coming via slow boat from China and I won't see it until the end of March. So I've put the scope back together and it's still running fine.  I'll look into the replacement of the capacitors on the main board and double check all the info I can find about loading new data into the DS1225Y while waiting for my programmer to arrive. I have my fingers crossed and am hoping I'll be able to read an image from the old chip.  I expect that I'll have to parallel the battery in the old chip, but that doesn't appear to be as difficult as removing the chip from the board.

Thanks for all the contributions on this thread.



Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on February 09, 2016, 08:08:49 am
For those replacing the Dallas you may find some good information here.

http://worldphaco.com/uploads/TEKTRONIX_2465b_OSCILLOSCOPE_CALIBRATION___REPOWERING_THE_DS1225.pdf (http://worldphaco.com/uploads/TEKTRONIX_2465b_OSCILLOSCOPE_CALIBRATION___REPOWERING_THE_DS1225.pdf)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on February 10, 2016, 05:22:36 am
Thanks Bryan for the article.   I had found that one before starting on the scope and it has a lot of good info.

Back to cooling - Actually MSO, if that fan does turn out to be a problem, you would do me a favor by letting me know.   I bought it 3 months ago from Digi-Key (their #P15646-nd) for $13.61.   I think it has 15-20 hours on it so far and running good.

Another parallel effort was cooling U800, the IC that has been reported by others as running too hot.   As I recall from reading further back in this thread, Tektronix turned their production of this chip over to Maxim to produce.   As it turns out, my chip is an original Tektronix one which is said to run cooler.   Running uncovered on the bench, it runs fairly warm to touch, but not hot.   Looking closer, my finger indicated that the heat sink end of the chip was hotter than the opposite end.   So it would appear that their was a reason for putting the heat sink on that end.   Conclusion was that this Tek chip probably did not need additional cooling.   But, since it's all apart, a little more frosting on the cake can only help.   So the decision was to add a heat sink to the existing heat sink on the hot end of the chip.   Laying a heat sink across the top of the chip will certainly help, but the concern was the questionable thermal resistance through the plastic case.

This heat sink was aluminum machined to 5/8 " OD x 3/8" high with 8 radial fins on sides and top.   It screws onto the existing stud on the hot end of the chip.   I drilled the tap hole a few thousands smaller than normal to get slightly more thread contact for better thermal conduction.   Then I lubed the threads and the seating surface on top of the existing nut with a thermal conducting paste to further aid in conducting the heat out.   The heat sink bottoms out on the existing nut which was just high enough so that the bottom of the heat sink cleared the top of the IC.   The top of the heat sink is < the height of the surrounding parts.   This way, none of the existing hardware had to be disturbed, but it does rely on the thermal energy conducting up through the face of the nut and the threaded stud.   Could have made the heat sink larger in diameter, but didn't want to shade to much of the IC from the cooling air coming in through the bottom of the case.   It was an intuitive tradeoff.   The new heat sink feels to be the same elevated temp as the chip, so apparently it is conducting as planned.   But, the heat sink fins need air moving past them to do any good, as through the vent holes in the bottom of the case. 

I have pictures to insert, but can not figure out how to add them.   Tried Copy & Paste, and I found the Insert Image button, but nothing works.   "Help" only says that it can be done.   Can someone please advise?

More later with photos.
Old-E
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on February 10, 2016, 06:10:19 am
@Old-E
Using Atttachments and other options, select a forum compatible file and upload with your post. Pics do not have to be large to show good detail and normally ~100Kb is plenty.
When your post is made you'll have a thumbnail at the foot of the post and if you copy that URL you can edit your post with the URL inserted between the IMG quotes.

Use Quote on somebody's post with imagery to see the syntax used.  ;)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on February 10, 2016, 06:59:04 am
Thanks for the tantalum info FireFragon, I'm from the firmware side of things, so my EE skills cause me more problems then they solve.

. . .

You did set a bit of a high standard when you replaced all the 'lytics on the main board, though, and it seems foolish of me not to do the same thing.  Did you replace the main board caps with tantalums or did you use new electrolytics?

I only replaced the aluminum electrolytics. I did buy many of the tantalums, but decided to leave them alone. There really aren't that many tantalums, the problem is that the parts list does not distinguish between aluminum and tantalum and bipolar. The only way to find out is to have someone tell you or to actually look at the original parts. The latter can be difficult before removing the boards.

Some tips on removing the main board. The removal instructions give a complex process to remove the power switch assembly. Completely unnecessary. Just unscrew the screw at the front that holds in it, then you can just twist it out of the piece of connecting plastic and (holding it carefully!) remove the entire assembly in one piece. Putting it back is just as easy. Just be really, really careful with the CRT leads. They are very delicate. If you don't have a steady hand, lots of patience and plenty of small tools then I wouldn't recommend removing the main board - you really don't want to fark up the CRT!

Make sure to get lots of pictures on how things go back together - especially for the CRT leads which are in a dark hole. Also be careful replacing the capacitors under the delay line. I propped up the delay line with something to give me just enough room to work. It was still tight. There is also a wire that is held down by a retainer in the board. Mine broke! Pretty trivial, I will use a piece of Kapton tape to hold the wire down because I don't have a replacement, but hopefully forewarned is forearmed!

Here is my parts list for the main board. My scope is pre-B050000, but the parts lists does not list any changes that affect the electrolytics so my replacement list should be adequate. I purchased everything at Mouser. For a small shipment Digi-Key has slightly less shipping, but includes tax. In this case, Digi-Key either doesn't have the parts that I used or are as much as 50% higher in cost. To be fair, there are a lot of parts that Digi-Key has and Mouser does not (but not for this project).

   C0102  290-0973-00  100uF    20%     25VDC                 UPW1V101MPD  100uF  35V 20% 105c 0.24
   C0107  290-0943-02   47uF    20%     25V                   UHV1V470MDD   47uF  35V 20% 105c 0.212
   C0114  290-0943-02   47uF    20%     25V                   UHV1V470MDD   47uF  35V 20% 105c 0.212
   C0121  290-0943-02   47uF    20%     25V                   UHV1V470MDD   47uF  35V 20% 105c 0.212
   C0130  290-0776-01   22uF    20%     10V                   UPW1E220MDD   22uF  25V 20% 105c 0.16
   C0152  290-0943-02   47uF    20%     25V                   UHV1V470MDD   47uF  35V 20% 105c 0.212
   C0185  290-0943-02   47uF    20%     25V                   UHV1V470MDD   47uF  35V 20% 105c 0.212
   C0218  290-0943-02   47uF    20%     25V                   UHV1V470MDD   47uF  35V 20% 105c 0.212
   C0221  290-0943-02   47uF    20%     25V                   UHV1V470MDD   47uF  35V 20% 105c 0.212
   C0307  290-0943-02   47uF    20%     25V                   UHV1V470MDD   47uF  35V 20% 105c 0.212
   C0325  290-0943-02   47uF    20%     25V                   UHV1V470MDD   47uF  35V 20% 105c 0.212
   C0335  290-0943-02   47uF    20%     25V                   UHV1V470MDD   47uF  35V 20% 105c 0.212
   C0512  290-0246-00    3.3uF  10%     15V  Axial Tantalum
   C0536  290-0246-00    3.3uF  10%     15V  Axial Tantalum
   C0723  290-0943-02   47uF    20%     25V                   UHV1V470MDD   47uF  35V 20% 105c 0.212
   C0731  290-0944-01  220uF    20%     10V                   UPW1C221MPD  220uF  16V 20% 105c 0.25
   C0732  290-0944-01  220uF    20%     10V                   UPW1C221MPD  220uF  16V 20% 105c 0.25
   C0733  290-0943-02   47uF    20%     25V                   UHV1V470MDD   47uF  35V 20% 105c 0.212
   C0738  290-0943-02   47uF    20%     25V                   UHV1V470MDD   47uF  35V 20% 105c 0.212
   C0740  290-0943-02   47uF    20%     25V                   UHV1V470MDD   47uF  35V 20% 105c 0.212
   C0957  290-0804-00   10uF   +50-20%  25V                   UPW1V100MDD   10uF  35V 20% 105c 0.16
   C0977  290-0246-00    3.3uF  10%     15V  Axial Tantalum

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on February 10, 2016, 07:29:03 am
Thanks for the tantalum info FireFragon, I'm from the firmware side of things, so my EE skills cause me more problems then they solve.

My scope was working, so my goal was to replace all the electrolytic caps before they ruined the boards.  I did replace all the electrolytic caps with new electrolytic caps rather than attempting to spec tantalum replacements. From what I could gather, the tantalums require a bit more knowledge of their usage than I possess, so I stuck with the 'lytics.

I am also from the software side - including firmware. My EE skills definitely need improvement, but I am getting there.

I have seen a lot of statements that replacing a tantalum with an electrolytic requires around 10 times the capacitance. I think that is a hang over from the state of affairs ages ago. The reasoning seems to be that tantalums have a low ESR compared to electrolytics.

Things have changed! Tantalums are more reliable, but also most tantalums appear to have an ESR of 1-3 ohms. There are lower ESRs, but they are hard to find and apparently not common. So presumably not the subject of the older advice. Most of the electrolytics that I used for replacement have ESRs which are well below 1 ohm. So I don't see any need to replace electrolytics with tantalums. And if you REALLY need low ESR use ceramics which can be 0.01 ohms or even lower.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on February 10, 2016, 05:21:53 pm
With this set of replacements, the scope passes the smoke test and all diagnostics.  :)

Replaced bridge, surge suppressors, one more resistor and one of the thermal resistors. Only the bridge was necessary.

A major milestone, but the saga isn't over yet. I am still waiting on the replacement for the other thermal resistor. That is a custom part. Also I am waiting for the LEMO style connectors (knock off, from China) so that I can add two probe power sockets. And calibration along with replacing the RAM with FRAM. At this point none are critical, so I will take those in the order they become possible. I still have to LEARN how to use the scope! But it looks like all of the features are present and working, but without more testing I could still find problems.

Replaced parts. (http://imgur.com/p2kamJD.jpg)

Diagnostic test result. (http://imgur.com/mCxElwz.jpg)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Muxr on February 10, 2016, 05:28:45 pm
Nice!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on February 10, 2016, 06:43:45 pm
Thanks tautech for the instructions on posting photos.   But I need more information!   I have the forum compatible photos ready to go.   Then - if I understand correctly -

1.  Place the curser where the photo is to be located on the text page and left click.   This pegs the location for the photo.
2.  Click on the "Insert Image" icon (located above on the far left side).   This displays the "IMG's" where the photo is to be located.
3.  Click on "Attachments and other options" (below).   This displays the "Attach:" path.
4.  Click on "Browse."   This displays the "Choose file to up load" page.
5.  Locate intended photo on the up load page, then click on the "Open" button (lower right).   This displays the photo file info in the "Attach:" path.

If this is correct so far, I got that.   But now what?   Clicking on "Preview" displays the message text, but no indication of a photo.   It appears that something is missing.   And if I click on "(Clear Attachments)," nothing happens.   I would like to get it right before posting on the blog, but there does not seem to be a way to do that!

Frustrated. 

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on February 10, 2016, 06:53:11 pm
Well, some how one of the photos attached to the last message, but I don't know how.   I'll experiment more to see if I can make it happen again.

Frustrated.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on February 10, 2016, 07:13:29 pm
I have been playing with my 2465BCT. So far everything that I know to try has worked. My only signal source is the calibrator signal, but it works on all four channels. The scope can do at least some measurements - but I need to learn more to really test that. I recreated everything I was doing when the scope failed and it all worked as expected.

I do appear to be missing a bolt. One of the two on the middle back that is about 3/4" long. I think that I probably used it somewhere internally because I have an extra short one. I got a replacement (Philips head, though) from my junk screw bowl and used that. If the original doesn't turn up, I will probably buy a replacement so that they all match.

There is one possible glitch - I am not sure the fan is working. After I had the scope on for some time (not sure, perhaps an hour or so), I noticed that the top was mildly warm to the touch. However, I was unable to feel any fan exhaust. Perhaps it wasn't hot enough to kick on or it was running very slowly.

But - perhaps the fan isn't working. I need to investigate that. It could be the fan, the soldered connections, the pass through capacitor or the fan control circuit. I'll look at that tomorrow, its about my bedtime now. I don't like the pass through capacitor. I shouldn't need to solder / unsolder the fan every time I want to do some maintenance. Also, it is much too close to the chassis. Just for safety, I put some Kapton tape on the chassis wall to prevent accidental contact with the fan's positive supply.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MSO on February 10, 2016, 09:22:38 pm
FireDragon:

Thanks for the part list; it'll make the ordering process a lot easier.  I'll order those caps for the main board and the two caps on the A9 board.  Once they're in hand, I'll be pushed into actually replacing them.

Congrats on bringing your scope back to life; it's nice to see it performing again. I've made note of the surge protectors for future reference.  I didn't test mine when I had the scope apart.  BTW, I also came up with one extra screw; it's a short one with no washer attached. I'll keep you posted if I ever find where it came from.

OLD-E, that looks like a nice heat sink. Mine has one of those grounding fingers mounted on the heat sink end, but it is formed such that it won't touch the bottom of the case.  I don't know who did it, but it's there.

Here's (I hope) a picture of my scope with a 500MHz signal @ 13dBm fed into channel 1 with the x10 mag enabled. The old scope is pretty quick for its age.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MSO on February 10, 2016, 09:32:46 pm
FireDragon,

 When I put my scope back together, I had mounted it backward so the support bracket was pushing on the fan axel preventing it from moving.  My 'lab' is kept cool, 60f or so, but the fan turns on immediately; at least it does after mounting it correctly.

I was suckered by the indents on the back side of the fan housing that matched up perfectly with the two little pegs incorporated in the fan mounting plate.  They fit together perfectly, they aligned the fan perfectly and there were no such indents on the front side of the fan. Hey, that's the way its got to go right? 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on February 11, 2016, 02:49:23 am
FireDragon,

 When I put my scope back together, I had mounted it backward so the support bracket was pushing on the fan axel preventing it from moving.  My 'lab' is kept cool, 60f or so, but the fan turns on immediately; at least it does after mounting it correctly.

I was suckered by the indents on the back side of the fan housing that matched up perfectly with the two little pegs incorporated in the fan mounting plate.  They fit together perfectly, they aligned the fan perfectly and there were no such indents on the front side of the fan. Hey, that's the way its got to go right?

I may have done that. I will have to check after breakfast and a grocery store trip.

Is the fan supposed to blow into the case or out of it? Normally, a fan will blow into the case.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on February 11, 2016, 04:48:05 am
   C0102  290-0973-00  100uF    20%     25VDC                 UPW1V101MPD  100uF  35V 20% 105c 0.24
   C0107  290-0943-02   47uF    20%     25V                   UHV1V470MDD   47uF  35V 20% 105c 0.212
   C0114  290-0943-02   47uF    20%     25V                   UHV1V470MDD   47uF  35V 20% 105c 0.212
   C0121  290-0943-02   47uF    20%     25V                   UHV1V470MDD   47uF  35V 20% 105c 0.212
   C0130  290-0776-01   22uF    20%     10V                   UPW1E220MDD   22uF  25V 20% 105c 0.16
   C0152  290-0943-02   47uF    20%     25V                   UHV1V470MDD   47uF  35V 20% 105c 0.212
   C0185  290-0943-02   47uF    20%     25V                   UHV1V470MDD   47uF  35V 20% 105c 0.212
   C0218  290-0943-02   47uF    20%     25V                   UHV1V470MDD   47uF  35V 20% 105c 0.212
   C0221  290-0943-02   47uF    20%     25V                   UHV1V470MDD   47uF  35V 20% 105c 0.212
   C0307  290-0943-02   47uF    20%     25V                   UHV1V470MDD   47uF  35V 20% 105c 0.212
   C0325  290-0943-02   47uF    20%     25V                   UHV1V470MDD   47uF  35V 20% 105c 0.212
   C0335  290-0943-02   47uF    20%     25V                   UHV1V470MDD   47uF  35V 20% 105c 0.212
   C0512  290-0246-00    3.3uF  10%     15V  Axial Tantalum
   C0536  290-0246-00    3.3uF  10%     15V  Axial Tantalum
   C0723  290-0943-02   47uF    20%     25V                   UHV1V470MDD   47uF  35V 20% 105c 0.212
   C0731  290-0944-01  220uF    20%     10V                   UPW1C221MPD  220uF  16V 20% 105c 0.25
   C0732  290-0944-01  220uF    20%     10V                   UPW1C221MPD  220uF  16V 20% 105c 0.25
   C0733  290-0943-02   47uF    20%     25V                   UHV1V470MDD   47uF  35V 20% 105c 0.212
   C0738  290-0943-02   47uF    20%     25V                   UHV1V470MDD   47uF  35V 20% 105c 0.212
   C0740  290-0943-02   47uF    20%     25V                   UHV1V470MDD   47uF  35V 20% 105c 0.212
   C0957  290-0804-00   10uF   +50-20%  25V                   UPW1V100MDD   10uF  35V 20% 105c 0.16
   C0977  290-0246-00    3.3uF  10%     15V  Axial Tantalum

FireDragon  :clap: , thanks a lot for listing down the caps for the A1 board.

To recap this big A1 board is already in my to do list, its just I'm too scared, really appreciate the tips on removing it, noted in my to do list for my 2465B.

Just curious if there is any bad effects if I replace them with quality polymer cap like Oscon caps ? Apart from the price of course.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on February 11, 2016, 04:54:35 am

....<snip>.... Hey, that's the way its got to go right?
Is the fan supposed to blow into the case or out of it? Normally, a fan will blow into the case.

The fan is blowing out of the case at the rear as I dissembled it for the 1st time.

I'm not the expert, but after looking at the vent holes like these, I believe their purpose are to have fresh cooler air get suck in and to blow straight at the hot parts, like the U800 and others.

Reposting my tear down photos to show what I mean.

Scope's bottom view, the U800 is located at the left top one.
(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=16761;image)

Close up view on the vent holes, you can see the U800 is located straight below.
(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=16763;image)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MSO on February 11, 2016, 05:25:46 am

Is the fan supposed to blow into the case or out of it? Normally, a fan will blow into the case.

Straight from page 2-1 of the service manual:

    "INSTRUMENT COOLING" 
To prevent instrument damage from internally generated
heat, adequate air flow must be maintained. Before
turning on the power, verify that the spaces around the
air-intake holes on the bottom of the cabinet and the fan exhaust
holes in the rear panel are free of any obstruction
to airflow."

So the fan sucks in from the bottom and blows out the rear.  I wanted to make a joke here, but decided not to.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on February 11, 2016, 07:27:39 am
Ok - - we'll see if I can make the picture attachment work in order to conclude the cooling issues from a few days ago.

This is a picture of the U800 IC that runs warm - hot.



This shows the new aluminum heat sink added.

(http://)

The heat sink is designed to shed heat best when cooling air is being pulled in through the vent holes in the bottom of the case.   It's not as efficient when operating in the open like this in still air.   But, while the case was off the temperature was measured with a digital thermocouple (TC) meter anyway.   This was done by holding the TC in-between the fins of the heat sink with a tooth pick and a dab of thermal conducting paste.   Then it was moved to the stud at the opposite end of the IC.   The stabilized temps were -
120 deg. F on the heat sink.
114.4 deg. F on the threaded stud at the opposite end of the IC.
60.6 deg. F shop air temp.

A 55.4 deg. rise in temp seems like a lot, but this is with the case off.

Then at a later date the temp was measured again, in still air and with the old removed fan blowing, with the scope laying on its side as in the picture below.   The temps were -
122 deg. F on the heat sink in still air.   This is probably better for convection cooling than with the scope upside down.
84 deg. F on the heat sink in moving air.
65.1 deg. F shop air temp as seen on the digital meter.   In this photo the thermocouple can be seen suspended in mid air.

This illustrates how moving air helps in cooling the heat sink.

(http://)

Unfortunately, I didn't measure the temp before installing the heat sink, or while in the case.   So all I can say is that the heat sink should help and I'm not too concerned with the temp of this Tek chip ether way.   But, if it was running inside a tent on the Sahara Desert in the summer, I might be concerned.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on February 11, 2016, 07:34:26 am
Guess I still don't have the picture part working yet.   This is frustrating!   There must be detailed instructions some place on how to add pictures to a message.

Frustrated
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: miguelvp on February 11, 2016, 07:46:42 am
Service manual:

http://bama.edebris.com/manuals/tek/2465service/ (http://bama.edebris.com/manuals/tek/2465service/)

Other manuals here:
http://bama.edebris.com/manuals/tek/ (http://bama.edebris.com/manuals/tek/)

Look for:
2465b
2465b-mil
2465bfull
2465dmm
2465service (linked above)

As for posting pictures, click on the choose file and make sure it's one of the allowed fie types and the image is less than 1000KB as this screenshot depicts:
(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=200673;image)

Once posted click on the picture to make it bigger, right click on the image and select "Copy Image Address" (at least that's what it is in Chrome)

Then edit your message and add

Code: [Select]
[img]https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=200673;image[/img]
where the link between the begin img and end img is the link you just copied.

The example above is my image that I attached to my post and added later to my post.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on February 11, 2016, 08:34:23 am
Thanks tautech for the instructions on posting photos.   But I need more information!   I have the forum compatible photos ready to go.   Then - if I understand correctly -

1.  Place the curser where the photo is to be located on the text page and left click.   This pegs the location for the photo.
2.  Click on the "Insert Image" icon (located above on the far left side).   This displays the "IMG's" where the photo is to be located.
3.  Click on "Attachments and other options" (below).   This displays the "Attach:" path.
4.  Click on "Browse."   This displays the "Choose file to up load" page.
5.  Locate intended photo on the up load page, then click on the "Open" button (lower right).   This displays the photo file info in the "Attach:" path.

If this is correct so far, I got that.   But now what?   Clicking on "Preview" displays the message text, but no indication of a photo.   It appears that something is missing.   And if I click on "(Clear Attachments)," nothing happens.   I would like to get it right before posting on the blog, but there does not seem to be a way to do that!

Frustrated.
You've nearly got it.....

You can upload numerous files/pics in posts up to the limit allowed per post.
They'll be either a thumbnail or a file available for download by members.
So use "Attachments" and (more attachments) for more than one upload.

If you want to attach a large image do it like this:
Copy the thumbnail URL.
Edit your post and Paste the image/s URL within in the IMG brackets.

(https://www.eevblog.com/forum/index.php?action=dlattach;topic=5397.0;attach=200457;image)

Note this is a much larger file than is needed and to be fair to Dave's server you should reduce the size of images to les than 100Kb whenever possible.
Quote this post to see the syntax used.  ;)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on February 11, 2016, 08:53:28 am
Thanks miguelvp - Yes, I have the photos in the acceptable jpg format and reduced to < the pixel count limit.

Do I understand correctly that none of the icon buttons at the top are used to post a picture as I have been trying to do?

After clicking on "Attachments and other options" the "attach:" path is displayed.   But it's blank.   There is no "Choose file" or "No file chosen" as shown in your example.   The only other option I have is to click on "Browse" (or any place on the "Attach: path)."   This brings up my pictures displayed on the "Choose File to Upload" page.   From there I can select a photo, click on the "Open" button which displays the photo address back in the Attach path.   But then how to I get that attached to the message?

Maybe another problem I'm having is trying to locate photos between text lines.   Maybe photos can only be added at the end of the message.   Is this true?   I hate to clutter up the blog with test entries.   I've looked everyplace on this site for instructions.   The process seems much more complicated than necessary.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: miguelvp on February 11, 2016, 09:51:11 am
Attach one picture then and look what that does on the post.

As for the buttons, if you look on the 2nd row, the first column that is the icon that will allow you to get the format for inserting a picture, but you can type it too.
Code: [Select]
[img]url link to picture on the web or attachement[/img]

For now just use the attachment to post the picture. At least that way, members can click on the thumbnail and it will expand to full size.
Even if it doesn't look like my screen capture, use the browse to select the image to attach and say ok and then post.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on February 11, 2016, 10:02:59 am
After investigation - the fan on my 2465BCT was NOT running!

However, the fan is ok and the control voltage is ok. It turns out that the feed through capacitor 281-0697-00 is shorted. I bypassed the capacitor and the fan works normally. So, I need to replace that. I don't have a really good definition of the part, but I think that 2425-018-X7W0-502PLF at Mouser is possibly a fit. It appears to match all of the available specifications. It has 8-32 threads which are close to the measured threads on the removed part. I can take it to Lowes to see if the existing part has 8-32 threads.

I did put the fan in so that it fit into the detents on the case. However, there is only one way to do so, so that the wires reach and the fan cover does not rest directly on the fan hub, preventing it from turning. In particular the logo of the fan faces outwards. So I had that correct and the only problem is the capacitor.

The above part is $7.84. I may replace the fan as well to reduce noise and / or improve air flow.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on February 13, 2016, 07:47:20 pm
Back to refurbishing my 2465B scope with the cooling issues/solutions previously reported and laid to rest.

When first receiving it, it had an intermittent problem with the signal trace lines jittery.   While looking for the problem they continued getting worse to almost full time jumping around vertically.   But it always passed the initial self test and never displayed an error message.   Photo of display below is using a short time exposure.

But before any work could be done on the scope, it needed a fixture to stand it in for removing the case.   I'm told that tech's usually use the plastic face cover to stand it up in, but that was missing from scope.   And I understand that front controls are sometimes broken from owners trying to remove the case without any protection.   So first step was to make a stand-up fixture.   Photo below shows the one I made out of wood which works very well.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on February 13, 2016, 07:53:11 pm
Still having picture problems.   Whenever I load one, it erases the previous one.   I've posted countless pictures on various media and blogs and never had this much trouble.

Anyway this is a photo of the jittery trace that was supposed to be with the last entry.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on February 13, 2016, 08:34:33 pm
Once the case was off, a neighbor friend and I started looking for the cause of the jittery trace.

Fist step was a visual of everything inside looking for anything that did not look right, but nothing caught our attention.

Power supply voltages at J119 were all perfect.

When starting to probe through the digital logic on the A5 board we found the 3 leaking caps, C2011, C2331, C2113, which we had not previously read about.   But since, have found numerous entries here and other places about this time bomb.

We also found the 2 reference voltages (~ .142 mv) on pin 14 & 15 of the DAC, U2101, were moving around a few millivolts as measured with a digital voltmeter.   The resistor divider network feeding pins 14 & 15 are near the 3 leaking caps.

The photo below shows the original 3 aluminum electrolytic caps and the corrosive damage to the adjacent components.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on February 13, 2016, 08:44:19 pm
Unfortunately pretty typical issue. Make sure to replace the caps and I believe there is a fourth on the far right side of the board. I would also replace the SMD components near the corrosion and absolutely make sure you clean the board thoroughly around the corrosion. Hopefully there has been no damage to the traces.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on February 13, 2016, 08:55:13 pm
Regarding the jittery trace; looking more closely we found the 4th cap, C2965 on the A5 board also leaking.   The adjacent screw was also corroded.   It appears like much of the leaking material might be in a gas form, because of the way it collects on anything metallic in the area.   Photo shows the 4th aluminum cap with the adjacent damage.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on February 13, 2016, 09:28:27 pm
After finding the leaky caps - and numerous other entries looking just like this, the old caps were removed, board was cleaned with alcohol and new caps installed.   The old caps were measured after removal and found to have <1% of the original capacity.   The caps were replaced with 10 uf, 35 v & 33 uf, 10 v tantalums from Digikey for a few dollars each.   The corrosion had not eaten through any of the traces, so the mess was cleaned up and all the other parts were left, even though the solder had been clearly attacked too.

The result was no more trace jitter!   And the wandering reference voltages on pin 14 & 15 of U 2101 are now rock solid.   At this point the scope was working perfectly, so we started stepping through the functional tests when the readout digits started going crazy.   The individual pixels, making up each digit, were modulating in the z axis/intensity.   With time they got so bad they would temporarily disappear and they began to affect the trace line.

Photo below shows 3 of the 4 new tantalum caps (yellow) in place.   
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on February 13, 2016, 09:50:35 pm
At this point the scope was working perfectly, so we started stepping through the functional tests when the readout digits started going crazy.   The individual pixels, making up each digit, were modulating in the z axis/intensity.   With time they got so bad they would temporarily disappear and they began to affect the trace line.

Photo below shows 3 of the 4 new tantalum caps (yellow) in place.   

That could be a adjustment may be needed on the Grid Bias. Have a look at 2465B CRT adjustments -Grid Bias in the service manual.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on February 14, 2016, 10:07:54 pm
Thanks Bryan for the much appreciated suggestions.   Are you saying the grid bias pot may have become intermittent/noisy?   This scope is all a learning experience in process.

Continuing on (several weeks ago) in search for the cause of the jittery readouts, we started looking at various digital signals and voltage levels on the A5 bd.   In the mean time the condition was getting worse to where the readout digits started displaying rows of 1's and dashes across the screen and diagonally.

On the board, the first problem encountered was that some voltages were not showing up where they should be.   This led to ohming out signal lines which led to the realization that there are numerous errors on the schematic.   This is a surface mount bd with s/n > 50000 in a 2465B scope.   And the documentation in the Service Manual correctly reflects those numbers.   It appears that somewhere in the design phase, the last design iteration did not get updated on the schematic.   The thought of reverse engineering the bd by buzzing out every connection, to every other connection, seem impractically daunting.   The changes/errors found so far are in the vicinity of the gates across the lower part of the schematic, and add up to 13!   Some changes were also confirmed visually by following the traces on the bd.   In some cases where they disappeared under an IC, they could be found in close up photos taken by others of the bd after certain IC's had been removed.   

The next issues were found around resistor R 2590, listed as 1k on the "Readout" schematic.   A closer look found that the 1k resistor was really stamped as 332 ohms!   And the parts list showed it as 332 ohms.   But there was also a voltage drop across that resistor that did not compute.   Tracing signals to find what else was connected to that line, we found it fed inputs to 3 other gates which should all be high impedance and should not pull that line down to ~ 2 volts.   The digital lines running off the +5v supply should always be very near 0 or 5v, except when transitioning.   Something was abnormally loading it.   As much as I hated too, started lifting the input pins from the gates on that line.   The line remained loaded until the last one was lifted, pin 2 of U2890 A.   Soldering the pin back down again did not recreate the load, so maybe some thermally sensitive part inside fixed itself.

So U 2890 (74HCT00) was replaced.   Finally - clean and stable readouts!   But - there was sometimes a hiccup on power up when going through its self test.   It would stop midway and show something like TEST 03 PASSED.   Never indicated anything failed.   Pressing A/B TRIG returned the scope to normal operation where it worked perfectly.   Following a couple of days of occasionally fiddling with it, that problem went away and now it can not be recreated.   The scope was even set to continually loop through all the self tests - and it did that for hours without a hiccup.   Checked all the PS voltages at J 119 and they are all golden, but I did not follow them through the turn on cycle.   So something is still amiss and is highly likely to eventually return.

The Service Manual I'm using is -
Tektronix
2465B & 2467B
070-6863-01
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on February 15, 2016, 04:45:02 am
Still having picture problems.   Whenever I load one, it erases the previous one.   I've posted countless pictures on various media and blogs and never had this much trouble.

Old-E, pay attention at the attachment dialog box, to have more than one attachment, you have to click the "(more attachments)" at below example provided by miguelvp.

Watch closely below picture as its easy to miss  :P (its hiding between the two red highlighted box) , once clicked, it will pop up another "Choose File" dialog box for you to select another attachment for uploading, just keep doing that if you have more, and up to ten attachments are allowed in single post.

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=200673;image)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on February 15, 2016, 08:41:12 am
Thanks Bryan for the much appreciated suggestions.   Are you saying the grid bias pot may have become intermittent/noisy?   This scope is all a learning experience in process.

No, what I meant is you may need to perform the Grid bias adjustment procedure. This adjustment will help the flickering of traces and readouts, although from what you describe your issue may be something much more.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MSO on February 15, 2016, 04:15:10 pm
OLD-E,

Probably a typo, but maybe wrong schematic. I was unable to locate resistor R2590 anywhere in the service manual.  I did find R2830 (322ohms) on the 10MHz line feeding one of the clock inputs on U2830.  U2890 drives one of the master resets on U2830, so I though that might be the one you were looking at.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on February 17, 2016, 04:42:38 am
MSO

That would really be nice to find it was as simple as the wrong schematic!   But looking again (on my paper work) - it is R2890 and it is next to U2890 B which is located on the schematic at position 6L which is confirmed by the parts list on the same page, as 6L.   The schematic I'm looking at is listed as Figure 10-10 in the Manual under LIST OF ILLUSTRATIONS on page iii.   But this schematic page is actually located between Fig. 10-10 & 10-11 and has no figure number on it.

As you probably know, when the manual pages are displayed, one can press F4 on the key board to bring up a column of thumbnail pictures down the left side of the monitor screen.   You'll have to reduce the size of the schematic page some to acquire the blank space down the left side.   These thumbnail page numbers are much easier to navigate through the Manual.   In that straight sequential order, this is page 433.

This page is listed for S/N > 50000,   The schematic for S/N < 50000 does not have a resistor on the output of U2890.   Also, R2885, located on the far lower right corner of the schematic is shown as 1k, but the parts list says it is 332 ohms.   And, likewise, R2885 does not seem to exist in the earlier S/N model.

Brian -

Replacing U2890 appears to have fixed the jittery readouts.   I've heard of the Grid Bias adjustments, but am not familiar with it, but will keep that in mind if the readouts act up again.

Regarding pictures;   Oh - THAT "More Attachments!"   Who would have ever thunk it?   Hmmm - well that one passed right through me.   Next time I'll have something new to try.   thanks!   
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on February 17, 2016, 06:20:54 am
Quote
Brian -

Replacing U2890 appears to have fixed the jittery readouts.   I've heard of the Grid Bias adjustments, but am not familiar with it, but will keep that in mind if the readouts act up again.


The Grid Bias Adjustment is one of the procedures outlined in the calibration procedure that you will no doubt be following shortly once your scope is all fixed and operating properly.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on February 17, 2016, 07:04:13 am
Regarding pictures;   Oh - THAT "More Attachments!"   Who would have ever thunk it?   Hmmm - well that one passed right through me.   Next time I'll have something new to try.   thanks!
LOL
Now you're got it.  :clap:
 :phew:
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on February 17, 2016, 07:30:17 am
I'm turning the scope on every day and so far it refuses to hiccup on the initial self test and everything is working perfectly including the calibration.   You might say I should not brag about that or it will speed the arrival of a problem.   But finding that illusive bug from a couple of weeks ago is exactly what I want.   It has to appear first in order to fix it.

In the mean time, need to move on to other issues.   And the next issue on the priority list is the Dallas DS1225Y with the embedded battery.   First order of business is to determine the date of manufacture, which is printed on it as date code 9134d3.   If I read that right in the Dallas spec sheet, it was manufactured in the year 91 (1991) & in the 34th week.   If that is correct, this battery is still running after nearly 25 years!   It's guaranteed for 10 years!   So that needs to be replace ASAP.

Reading Dr. H. Holden's great report "Tektronix 2465B oscilloscope - - - ," dated June 2015, I decided to follow his lead and replace the DS1225Y with the ferroelectric FM16W08 which does not need a battery.   But there is one issue with the timing of the /CE enable line.   According to Holden, the scope is wired to assert the /CE enable at each address location, which is what the FM16W08 requires.   While the DS1225 does not need that asserted for each address location, it will obviously work when it is.   Therefore as luck would have it, the FM16W08 should be a drop in replacement, except that it's only available in surface mount.   The existing DS1225Y is a DIP version soldered through the board.

The physicals of the surface mount issue can be easily fixed by ordering -
Adapter board # 28-650000-10 from Digi-key for $18.54
28 pin socket, to plug the adapter board into, # 828-AG11D-ESL-LF from Digi-Key for $2.34
FM16W08 from Mouser, to solder to the adapter board, for $10.29

The next challenge is to find a programmer to read the DS1225Y and then write to the FM16W08.   Again, I followed Holden's lead and bought a GQ-4X Universal IC programmer along with the other items above.   But I wanted to make sure this all works before removing the DS1225Y from the scope.   The GQ-4X supports the DS1225Y, but does not support the FM16W08.   So we set the programmer up for the DS1225Y with an FM16W08 in the socket.   With the help of a neighbor friend who is more up on programmers, we were able to read & write to the FM16W08 using another set of cal data found on line that was copied out of a another 2465B.   But it will only read the first address location which means it apparently does not assert the /CE for the additional addresses which, of course, is not required for the DS1225Y.

So- don't know how Holden got it to work.   We went on line and found an older version of software for the GQ-4X thinking Holden might have used that one which may have toggled for each address, but that software would not run on my newer version of the Programmer.   I had previously stepped the scope through the Hex codes in the internal test routines out of EXER 02 and hand copied them thinking that in the worst case I could manually enter the data into the GQ-4x to program the FM16W08 (it's a long list of codes, but not impossible).   But that won't work if the programmer won't write to the IC.   We also tried some trickery to no avail.

Next step was to contact the manufacturer of the GQ-4X.   They confirmed all what we had surmised and said that if we had their latest hardware version (GQ-4X4), it has more flexibility and the FM16W08 can be easily added.   The indications are that I have the latest version, not to mention that I just bought it.   So, I'm going to contact them again tomorrow to confirm my version and see what's needed to get them to add the FM16W08 to their programmer.

In the interim, incase this will take too long, I may just replace the existing DS1225Y with another new one that I can program.   Then switch it out (I'll be adding a socket) for the FM16W08 later.

So this is where the scope is now.   It's certainly a much bigger project than I ever imagined when I bought it.   But, it is an education.   And reading all the entries on the internet about the pitfalls and should dos, has been a great help.     
 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MSO on February 17, 2016, 07:42:16 am
That would really be nice to find it was as simple as the wrong schematic!   But looking again (on my paper work) - it is R2890 and it is next to U2890 B which is located on the schematic at position 6L which is confirmed by the parts list on the same page, as 6L.   The schematic I'm looking at is listed as Figure 10-10 in the Manual under LIST OF ILLUSTRATIONS on page iii.   But this schematic page is actually located between Fig. 10-10 & 10-11 and has no figure number on it.

As you probably know, when the manual pages are displayed, one can press F4 on the key board to bring up a column of thumbnail pictures down the left side of the monitor screen.   You'll have to reduce the size of the schematic page some to acquire the blank space down the left side.   These thumbnail page numbers are much easier to navigate through the Manual.   In that straight sequential order, this is page 433.
 

Got it OLD_E, on my schematic it's listed as <7> Readout (hi-serial) on page 10-31; sequential page 433. I usually have the schematics and part layouts magnified up around 200% so rather than scrolling up or down to find where I'm at, I'll just go up to the File->Print... menu and then select current page in the left-center of the dialog. That will show the chapter/page numbers and then in under the lower left of the preview box it lists the sequential page number.

Anyway, R2890 is marked as 1K on my schematic as well with the parts list showing it to be 332 ohms also.  I was looking to see if perhaps my schematics may have been corrected.  No luck there.

I got my TL866A programmer today so I pulled the DS1225Y off the A5 board, put a socket on the board, plugged the NVRAM into the TL866 and got a good copy of the data.  After programming a new DS1225Y, I installed it into the new socket, installed that new fan you found, buttoned up the 2467B and everything is good to go.  With the socket in place and the 21 years the original DS1225Y lasted, I decided to pass on the FM1608 family of replacements. 15 years from now, I'll just pop the NVRAM out and replace it again. Of course, I'll be over ninety by then and will probably have replaced the 2467B with the new AgilTronics 6667A 50 THz quad channel self-calibrating storage scope and spectrum analyzer.

I decided that if any of the electrolytics on the main board leak, the drippings will fall harmlessly on to the bottom of the cabinet instead of on to the PCB, so I'll wait until I have a failure before recapping the main board. Discretion is the better part of valor or some such came to mind.

Good luck with your 'scope and thanks for the info on the fan.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on February 18, 2016, 03:04:22 am
MSO -
Thanks for double checking the schematic.   Unfortunately, there are many errors on that schematic of the A5 bd.

Good work with the DS1225Y!   Were there any particular challenges in removing that IC?      I'm looking forward to replacing mine, hopefully soon.  Looks like the board should be an easy removal.

When you removed the Dallas IC, did you use a solder sucker, or - - ?   Also, is there a problem if the pins on the IC are momentarily shorted during removal?   If that maters, keeping the solder sucker or iron from getting between them could be challenging.

Given that I'm apparently about the same age as you, going the extra mile to get more than 15 years of future life out of the IC replacement probably makes little sense.   But it's hard to shake the habit of believing that me and the stuff I work on will last forever.   And I'm thinking that the special scope on your wish list (and now mine) may be waiting for me at my next destination.   So there's no point in spending your cash on it in 15 years, when you can't can't take it with you anyway.   At least that's what they say.

My next task after the Dallas IC is the PS Bd caps which are still working fine for now.   Then I'll take a good look at the main bd including reports from others.   leaving it may be a good choice.   Thanks.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MSO on February 18, 2016, 05:14:08 am
OLD_E,

I've had many runarounds with manuals from the web; pages missing, out of order, illegible and some, without taking the time to prove it, with pages mixed from different versions of the manual in question. Particularly with those oversized pages such as schematics and part locators.  So I generally double check my work.

The DS1225Y came out with no trouble; I did cheat though, I used my Hakko 808 desoldering gun.  About eight years ago, I built an Elecraft K2 with all available options, four Elecraft transceivers and just about every kit they offered. I was new to kit building then, so the Hakko 808 saved my bacon when I lost focus on the task at hand. It was a real life saver then and it handled that DS1255Y with aplomb.

I don't think you need to worry about shorting pins while removing the hybrid.  The positive terminal on the hybrid's battery is only connected to pin 7 of the embedded DS1218 and pin 7 is connected to nothing else. Short of slicing into the hybrid and shorting pin seven to ground, the power supply should remain intact.

I thought about the 'best' solution to the SRAM backup problem, but with more than 20 years of use already on the original DS1225Y (25 years on yours) I looked on the datasheet for the FM1608 and saw that it had a data retention life of 10 years at 85 C and just thought I'd have to replace it as well somewhere down the road, so better the horse I know than buying a pig in a poke.  Besides, while I doubt very much that Tektronix is going to offer an upgrade to the ROM chip that changes the behavior of the CE line, I can't know for sure that that the scope always drops the CE line for every write.  When the choice is between something I know will always work and something else that appears to work to most of time, my OCD kicks in to high gear.

As you delve into the power supply boards, beware that caps C1274, C1291 & C1292 on the A2A1 board are bipolar. I almost missed that, but when looking for the polarization orientation on the caps, I found that there weren't any.   I replaced those with the Nichicon 1uf 50V cap UVP1H010MDD1TD with good results.

Here is the list of caps I found and those that I replaced them with:

Board A2A1:
C1016   0.068uf 250v      -  0.1uf 630v 110c   KEMET F862BK104K310ALR0L
C1018   0.068uf 250v       -  0.1uf 630v 110c   KEMET F862BK104K310ALR0L
C1220   10uf   100V 105c         -  10uf  160V 105c      Nichicon UPW2C100MPD
C1240   10uf   100V 105c           -  10uf  160V 105c      Nichicon UPW2C100MPD
C1260   100uf   50V 105c   -  100uf 50V  105c      Panasonic EEU-EB1H101S
C1274   1uf   50V  85c           -  1uf   50V   85c      Nichicon  UVP1H010MDD1TD
C1280   100uf   50V 105c   -  100uf 50V  105c      Panasonic EEU-EB1H101S
C1291   1uf   50V  85c           -  1uf   50V   85c      Nichicon  UVP1H010MDD1TD
C1292   1uf   50V  85c           -  1uf   50V   85c      Nichicon  UVP1H010MDD1TD
C1300   100uf   50V 105c   -  100uf 50V  105c      Panasonic EEU-EB1H101S
C1330   100uf   50V 105c   -  100uf 50V  105c      Panasonic EEU-EB1H101S
C1350   100uf   50V 105c   -  100uf 50V  105c      Panasonic EEU-EB1H101S
C1400   47uf   25V  85c           -  47uf  35V  105c      Nichicon UPW1V470MED1TD
C1402   47uf   25V  85c           -  47uf  35V  105c      Nichicon UPW1V470MED1TD

A3:                        
C1020   2200pf  250V      - 2200pf 1.25KVDC   KEMET PHE850EA4220MA01R17
C1021   290uf  200V   85c   -
C1022   290uf  200V   85c   -
C1025   100uf  50V   105c   - 100uf 50V  105c      Panasonic EEU-EB1H101S
C1051   2200pf 250V      - 2200pf 1.25KVDC   KEMET PHE850EA4220MA01R17
C1052   10000pf 250V      - 10000pf 1.25KVDC   KEMET PHE850EB5100MB04R17
C1066   4.7uf   35V      - 4.7uf   50V           Nichicon UPS1H4R7MDD1TD
C1072   3.3uf   350V   85c          - 3.3uf   350V         Nichicon UVZ2V3R3MPD1TD
C1101   100uf  50V   105c   - 100uf 50V  105c      Panasonic EEU-EB1H101S
C1102   100uf 50V   105c   - 100uf 50V  105c      Panasonic EEU-EB1H101S
C1110   250uf 20V   105c   - 330uf 50v  105c      Panasonic EEU-EB1H331
C1111   250uf 20V   105c   - 330uf 50v  105c      Panasonic EEU-EB1H331
C1112   4.7f   35V    85c           - 4.7uf   50V           Nichicon UPS1H4R7MDD1TD
C1113   180uf   40V   105c   - 330uf  50V  Panasonic EEU-EB1H331
C1114   250uf   20V   105c   - 330uf 50v  105c      Panasonic EEU-EB1H331
C1115   10uf   160V   85c           - 10uf 16V  105c       Nichicon UPW2C100MPD
C1116   180uf   40V   105c   - 330uf  50V  Panasonic EEU-EB1H331
C1120   10uf   100V  105c   - 10uf  160V 105c      Nichicon UPW2C100MPD
C1130   10uf   100V  105c   - 10uf  160V 105c      Nichicon UPW2C100MPD
C1132   250uf   20V   105c   - 330uf 50v  105c      Panasonic EEU-EB1H331

Good luck with your adventures.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on February 19, 2016, 07:41:17 am
Good news DSO!   I'm apparently a day behind you and it all works!!!

As written before, I was wanting to replace the DS1225Y on the A5 bd before it's nearly 25 year old embedded battery expired, loosing the cal data.   To do that I had bought a GQ-4X4 programmer on line for $99 from MCUmall.   It's software included the DS1225Y, but not the FM16W08 that I wanted to replace the DS with.   Tried making it work by calling the FM a DS, but there was one difference in the way it enabled the address line and so it would not read data off the FM.

Two days ago , the 16th, I contacted support at the GQ manufacture and they modified their existing program to include the FM IC, and e-mailed it to me last night!!!   I was unable to get to it before noon today, but the deal was, I was supposed to do the testing since they didn't have that FM IC in hand.

With the help of a programmer, neighbor, friend, we tested as much as we could with cal data copied off the internet from someone else's scope - and it worked!!!   So we removed A5 bd, then desoldered the DS IC from the bd using a recently purchased Aoyue, INT 474++ desoldering system.   This was my first real use with a vacuum solder remover.   It worked great on all but about a half dozen of the 28 pins, which took more coxing with some solder wick.   But eventually the DS was free with no damage to anything.   In the GQ programmer, it was able to read the data on the DS IC, and successfully write it back into the FM IC.

Back at the scope, a 28 pin socket was soldered in place where the original DS IC had been.   Then the surface mount FM16W08, which was soldered to a 28 pin dip adapter board, was plugged into the socket.   Results were; today, the 18th, the scope turned on with its function and calibration as if nothing had been done to it - it all worked perfectly.   More later.
     
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on February 20, 2016, 04:53:04 am
More on the Dallas IC up-grade.
I powered up the 2465B again today and all appears well, so the FM16W08 appears to be holding its memory.   But, just in case, I ordered a spare DS1225AD today to copy the scopes cal data to and then put it in storage, just in case.   I have a spare FM16W08 and adapter board that I'll do the same with.   AT this point, it's cheap & easy backup.   Then if we get hit with an EMP or a super solar storm, maybe one will survive, assuming the rest of the scope makes it.

DSO - I think there may be some confusion about the data retention of the FM16W08.   See data below.   The 10 years at 85 Deg. C is hot.   At 65 Deg. C (that's 149 F) the data retention is 151 years - according to the Cypress data sheet.   So, if I keep it below 75 F, it might even out live us.

(http://)

There was a concern of shorting the pins on the Dallas DS1225Y when removing it.   But after looking at the expanded diagram of that IC posted by Holden, I concluded that if they were momentarily shorted, it would be through high impedance paths.   So the battery should survive that.   And I used the smallest tip on the vacuum desolder tool, so I don't think they ever shorted.

After removing the DS1225Y, I was about to plug it into a conductive piece of black foam, but then had second thoughts about it discharging the battery through possible high impedance paths via. the foam.   But, then while looking up DSO's concern about the IC's life, I found where the data sheet seems to think it's not a problem - if I understand it correctly.  So, you're probably right - not a problem.

Also, for the sake of science, I want to excavate through the top of the old IC to the battery, to measure the remaining voltage.   If done right, the IC will not be functionally harmed.

DSO - When using my vacuum desolder tool, most of the pins desoldered ok.   But half dozen or so pins were a challenge.   It just would not pull all the solder out.   Even turned the board upside down to get help from gravity.   Cleaned the tip orifice, but it was clear and the vacuum was working at the tip.   Since this is my first real application with it, I wanted to ask what temp you had yours set to?   This one was set to 300 C.   Another possibility was, the tip might be too small to transfer enough heat through the multi-layer board.

Below are photos of the board before and after replacing the Dallas memory IC.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on February 20, 2016, 05:01:46 am
Well, the pictures were lost again.   This is the most unfriendly picture loader.   No way to see in advance what is ready to be posted.   Will try to get 3 of them back here.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MSO on February 22, 2016, 07:18:24 am
OLD-E,

On the DS1225Y, the battery is located near the bottom of the chip, not the top (at least that's what I gleaned from Holden's write up).  Holden goes on to recommend evacuating pin 7 on the embedded DS1218 memory controller if you need direct access to the battery's positive node.

When sucking solder with a Hakko or any other desoldering gun, it's common to have some pin/hole combinations not fully evacuate. The normal course of action is to resolder those pins and then try again. The fresh solder aids the heat transfer from the gun through the pin/hole and usually results in complete evacuation of the solder.

It's recommended that when using a desoldering gun to get the pin into the orifice of the gun and apply side pressure on the pin to aid heat transfer. I also try to get the gun to the solder filet itself, but not far enough to actually touch the solder pad. When I see the solder melt, then I apply the vacuum and that usually clears the solder. Some of the pins have been bent over to hold the chip in place during the manufacturing process, so those pins require a two step process; just touch the solder filet with the gun and suck up as much solder as will easily come. Then straighten the pin, apply new solder if needed and then follow the normal sequence.

Finally, you will encounter situations where the soldered pad has little thermal relief; the pad is part of a large trace or ground plane that dissipates the heat from the desoldering gun, making it difficult to get an easy flow of solder.  In these situations, you may need to raise the temperature of your desoldering gun to get enough heat to get the solder to flow easily.

Having said all that, I set Hakko 808 to 350 C when desoldering. That high of a temperature requires a lot of care not to lift a pad.  While it's good to touch the pin and the top of the solder filet, you really don't want to touch the pad itself and you don't want to apply the heat for too long.  If the joint doesn't fully desolder, move on the next joint and come back to the failed one later.  Apply new solder to the failed joints and then try those again.

There may be a joint or two (I didn't encounter any when re-capping the 2467B) that simply won't submit to the desoldering gun. With those, you'll either have to heat with an iron while simultaneously lifting the component or, in the worst case, cut the pin off on the component side of the board and then use solder wick to clear the hole.

Almost forgot; I used a desoldering tip with a 1.0mm hole for all of the components on the 2467B.  The two large 290uf caps C1021 & C1022 on the A3 board had the largest diameter leads and pushed my 1.0 mm tip to its limits, but with a little solder wick to remove the excess solder on the top of board, I was able to use the gun to clear those whales properly.

As an aside, I checked all the caps that I pulled out of my 2467B and found only the RIFA caps (those rectangular caps with translucent plastic cases) were out of spec.  All the aluminum electrolytics, even those that had started leaking, were still measuring OK, so it looks as though I caught them all in time.

It's good to hear that you were able to save your calibration data; I know I sighed a huge sigh of relief when I was able to read mine with my programmer.  I was paranoid enough, though, to read the bin file and double check that all the calibrations I had recorded via EXER 02 before starting work on the scope matched those in the bin file. I now have backups of the DS1225Y on another DS1225Y, on my hard drive, on a backup hard drive, on a USB memory stick stored with my manual and on a CD rom.  How's that for OCD?

 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on February 23, 2016, 03:44:08 am
I now have backups of the DS1225Y on another DS1225Y, on my hard drive, on a backup hard drive, on a USB memory stick stored with my manual and on a CD rom.  How's that for OCD?

Not bad for the OCD :-DD, but you forgot putting it into cloud storage, and another usb stick stuck with duct tape inside the scope.  >:D
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MSO on February 23, 2016, 04:18:44 am
I'll get there Bravo, I'm just getting warmed up.

BTW, thanks for all your contributions to this thread. I don't think I would have been successful without the myriad pictures, tips, observations and comments that you and many others have made here.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on February 23, 2016, 05:08:45 am
MSO, my pleasure and thanks to other contributors too that made up this thread.  :-+

PS : Actually I created this thread just to share this beast teardown photos at 1st, never thought it grows into this giant.  :o
Title: 2465BCT Repair and Modifications
Post by: FireDragon on February 23, 2016, 08:26:42 am
I got the latest set of parts in and made the latest round of repairs and modifications.

I replaced the feed through fan capacitor (which was shorted) and the fan with a higher capacity fan with about the same noise level. I also added an 0.1uF ceramic bypass capacitor to help suppress noise on the fan input voltage to prevent it from feeding back into the scope. That should reduce the overall temperature inside the scope because the default will be higher airflow.

Additionally, I was unhappy with the noise level on the various power supply voltages. All of them were well within specification, but the noise was still much higher than I liked. So, on board A2A1 I replaced the 100uF filtering capacitors - C1260, C1280, C1300, C1330, C1350 - with 150uF capacitors. Additionally, I added a 150uF capacitor across VR1293. The reason for this, is that all of the output voltages have some sort of filtering across them - except for the 10V reference voltage. Its noise specifications are very loose, and any noise on it will be copied by all of the other output voltages because they will attempt to match the reference voltage, noise and all.

I also added a 50 ohm resistor between ground and the Option 1E input signal to provide proper termination.

Finally, I replaced the 10.000Mhz crystal with a 10.0000Mhz crystal. To support that I changed C2550 and C2551, respectively to 33pF and 39pF (this was actually no change for C2550, but I replaced it anyway). This gives me 10.00014Mhz whereas before it had been somewhere around 9.99280Mhz. I am measuring the frequency with the scope itself and I have reason to believe that it is reading high - but by how much I don't know yet since the scope isn't calibrated yet and I don't have a calibrated frequency reference. Changing the crystal won't improve the scope's performance or accuracy, but it should bring the resulting calibration constants closer to "zero" and so less likely to hit an extreme point. I couldn't easily get the frequency close to 10Mhz. When I had C2551 at 33uF I had 10.00047Mhz, and 39uF gives me 10.00014. The next step up would be 43uF which would probably be too much - especially if the scope is reading the frequency high.

The result of the power supply changes is a drastic reduction in noise on the all of the output voltages.  I probably should have replaced C1220 and C1240 but I didn't have any higher voltage, high capacity capacitors on hand. Still, most of the output voltages now have total noise at around 1-2mv with no observable line noise. One of the  +5v supplies (J119-2) has about 20mv noise which may be line related, but up to 30mv line related noise is allowed and up to 150mv total noise. So, a definite win!

I'm getting pretty good at taking this scope apart and putting it back together with all of the practice I'm getting!

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on February 25, 2016, 06:21:23 am
LOL - - Following the stress, and then the joy, of getting the cal data out of the old DS1225Y, I understand the desire to have back up memories for the backups, etc.  So it might be said; the more intense the emotional experience, the more memory backups.

My new DS1225AD arrived today, so I can program it along with a spare FM16W08.   Then I'll have 3 back ups (counting the hard drive) in addition to the new FM IC installed in the scope.

In addition to all that, I still have the old DS1225Y removed from the scope.   I excavated through the epoxy of its underside this evening to get to pin 7 on the DS1218 as MSO suggested.   It probably was easier than going through the top to reach the top of the battery case.   The end result was that I reached the pin without damaging the function of the IC (I think).   I was surprised to measure the battery at 3.304 volts!   So it appears that it still has considerable life left.   Dr H. Holden claims in his article that it remains functional down to ~1.8 volts.

But in the process, I ran into an unexpected snag.   When I reached the first sign of metal, while following Holden's sketch on page 6 of his article, I tried to read the voltage, but kept getting zero.   So I kept excavating and testing with no progress.   Finally, returning to square 1 and working back through everything, I found that his illustration was wrong!   Important to know for anyone else trying the same.

His illustration shows a bottom view of the DS1225Y.   But the 2 rows of pins are transposed - move the upper row straight down and the lower row up and all is well.   Looking at the illustration, I had the meter lead clipped to the "Gnd" on the lower right pin, and it should have been on the upper right.   He has another illustration on page 21 which is a top view of the DS1225Y and those pins are not transposed.

Over the last many days, I've powered up the scope to confirm that all is well.   But recently the previously mentioned bug occasionally reappears.   It always happens on power on when it goes through its health check.   Some times it stops with all 1's and dashes where the readouts should be.   It has also read "TEST 03 PASSED."   One time it stopped reading "ALL 00   FAIL 03."   Another time it read "TEST 03   FAIL 02," which the lookup says is "Readout Ram failure."   It did this this before I replaced the DS1225Y.   But in all cases, pressing "A/B TRIG" returns the scope to normal operation where everything is perfect.   I even retuned to test mode and started it looping through all the startup tests and left it run for an hour with no hiccups.   I have some remote ideas to look at, and I want to recap the power supply.   Thanks to MSO I have his capacitor list for guidance.

FireDragon - Thanks for sharing.   A lot of good info on this site.   Starting at the beginning with BravoB's 1st entry it took a long time to read it all.   But like a best seller, it was hard to put down.

Thanks DSO for all the tricks in using a vacuum tool.   Yes, I was using the small, 1mm tip too.   I'll get more experience on the PS board. 

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on February 25, 2016, 06:58:22 am
I well up in tears when I read users who successfully replaced their DS12257. I tried replacing mine  a year or so ago, did everything right in prep, unsoldering properl. Went to read it on the programmer and all the data was 00 or FF, can't remember, something went wrong during the removal process and it erased the memory. Tried all the tricks I could dig up in trying to recover, but I guess the battery in mine was at the point that the removal or memory read brought the voltage down ever so slightly past the threshold and everything was lost. Didn't know at the time that the memory was available on screen, could have taken some pictures and added the data back manually to the new chip with the programmer. Oh well.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: casinada on February 25, 2016, 07:10:31 am
If you lost your data ( I did) you can use somebody else's backup as a starting point, that way your scope might be out of calibration but it will be easier than to start from scratch. In some cases it will come back without showing errors. Calibrating can be lots of fun. I had to do it with my 2465BDM  :)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on February 25, 2016, 07:11:54 am
Yes, that's what I did, had to try a number of backups that are available, I think I came close, but it still will need a full calibration.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on February 25, 2016, 04:04:30 pm
Bryan - Yes, I remember reading a ways back about losing your memory.   Bad news!   But maybe - I'm new to all this - but some thoughts are, you might try reinstalling it back into your scope to see if it may still work.   If you happen to have installed a socket, it would be an easier install.

Another (better) thought is; according to Holden, the battery could go below the threshold level of the embedded DS1218 battery controller.   But the memory is not actually gone.   In that case, an external battery could be piggy backed on to the DS1225Y to bring the voltage back up.   Then it could be read on the programmer.   As written below, I just excavated down to pin 7 of the battery controller for the positive battery connection.   Then the return line goes to pin 14 on the DS1225Y.   That can be done in a hour or so.

Another possibility could be that a lack of static control might have caused a non-fixable problem.   From what I could see, shorting the pins should not be a big deal.   Maybe if shorted for a long time (years) , it might speed up the discharge of the battery.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on February 25, 2016, 08:10:08 pm
More thoughts.   To avoid soldering to the the dead DS1225 before inserting it into the programmer, one could connect the external battery return wire to pin 14 by just looping it around the top of the pin, or inserting the return wire into the pin receptacle of the zero insertion force socket of the programmer.   Likewise, once pin 7 (+battery point) is exposed, one could just hold a sharp pointed probe on the pin during the programmer read time.   Again, no soldering to the DS2018 pin.   And it is my guess, that even if your battery connections are noisy, the existing battery will take on a certain amount of charge which will produce a constant voltage above the threshold to the DS1225Y during the read time.   This is all for a temporary read, so make shifting might be a safer and quicker way to go.

Picture below is of my DS1225 after excavation.   And I removed more potting than necessary for a temporary connection.   The exposed metal pin is visible next to the body of the DS2018.   Excavation was accomplished with a pointed X-acto Knife and a needle pointed probe tip.   The biggest challenge was in to minimize bending the DS1225Y pins during excavation.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on February 26, 2016, 04:44:51 am
Thanks, yes I had tried that when I originally attempted to replace the Dallas. No luck at the time, may try again, perhaps I may get lucky. But doubt it. The voltage of the battery was less than a volt.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on February 26, 2016, 04:00:11 pm
Oh - bad news!  My condolences.

A battery voltage down to 1 volt is probably not enough to keep it alive.   I'm curious (for the sake of science) did you happen to measure the battery voltage again after the external battery had been disconnected?   Based on my battery experience, I'm betting that the nearly expired battery will take on a charge that will last much longer than needed to read the memory, maybe even for days.   If that is true than one would not need a makeshift probe on the underside of the DS when reading.

Thanks for sharing.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on February 27, 2016, 09:39:31 am
Oh - bad news!  My condolences.

A battery voltage down to 1 volt is probably not enough to keep it alive.   I'm curious (for the sake of science) did you happen to measure the battery voltage again after the external battery had been disconnected?   Based on my battery experience, I'm betting that the nearly expired battery will take on a charge that will last much longer than needed to read the memory, maybe even for days.   If that is true than one would not need a makeshift probe on the underside of the DS when reading.

Thanks for sharing.

The voltage of the battery is after it had been in storage for over a year. Always thought there was a hope of recovery, but nope. Tried again on the programmer and all I get is 0x00 and 0xFf in what seems to be 3-4 banks of memory. I am not sure what went wrong, could have been anything. Still kicking myself for not taking pictures of the CRT that shows the memory allocations. Would have been a lot of work to rebuild, but at least I would have had something.

I have a TG501 and a SG503 so think I have the basics for a decent recalibration by myself. Just need to put together some accurate voltage references. Although going by memory the voltage levels have to be a square wave. Can probably use a function generator and calibrate the voltage level. Just needs to be within 3% anyways. I find I don't use the scope much, handy if I want to look at some higher frequencies than what my Rigol DS1052E can do. Afraid the days of the analog scope are becoming closer to a end, just so much more you can do with a digital scope. Although nothing sweeter than the glow of a CRT, one of the reasons I still keep it<g>
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on March 01, 2016, 06:33:28 am
Seems that everything has its share of kinks (trivia reporting).

Got together with my programmer friend yesterday to get the stored cal data transferred from my old XP computer, into the 2 spare IC's.   I had soldered the spare FM16W08 onto the adapter board and the spare DS1225AD had arrived, so repeating the data transfers should have been an easy task.   We started out by reading what was on the FM IC, and that appeared to work.   So we tried to perform some simple tests, like entering all ff's for example, and it would not complete the write,   Tried transferring real data into it with similar "failed" status.   So thinking that maybe the FM IC had a problem, we plugged in the new Dallas IC and had similar problems.   After spending a few frustrating hours on trying to get something to work, we decided to at least get a screen print of the data file from the programmer so that I could have a hard copy for my note book.   But then could not get the printer to work without freezing up.

Decision was finally made to quit for the evening with a plan to start at square one on Monday.   So, today I put in a call to my Computer Angel service, that I have available on call, to go through the older XP computer to get it cleaned up and debugged if needed.   Once I feel comfortable with that, then the plan is to reload software into the programmer, etc.   Eventually we'll get it - I hope.   But at least we have a new working FM IC in the scope - whew!

Today the computer allowed me to get a hard copy of the cal data printed out so something is strange there.   With cal data printed out, I was then able to easily compare that with the hand copied data from the scope CRT.   It takes awhile, but it can be done.   This turned up about a dozen errors.   From that, I compared the errors directly with the digits on the CRT.   Bottom line was, in all cases the printed out data from the programmer agreed with the data read off the scope CRT.   This is what should be, but just wanted to confirm that.   In most cases, the errors were where the spine of a B or the left edge of a 3 was perfectly centered under a vertical reticle line.   So using an eye loop and fuzzing out the focus a little, I was able to see the spine of the B showing on both sides of the reticle line.   So I think my hand copied data off the scope screen, and the printed data from the programmer is now all correct.   So while some things are coming together, it's not without its challenges and set backs.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MSO on March 03, 2016, 05:56:33 am
OLD-E,

I just spent the better part of hour writing a response to your last post and then a made a typo of some sort and lost the entire post. The replay window simply disappeared. That’s probably much better for you as I now, by rewriting the response, I can eliminate some of redundancies and extraneous comments.

I would expect some differences to exist between the NVRAM currently installed in the ‘scope and the DS1227 that you replaced.  Running time, the On/Off count and the set up in effect the last time you used the scope come to mind.  I’m not sure if there would be any changes made to the calibration area of the NVRAM; for instance balancing the channel 1/channel 2 inputs might end up there.

When you have doubt about your programmer reading the device properly, you’ll find a tool such as Beyond Compare to be invaluable.  Simply read the NVRAM device in the programmer, save it to a binary file then read it again and save to a second binary file. Using Beyond Compare, compare the two files just read. If there are differences, then you know the programmer isn’t reading properly.

Be aware though, that many programmers keep the data they last read in an internal buffer and won’t modify that saved data if they can’t read the device a second time. So it’s best to force the programmer to dump the data in its internal buffer before reading the device a second time. If the programmer’s software allows you to directly edit its buffer, insert a series of known values near the start of the buffer; I’ll usually use a few series of AA, 55, AA, 55 values to ensure that the programmer actually read the device a second time.  Depending upon your programmer/software, you may have to close the software and restart it again or try loading a different, unrelated binary file between first and second reads.

You can use this approach when comparing reads between two different NVRAM devices as well. If one of the devices has more memory than the other, then just ensure that the two devices match up to the size of the smallest device.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: ChunkyPastaSauce on March 03, 2016, 06:09:01 am
Question...

I bought one for basically nothing because from a university. Basically nothing because it doesn't work....other than that,very good condition  ::)

The calibration is probably still there as the date code isn't that far out.

It likely died due to a very failed fan. I measured the voltage rails..... they are all over the place. Some of them are low and if I remember correctly....some of them higher than they should be.

So my question...... is it worth trying to fix the PSU when some of the rails are higher by like 150%? Or is it likely the higher voltage damaged other parts of the scope and not worth the effort?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MSO on March 03, 2016, 07:36:16 am
ChunkyPastaSauce,

I'm not knowledgeable enough to answer your primary question (is it worth it), but having re-capped both power supply boards and the A5 control board for roughly $50, I'd say it's worth a shot. My suspicion is that the overheating may have damaged a couple of the main board chips, but for $50 and little time and effort (for me it's an enjoyable hobby) you can determine if its worth pursuing further.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on March 04, 2016, 02:01:46 am
The 2465B is pretty rugged and well designed, I would invest in the time and cost to get the power supply fixed and go from there. More than likely the caps are toast and there may be some other issues on the power supply board. If you scour the service manual you will see that much of the other circuitry on the power supply board and other boards have pretty good protection if something goes wrong on the power supply side of things.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: ChunkyPastaSauce on March 04, 2016, 03:10:55 am
Ok, thanks to both  :) It looks to be a nice scope, certainly better than the working one I have now (which isn't bad either tek2235).
Typically pass on doing anything on PSU high sides.... basically they frighten me. Also the fact there is a CRT. Right now, I'm nervous about getting the board out.....

Ive checked the main caps on the PSU for residual charge at the black plastic shield check points, they are empty. Anything else on the PSU board I should be aware of that may have the potential to make me have regrets messing with it? Or generally pretty safe if the charge check points, at the black plastic shield, are around 0V? 

I've check all the caps for obvious problems that can be checked, without having to pull the PSU boards out.

Thanks again.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on March 04, 2016, 03:31:56 am
Chunky,

I happen to love the fine qualities of my Tektronix 2465B scope (assuming that's what you have).   For me, it's worth the dollars & effort to have a reasonably great and high performance scope, not to mention the education and hobby element.   From what I've seen on E-bay, these scopes in good clean condition and working perfectly are going for $1,000 - $1,400.   I saw a copy of an old brochure (circa 1990) advertising a new scope like mine for $9,200.

But if your thoughts are to get it working in order to turn a quick profit, well, that might work if you value your time at 10 cents an hour (exaggerating, well maybe).   If your interests are profit (nothing wrong with that), then you might be better off parting it out on E-Bay or selling it as is.

My concern would be that the failed fan, followed by failed power supplies, leading to over voltage conditions, could have wiped out many IC's, etc.   This could be a costly / time consuming over hall relative to the numbers we're talking about.    You say the memory IC has a recent date stamp.   But if it's older than 10 years, which is the guaranteed life, then you should be looking at replacing it.   The cost of a replacement IC, or later version with no life limits, plus a programmer will total about $150.   The other parts, as MSO indicated, are fairly cheap, providing all the mechanical stuff is ok.   Then there is quite a bit of labor.

But, if you are interested in, and reasonably ok at working with electronics, and would find a project like this rewarding, then this could work well for you.   Forums, like this one, are a treasure trove of information and help.   Others here may have different thoughts. 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: ChunkyPastaSauce on March 04, 2016, 06:06:00 am
Hi Old-E

Yep it's the 2465B 8) If I can get it working, not selling it, unless it's not for me for some reason. I bought it for fun at $35 knowing it would be some level of a project and knowing I might not be able to get it working at my skill level, somewhere beginner-intermediate hobby range (I'm a ME not EE). If I can, great, if I can't then no big deal and Ill probably put it up for anyone willing to pay shipping if they want to have ago at a fairly desirable analog scope or need parts.

I went ahead and pulled the inverter and regulator boards out.. Nothing too horrendous looking (the board is very clean by the way, no dust except a cm or 2 at the fan entrance). The rectangular cap packages, a number of those are somewhat bloated...almost all have hairline cracks. The other caps looked ok visually, except possibly some of the silver guys near to bottom but hard to tell (Edit - found some baddies after removing  :-+). I checked the diodes and all of them seem reasonable.. I thought I found some bad ones but after lifting they were fine... got excited for a few.

So Ill pull the caps; although I plan on replacing all anyway, ordering ESR meter for fun.


On the date code, I was reading about that. I thought it was 20 year life but now looking at the spec sheet..... uhoh lol. We will see...  Wouldn't the cal data be kinda useless after repairing the power supply board, it would need a recal anyway?

Thanks again
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: ChunkyPastaSauce on March 04, 2016, 09:51:35 pm
Baddies.

(http://i.imgur.com/gNu41uG.jpg?1)

All of these probably, hairline cracks on case likely ballooned caps
(http://i.imgur.com/TuZayZo.jpg?1)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on March 05, 2016, 02:36:54 am
Another tell tale sign is the caps will give off a horrible fishy smell once unsoldered.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on March 05, 2016, 05:01:42 am
Mr. Sauce,

You wrote:  "Wouldn't the cal data be kinda useless after repairing the power supply board, it would need a recal anyway?"
I don't know of any reason the calibration would change when rebuilding the power supplies.   I counted 9 regulated voltages not counting the CRT HV.   But all of those are supposed to be at specified DC levels.   These voltages and their tolerances, including allowable ripple, are noted on page 5-3 of the "Tektronix Service Manual" and are available for measurement at J119 on the main board (bottom of scope).  Service Manual is available on line.   You may already have all this info.

I have not started on my PS boards yet.   But beware - there is an error in Service Manual regarding value & location of a couple of the caps.   Replacing them with the same ratings as is there now works ok, but removing them all and then using the Service Manual as a guide to install the new ones will be a problem.   Previously, and on page 26 MSO explained in more detail, and made a number of entries on replacing these caps.   Also, I made a recent entry on replacing the fan including the part # that may be of use for you.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on March 05, 2016, 07:03:46 am
Baddies.
All of these probably, hairline cracks on case likely ballooned caps
(http://i.imgur.com/TuZayZo.jpg?1)
Quite common in X and Y rated caps, they can survive for years in this condition in a dry climate.
When they finally let go...poof, it's more of an inconvenience than anything else plus the mess they can make.  :palm:
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: ChunkyPastaSauce on March 05, 2016, 07:04:44 am
Mr. Sauce,

You wrote:  "Wouldn't the cal data be kinda useless after repairing the power supply board, it would need a recal anyway?"
I don't know of any reason the calibration would change when rebuilding the power supplies.   I counted 9 regulated voltages not counting the CRT HV.   But all of those are supposed to be at specified DC levels.   These voltages and their tolerances, including allowable ripple, are noted on page 5-3 of the "Tektronix Service Manual" and are available for measurement at J119 on the main board (bottom of scope).  Service Manual is available on line.   You may already have all this info.

I have not started on my PS boards yet.   But beware - there is an error in Service Manual regarding value & location of a couple of the caps.   Replacing them with the same ratings as is there now works ok, but removing them all and then using the Service Manual as a guide to install the new ones will be a problem.   Previously, and on page 26 MSO explained in more detail, and made a number of entries on replacing these caps.   Also, I made a recent entry on replacing the fan including the part # that may be of use for you.

Thanks!  :-+ I have the service manual, but miss understood the difference between a recalibration and performance check & adjustment. Manual saya to do a performance check /adj if any repairs are made to power supply, but doesn't mention the need for a autorecalibration. Autocalibration, has to have correct equipment, performance check & adjust is a lot more flexible.....So hopefully mine still holds the calibration constants...

Thanks for letting me know about the caps, Ill check the pages you mentioned. Ive only removed the 6 silver caps so far.... so hopefully I can sort those out. I didn't take pictures or log because i was going to go via the manual ::)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: ChunkyPastaSauce on March 05, 2016, 07:07:57 am
Another tell tale sign is the caps will give off a horrible fishy smell once unsoldered.

Didn't know that...looked it up...Dimethylamine
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: ChunkyPastaSauce on March 05, 2016, 07:19:12 am
Baddies.
All of these probably, hairline cracks on case likely ballooned caps
(http://i.imgur.com/TuZayZo.jpg?1)
Quite common in X and Y rated caps, they can survive for years in this condition in a dry climate.
When they finally let go...poof, it's more of an inconvenience than anything else plus the mess they can make.  :palm:

Hmmmm... I was feeling motivated but now a laziness opportunity...  replace now or be lazy....  :-//

Most of the others have cracking but are flat on the sides at closer look, this one has a bulge on the side (hard to see in pic), so I think this one maybe ready to go if it's not already gone.

I was wondering about the design of these, the casing is to keep humidity out?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on March 05, 2016, 08:38:26 am
Baddies.
All of these probably, hairline cracks on case likely ballooned caps
(http://i.imgur.com/TuZayZo.jpg?1)
Quite common in X and Y rated caps, they can survive for years in this condition in a dry climate.
When they finally let go...poof, it's more of an inconvenience than anything else plus the mess they can make.  :palm:

Hmmmm... I was feeling motivated but now a laziness opportunity...  replace now or be lazy....  :-//

Most of the others have cracking but are flat on the sides at closer look, this one has a bulge on the side (hard to see in pic), so I think this one maybe ready to go if it's not already gone.

I was wondering about the design of these, the casing is to keep humidity out?
Of course and humidity/and or time spent unplugged will allow ingress, then pop.
As these X and Y caps are across mains AND when they go pop, it's not just the mess but the physical damage the might do to the PCB not to mention the chance of carbonising the top layer and resultant chance of further flash overs in the future.
C'mon do the job properly or not at all, they're easy to get, cheap and peace of mind that they've been replaced will help you sleep well.  :)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on March 05, 2016, 09:37:00 am
There is a few spreadsheets floating around if you need the drop in replacements for the replacement caps. Here is one that I have and slightly modified to correct for some issues that I encountered with wrong pin spacing on some of the caps.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: ChunkyPastaSauce on March 05, 2016, 07:29:32 pm
C'mon do the job properly or not at all, they're easy to get, cheap and peace of mind that they've been replaced will help you sleep well.  :)


Thanks. Ill be doing it right. Laziness opportunity was more of a joke... as well as a small dream.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: ChunkyPastaSauce on March 05, 2016, 07:34:03 pm
There is a few spreadsheets floating around if you need the drop in replacements for the replacement caps. Here is one that I have and slightly modified to correct for some issues that I encountered with wrong pin spacing on some of the caps.

Thanks a ton for this! Takes a lot of the work out.

I noticed are replaced with different values, is this an availability/convenience thing or an 'upgrade' thing? [edit] Excel states upgrade
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on March 05, 2016, 08:49:42 pm
Thanks to all those who published their parts lists for cap replacements.   I made hard copies of them (data not lost to an EMP) for the upcoming replacement project.

Mr. Sauce -

If I understood your question correctly regarding capacitor replacements; They can be replaced with higher voltage ratings.   Actually higher is better for longer life.   As technology advances, sometimes the same size capacitor is available in a higher voltage rating.   Also, if the original voltage is not available, the next size up is better, providing it will physically fit the board.   Sometimes higher voltage means larger physical size.

Capacity values (uf) should be closer to the original size.   In the case of filter cap's which I think most on the PS boards are, their capacity values can be increased to the next available size.   The larger capacity values will filter the DC line they serve to a higher degree, which is good.   But increasing the capacity too much, or too many higher values on the same PS line, could have an additive effect that could be a problem.

A capacitor tends to look like a short circuit to ground for the first small fraction of a second after power is applied.   Depending on the circuit design, if the capacitor is too large, it can stress the components feeding it, or even blow a fuse in an extreme case.   Like many things, sometime more is better, but beyond a certain point becomes detrimental.

For example; (without looking at the circuit) the first capacitor listed is .068 uf.   Increasing it to .1 uf, as shown, should be ok.   Increasing the voltage from 250 to 630 is great, providing the physical size will fit.

There are other places where capacity values are critical, like in timing applications.   In those cases, the value (uf) should be the same, even if you have to combine cap's to obtain the same value.   In the case of critical values, it should be called out on the documentation, or maybe have a much tighter tolerance.

You may already know much of this.   If not, hope this helps.   
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on March 05, 2016, 09:01:33 pm
There are other places where capacity values are critical, like in timing applications.   In those cases, the value (uf) should be the same, even if you have to combine cap's to obtain the same value.
You may already know much of this.   If not, hope this helps.   
One could add that timing caps are not normally under the same stresses as PSU, local bulk capacitance or decoupling caps and therefore the need for replacement is uncommon.
Sure, when there's trouble obtaining the range of adjustment needed in timing circuits (that can be adjusted) the timing caps then should be suspect, but not always.

Widespread replacement of caps should be avoided IMHO, excluding PSU's and local bulk capacitance of course.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on March 05, 2016, 09:18:05 pm
Just a note, if you want to power the power supply boards outside the circuit. (recommended if you make a mistake) you HAVE to use the appropriate load resistors and they have to be rated correctly. Without the correct load resistors you will likely also notice Q1062 and R1071 getting hot. On mine R1071 actually burned up. This had me sidetracked thinking something was wrong in this area, but it wasn't and had me chasing ghosts. Probably just a bad design and the circuit started oscillating. Could also hear a faint whistling. Anyways point being is the service manual I believes states to start at the 87v and work downward (actually it's the 10v reference) so there is probably a short somewhere on one of the voltage lines and the current limiting is kicking in.

On the 87v I used a 2k resistor. In the theory of operation in the service manual. 87v rail should not exceed 100ma. -8v rail should not exceed 480ma.. +42v rail should not exceed 400ma, so I used a 150 ohm. Basically size your resistors accordingly so not to overload and have the current limiting kicking in, which will start part of the power supply to shut down making it difficult to diagnose.

I did not find it necessary to load the +10v reference.

As well as it has pointed out there is a error on the schematic for one of the capacitors and it's orientation so take a picture of your board caps before removing for references. On certain board revisions , and I am going by memory there is one more or one less bi-polar cap. I think it was one more.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on March 05, 2016, 11:30:01 pm
It's all good advice for me too.

Tautech - I agree completely with your thoughts on caps.

MSO - Regarding the programmer, yes, most of those things are or have been done.   The two different IC's have the same memory capacity, pin outs and voltage ratings, etc.   One exception is the toggling of the address line, which is supposed to be compatible with the 2465B.   I had also read where that conversion had been done successfully, so proceeded ahead.   And we did successfully copy the data from the old DS1225Y and transfer it to the new FM16W08 without any snags.   And the scope does work as well as it did before changing IC's.   We also successfully compared Write & Read copies off the programmer as you suggested.   Problem I'm having now is getting the next (spare) FM16W08 to be programmed.   As a test, tried programming another DS1226AD (they are supposed to be the same as a Y version), and it was having problems too.   Have a message into the GQ Support office that I may get a response to on Monday.   Thanks for your thoughts that are always appreciated.

On a different issue - FYI
I'm set up with all the anti-static hardware for working on the scope.   The mat was in good condition, but used long ago.   So I cleaned it up and put it back in service.   But the question was - how can I test it?   Common ohm meters don't work, and I would hate to be adding ESD failures to the scope's existing issues.

Solution - I found a short thread on this Forum where others had the same concerns.   Then it occurred to me.   There's a really simple way to test it.   My write up is at the end of this thread.  https://www.eevblog.com/forum/beginners/measuring-surface-resistance-of-esd-mat/ (https://www.eevblog.com/forum/beginners/measuring-surface-resistance-of-esd-mat/)
 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on March 06, 2016, 04:28:29 pm
Mr. Sauce,

You wrote:  "Wouldn't the cal data be kinda useless after repairing the power supply board, it would need a recal anyway?"
I don't know of any reason the calibration would change when rebuilding the power supplies.   I counted 9 regulated voltages not counting the CRT HV.   But all of those are supposed to be at specified DC levels.   These voltages and their tolerances, including allowable ripple, are noted on page 5-3 of the "Tektronix Service Manual" and are available for measurement at J119 on the main board (bottom of scope).  Service Manual is available on line.   You may already have all this info.

I don't completely agree with this statement. Power supply issues can potentially affect calibration, especially if you have a 2465 series with options. When I acquired a 2465 DMS with the DMM and CTT (Counter, Trigger, Timer) options it had a power up fail stating that the Counter was out of calibration. I also discovered later on that the DMM was in need of calibration but the power up routines don't check that. (And that's as per the DMM options manual). If the cal data is stored in ROM how did these options get out of calibration? I can't say and I don't know the history of this 2465 DMS. I was able to get both options calibrated and operating properly but lately I noticed an issue that led me to believe that subtle power supply issues can possibly affect calibration and definitely will affect operation.

Lately I noticed that DMM and Counter were both drifting slightly. For example: against my 10.000 VDC standard the DMM would slowly drift to 9.997 VDC. Against the 1.000 VDC and 100.0 mv standard it was rock steady. The Counter over time against a 1.000 MHz signal would drift down about 50 Hz. Granted, that's not a lot but I still wondered why this was occurring. I suspected there was a power issue that I was missing and it turns out I was correct.

The DMM board takes a 5.5 VAC @ 25KHz from the Inverter board and steps it up to +/- 12VDC. Those voltages were in spec. But it also gets a +5.00 VDC digital voltage from the mainframe. That measured +4.78 VDC which is out of spec. But if I measure the +5.00 VDC at J119 on the main board it was exactly +5.00 VDC. Clearly something is not right and I found the cause. All the options (DMM, CTT, etc) get their +5.00 VDC directly from the Inverter board, not the Regulator board. So I guess it's time to pull the Inverter and Regulator board and at least re-cap them. I bought all the caps a few months ago for that day when I'd have to pull it apart so for the past 2 days I did it.

I don't care what anybody says. Pulling one of these puppies apart to get to the power supply boards, especially if you have full options, is a royal pain in the nutz.  :-- Not enjoyable to me at all. But I got it done. It appears that all the caps were original 1985 build vintage. But I didn't find any leaking or swelling. I didn't test them. I just did a mass replace. The result? That +5.00 VDC supply to the options boards now measures +4.90 VDC. Success!

I still have to go back and verify the calibration of the DMM and CTT but I'm pretty sure the drifting issue is fixed. Time will tell.

I have some pictures that I will share. I really wasn't concentrating on doing a “show and tell” teardown. I just wanted to get the damn thing done.   


Here is the section of the Inverter Board that supplies the +5.00 VDC to the Option boards at J303. From Section 9 of the 2465 Service Manual. I assume 2465A and 2465B are similar.


The DMM Board before removal


The top plate after removing the DMM Board. The CTT Board and Buffer Board are attached to the underside of the plate and pull up with it when removed.


The A5 Board on the older vintage 2465 (no suffix). No Dallas chip or battery to deal with. Uses EAROM for cal data.


The Regulator Board before re-cap. As near as I could tell all caps where original 1985 vintage.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on March 08, 2016, 12:21:00 pm
I finally got all of the parts I needed to install the probe power connectors on my 2465BCT. This is Option 11, but is not available from the factory for a BCT because there aren't enough allocated connector locations. Previously, I installed Option 1E, but is just removing a resistor and adding a capacitor on the CTT board (I also added a 50 ohm resistor for proper termination which Tektronix (intentionally) omitted). I found two locations that would work, and drilled the holes for the connectors while I had the board out of the chassis. The cable routing for the top connector wasn't a problem. For the bottom connector, I slightly enlarged an existing hole in the chassis (the hole was due to how the metal was folded).

The bottom connector would have been too close to the main board. So, I took a 1/2 OD, 3/8 ID steel bushing, and cut off appropriate lengths from each end (so that one end of the resulting standoff washer was rounded and the other flat). That also moved the top of the connectors to near the surface of the plastic.

I also had to make two small nibbles on the edge of the plastic shield. One at the top for the edge of the washer & nut for the top connector and one at the bottom for routing the bottom cable. If I had placed the top hole just a fraction of an inch (0.05, perhaps) to the left I could have avoided the nibble at the top.

Unfortunately, I did not have my drill press and the need to measure the placement of the holes in the plastic extremely accurately resulted in some raggedness of the holes in the plastic - and one drill mishap that nicked the nearby plastic. Still, not too bad.

One parts gotcha is that the maximum wire size for the LEMO type connector (actually, I used a knock-off from China - a good bit cheaper) is 26 ga stranded  or 24 ga solid. The only two wire sizes for the header were 22 ga and 24 ga. That meant that I had to use 24 ga, solid. Of all the wire I have sitting around, that was not one of the sizes. I had to make an extra DigiKey order to get 2$ of wire.

Here are the pictures for the modification.

Probe Power Parts                      (http://imgur.com/jdqkpvC.jpg)
Top Probe Power Connector              (http://imgur.com/JEvVgbS.jpg)
Bottom Probe Power Connector           (http://imgur.com/VdaxT7K.jpg)
Top Probe Power Connector in Case      (http://imgur.com/WXaJqWY.jpg)
Bottom Probe Power Connector in Case   (http://imgur.com/e99mC5k.jpg)
Top Probe Power Shield Nibble          (http://imgur.com/tFrmYQI.jpg)
Bottom Probe Power Shield Nibble       (http://imgur.com/EbjJrfK.jpg)
Probe Power Headers 1                  (http://imgur.com/5q5dGux.jpg)
Probe Power Headers 2                  (http://imgur.com/iObL35d.jpg)
Probe Power Routing 1                  (http://imgur.com/8V88Yok.jpg)
Probe Power Routing 2                  (http://imgur.com/lvS5cS3.jpg)
Bottom Probe Power Routing 1           (http://imgur.com/8SEb8Rf.jpg)
Bottom Probe Power Routing 2           (http://imgur.com/EnTkSRu.jpg)


Title: Re: Tektronix 2465B oscilloscope teardown
Post by: z01z on March 13, 2016, 03:32:12 pm
I've a 2465A, on this all replaced caps were still in specs but all the 180uF/40V and 250uF/20V caps started bulging plus the Kemets developed some cracks.
The backup battery was also replaced, the original still had some juice in it after 29 years!  :-+

Just for the fun I've also made a few thermal images, enjoy!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: FireDragon on March 14, 2016, 07:46:37 am
Just for the fun I've also made a few thermal images, enjoy!

The thermal images are nice!

Note that the temperatures are low enough that heat sinking the U800 isn't needed. They aren't any worse that a hot summer's day down south (in the US) and better than the desert areas.

Of course, when I'm down there, I need a heat sink!

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: z01z on March 14, 2016, 12:33:23 pm
About the heatsink on U800, it did have one, sorry.
So I took it off, took some pictures, put it back on and took some more.

Without the heatsink the U800 definitely runs warmer.
Now, it can be argued how good the heat transfer to the heatsink is. From the close-up image it appears that the body underneath has about the same temperature as the heatsink.
Another thing is that these images show a state when the board is in the open and a fan blowing on it. When the case is on, it will surely change the whole situation and not for the better I think.
 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on March 14, 2016, 07:36:31 pm
Should be remembered that the thermal images are without the case.   As pointed out here many times, the holes in the bottom of the case directly under U800 force moving air past U800.   That should make a considerable reduction in temperature, especially with a finned heat sink installed.   A "case on" temperature measurement would be an interesting test.

Thanks for the images.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: z01z on March 15, 2016, 06:23:26 pm
OK, last test from me. The pictures were taken after the scope running ~30min both with and without heatsink on U800 with the case on. Then the scope was powered off, the case was quickly removed then the pictures taken.
The difference now is smaller than the scope was running open, U800 still appears to be the warmest spot.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on March 16, 2016, 04:35:56 am
Nice work z01z!   If I understand correctly, the temperature with the heat sink in place, and in the case, is about the same as when it is out of the case and an external fan blowing on it.   That seems to make logical sense.   And the heat sink appears to be doing some good too.

I previously missed the part about an external fan blowing on U800 with no case.

Thanks
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on March 16, 2016, 04:49:01 am
z01z, thanks for sharing those IR shots, really appreciate it.  :-+

Hope this will bring more awareness of blowing the whole big A1 with a big fan when working without the case.

If its not too troublesome, appreciate if you can post photos of your U800 mounted with heatsink, curious how does it look like.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: z01z on March 16, 2016, 08:14:54 am
If I understand correctly, the temperature with the heat sink in place, and in the case, is about the same as when it is out of the case and an external fan blowing on it.
Exactly. Except that it took some time until the case was removed and the picture taken, so it must have been a bit warmer inside the case than on the pictures.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: z01z on March 16, 2016, 08:27:23 am
If its not too troublesome, appreciate if you can post photos of your U800 mounted with heatsink, curious how does it look like.
Sure, no problem, I can take pictures when I get home.

I've used this heatsink (http://uk.farnell.com/fischer-elektronik/ick-pga-17-x-17-x-12/led-heatsink-with-pins-square/dp/1850035), cut it to match the width and filed away some of the fins so that the nut can be fit. I've also put a small insert between the metal tab and the heatsink.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on March 24, 2016, 04:08:36 am
Ok - As written above, was successful in removing the original DS1225Y from my 2465B scope and retrieving the cal data using a GQ-4X4 programmer.   Then the data was successfully written onto an FM16W08 which has been working great in the scope for the last several weeks.

The last problem was getting the same data to write to a spare FM16W08.   It's symptoms were that the D1 data line would only write a "1."   Contacted GQ Support for suggestions (they supplied the custom software for me that includes the FM device).   They made some general suggestions that we had mostly tried, and said they would order an FM IC and troubleshoot the software problem at their location.   So I ordered 2 more FM IC's as a shot in the dark from my end.

My replacement IC's came in yesterday.   Soldered an FM IC to the new adapter board, inserted it into the GQ Programmer - and it work perfectly!

We re-tested the failed FM IC and the problem with the D1 data line was the same.   Taking a closer look at the physical pins with an eye loop, magnifiers and bright lights from various directions revealed that pin 12 (D1 data line) had less solder than all the other pins, but otherwise looked ok.   As another shot in the dark, I re-soldered pin 12, inserted it into the programmer - and it worked perfectly!   Whewww!

Then we turned to the new DS1225AD I had previously purchased for a parallel effort with the FM16W08.   Problem was, it too had failed to write/load correctly.   As before, it loads all the data correctly except for the first byte which displays "FF" (hexadecimal code).   Again we tried everything thinkable with no luck.   The DS IC does not need an adapter board so there are no solder issues there.

Sent this most recent information off this evening to GQ Support including the issue with the DS IC.   So, the present status of my coveted scope cal data is - - -  One new FM IC installed in the scope.   Two spare FM IC's on adapter boards correctly programmed and stored.   The cal data is stored on my XP computer.   The cal data is stored in 4 places in my Windows 8.1 computer.   A copy is on a memory stick.   And I have a hard copy of it stored in the scope binder.   And, not to mention the DS1225AD that may get working.   And, the original DS1225Y that was removed from the scope is still alive and showing good battery voltage.   Oh yeah - someone else here suggested that one needs another memory stick duck taped to the inside of the scope housing.   This way, when the EMP strikes, at least one memory of the data should survive - but of course the scope won't :palm:

Nothing paranoid here about saving cal data.   Its just that it takes so much effort to retrieve and save, that no one wants to risk loosing it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: ChunkyPastaSauce on March 24, 2016, 05:07:42 am
I need to order those caps....

Send an e-mail to yourself if you have something like gmail, or upload to cloud.

Or upload here so if people what to look at the cal data they can and you have a backup copy.

Id put one of the FM ICs inside the case. Then if you need it, it's there.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on March 24, 2016, 05:18:30 am
Old-E, really appreciate the sharing of your experiences here, thanks.  :-+


.....<snip>...

   And I have a hard copy of it stored in the scope binder.   ...


Do you mean hard copy as printed in hex at paper ?  :o

If it is, make sure you're using acid free paper that will last few hundreds of years.  >:D  ...j/k


Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on March 24, 2016, 07:56:41 pm
Good point!   Share it here and use the forum like a cloud.

Anyway, I can attach the Xcel file here of the Hex code that was manually read from my scope CRT display.   Preceding it is a page showing how to get to the scope data in order to manually copy it (not to be confused with electronically reading it from the DS1225Y once removed from the scope).

For simple minds like myself, start in the upper left corner on page 1 where it says "Press delta V & delta T + SLOPE" using the control buttons on the face of the scope.   This gets you into the Diagnostic mode which is displayed on the CRT as noted in the display column of the Excel form.   "ALL 00" is displayed at the bottom of the CRT.   Moving right the 3rd column shows that the "VERT" button is illuminated.

You may continue moving right or return to the first column and press "MODE up" button to cycle from ALL 00 to "TEST 01, which illuminates the "CH-1" button.   To test any of these routines, move to the 4th column "Action" and press "COUPLING up" button.   If that test finds no problems, it will display "TEST 01 PASS."
The chart on the 2nd half of the page is an extension of the first half, extending to the right as shown by the connecting line.

To find the cal data, toggle down to "EXER 02" and find the upper left corner of page 2.   Then follow the sequence - press "TRIG COUPLING" to display the first data point (for my scope it is "0013").   Then to continue cycling through the rest of the cal data, continue pressing "TRIG SOURCE."   The first 2 digits to the left of the cal data starting with "00" is the address location for the stored data.   This shows up in the data copied from the DS1225Y shown on the GQ Programmer display.

Following the order of the sequence laid out in the Excel spreadsheet it should be pretty straight forward and probably easier then following my verbal description here.

Note:  In theory, one could manually enter this data into a programmer and then write it to a replacement IC.   It would be time consuming and it would need to be double or triple checked to eliminate any errors, but it could be done.   I copied my data manually first because the DS1225Y was way past it's battery life expectancy, and just incase it died before it could be read electronically, at least I would have a printed copy of the cal data.  (An error in this paragraph has been corrected)

I'll write more about this later.

(The attached Excel spreadsheets have been updated with a couple of corrections, additions and an improved layout - easier to follow.  4-23-2016)
 Problem:  Page 1 of the new Excel spreadsheet wants to come up in portrait rather than landscape format.   To fix; after opening click on "Enable Editing" at the top of the page and the formatting will fix itself.   Sorry about that.   Unable to find the cause.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: ChunkyPastaSauce on March 24, 2016, 08:10:49 pm
Cool, pretty nice too
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on March 25, 2016, 08:10:12 pm
Regarding my last entry, might also mention that one could download the attached Excel file to your computer and erase just the cal data (hex code).   Then you would have a blank form to enter your own scope data on as you read it off the CRT display.

Another thought is that if you should lose your scope cal data, my understanding is that you could program your new RAM IC using this data.   Your scope then would not be precisely calibrated, but it would be close enough to get it back in operation.   Also, your recorded operating hour and power cycles would not be relevant to your scope.

Attached below is a screen print of the GQ-4X4 Programmer with my scope's cal data displayed in the buffer as if ready to be written to a FM16W08.   The FM16W08 device, indicated in the upper right, has been called up from the GQ library.   The reason I'm able to pull that IC up from the library is because I'm using the new "Hotfix" software from GQ Electronics, Support group.

FYI - Looking at the screen print shown, find the far left address column in pink.   Then find address location "00001E00."   That is where the cal data for my scope starts.   That can be seen by comparing the first series of bytes "00 13 06 BF 26 EB," etc,. - to the first data points in my Excel data sheet, page 2 (attached in my previous entry) "0013, 06BF, 26EB.   Those bytes should compare correctly all the way to the bottom of the screen print where once again we can compare the last bytes "00 27 00 00" - to the bottom of page 3 of my Excel spreadsheet where 0027, 0000 was copied from my scope's CRT display.

Obviously, above address location 00001E00 of the screen print, is a lot more recorded Hex data.   So, what is that?   It apparently it is not cal data, because it is not displayed on my scope.   I believe it is non-critical stuff, like hours of operation, scope set up sequences (where one can record the scope settings by pushing a button, and then retrieving it in the future for the same setup, and who knows what else.

Correction - In my previous entry, I wrote -  (Previous entry now corrected)
Note:  In theory, one could manually enter this data into a programmer and then write it to a replacement IC.   It would be time consuming and it would need to be double or triple checked to eliminate any errors, but it could be done.   One problem with this is that, the GQ Programmer that I used here is not sophisticated enough to manually load data - per my limited knowledge.
Facts are - A friend pointed out that the GQ Programmer can manually load data!   But if one was loading only what was copied off the scope CRT, it would be missing all the data we see in memory preceding the cal data.   And this brings me back to the question of, is the preceding data critical to operations?

Another thought that might work (per my limited knowledge), would be to load a full set of data from another scope electronically into your RAM IC.   Then go back and manually modify just the cal data part to what you had copied off the CRT display on your scope before the Dallas IC died.

I'll write more later. 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on March 25, 2016, 08:19:43 pm

Correction - In my previous entry, I wrote -.........

I'll write more later.
Do consider Edit or Modify to a previous post so your great info reads correctly in that one post.

I't not a crime to make Edits and best if you also make a post to say that you've done so in case readers had saved your very good info.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on March 25, 2016, 09:29:26 pm
Tautech - Good suggestion.   Correction above dually noted.   Thanks.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on March 26, 2016, 07:46:56 pm
More about the GQ-4X4 Programmer.

As mentioned before, the GQ programmer does not include the Ferromagnetic IC FM16W08 in its library, that some of us have used to replace the battery powered RAM DS1225Y.   The advantage of switching to the FM16W08 is that it will not lose it's recorded data when the power is switched off - no need for battery backup.   To the external world, everything looks the same (voltages, pin outs, etc.) except for one detail.   And that is the way the data lines are toggled.   But the good news is that the scope happens to be logically configured to work with either IC.

So, following someone else's report, I bought this GQ Programmer and tried to write to an FM16W08 by using the DS1225Y listed in the Programmer's library.   And it didn't work.   Even tried down loading some older software thinking that maybe the report writer might have used it with success.   But no luck.   I contacted GQ Support for help.   They confirmed that the GQ programmer would not load an FM16W08 in place of a DS1225Y.

And further more, only their recent latest model, GQ-4X4, could even be configured to do that (GQ-4X model could not).   The way to determine if you have the 4X4 version is you will hear 2 audible beeps when you apply power to it using the USB cable to your computer.   Mine beeped twice.   Wheeew!

John in Support was very helpful and, a number of communications later, he sent a custom Hotfix program for my Programmer.   After loading it, there was the FM16W08 IC in the library.   Skipping more details, the Programmer worked great in transferring the data from the DS1225Y to the FM16W08.   John said they would be including that IC in their next updated software version.   I get the impression they release newer versions every year or so.

Getting to the bottom line here, I received confirmation from John at GQ Support a couple of days ago, that it would be ok to share the modified software with anyone that wanted it.   I had told him about my entries in this forum about the GQ Programmer, and had received a request for a copy from one of the forum people.   The latest standard software version is 7.07,   This modified version is 7.08 (3.81 meg).

Assuming this attachment process works, and you have it down loaded on your computer, I would suggest that you disconnect your computer from the internet for the duration that your Programmer is displayed/open.   Reason is; as soon as you open it, the programmer automatically goes on line looking for the latest version of software.   Version 7.08 is later than 7.07, so this should not be a problem, but I didn't want to chance getting the 7.08 version overwritten with something else.

Got a problem - This attachment will not work here.   Tried several times.   Error message says it may be too big of a file.   So plan B might be to see if it can be made available on line for readers to download from the GQ site.   In the meantime, I can send it by e-mail to any individuals that contact me at  don9@tds.net

Sorry about that!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on April 02, 2016, 01:34:40 am
Finally - total success!!!

Received the latest version of custom software from GQ Electronics.   The degree of special help I've received from them has been amazingly positive!   My communications are almost always answered in a few hours, and almost anytime of day or night!   It's pretty incredible!

This software version 7.08B was to also add the DS1225AD to the library.   I was unable to write correctly to the AD version when using the Y version in the library.   Both chips are supposed to be the same, in that respect, so it appears there was a bug in the Y version of the software.   But, regardless, the AD version is there now and works with an AD chip.   The DS1225Y has been noted as obsolete, and superseded by the AD.   So, now I have more than an adequate number of IC's loaded with my scope's cal data.

For anyone wanting to obtain a copy of the latest version of custom software that now writes correctly to the DS1225AD and the FM16W08, I'll be happy to e-mail you a copy, because the file is too big for this Forum.   Eventually it will be included in GQ's next published upgrade.

Don
don9@tds.net

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MSO on April 02, 2016, 06:20:20 am
Nice work, Don.

For those who might attempt restoring their calibration data from the data read using EXER 02, the bytes are not swapped in binary image; that is if a location reads on the scope's display as 2071, it's 2071 (not 7120 as Intel does it) in the binary image as well.

I've attached both a binary copy and an ascii (human readable) copy of my NVSRAM image for those who might find it useful.  My 2467B is serial number is one of the newer ones beginning with B053xxx. I don't know if it makes any difference, but just so you know.

You can load the binary (.BIN.HEX) file directly into your programmer; the ascii (.TXT) file would have to be converted to binary before it would prove useful. Beware though, most programmers will load the text file and write it out to chip, making the chip as useful as pebble, so don't do that.  I use the text version just to browse the data and see what's in it.

 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on April 05, 2016, 04:57:00 am
Bit of trivia - - 

:palm:    "Finally - total success!!!"   Opening my last message with this sounded a little too absolute at the time.   And sure enough, as soon as I notified the world, including this forum, that the last remaining obstacle in the GQ software tested good, I received this message back from GQ Support -

Hi? Don?

Thank you for your update.

It is the best to test the new software with FM16W08 .  Because there are partially over lapped.

The new version will be released once other chips been added.

Best Regards.
John

In other words, their last software mod that fixed the DS1225AD problem had elements common to the FM16W08.   So, confirming that the DS1225AD worked, did not mean that the FM16W08 still did.   This produced the Ohhh! Nooo! moment.

So, over the weekend, I pulled one of my previously programmed FM16W08's out of storage to run through a test routine.   FYI - That consisted of loading all FF's in the programmer buffer.   Then writing that over the top of the scope cal data, and reading it back to confirm that indeed all FF's were displayed.   All FF's sets all the inputs high.   Then it was repeated with all 00's to set all the inputs low.   Then repeated again with all 55's, and then all AA's, to load the IC with alternating highs and lows.   When that was successful, the scope's cal data was loaded back in the IC, and confirmed before putting it back in storage.   Wheeew!

It worked!   So now I don't have a lot of explaining to do.   Notified GQ Support and received the following reply.

Thank you very much for your testing.

Now we can claim those two chips are supported.

Cheers.

John


So, whenever GQ's next software version is released to the market place, these 2 IC's will be in it.   In the meantime, I can share it with the forum.
Title: Re: Tektronix 2465B cal
Post by: Mosaic on April 08, 2016, 04:16:20 pm
Hi all:
I justed posted this item on EBAY 131775163056
It is for the SG504 Leveled Sine wave gen - a better substitute head.

Ancel
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: RF_Pursuit on April 09, 2016, 07:23:40 pm
After thanking med6753 for welcoming me and his valuable suggestions, I continue my post which I started here
https://www.eevblog.com/forum/repair/tektronix-2465b-tear-down-and-rejuvenation/ (https://www.eevblog.com/forum/repair/tektronix-2465b-tear-down-and-rejuvenation/)

Today, I cleaned the A5 board from oil leaked from the capacitors and made a list of Tantalum capacitors to order and substitute.

I added a 1mm thick copper plate as cooling fins to extra cool the U800, not optimum, but a T-shirt less for the Summer!

And here comes the adventurous part (I'll post the images later). I dismantled the A5 board and I immediately started milling the DS12225 as I read in this article  http://www.worldphaco.com/uploads/TEKTRONIX_2465b_OSCILLOSCOPE_CALIBRATION___REPOWERING_THE_DS1225.pdf, (http://www.worldphaco.com/uploads/TEKTRONIX_2465b_OSCILLOSCOPE_CALIBRATION___REPOWERING_THE_DS1225.pdf,) because I once got an error message (test 05 fail 44).


Unfortunately, I reached almost 4.5mm deep until I saw three metal traces. I measured one of which (the mid one) to find it is 3.25 volts!

but I struggled to solder a wire on it and then sealed the hole and fixed the wired with resin.
I have the CR2032 but solder doesn't stick on it. I have to wait to buy a lithium battery micro size.

Fortunately, the SD1225 hasn't lost data.

Now there are two other problems, a broken SEC/DEV potentiometer which I fixed with  instant adhesive, and the bend traces of channel 1 and 2.  I assume this one has to do with aging capacitors in the power and vertical horizontal circuits???? I'm going to work on these boards after some consideration and collecting information.







Title: Re: Tektronix 2465B oscilloscope teardown
Post by: RF_Pursuit on April 10, 2016, 09:05:14 am
Can someone please tell me how to get to the information on 'Switch on off times' and 'Number of Operation Hours'? Thanks!

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: rf-loop on April 10, 2016, 05:02:55 pm
Can someone please tell me how to get to the information on 'Switch on off times' and 'Number of Operation Hours'? Thanks!

RTFM!  (example: 070-6873-00_2465bSvc_Sep89.pdf )


All is explained in service manual. Also even how to change these values what ever you want. (But, seriously, because you need ask this question: Warning, DO NOT enable CAL and play with CAL routines if you do not know exactly what are you doing there! )

Without enabling CAL, just only need use front panel. You need go to EXER 06 routine. It tell this info.

Page 6-10 in service manual. There is "Diagnostic routines" explained. Also how to enter to these routines.

Or, more easy: Operator manual.
http://exodus.poly.edu/~kurt/manuals/manuals/Tektronix/TEK%202445B,%202455B,%202465B%20Operator.pdf (http://exodus.poly.edu/~kurt/manuals/manuals/Tektronix/TEK%202445B,%202455B,%202465B%20Operator.pdf)

There Appendix A "Extended functions with diagnostic exercisers"

Manuals are for reading!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on April 10, 2016, 07:05:59 pm
RF_P -
The total scope hours and the number of power on/off cycles can be found in the scopes memory.   To access that place in memory you can follow the procedure in the Service Manual as rf-l indicated, on page 6-10 or the actual page count is 232.

Simple way to get there is -
Hold down the delta V & delta T buttons on the front panel, , then simultaneously press "+ SLOPE."   This enters you into the diagnostic mode and you will see "ALL 00" displayed at the bottom of the CRT screen.

Then press "MODE" up, button to cycle from "ALL 00" to "TEST 01."   Continue pressing "MODE" up button to cycle down to "EXER 05."   Here, you will see that the "ADD" button is illuminated.   (Pressing the "MODE" down button reverses the order)

Then press the "COUPLING" up button.   This should display your scope's hours and power cycles across the top of the screen.

To exit - press the "COUPLING" down button.   This returns you to the DIAGNOSTIC page.

Then press "A/B TRIG" to exit the DIAGNOSTIC page, returning your scope to normal operation.

There are many more options that can be accessed in the diagnostic mode.   This is just the straight line path to your requested information.

Let us know your scope numbers.   By the look of the dirt accumulated on the fan, it would appear that it has been operated outside of a clean room environment.   This can and should all be cleaned up.   And the 4 electrolytic capacitors on the A5 board should be replaced ASAP.   It appears that the board around those caps in your photo is still in good shape.   So, count your blessings.   Too often the stuff leaking out of those caps eats up traces and other components in the near vicinity.

My scope indicates over 20,000 hours & 1,100 power cycles.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: RF_Pursuit on April 13, 2016, 10:15:41 am
Can someone please tell me how to get to the information on 'Switch on off times' and 'Number of Operation Hours'? Thanks!


Also even how to change these values what ever you want. (But, seriously, because you need ask this question: Warning, DO NOT enable CAL and play with CAL routines if you do not know exactly what are you doing there! )

Without enabling CAL, just only need use front panel. You need go to EXER 06 routine. It tell this info.

Manuals are for reading!

Thanks a lot I appreciate your drawing my attention not to fiddle with CAL, you're right I could've fallen in that swamp!

I was mainly busy downloading different manuals and skimming through them. And of course looking for A3 schematics but I managed this by magnifying the A4s.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: RF_Pursuit on April 13, 2016, 10:33:24 am
RF_P -
The total scope hours and the number of power on/off cycles can be found in the scopes memory.   To access that place in memory you can follow the procedure in the Service Manual as rf-l indicated, on page 6-10 or the actual page count is 232.

Simple way to get there is -
Hold down the delta V & delta T buttons on the front panel, , then simultaneously press "+ SLOPE."   This enters you into the diagnostic mode and you will see "ALL 00" displayed at the bottom of the CRT screen.

Then press "MODE" up, button to cycle from "ALL 00" to "TEST 01."   Continue pressing "MODE" up button to cycle down to "EXER 05."   Here, you will see that the "ADD" button is illuminated.   (Pressing the "MODE" down button reverses the order)

Then press the "COUPLING" up button.   This should display your scope's hours and power cycles across the top of the screen.

To exit - press the "COUPLING" down button.   This returns you to the DIAGNOSTIC page.

Then press "A/B TRIG" to exit the DIAGNOSTIC page, returning your scope to normal operation.

There are many more options that can be accessed in the diagnostic mode.   This is just the straight line path to your requested information.

Let us know your scope numbers.   By the look of the dirt accumulated on the fan, it would appear that it has been operated outside of a clean room environment.   This can and should all be cleaned up.   And the 4 electrolytic capacitors on the A5 board should be replaced ASAP.   It appears that the board around those caps in your photo is still in good shape.   So, count your blessings.   Too often the stuff leaking out of those caps eats up traces and other components in the near vicinity.

My scope indicates over 20,000 hours & 1,100 power cycles.

I'm grateful to you as you saved me a lot of time and eye sharpness for the coming years! I appreciate pädagogical and informative instructions which help one to arive at target.

As for the A8 board, I cleaned it thoroughly and I am going the change all capacitors as I ordered them. I'm going to replace most/ all of the capacitors on the power baord too; these I have to order them from different sources as I couldn't easily find them at one store!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on April 13, 2016, 02:31:46 pm
Great to know about the GQ support folks. I've been searching for a better alternative for my TL866 programmer, which did successfully read/write several of my 246xxx series scopes Dallas ICs, but having issues with some Atmel AT89C51ED2 / AT89C51RD2 MCUs in another project. I don't see those in the GQ-4X4 list of supported devices, (I only see AT89C51).
and have an email to MCUmall to see what they say. Still sounds like a great programmer for the bux.

Thanks for all the info!!


Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on April 14, 2016, 08:53:31 pm
Update since my last entry on March 7th......

There has been progress and also a major setback.

After replacing all the caps on the supply boards I did a 6 hour “burn-in” to insure all was OK. I verified the 10 VDC reference and it was 10.1 VDC which is in spec. (It was prior to the re-cap too) All the supply voltages to J119 on the main board are in spec (Again, they were prior to the re-cap) The minor drifting issue with the Counter and DMM options is fixed. I performed a re-calibration of the Counter and it's now dead nuts as shown:

Sidelight: The 2465 does not have the EXER 05 and I can't check the power on hours or on/off cycles. And I haven't found any reference in the service manual to access it.

Major setback: I accidentally damaged the front end in the DMM option while attempting a calibration. It now has a solid DC offset error and won't zero. I had originally performed a DC calibration with the required “constants” of 0.19 VDC, 1.9 VDC, 19.0 VDC, and 190.0 VDC. The last “constant” required was 500 VDC. I built up a source to supply this constant. Unfortunately the source had an intermittent connection and it threw a spike into the DMM. I discovered that this DMM option does not have the best input protection and something got FUBAR'ed.       

I verified that all the precision resistors in the input/attenuation network are OK so now I'm going after the active components. Troubleshooting in this area is very difficult because of the high impedances and even a 10MEG DMM loads down the circuit. So I chose the most likely suspects and doing a mass replace. I've sourced all the parts except one op-amp which appears to be unobtanium. Luckily it's further down the chain of components so hopefully it's OK. I'll update after I get and replace the parts.

And finally. I still have this pesky BU Test F1 Fail 10 on power up. It's a Buffer board EAROM checksum error. As near as I can tell it might only affect the GPIB and the Word Recognizer options. I don't use those options so this error is low priority at this time. While going through the cal routines I noticed the ability to calibrate the Buffer board but no mention of it in the 2465 Options Service Manual. But it IS in the 2465A Options Service Manual. So I performed the calibration and on the first power up cycle the error went away. But then it came back. So this needs more work but after I get the DMM fixed. 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on April 14, 2016, 10:02:42 pm
...
And finally. I still have this pesky BU Test F1 Fail 10 on power up. It's a Buffer board EAROM checksum error. As near as I can tell it might only affect the GPIB and the Word Recognizer options. I don't use those options so this error is low priority at this time. While going through the cal routines I noticed the ability to calibrate the Buffer board but no mention of it in the 2465 Options Service Manual. But it IS in the 2465A Options Service Manual. So I performed the calibration and on the first power up cycle the error went away. But then it came back. So this needs more work but after I get the DMM fixed. 
Here's the 2445/2465 (plain, not A or B) of the CT and WR service manual if you want it:

https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg710773/?topicseen#msg710773 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg710773/?topicseen#msg710773)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on April 14, 2016, 10:15:18 pm
...
And finally. I still have this pesky BU Test F1 Fail 10 on power up. It's a Buffer board EAROM checksum error. As near as I can tell it might only affect the GPIB and the Word Recognizer options. I don't use those options so this error is low priority at this time. While going through the cal routines I noticed the ability to calibrate the Buffer board but no mention of it in the 2465 Options Service Manual. But it IS in the 2465A Options Service Manual. So I performed the calibration and on the first power up cycle the error went away. But then it came back. So this needs more work but after I get the DMM fixed. 
Here's the 2445/2465 (plain, not A or B) of the CT and WR service manual if you want it:

https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg710773/?topicseen#msg710773 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg710773/?topicseen#msg710773)

Thanks. I have all the manuals for the 2465, both the mainframe and the options manual. What is strange is that the calibration routines that appear on CRT give the ability to do a Buffer Board calibration but the 2465 options service manual makes no mention of it. I just happen to have the 2465A options service manual and it does mention it. Either it's an error or most likely I'm missing an update.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on April 15, 2016, 02:57:39 am
...
Thanks. I have all the manuals for the 2465, both the mainframe and the options manual. What is strange is that the calibration routines that appear on CRT give the ability to do a Buffer Board calibration but the 2465 options service manual makes no mention of it. I just happen to have the 2465A options service manual and it does mention it. Either it's an error or most likely I'm missing an update.
The 2445/2465 Option 10 GPIB Service Manual (pub #070-4640-00) mentions that "BU CAL F1" has to be performed before the GPIB cal "GP CAL 11".

But there's no description of exactly what "BU CAL F1" does.  What does it do on the 2465A?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on April 15, 2016, 11:44:04 am

The 2445/2465 Option 10 GPIB Service Manual (pub #070-4640-00) mentions that "BU CAL F1" has to be performed before the GPIB cal "GP CAL 11".

OK, I figured out what's going on. The 2465 options service manual I have only covers options 6 and 9. I have a separate 2465 service manual for the DMM (option 1). Do you know of a source for the Option 10 manual?

But there's no description of exactly what "BU CAL F1" does.  What does it do on the 2465A?

The 2465A options service manuals covers all the options. Here's what it says with regards to calibrating the Buffer Board.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on April 15, 2016, 03:26:28 pm
OK, I figured out what's going on. The 2465 options service manual I have only covers options 6 and 9. I have a separate 2465 service manual for the DMM (option 1). Do you know of a source for the Option 10 manual?
The 2465 service manual is equally uninformative; (irr)relevant page attached.

I only have the GPIB Option 10 service manual in electronic form and I don't recall where I found it.  It was at least 11 or 12 years ago.  I will send you a PM to get it to you.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on April 16, 2016, 05:30:56 am
SoundTech-LG -

Yes, I found GQ Support to be unbelievably helpful.   Of course I'm only a sample of one, which does not say much about a continued trend, but it is a good start.   If you wish, feel free to use my name and experience with them as a reference.

Regarding the AT89C51 listed in the GQ-4X4 library, the question that comes to mind is; are the electrical characteristics close enough to your IC's to work correctly.   GQ Support should be able to answer that.   If they are not compatible, it has been my observation that they probably/might be interested in adding it.   They sound like they are always on the lookout for additional IC's to add.

Just for the record, I'm a novice in the world of programming.   Learning as I go.   A neighbor friend has been helping me over the hard spots with the DS and FM IC's and explaining things as we go.   While I now feel pretty comfortable in reading or writing existing programs to IC's, I think there's so much more out there that I don't even know exists yet.

Let me know how things go with GQ. 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: RF_Pursuit on April 16, 2016, 06:24:58 pm
Hi everybody!

On the road to change as many capacitors as possible in the power supply  PCB, I replaced most of the capacitors except C1016 and C1018 those are plastic (0.068uF X2 250VAC) can I replace each with a RIFA PME 271 M (220n X2 275VAC)?

I also have a some (0.1uF 275VAC) but not X2 can I use these to replace the 0.068uF X2? Which would be suitabel the 220n X2 or the 100n?

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on April 16, 2016, 06:37:57 pm
Hi everybody!

On the road to change as many capacitors as possible in the power supply  PCB, I replaced most of the capacitors except C1016 and C1018 those are plastic (0.068uF X2 250VAC) can I replace each with a RIFA PME 271 M (220n X2 275VAC)?

I also have a some (0.1uF 275VAC) but not X2 can I use these to replace the 0.068uF X2? Which would be suitabel the 220n X2 or the 100n?

See attached list.....which I give credit to the Yahoo Tek group. I used the recommended 0.1 uF 275VAC X2 for C1016 and C1018 and they are working fine.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: RF_Pursuit on April 16, 2016, 07:42:58 pm
Hi everybody!

On the road to change as many capacitors as possible in the power supply  PCB, I replaced most of the capacitors except C1016 and C1018 those are plastic (0.068uF X2 250VAC) can I replace each with a RIFA PME 271 M (220n X2 275VAC)?

I also have a some (0.1uF 275VAC) but not X2 can I use these to replace the 0.068uF X2? Which would be suitabel the 220n X2 or the 100n?


See attached list.....which I give credit to the Yahoo Tek group. I used the recommended 0.1 uF 275VAC X2 for C1016 and C1018 and they are working fine.

Thank you, I followed the that list in ordering the capacitors. Unfortunately, I couldn't get all of them as recommended.


And reading the tiny writing on the 0.1 capacitors I found the X2 within. So, that's done with.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on April 16, 2016, 07:47:42 pm
Hi everybody!

On the road to change as many capacitors as possible in the power supply  PCB, I replaced most of the capacitors except C1016 and C1018 those are plastic (0.068uF X2 250VAC) can I replace each with a RIFA PME 271 M (220n X2 275VAC)?

I also have a some (0.1uF 275VAC) but not X2 can I use these to replace the 0.068uF X2? Which would be suitabel the 220n X2 or the 100n?
The absolute value is not as critical as the X2 and voltage ratings that must be maintained.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Micma on April 19, 2016, 07:09:29 am
Hello everyone, I am new to this forum and wanted to thank you all for sharing valuable information!
A friend of mine gave me a 2465B does not work (he wanted to throw it!) and recently I bought another one in like-new condition!
Unfortunately I have to replace the NVRAM. Following the instructions that I found in this forum I have already ordered everything needed and  it should reach me in a few days.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on April 24, 2016, 03:12:47 am
NOTE -

The Excel spreadsheets attached to Reply #703 back on 3-25-16, have been replaced.   The updated version has a couple of corrections, additions and an improved layout - easier to follow.  (4-23-2016)
 Problem:  Page 1 of the new Excel spreadsheets wants to come up in portrait rather than landscape format.   To fix:  After opening click on "Enable Editing" at the top of the page and the formatting will fix itself.   Sorry about that.   Unable to find the cause.   It opens fine on my computer, but opens strange in the forum.

These are the spreadsheets showing the sequence to access the internal tests and Calibration data stored in the scope's RAM.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on May 07, 2016, 02:56:07 pm
CHASING THE ILLUSIVE MILLIVOLT & NANOSECOND – PART I

My 2465B appeared to be working perfectly (even though the PS caps have yet to be replaced) until it was pressed toward its limits.   Then some anomalies turned up that I felt needed to be understood.
Started by looking at sine waves from my fastest generator which tops out at 264 MHz (Tek. SG 503).   Peak to Peak (P-P) voltage was measured by using the manually adjusted cursors, accessed by pressing delta V.   This indicated 177 mv P-P.

Then pressing the lower red “HELP” button, followed by the “CHAN 2” button, commands the scope to measure the voltage from internal sources.   This indicated 134.7 mv P-P (reads on screen “CH1: PK-PK 134.7 mv”).  This is 24% lower than the cursor set measurement above.

Ok, so which number is correct?   I trust my digital multimeter, but not at that frequency.   So using a 60 Hz generator, the test was repeated.   This time, the internal scope function measured 2.5% higher than the manually adjusted screen cursors, and 1.7% higher than the digital multimeter.

Returning to the high frequency generator, I compared the voltage readings at different frequencies.   The result was; the internal sourced voltage measurements compared more favorably to the cursor reading as the frequency was reduced from 264 MHz.

On a hunch, I used a Tek. PG 502 pulse generator to generate a flat topped pulse train.   The short version of the findings were that the internally sourced voltage measurement needs some dwell time at peak voltage to capture the P-P voltage number.   That dwell time was experimentally found to be about 12 ns.   Problem with a sine wave is that it has very little dwell time at its peak voltage.   Following data illustrates the accuracy vs. flat top dwell time, with 1.00 volts high pulses displayed on screen.
3 ns = .934 v P-P
5 ns = .964 v P-P
9 ns = .996 v P-P
10 ns = 1.001 v P-P
12 ns = 1.011 v P-P
100 ns = 1.010 v P-P
(http://)

Next question is; what happens to the flat top time requirement when the repetition rate of the pulse train is varied?   For this test the top pulse width was set to 10 ns.   Then the rep rate was adjusted between 10 us and 10 ms.   But no significant difference was found.   So pulse repetition rate does not appear to affect the internal P-P voltage measurement.

Ok, so where does that inaccuracy begin with a sine wave?   Skipping to the bottom line, the following data was collected by using the SG 503, inputting 100 mv P-P at various frequencies, and then commanding the scope to measure the P-P voltage.
5 MHz = 99.9 mv
10 MHz = 99.6 mv
15 MHz = 99.1 mv
20 MHz = 98.7 mv
25 MHz = 97.2 mv
50 MHz = 89.7 mv
75 MHz = 85.8 mv
100 MHz = 83.1 mv

Conclusion: The scope can accurately measure P-P voltage of a flat topped pulse, providing the flat top is longer than 12 ns.   And, same for a sine wave that is <20 MHz, depending on the accuracy one is looking for.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on May 07, 2016, 10:22:50 pm
Update from my last entry on April 15th.....


The DMM Option Board is fixed. The culprit was dual FET Q5070. I also had on hand Op-amp U5060 but it's OK. Luckily Op-amp U4970 is also OK because so far that part has been unobtanium. I calibrated the DC voltages with my home built calibrator with the exception of the 500VDC range. I don't want to risk blowing out that FET again. I don't foresee needing to accurately measuring voltages that high anyway. I also recalibrated the ohms. AC volts calibration is pending until I can figure out an accurate calibration constant source of 0.19V, 1.9V, 19.0V, 190.0V, and 500V.

Here's the schematic of the front end of the DMM Option.

And here's a sample measurement to my 10VDC standard.


The last repair pending is the Buffer Board checksum error.   
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on May 08, 2016, 04:13:05 am
CHASING THE ILLUSIVE MILLIVOLT & NANOSECOND – PART II

While testing the scope’s limits, the next area of interest or anomalies is the frequency measurements.   This was accomplished by using a Tek. SG 503 sine wave generator at its highest frequency setting of 264 MHz.

Comparing the scope to itself, in the 1st photo, I carefully measured the cycle time at 3.82 ns using the manually adjusted screen cursors by pressing delta T.   This calculates out to a frequency of 262 MHz.   Then pressing the delta T & delta V simultaneously reads out the frequency, which also indicated 262 MHz.

In all of my tests, the numbers measured from the manually adjusted cursors were always exactly in agreement.   That includes the period & frequency, and the screen grid or graticule.

Then pressing the red lower “HELP” button, followed by the “CHAN 1” button, commands the scope to automatically measure the frequency from its internal sources (no connection to the cursors).   This indicated 266 MHz, which is 1.53% higher than the cursor measured number.   The frequency meter on the SG 503 generator indicated 264 MHz (only reads 3 places), which is in the middle of the numbers.
   
To determine if the input frequency has any effect on the accuracy,  the above measurements were repeated at various frequencies.   These included one point at 462.5625 MHz.   This came from my FRS Walkie Talkie.   I held its antenna near the scope probe while transmitting.   Can’t say anything about the amplitude, but this frequency is accurate for channel 1.   At this frequency, the 400 MHz scope and 300 MHz probe have rolled off quite a bit in amplitude at 462 MHz.   But, the scope manual says it will trigger up to 500 MHz, and so it can display 462 MHz as seen below.

Adjusting the cursors closer together will indicate a frequency up to 20 GHz (20,000 MHz), but of course the scope won’t actually display anything that high.   Need to find a higher frequency source to see how high it will go.

Letting the scope automatically measure the 462 MHz frequency via. the red HELP button, indicated 474.7 MHz, which is 2.3% high.

Additional lower frequencies were set up with the screen cursors, and then compared to the scope’s internal frequency measurement via. the red HELP button.   They were 100 MHz, 10MHz, 1 MHz, 50 KHz and 60 Hz.   These lower frequency readouts all agreed within the limits of being able to set the cursors which is a fraction of 1%.
 
Conclusion; All the lower automatic frequency measurements appear to agree well with the screen set cursors.   However, they read a few percent high at the higher frequencies.   And given that the cursor settings were right on for 60 Hz and 462.5625 (the 2 frequencies I knew for sure), and they mostly agreed with the lessor known accuracy of the frequency meter built into the SG 503 generator, I believe the cursors are accurate across the scope’s frequency spectrum.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on May 16, 2016, 05:04:27 am
CHASING THE ILLUSIVE MILLIVOLT & NANOSECOND – PART III

In search of more performance limits, I looked at RT (Rise time).   RT can be theoretically determined from the frequency.   The 2465B has a specified frequency response of 400 MHz (at the -3 DB roll off point).   Using the generally accepted formula of .35/Freq = RT, we have .35 divided by 400 MHz.   This = a rise time of .875 ns.

Should also point out that -3 DB in signal amplitude means the peak voltage at 400 MHz will read 29.3% less!   To maintain reasonable amplitude accuracy, of say -3%, the upper frequency limit would be about .30 x 400MHz, which brings the usable frequency (for amplitude accuracy) down to 120 MHz!   A good Tektronix article on this and the approximation of RT can be found at - http://www2.electron.frba.utn.edu.ar/~jcecconi/Bibliografia/06%20-%20Osciloscopios%20de%20Almacenamiento%20Digital/Understanding_Oscilloscope_BW_RiseT_And_Signal_Fidelity.pdf (http://www2.electron.frba.utn.edu.ar/~jcecconi/Bibliografia/06%20-%20Osciloscopios%20de%20Almacenamiento%20Digital/Understanding_Oscilloscope_BW_RiseT_And_Signal_Fidelity.pdf)

Ideally, to measure RT accurately, one needs a pulse generator with a RT of roughly 10x the .875 ns RT of the scope, or 87.5 ns.   Unfortunately, the best I could do was to borrow a Tek SG503 pulse generator.   It’s specifications give a rise time of 1 ns or better, which places it roughly equal to the scope.

When one begins to measure RT, a number of other questions arise.   Tektronix specifies it to be measured between the 10% & 90% of amplitude.   That’s easy in a perfect world where pulses have square clean corners.    But there is the “pre-shoot and overshoot of the leading edge of the displayed pulse.   I wrestled for some time with how to deal with that in making the RT measurement.   In the article above, they illustrate the answer which I like because it simplifies the measurement.

In order to minimize the leading edge distortions, I found the best results by connecting a 40 inch piece of 50 ohm coax directly between the SG503, using its internal 50 ohm output option, and the internal 50 ohm input to the scope.   When using a 50 ohm terminator feed through into the 1 meg ohm port, or a 300 MHz (unfortunately) scope probe into the 1 meg ohm port, the displayed pulse was not as clean.

All this wordiness was needed to qualify the following measurements.

The 1st photo below shows the displayed pulse with the amplitude adjusted to sit on the reticle 0% dotted line and the stabilized top on the 100% dotted line.   The under & overshoots pass outside those limits.

In the 2nd photo, the same pulse is shown with the sweep speed at max using the “x10 MAG”.   Measuring the time between the 10% & 90% crossings on the reticle, the cursors indicate 1.55 ns.   But the 1st photo shows the leading edge of the pulse rounding over before it plateaus across the top.   This will lengthen the measured RT.   Following some thought and experimentation, I came to the conclusion that, this distortion is coming from the source rather than the scope.   If so, then eliminating it would be fair.

The 3rd photo shows the elimination of the rounding and distortion across the top of the pulse.   This was done by reducing the pulse width to its minimum.   But this also shortens the height of the pulse.

The 4th photo shows where the pulse has been increased in height to again align with the 0% & 100% dotted lines.

In the 5th photo the sweep speed is increased to its max and the cursors are set on the 10% & 90% lines to indicate a rise time of 1.04 ns.

Letting the scope measure the rise time via the red “HELP” button, it indicates a rise time of .89 ns or .93 ns, depending on the repetition rate of the pulse generator.   A little discouraging, but again underscores the manually set cursors as being the most accurate.

Using the formula, .35 / 1.04 ns = 337 MHz.   But of course, that is the speed of the combined rise times including the scope, generator and cable.   But we can estimate the individual RT from the composite.   A published formula for this is - the square root of the sum of the individual squared rise times.

In this case – if we assume the cable is perfect for simplicity, it leaves us with 2 unknowns, the RT of the scope and the RT of the generator.   Since the scope RT is spec’d at .875 ns, and the generator is spec’d at equal to or better than 1 ns, we can further simplify by assuming they are both the same.   Using the formula above, then gives us an individual RT of .73 ns.   And since .73 ns is a safe margin below the spec’s of both instruments, I think it’s safe to say that the scope RT is equal to or better than .875 ns.   If we were to factor in something for the non-perfect cable, we would have an even larger margin.

This is not as perfect as I would like, but lacking a better pulse generator, it’s the best I can do.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on May 16, 2016, 05:46:35 am
When one begins to measure RT, a number of other questions arise.   Tektronix specifies it to be measured between the 10% & 90% of amplitude.   That’s easy in a perfect world where pulses have square clean corners.    But there is the “pre-shoot and overshoot of the leading edge of the displayed pulse.   I wrestled for some time with how to deal with that in making the RT measurement.   In the article above, they illustrate the answer which I like because it simplifies the measurement.
Tek are stating what is the common interpretation of rise time and what we most use.
However I believe one can overlook pre-shoots and overshoots and focus on measurement of the step function as mentioned in this Wiki article:

https://en.wikipedia.org/wiki/Rise_time

In electronics, when describing a voltage or current step function, rise time is the time taken by a signal to change from a specified low value to a specified high value.[1] These values may be expressed as ratios[2] or, equivalently, as percentages[3] respect to a given reference value. In analog or digital electronics, these percentages are commonly the 10% and 90% (or equivalently 0.1 and 0.9) of the output step height:

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on May 17, 2016, 01:16:43 am
tautech -

Yes, the link to the Tek article in my previous post clearly illustrates that the pre & overshoot on the leading edge of a pulse is to be ignored when making RT measurements.   Looking back, I neglected to actually state that.   That small difference can make a significant difference in the measurement outcome.

Getting into the sub-nanosecond arena, things starts getting rather spooky.   Things that have little or no effect at the lower frequencies, now can totally upset things.   And to make accurate measurements or properly functioning designs, those fine "spooky" points need to be addressed.

Thanks
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: nicnac117 on May 20, 2016, 08:31:13 pm
For information on the EAROMs in the 2445,2465, I opened  a thread  which may be of interest to the "A" and "B" guys....just search for EAROM
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on May 20, 2016, 09:12:09 pm
For information on the EAROMs in the 2445,2465, I opened  a thread  which may be of interest to the "A" and "B" guys....just search for EAROM
Editing your above post and inserting a link would be better.  ;)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on May 21, 2016, 06:13:11 pm
For information on the EAROMs in the 2445,2465, I opened  a thread  which may be of interest to the "A" and "B" guys....just search for EAROM
Editing your above post and inserting a link would be better.  ;)

Here's the link....

https://www.eevblog.com/forum/testgear/tektronix-2445-2465-cal-settings-earom-er1400/ (https://www.eevblog.com/forum/testgear/tektronix-2445-2465-cal-settings-earom-er1400/)

I'm very interested in how this turns out.


More steady progress on getting everything on my 2465 DMS fully functional and calibrated. Since my last update on May 8th I've starting tackling getting the AC volts on the DMM calibrated. The “calibration constants” to calibrate the AC volts are:

0.19V @ 60Hz
1.90V @ 60Hz
19.0V @ 60HZ
19.0V @ 20KHz
190.0V @ 60Hz
500.0V @ 60Hz
(All RMS)

I used a function generator with a pot as a voltage divider to get the 0.19V and 1.90V constant. But the maximum output of the function generator is 20.0V p-p so it can't do the 19.0V. I'm in the early stages at looking at possible designs to boost the generator output to about 60V p-p and above. If someone has some ideas I'd like to hear them. I'm not going to try the 190.0V and 500.0V constants because those are insane p-p voltages.

Here's the DMM measuring a 1.0VAC Sine with the Fluke 87. Not bad but may require further tweaking. The dots on the screen are the DMM logic warning of a potential out of calibration condition. The dots do not appear when measuring DC volts or ohms.


Measuring mains voltage with the Fluke 87. Clearly needs more work. I think if I can get the 19.0V range calibrated it will be much better.


Follow on: I'm going to build a temperature probe since the DMM has temperature capability. And awaiting the results of the EAROM experiment so I can fix the Buffer Board check sum error.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on May 21, 2016, 08:00:13 pm
...
I used a function generator with a pot as a voltage divider to get the 0.19V and 1.90V constant. But the maximum output of the function generator is 20.0V p-p so it can't do the 19.0V. I'm in the early stages at looking at possible designs to boost the generator output to about 60V p-p and above. If someone has some ideas I'd like to hear them. I'm not going to try the 190.0V and 500.0V constants because those are insane p-p voltages.
...
Ok, here are some ideas...

You could drive a power transformer backwards with the function generator to step up the voltage.  You don't need any current to speak of for the DMM input, so 60V should be fairly easy to hit.  At 20kHz, a power transformer may not work well, but you could try a small audio transformer (like the kind in old transistor radio).

If your function generator does not have enough output power to reach the desired output voltages, you could add an audio amplifier to drive the transformer.  And if it's an amplifier with a high enough output, you might be able to dispense with the transformer altogether.

If using a transformer, use the scope input to make sure the sine wave is still clean before relying on it for RMS calibration.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on May 22, 2016, 04:27:14 am
MarkL reflected some of my thoughts on generating higher voltages.   Another thought might be to feed 120 v ac into a variac for voltage control, then feed that output backwards through a 24 volt doorbell transformer.   That would easily give you 500 volts.   I think the winding insulation is rated higher than that.   Cost on-line should be less than $10.

I recently used the same transformer to step up 120 v to 240 v by using the 120/240 volt primary as an auto transformer (120 into the center tap and one end - 240 out across both ends of the same primary).   The 24 v secondary leads were dead ended (not used).   Similar to your case, I was powering 2 digital panel meters that only draw milliamps.   $6.25 each on-line.

Question - How do you know if it's the scope or the Fluke (or both) that are in error?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on May 22, 2016, 02:23:36 pm
Guys, thanks for the responses. Here I was trying to think of what was turning out to be a complex solution and a simple transformer solution was staring at me the whole time. Unfortunately this project is going to have to go on the shelf for a few weeks because I'll be involved in other pressing activities. But I'll provide an update when I get a chance.


Question - How do you know if it's the scope or the Fluke (or both) that are in error?

A very legitimate question and I'll try to provide a satisfactory answer. It goes back to the 1980's when I built a voltage/resistance “standard” based upon an article in an electronics magazine. It provides 10.00VDC, 1.000VDC, 100.0mVDC, 1.0VAC as well as some resistance “standards”. I used a borrowed and freshly calibrated Fluke 8050 to set it up. And documented the results. I also checked my then Fluke 77 and documented those results. I still have those documents to this day. And in the 30 years since building this unit I have never had the need to perform any further adjustments.

Around 1997 the Fluke 77 was damaged beyond repair by a leaking battery. So I purchased this current Fluke 87. I also documented how it compared to my “standard” and it was spot on. From about 1998 until very recently I was mostly inactive in this hobby and the equipment sat mostly unused. The 87 was rarely used and was never molested or damaged or overloaded. The only time it was opened was to replace the battery. So about 6 months ago when I got active again I compared the “standard” to the 87 to the 1997 readings and they were the same. I highly doubt both of them would have drifted the same amount so I trust what the 87 is telling me. And I often check both to make sure nothing has changed.

So I used the 87 as a reference point when applying the “calibration constants” to the 2465 DMM. Those constants do have a little bit of “wiggle” room but if it's too far out I get an “Out of limits” message on the CRT. Now will the 2465 DMM meet it's published specs? Of course not. But at least I know I'm close.

Now if I knew someone who had a Fluke 5101B and a Fluke 5205A I could have the entire 2465 DMM calibrated in about a half hour. But what's the fun in that? Redneck solutions are much more fun. “Hold my beer and watch this”.        ;D
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on May 22, 2016, 04:36:37 pm
“Hold my beer and watch this”.

Wasn't that the statement most often heard just before a car crash in redneck territory?  :)

Sounds like you have the cal issue pretty well nailed down as I assumed you did.   Just curious as to what route got you there.   Good work!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on June 01, 2016, 05:50:50 pm
CHASING THE ILLUSIVE MILLIVOLT & NANOSECOND – PART IV

Looking further into the 2465B’s abilities, the scope can also function as a time domain reflectometer.   For those unfamiliar with this, the scope’s speed is fast enough to measure the transit time of signals traveling through conductors.
 
For this test, I connected a BNC T to the scope 50 ohm input at channel 1.   A 50 ohm cable connected one port of the T, to the 50 ohm output of the SG503 pulse generator.   The addition of the T was found to have no measurable effect on signal level or rise time.   The 1st picture shows the shortest pulse width out of the generator measuring 1.71 ns at 50% of amplitude.   The height of the pulse is adjusted to extend from the 0-100% markings on the scope screen.

Then a 41 inch piece of 50 ohm cable was connected to the remaining port on the T, and the other end of the cable was left open (no connection).
 
The pulse coming from the generator is split at the T which sends 50% of the total pulse power down the open ended coax, and 50% of the pulse power into the scope.   This results in the voltage at the scope dropping to .707 of the original voltage.   If we were reading the current, it would indicate the same drop.   Then when multiplying the reduced voltage x the reduced current, the pulse power would = ½ of the total from the generator.   In the meantime, the pulse going down the open ended coax finds an open (very high impedance).   This mismatch results in reflecting the pulse back toward the T where it splits again, sending 1/2 back to the generator and 1/2 to the scope input, but at a later time.   It is this time difference and relative voltage levels that can used to measure conductor characteristics.

The 2nd picture shows the time delay of 9.0 ns between the primary pulse and the reflected one, and the reduced voltages from each split at the T.   Again, the coax is 41" long.

So how does that calculate out?   Light & electricity travel at 186,000 miles per second, or 11.8 inches per nanosecond.   Therefore; 9.0 ns x 11.8” = 106.2” of electrical length.   But the pulse only travels a round trip through the cable of 82”.   The difference is the velocity factor.   That is; the pulse travels slower through the cable, because of the dielectric materials making up the cable, then it does through free space.   So if we divide 82” by 106.2” we get a velocity factor of .772.   That is; the signal is traveling through the coax at roughly ¾ the speed it would in free space.   Now that I know that number, I can determine the physical length of another piece of coax off the same spool, or find the point of damage along an existing coax, etc.

The same test with a 62 inch piece of coax gave a reflected delay of 15.80 ns.   This times 11.8 inches gives a round trip electrical length of 188.4”, which results in a velocity factor of .665.   Even though they are both 50 ohm coax, they are made up of different dielectric materials resulting in different velocity factors.   The 41” coax is stamped RG58/U, and the 62” coax is stamped RG58C/U.

Same test again with a 13 ¼” length of coax resulted in a reflected delay of 3.4 NS.   This calculates out to a velocity factor of .661.

Looking closer at the peak voltage of the pulses, as mentioned above, the primary pulse should be reduced to .707 of the original when adding a 2nd cable at the T.   In a perfect world, that would reduce the pulse height on the scope screen from 5 divisions (cm) to 3.54.   But the scope is actually displaying slightly less at 3.40 cm.   This difference can be from any number of minor dimensional errors in the coax or connectors.

The voltage of the reflected pulse indicates 2 cm high when it should be 2.5 cm.   The primary pulse power is first split when entering the T, and then the reflected pulse is split again.   That’s a voltage reduction of .707 x .707 which = .500, or 2.5 cm.   Part of that difference can be attributed to the cable attenuation at 400 MHz, and the remainder is probably caused from minor imperfections in the cable and connectors.   RG 58 coax gets fairly lossy at these frequencies, which is why they use RG 8 or better for any significant length.   For example, 100 feet of RG58C will lose (absorb) nearly 95% of the input power at 400 MHz.   RG8 will lose 45%.   A cable loss calculator can be found at - http://www.qsl.net/co8tw/Coax_Calculator.htm (http://www.qsl.net/co8tw/Coax_Calculator.htm)

I realize this is pretty basic stuff for many reading this, but hopefully others may find these tests interesting as I did.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on June 01, 2016, 10:37:04 pm
You don't need to use power to calculate predicted amplitudes.

In the case of just the scope with its 50R termination, you have a 50R transmission line feeding the internal 50R resistor and measured at that junction.  The amplitude, as compared to open circuit (or 1M impedance setting) can be calculated as a simple resistor divider 50R/(50R + 50R).  So, when termination is turned on in the scope the amplitude is 50% of the unterminated setting.  Most people are familiar with this behavior and there are no lengthy stubs to observe pulse reflection behavior.

When you add the second coax transmission line, you're adding another 50R impedance at the scope's input (and also creating a discontinuity in impedance).  The amplitude of the pulse is now reduced because there's another impedance in parallel with the first two and creates a 3-way divider.  It is 50R/(50R + 50R + 50R), which 33.3% of the open circuit amplitude.  Or 66.6% if you want to use the terminated (50%) amplitude as the baseline.

The terminated pulse height you report as 5cm.  The pulse height with the second coax attached should be 5 * 66.6% = 3.33cm.  You report 3.40cm, which is within about 2%.  That's pretty good.

For the pulse on the way back, it is split again as you describe, but the amplitude should be 66.6% of 66.6% = 44.3%.  5cm * 44.3% = 2.21cm and you report 2cm.  Looking at the screen shots and using your 0 to 100% graticule, it looks like it might even be a little more than 40%, which again is exactly right.

When doing TDR with a scope, I usually leave the scope unterminated internally.  It's less confusing if you don't have the scope as a third impedance on the line.

More reading:

  http://cp.literature.agilent.com/litweb/pdf/5966-4855E.pdf (http://cp.literature.agilent.com/litweb/pdf/5966-4855E.pdf)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on June 01, 2016, 10:51:19 pm
Hmmm.   I'll give that some thought.

Thanks MarkL
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on July 04, 2016, 01:11:15 am
Update from my last entry on May 22nd....

June was a busy month with other activities and finally got some time to do some additional work on the 2465 DMS.

The DMM option has temperature readout but I didn't have the Tek P6602 Temperature Probe. In checking E-bay and other sources it turns out this is a pretty rare animal and the prices reflect that. In other words...no way. Decided to build my own and the total cost was about $6 USD.

A scrap collapsible antenna, glued on rubber plug to make it immersible in liquids, Heraeus M1020 PT100 Class B sensor. Some banana plugs and done.


The results. Immersed in an ice bath. Sorry gang but this old school Yank prefers Fahrenheit over Celsius.


More updates to follow..stay tuned.       :D
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on July 04, 2016, 10:47:43 am
That is one hell of expensive thermometer  :o, considering how valuable this old gem is for that purpose.

But congrats on proofing it that its still performing very good, a temp reading using a scope.  >:D

Thanks for sharing.  :-+
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on July 04, 2016, 12:15:37 pm
That is one hell of expensive thermometer  :o, considering how valuable this old gem is for that purpose.

But congrats on proofing it that its still performing very good, a temp reading using a scope.  >:D

Thanks for sharing.  :-+

You ain't kidding. The list price for a 2465 DMS in 1985 was $8400 USD.  :o More than the cost of a decent car at that time!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on July 08, 2016, 03:00:03 pm
As promised, more updates....


The DMM option on the 2465 DMS is calibrated as far as I can go with the equipment currently on hand. Thanks to MarkL's suggestion I used a power transformer connected secondary side to a function generator to get the 19.0V RMS@60Hz. Unfortunately the power transformer could not pass the required calibration constant of 19.0V RMS@50KHz. The best I could get out of it was about 7.0V RMS. So the ranges not done are:

500V DC
19.0V RMS 50KHz
190V RMS 60Hz
500V RMS 60Hz

So unless I can beg, borrow, or steal  :P a Fluke voltage calibrator at this point the DMM option is a done deal and I'm pleased with the results.

One issue left....the Buffer Board checksum error. I'm working it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on July 10, 2016, 12:17:44 am
The last issue on this Tek 2465 DMS:

BU TEST F1 FAIL 10
Buffer Board checksum error.

If I perform the DC Balance routine as defined on the attached troubleshooting chart I get some interesting results....


Upon immediate power up the scope comes up with all tests pass.
If I leave it off for about 10 minutes or so it still powers up all tests pass.
If I leave it off for about a half hour or longer the checksum error comes back.

To my simple mind I think this is telling me that the Buffer Board EAROM is defective and after a certain time frame it is dropping data.

In the reading thru the service manual it appears that EXER 02 will read the EAROM data out of both the A5 main board as well as the Buffer Board. Beyond that I'm a little ignorant (and perhaps a little fear of “fail”) as to what I can do with it. I have no experience in dealing with these types of circuits. And I'm not sure if I want to go thru the expense and learning curve to put together an ROM writer and write a new chip. Especially since it appears that this checksum error has no affect on other functions of the scope other than being an annoyance upon power up. So I'm tempted to leave it until it's a total crap out. Which may or may not ever happen. What say the group? Fix it or leave it? I'm open to suggestions.

So in summary this 2465 DMS has been an adventure since getting it (free) last year. Repaired or calibrated:

Noisy fan fixed.
Counter/Trigger option calibration power up fail fixed.
C/T and DMM option drift problem fixed after total recap of Inverter and Regulator boards.
DMM option fail fixed after self inflicted gun shot wound then calibrated.
2465 Mainframe all functions appear to be in spec to the limits to which I can test them.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on July 10, 2016, 02:55:39 pm
...
To my simple mind I think this is telling me that the Buffer Board EAROM is defective and after a certain time frame it is dropping data.

In the reading thru the service manual it appears that EXER 02 will read the EAROM data out of both the A5 main board as well as the Buffer Board. Beyond that I'm a little ignorant (and perhaps a little fear of “fail”) as to what I can do with it. I have no experience in dealing with these types of circuits. And I'm not sure if I want to go thru the expense and learning curve to put together an ROM writer and write a new chip. Especially since it appears that this checksum error has no affect on other functions of the scope other than being an annoyance upon power up. So I'm tempted to leave it until it's a total crap out. Which may or may not ever happen. What say the group? Fix it or leave it? I'm open to suggestions.
...
I also had an intermittent EAROM, but mine was on the main board.  The scope would sometimes power up with a checksum error.  I don't recall if it was dependent on how long it was off, but it could have been the same issue since data in the EAROM was being written when front panel settings were changed.

Properly done the EAROM should have been replaced, but I was able to change the supply voltage slightly and I got it to work without failure:

  https://www.eevblog.com/forum/testgear/tektronix-2445-2465-cal-settings-earom-er1400/msg927144/#msg927144 (https://www.eevblog.com/forum/testgear/tektronix-2445-2465-cal-settings-earom-er1400/msg927144/#msg927144)

It may be a long shot, but easy to try.  The supply for the buffer board EAROM (signal OEA35) is connected to the one on the main board, so it's the same zener.

EXER02 is harmless.  You can use it to make a backup copy of the contents in both EAROMs.  Getting the data back in there, however, is another matter.  It would have been nice for them to provide a "write" option in the diagnostics.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on July 10, 2016, 04:07:52 pm
Looking further into the 2465B’s abilities, the scope can also function as a time domain reflectometer.   For those unfamiliar with this, the scope’s speed is fast enough to measure the transit time of signals traveling through conductors.
 
For this test, I connected a BNC T to the scope 50 ohm input at channel 1.   A 50 ohm cable connected one port of the T, to the 50 ohm output of the SG503 pulse generator. 

If you think about it you can obtain the same information using an edge (not a pulse) and without using a 50ohm termination. The waveforms will look different, but the same information is easily available.

Sub-nanosecond pulses are easy to generate. In my experience, three parallel (74LVC1G14+140ohms) will drive a 50ohm load very cleanly to half the supply voltage with a risetime of, I believe, ~650ps.

A "high" impedance input will have the advantage of a higher amplitude, and the disadvantage of a marginally longer risetime.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on July 11, 2016, 02:46:25 am
...
To my simple mind I think this is telling me that the Buffer Board EAROM is defective and after a certain time frame it is dropping data.

In the reading thru the service manual it appears that EXER 02 will read the EAROM data out of both the A5 main board as well as the Buffer Board. Beyond that I'm a little ignorant (and perhaps a little fear of “fail”) as to what I can do with it. I have no experience in dealing with these types of circuits. And I'm not sure if I want to go thru the expense and learning curve to put together an ROM writer and write a new chip. Especially since it appears that this checksum error has no affect on other functions of the scope other than being an annoyance upon power up. So I'm tempted to leave it until it's a total crap out. Which may or may not ever happen. What say the group? Fix it or leave it? I'm open to suggestions.
...
I also had an intermittent EAROM, but mine was on the main board.  The scope would sometimes power up with a checksum error.  I don't recall if it was dependent on how long it was off, but it could have been the same issue since data in the EAROM was being written when front panel settings were changed.

Properly done the EAROM should have been replaced, but I was able to change the supply voltage slightly and I got it to work without failure:

  https://www.eevblog.com/forum/testgear/tektronix-2445-2465-cal-settings-earom-er1400/msg927144/#msg927144 (https://www.eevblog.com/forum/testgear/tektronix-2445-2465-cal-settings-earom-er1400/msg927144/#msg927144)

It may be a long shot, but easy to try.  The supply for the buffer board EAROM (signal OEA35) is connected to the one on the main board, so it's the same zener.

EXER02 is harmless.  You can use it to make a backup copy of the contents in both EAROMs.  Getting the data back in there, however, is another matter.  It would have been nice for them to provide a "write" option in the diagnostics.


Mark, first....I want to publicly thank you for the prior assistance you've given me in getting this 2465 fully functional. It is greatly appreciated.  :-+

2nd, I saw your post in the other thread concerning lowering the voltage to the EAROM and I did wonder if perhaps it would help with mine. So I did some checking but I found a discrepancy in what you did vs what is currently in place and perhaps your memory of what you did 20 years ago is a little fuzzy.

I looked up A5 Board VR2003 and it's currently a 7.5 V Zener. You indicated that you lowered the voltage by 2 volts by installing a 9.1 V Zener. Isn't that actually RAISING the voltage by approx 2 volts? But you are correct. That line (OEA35) does supply the EAROM's on the both the A5 Board and the Buffer Board.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on July 11, 2016, 01:59:35 pm
Mark, first....I want to publicly thank you for the prior assistance you've given me in getting this 2465 fully functional. It is greatly appreciated.  :-+

2nd, I saw your post in the other thread concerning lowering the voltage to the EAROM and I did wonder if perhaps it would help with mine. So I did some checking but I found a discrepancy in what you did vs what is currently in place and perhaps your memory of what you did 20 years ago is a little fuzzy.

I looked up A5 Board VR2003 and it's currently a 7.5 V Zener. You indicated that you lowered the voltage by 2 volts by installing a 9.1 V Zener. Isn't that actually RAISING the voltage by approx 2 volts? But you are correct. That line (OEA35) does supply the EAROM's on the both the A5 Board and the Buffer Board.
You are most welcome!  I enjoy working on this old equipment and I'm usually looking for excuses to pop the lid off and get out the service manuals.  It's not something I get to do with more modern equipment I use on a daily basis for work.

On VR2003, note that it and CR2004 are used as a dropper from the +42V rail to supply the EAROM.  So, the end result to the EAROM is 42V - 9.1V - 0.7V = 32.2V.  The spec on the ER1400 says 35V +/- 8%, so the minimum happens to also be 32.2V.

I just verified the voltage on my EAROM (between pins 1 & 2) as 32.3V.  With the original 7.5V zener, this would be higher by 1.6V ( = 33.9V).
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on July 12, 2016, 12:43:10 am
On VR2003, note that it and CR2004 are used as a dropper from the +42V rail to supply the EAROM.  So, the end result to the EAROM is 42V - 9.1V - 0.7V = 32.2V.  The spec on the ER1400 says 35V +/- 8%, so the minimum happens to also be 32.2V.

I just verified the voltage on my EAROM (between pins 1 & 2) as 32.3V.  With the original 7.5V zener, this would be higher by 1.6V ( = 33.9V).


D'OH  :palm:. You are absolutely correct. It's a dropper circuit from the +42V supply. I think I have a 9.1V Zener in my pile of parts. If not it will be on my next parts order. Gonna give it try and see what happens.  :-+
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: smgvbest on July 13, 2016, 11:31:36 am
Hello,

I have a 2467B that I have a GPIB interface for and I'm kind of stuck.   
It came with a A20 Buffer Board (i believe the correct name for it).   there are connections labeled C/D/E that I can find on the A1 board to connect to but also on the A20 is a 34pin connection that looks like it would go to the A5 Board but there is no 34 Pin connection available on the A5.   there is a 40Pin  my Serial Number is B053273.

So I take it this A20 Buffer Board is not compatible with my Serial Number.

Heres a few pics of my A1, A5 and A20 boards.

To use this GBIP board what am I looking for?   I could not find a A20 board in the service manual or in the option manual unless I'm totally blind

TIA

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: smgvbest on July 13, 2016, 11:45:26 am
More of the images

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on July 13, 2016, 12:15:55 pm

To use this GBIP board what am I looking for?   I could not find a A20 board in the service manual or in the option manual unless I'm totally blind

TIA


I can't tell you specifically what you need to get the GPIB going but if you have the correct manuals the A20 Board is the Buffer Board. I have the 2465 options manuals and it shows it very clearly.

Artek Manuals has the 2467B Options Service Manuals on CD for $12.50 USD. If you don't already have that manual I would check it out.

Hope this helps.   
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Orange on July 13, 2016, 02:31:13 pm
Hello,

I have a 2467B that I have a GPIB interface for and I'm kind of stuck.   
It came with a A20 Buffer Board (i believe the correct name for it).   there are connections labeled C/D/E that I can find on the A1 board to connect to but also on the A20 is a 34pin connection that looks like it would go to the A5 Board but there is no 34 Pin connection available on the A5.   there is a 40Pin  my Serial Number is B053273.

So I take it this A20 Buffer Board is not compatible with my Serial Number.

Heres a few pics of my A1, A5 and A20 boards.

To use this GBIP board what am I looking for?   I could not find a A20 board in the service manual or in the option manual unless I'm totally blind

TIA
You need a GPIB board as well, see PDF excerpt
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on July 13, 2016, 02:37:26 pm
That 40-pin connector on A5 is J4241.

I don't have the 2467B options service manual, but on the other 2465/7 series scopes J4241 goes to the DMM option which is also a 40-pin connector.  A spot check on a bunch of signals on the 2467B J4241 connector shows they're the same as the DMM option pinout.

Without the manual I can't say for sure, but it's probably not coincidence.

That doesn't answer the basic question about your buffer board compatibility, though.

So, you obtained the buffer board and GPIB interface as an add-on?  (I.e., it didn't come with the scope?)

One seller on ebay (Qservice) has a listing for a 2467B GPIB retrofit kit:

  http://www.ebay.com/itm/381550986148 (http://www.ebay.com/itm/381550986148)

It looks like yours and is specifically for serial numbers < B50000.

So, it doesn't look too hopeful, but I agree with med6753 that obtaining the service manual is the next thing to do.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Orange on July 14, 2016, 01:22:52 pm
Hello,

I have a 2467B that I have a GPIB interface for and I'm kind of stuck.   
It came with a A20 Buffer Board (i believe the correct name for it).   there are connections labeled C/D/E that I can find on the A1 board to connect to but also on the A20 is a 34pin connection that looks like it would go to the A5 Board but there is no 34 Pin connection available on the A5.   there is a 40Pin  my Serial Number is B053273.

So I take it this A20 Buffer Board is not compatible with my Serial Number.

Heres a few pics of my A1, A5 and A20 boards.

To use this GBIP board what am I looking for?   I could not find a A20 board in the service manual or in the option manual unless I'm totally blind

TIA
Here is the interconnect diagram, it shows that there is no longer a buffer board in the 2467B (serials > 50000)

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on July 15, 2016, 02:14:19 am
Hello,

I have a 2467B that I have a GPIB interface for and I'm kind of stuck.   
It came with a A20 Buffer Board (i believe the correct name for it).   there are connections labeled C/D/E that I can find on the A1 board to connect to but also on the A20 is a 34pin connection that looks like it would go to the A5 Board but there is no 34 Pin connection available on the A5.   there is a 40Pin  my Serial Number is B053273.

So I take it this A20 Buffer Board is not compatible with my Serial Number.

Heres a few pics of my A1, A5 and A20 boards.

To use this GBIP board what am I looking for?   I could not find a A20 board in the service manual or in the option manual unless I'm totally blind

TIA
Here is the interconnect diagram, it shows that there is no longer a buffer board in the 2467B (serials > 50000)


Wow! Those wiley Tek Engineers found a way to combine the Buffer functions on the A5 Board. Great for them but bad for us 30 years later when we are trying to figure out exactly what we have.  :-// 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: smgvbest on July 15, 2016, 04:45:26 am
Thank you for replying
So the Buffer/GPIB and CTT boards I have will end up on eBay for sale as they do me no good as they are not supported by my serial number.

I do have the full service manual but had trouble understanding the A20 board and relation to my serial number.   This is when I really miss hardcopy.  sometimes it's easier to just have an open manual.



Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on August 07, 2016, 04:51:06 pm
On VR2003, note that it and CR2004 are used as a dropper from the +42V rail to supply the EAROM.  So, the end result to the EAROM is 42V - 9.1V - 0.7V = 32.2V.  The spec on the ER1400 says 35V +/- 8%, so the minimum happens to also be 32.2V.

I just verified the voltage on my EAROM (between pins 1 & 2) as 32.3V.  With the original 7.5V zener, this would be higher by 1.6V ( = 33.9V).

D'OH  :palm:. You are absolutely correct. It's a dropper circuit from the +42V supply. I think I have a 9.1V Zener in my pile of parts. If not it will be on my next parts order. Gonna give it try and see what happens.  :-+

Today I changed VR2003 from a 7.5V zener to a 9.1V zener. Original EAROM voltage was 35.19V. After the zener change it was 33.19V. Unfortunately I still have the Buffer Board checksum error. So the mod didn't help. It's looking more and more like that chip is on it's last legs. Oh well. I'm going to leave it for now and consider this a completed project.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on August 07, 2016, 07:41:14 pm
Oh well - sorry the mod didn't work for you.  It was easy enough to be worth a try.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: jscgvnc on August 11, 2016, 08:20:39 pm
Hey guys and gals,

I just got a 2465b, Serial B012202, and so far the only thing wrong is what I've buggered up. I pulled some jumpers out, thinking it was a 4-pin connector, and it's really 2 2-pin connectors. They are J902 and J903 on the High Voltage Supply and CRT drawing 8 of the service manual. I can figure out their numbering system for the pins. Is one the "bottom" or the "top". There seems to be a small arrow printed on the board for those jumper pins, does that indicate the start of the numbering?

I've attached a photo. I didn't take a picture of them before I removed them, so I don't know which way they go on, which I know is a rookie maneuver.

I really don't want to have to pry the whole board off to see if the pins are numbered on the other side. Can anyone help?

Thanks,

Josh
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: guido on August 11, 2016, 11:10:01 pm
There is an arrow on the board. And an arrow on the connector. They need to allign  :)
It looks like one of your connectors is not alligned.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on August 12, 2016, 02:37:16 am
The arrow points to pin 1 and an arrow on the connector housing also means pin 1.   It looks to me like you have the orientation right. 

If you want to double check, pin 1 on both J902 and J903 are ground, so you can check for continuity to ground on both pin 1's (cables unplugged).

If your question is which cable is which, you'll have to trace where they go if they're not labeled on the wire.  P902 goes to a coil near the front of the CRT and P903 goes to a coil further back on the neck.

If you have anything wrong with these connectors the scope is not going to blow up, but the beam alignment will be a mess.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: jscgvnc on August 12, 2016, 12:51:10 pm
MarkL,

Thanks for the info. Exactly what I was looking for.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: guido on August 12, 2016, 05:09:33 pm
Looks like the connector/wire was replaced. Not the usuall style with the arrow. Got me on the wrong track.
Google usually is your friend. First hit with 2465b high voltage supply in pictures:

(https://www.eevblog.com/forum/index.php?action=dlattach;topic=5397.0;attach=16699;image)

On this forum  ;D

Note i said usually. A two pin connector to the pcb on the HV supply in the 7603 has been swapped between revisions. Including the cable (from cross wired to straight or vzv). If you do not swap the cable and pcb at the same time it doesn't work if you have two versions of the board/cable.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on August 15, 2016, 03:31:19 am
Just realized that I still have the close-up photo on those J902 and J903 connectors orientation, and it's arrow (or pin 1) markings, put here as a reference for future owners that may experience the same problem again.  ;D
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: jscgvnc on August 15, 2016, 01:12:59 pm
Thanks guido and BravoV, very helpful!

I had made the leap that they had replaced the cable and therefore had different connector markings, but this is great info. I appreciate it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: GasGas on August 22, 2016, 02:58:36 pm
Hello.

This is my first participation in the Forum. I just buy a 2467B to 2465B to my company. I still have it in my hands, which happened soon, because I need to go search it in another state. Well, I want to accomplish the exchange of his Nvram because the photos I received from the seller, the date of Nvram is 1991 .... here in Brazil I am not finding the Nvram with DS1225Y-200 specification, only DS1225Y- 150.

Could someone tell me if this DS1225Y Nvram-150 can be used? I want to be with everything at hand at the time of exchange of the same.

Sorry for bad english, I'm using Google Translate.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on August 22, 2016, 03:17:18 pm
Could someone tell me if this DS1225Y Nvram-150 can be used? I want to be with everything at hand at the time of exchange of the same.

The DS1225Y-150 will work fine; it is just a little faster than the DS1225Y-200.  The DS1225AD is the replacement for the DS1225Y and can be used also.

Make sure to buy the DS1225Y or DS1225AD from a reputable seller and not on Ebay; they are commonly counterfeited.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: GasGas on August 22, 2016, 04:19:19 pm
Thanks for the quick response.

About where to buy Nvram, this is a big problem for me here in Brazil, because there are no reliable distributors like Digikey and others.

One way to check if the Nvram to buy in Brazil will work, would record data from Nvram posted several users in this topic? I have a TL 886. recorder If you can record it on the TL886 is likely to work after being installed in scope, right?

Thank you.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on August 22, 2016, 09:01:36 pm
A TL886 programmer is a good start.

The major problem is counterfeiters remarking old Dallas/Maxim NVSRAMs with current date codes and selling them so while programming the NVSRAM might indicate that it works, it may not last long because the battery is almost dead.  NVSRAMs are a good target because individually they are expensive.

So you do not have *any* distributors for Maxim's products?  I tried looking up their distributors for Brazil but Maxim's web site is broken; I cannot even order parts directly from them or contact sales.  I have always tried to avoid them because of poor support and it seems they are continuing that tradition.

If it helps, the ST Microelectronics M48Z18 or M48Z58Y NVSRAMs could also be used.

Maybe someone in the forum could recommend a reputable Ebay seller for these parts.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: GasGas on August 23, 2016, 12:00:06 am
I am very grateful for the help. I'll probably end up importing the Nvram via Digikey, however sending so are U$ 40.00 + taxes in Brazil.  :-[ :-[ :-[

You are right about buying a fake Nvram with the old manufacturing date, which will have its useful life much less than expected, however my biggest fear is loss of data at the time of withdrawal of the same, as in some cases reported in this topic. I will take care of maximum, with the help of Hakko 474 station.

I will copy all data via Exer 02 even without making sure someone could manually enter the data into the new Nvram.

I look forward to put the hand in the new scope, so that I could verify via Exer 05 it has only 1193 hours of use and 867 power on ... 8)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on August 23, 2016, 04:25:49 am
When I replaced the NVSRAMs in my Tektronix 2440, I was not able to read the data even though I did everything correctly.  It is possible that my programmer had problems with them but it worked fine on the replacements that I used.  Luckily doing the external calibration on a 2440 is much easier than on a 2465 series oscilloscope and I was prepared for that.

I now have a 2445B to worry about but I have not inspected it yet to check the NVSRAMs.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: GasGas on August 23, 2016, 02:04:13 pm
It is a worrying situation know that Nvram this in his last days and not be sure that I will be successful in your replacement. I do not have the necessary equipment to perform a recalibration (basically I have an HP 3324A signal generator and DMM Fluke 189).

I will have positive thinking that nothing goes wrong at the time of exchange ...

Thanks for everything. :-+
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on August 23, 2016, 04:39:41 pm
Now I am looking into the same thing for my 2445B.

The currently produced 8k x 8 STK11C68 should work as a direct replacement but its SOIC package will require an adapter.  The older but discontinued 32k x 8 STK16C88 should also work and I have a couple in DIP packages so I may try one of these first.  The STK16C88 is 32k instead of 8k but the pinouts are compatible; the extra two address lines need to be permanently tied to ground or Vcc.

These parts are made by Cypress Semiconductor and are SRAM memories backed up by EEPROM memory so they have no batteries to run down.  I used a pair of STK16C88s to replace the DS1230ABs in my 2440.

Unfortunately you will probably have just as much of a problem if not more trying to find these parts.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: GasGas on September 14, 2016, 01:03:21 am
As I had commented seek 2467B he had bought, for it was necessary to conduct a 1300Km travel round-trip, I was afraid that it was damaged in transit by using a carrier service.

When I arrived at the residence of the former owner, I did a quick test and everything seemed to function normally. When I arrived at my house, the first offers was to change the 110V voltage selector switch to 220V, which was promptly done. Well, after that I called the same and my joy did not last 30 seconds .... this was the time to listen to the sound of something frying and witness a beautiful cloud of smoke coming from within the scope .... I wanted to cry after an exhausting trip down a lot of rain witness that was very disappointing ....

The other day, I opened the scope to see what had happened and the first offers was to remove the power supply of your site and survey the damage. All it took was a quick visual inspection to realize that the film capacitor 68nf x 250V was broken out, which made me more relaxed because provavelmete replacement and more few components establish a fully functioning scope. As was already aware of the need for NVRAM and not finding any in Brazil dated back manufacturing to 2010 I decided to book with NVRAM socket, and all capacitors for Reconstruction the inverter board, power supply and A5 board, I also did not find quality electrolytic capacitors in Brazil. I made the purchase in the online store Digikey and requested shipping via Fedex which took exactly 7 consecutive days, yesterday received the box with all components:

(http://i1202.photobucket.com/albums/bb376/gasgas08/20160912_170741.jpg)

I started the exchange by film capacitors and you can see small cracks in the capacitor body what I believe is the cause for it to absorb moisture over the years:

(http://i1202.photobucket.com/albums/bb376/gasgas08/20160912_181606_1.jpg)

After finishing the exchange of film capacitors, the next step was the subsitution of electrolytic capacitors, which did not fail to cause surprises, as many original electrolytic capacitors (Nichicon Green) had a lower ESR than the new Panasonic and Nichicon...

Original Nichicon:

(http://i1202.photobucket.com/albums/bb376/gasgas08/20160912_173749_1.jpg)

New Panasonic:

(http://i1202.photobucket.com/albums/bb376/gasgas08/20160912_173818_1.jpg)

The capacitors showed fullness at the bottom of the body were changed, although its capacitance and ESR were perfect when compared to new:

Original:

(http://i1202.photobucket.com/albums/bb376/gasgas08/20160912_183348_1.jpg)

New:

(http://i1202.photobucket.com/albums/bb376/gasgas08/20160912_183602_1.jpg)

The only original capacitor which really had a high ESR was this 3.3 UF 350V.

Original:

(http://i1202.photobucket.com/albums/bb376/gasgas08/20160912_180004_1.jpg)

New:

(http://i1202.photobucket.com/albums/bb376/gasgas08/20160912_180036.jpg)

All capacitors replaced:

(http://i1202.photobucket.com/albums/bb376/gasgas08/20160912_224053.jpg)

After the exchange made the scope back to life!

(http://i1202.photobucket.com/albums/bb376/gasgas08/20160912_224022.jpg)

Now came the part that caused me concern, which was the exchange of NVRAM because lí some reports on this topic failures and loss of data at the time of replacement. Before replacing the NVRAM, I filmed with my phone all andress via Exer from the service menu. Not leaving anything to do, I removed the old NVRAM with 1991 manufacturing date and copied the data from it using a TL recorder 886 and after that the data was copied to the NVRAM with 2016 manufacturing date, which was embedded in a socket to intervene in a very distant future!

Old NVRAM:

(http://i1202.photobucket.com/albums/bb376/gasgas08/20160913_102753.jpg)

New NVRAM:

(http://i1202.photobucket.com/albums/bb376/gasgas08/20160913_102656.jpg)

This tool is essential for the success of the service:

(http://i1202.photobucket.com/albums/bb376/gasgas08/20160913_104335.jpg)

Very happy with my 2467B with very little use and no burn mark in the CRT!

(http://i1202.photobucket.com/albums/bb376/gasgas08/20160913_114007_resized_1_1.jpg)

(http://i1202.photobucket.com/albums/bb376/gasgas08/20160913_114019_resized.jpg)

Thanks for the help and information  :-+ :-+

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: cheeseit on October 17, 2016, 08:46:25 pm
This is a great thread - thanks to you all  for contributing with so much valuable information and knowledge! I've read more or less everything in the last few days and have bookmarked plenty of further reading but I haven't yet really gone beyond this thread.

Quick question while I await the arrival of a 2465B, which I bought for €53/$60 (my first Tek scope - yay), that is supposedly defective. The seller stated that it arced in either the tube or the HV-supply but was otherwise in perfect working condition and in calibration until that day. I know that it is kinda hard to speculate on without more information, and he did mention that a new tube might be needed which seems plausible, but any ideas what might be the source of this arcing?

I know nothing about its vintage, serial or what, if any, repairs have been done to it. The seller seems very honest, and even turned down several bids that were a lot higher since I was the first, and I don't believe that he has even checked what it might be so I'm hoping it might be simple but fear that it could be expensive.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on October 18, 2016, 01:02:55 am

Quick question while I await the arrival of a 2465B, which I bought for €53/$60 (my first Tek scope - yay), that is supposedly defective. The seller stated that it arced in either the tube or the HV-supply but was otherwise in perfect working condition and in calibration until that day. I know that it is kinda hard to speculate on without more information, and he did mention that a new tube might be needed which seems plausible, but any ideas what might be the source of this arcing?

The chances of the CRT being the source of the HV issue is rather remote, unless it's been subject to damage or shock. The best way to find the source of the arcing is to remove the case, darkened room, and look for the source. But keep your hands behind your back.  :P
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on October 18, 2016, 03:08:41 am
The seller stated that it arced in either the tube or the HV-supply but was otherwise in perfect working condition and in calibration until that day. I know that it is kinda hard to speculate on without more information, and he did mention that a new tube might be needed which seems plausible, but any ideas what might be the source of this arcing?

The AC line safety capacitors may have failed which is a common and easily repairable problem.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on October 18, 2016, 12:31:48 pm
The seller stated that it arced in either the tube or the HV-supply but was otherwise in perfect working condition and in calibration until that day. I know that it is kinda hard to speculate on without more information, and he did mention that a new tube might be needed which seems plausible, but any ideas what might be the source of this arcing?

The AC line safety capacitors may have failed which is a common and easily repairable problem.

Yes, but some of those capacitors are "hidden"; in the last week I've "done" a 2465 and 2445B, and while the "hidden" caps hadn't failed, they were crazed. FFI, see http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf (http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf)

And don't forget the infamous control board caps, q.v.

The HV supply arcing may simply be neons flashing.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on October 18, 2016, 05:25:54 pm
The seller stated that it arced in either the tube or the HV-supply but was otherwise in perfect working condition and in calibration until that day. I know that it is kinda hard to speculate on without more information, and he did mention that a new tube might be needed which seems plausible, but any ideas what might be the source of this arcing?

The AC line safety capacitors may have failed which is a common and easily repairable problem.

Yes, but some of those capacitors are "hidden"; in the last week I've "done" a 2465 and 2445B, and while the "hidden" caps hadn't failed, they were crazed. FFI, see http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf (http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf)

And don't forget the infamous control board caps, q.v.

The HV supply arcing may simply be neons flashing.

Those paper capacitors all seem to be universally bad having either physically degraded do to age like you describe or shorted out.  I think they have been changed in my 2445B but I have a few junked 22xx main boards where they are crazed and I do not bother pulling them for spares.

The reason I suggested them is that they do not always go out with a bang and their arcing may have been mistaken for a high voltage problem while not disabling the oscilloscope.  They are just something else to check.

I do not know of any reason they cannot be replaced with modern film or ceramic safety capacitors and of course they can always be derated.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on October 18, 2016, 06:50:22 pm
The seller stated that it arced in either the tube or the HV-supply but was otherwise in perfect working condition and in calibration until that day. I know that it is kinda hard to speculate on without more information, and he did mention that a new tube might be needed which seems plausible, but any ideas what might be the source of this arcing?

The AC line safety capacitors may have failed which is a common and easily repairable problem.

Yes, but some of those capacitors are "hidden"; in the last week I've "done" a 2465 and 2445B, and while the "hidden" caps hadn't failed, they were crazed. FFI, see http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf (http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf)

And don't forget the infamous control board caps, q.v.

The HV supply arcing may simply be neons flashing.

Those paper capacitors all seem to be universally bad having either physically degraded do to age like you describe or shorted out.  I think they have been changed in my 2445B but I have a few junked 22xx main boards where they are crazed and I do not bother pulling them for spares.

The reason I suggested them is that they do not always go out with a bang and their arcing may have been mistaken for a high voltage problem while not disabling the oscilloscope.  They are just something else to check.

Those directly across the mains in my 2465 "expanded rapidly" after 30s, and one of the associated series resistors disintegrated - leaving carbon across the board and the PCB's glass fibre weave exposed without prepreg :)

Quote
I do not know of any reason they cannot be replaced with modern film or ceramic safety capacitors and of course they can always be derated.

I just followed the information in the pdf I referred to, replacing them with X*/Y* caps as appropriate.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: cheeseit on October 18, 2016, 08:22:50 pm
The chances of the CRT being the source of the HV issue is rather remote, unless it's been subject to damage or shock. The best way to find the source of the arcing is to remove the case, darkened room, and look for the source. But keep your hands behind your back.  :P

According to the seller he just powered it up and somehow experienced arcing, that is all I know for the moment, so I don't think it was damage or shock. A good idea I hadn't thought of with the darkened room, and good advice too. :)

The AC line safety capacitors may have failed which is a common and easily repairable problem.

That was my first thought too but I shuck it off as wishful thinking so I am glad that you suggest this. Those will be the first I examine after having looked for anything obvious.

The HV supply arcing may simply be neons flashing.

Flashing as in worn out? As far as I know the scope does not work anymore, could these cause that if they are broken and/or kill other components?


Thanks all, you've raised hopes that it could be simple and less expensive to repair. I will surely post when I get it and most likely seek your advice and help again. :)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on October 18, 2016, 08:30:36 pm
The chances of the CRT being the source of the HV issue is rather remote, unless it's been subject to damage or shock. The best way to find the source of the arcing is to remove the case, darkened room, and look for the source. But keep your hands behind your back.  :P

According to the seller he just powered it up and somehow experienced arcing, that is all I know for the moment, so I don't think it was damage or shock. A good idea I hadn't thought of with the darkened room, and good advice too. :)

The AC line safety capacitors may have failed which is a common and easily repairable problem.

That was my first thought too but I shuck it off as wishful thinking so I am glad that you suggest this. Those will be the first I examine after having looked for anything obvious.

The HV supply arcing may simply be neons flashing.

Flashing as in worn out? As far as I know the scope does not work anymore, could these cause that if they are broken and/or kill other components.

They prevent the cathode-grid voltage from becoming dangerous. Normally that only happens after the power is turned off. Some Tek scopes also have a neon in the main PSU that flashes continually, but IIRC the 2465 doesn't.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on October 18, 2016, 08:45:21 pm
Flashing as in worn out? As far as I know the scope does not work anymore, could these cause that if they are broken and/or kill other components.

They prevent the cathode-grid voltage from becoming dangerous. Normally that only happens after the power is turned off. Some Tek scopes also have a neon in the main PSU that flashes continually, but IIRC the 2465 doesn't.

Exactly, they are used as zero leakage surge suppressors to protect various elements of the CRT and sometimes other circuits.  They usually only flash when power is first applied or when it is removed.  I have never seen them go bad.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: cheeseit on October 20, 2016, 11:28:23 pm
My 2465B has arrived. Frontcover but no probes, manuals or CRT filter. It looks great and has no nicks or scratches, is only slightly dirty and the BNC connectors could use a bit of polishing. A bit of dust inside in places but nothing that a bit of compressed air can't remove.

1989 vintage, all through hole and the serial is 134xxx and is from Guernsey in the Channel Islands. GPIB and TV trigger options.

No RIFA caps on the regulator board and no leaking or bulging caps or anything obvious burned or broken. The battery date code is 0589 and measures 3.696V at the terminals so cal data should be safe for now, right? I find that incredible for a 27 year old battery?

Still haven't turned it on an and worryingly, something rattles when I turn it around. I'm pretty sure it's from within the CRT metal shield in the wide part behind the front of the tube - a loose lamp? Is there anything in there that could short from a lamp rattling around and explain what the seller called arcing..?

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=263876;image)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: cheeseit on October 23, 2016, 02:47:45 pm
Well, of course it wasn't a lamp and there was no way one of those could come loose and rattle between the CRT shield and tube. But something is in there. I tried to make sure that it was lodged towards the front of the tube, away from any connections, and turned the scope on.
Good news is that it boots but bad news is that there is nothing on the screen and - worse - that something sure arcs in there somewhere. I only had it on a few times for 10-15 sec. max but the arcing started a few seconds into booting, with what sounded like an arc welder and the strong smell of ozon.
Unfortunately no blue glow to see anywhere through holes, between boards and so on, not even in a darkened room. I noticed though that the fuse on the HV-board started glowing the instant the arcing started.

Next step is to pull the A9-board and CRT out and see if I can locate where it is - there just has to be signs with that much noise and ozon - and get whatever is rattling out. Ideas, suggestions and advice is most welcome. :)

I'm unsure if I should start my own thread or continue in this one?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on October 23, 2016, 03:10:16 pm
Cheeseit, sorry to hear the progress, please just continue in this thread in you don't mind.

Curious as well how will this end up.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on October 23, 2016, 06:56:03 pm
Agreed, keep posting in this thread. It has become a "catch all" thread for 24XX issues in one convenient location.

Can't offer any advice at this point until you find out what the rattle is and you inspect the HV board. 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: cheeseit on October 24, 2016, 08:51:54 pm
Well, there's your problem.. And, sometimes you win, sometimes you lose.

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=264741;image)

Good news; I found the source of the rattling, and the source of the arcing.. Bad news; the tube is very much broken and it was two pieces of glass.  |O I kinda knew it as I was pulling off the CRT connector at the back since the tube was moving around as I was prying it off.

How are my chances that nothing else is damaged from this broken tube? Everything else looks totally undamaged and in excellent condition. After all, it has been turned on with the tube in this state.

I was contemplating posting images of the boards but decided that there is plenty throughout the thread. Let me know if you want images of something.

I have been looking at this sellers (http://stores.ebay.co.uk/Qservice-tech-shop/Tektronix-CRT-/_i.html?_fsub=4841171&_sc=1&_sid=75705061&_sop=3&_trksid=p4634.c0.m322) ebay shop and they have a lot of good stuff, and very good feedback. I've found a few other tubes on ebay, but haven't yet decided if I should wait for a for-parts scope which may have a bad and/or burned tube, or just buy this (http://www.ebay.co.uk/itm/Tektronix-154-0850-01-CRT-2445-2465-2445A-2465A-2445B-2465B-770662-/141862702361?hash=item2107ad0d19) which would cost me €134/$146 including shipping. It would still be a cheap 2465B in the end, if nothing else is damaged.

Any other sources for a good tube or for-parts scope? Or anyone that has a suitable tube or donor scope? Has to be within EU because of tax and shipping.

Tubes from 2445, 2445A, 2445B, 2465, 2465A, 2465B,2430, 2430A, 2432, 2432A and 2440 are all suitable, right?

I don't need this scope now but I really want it now. It would also be the fastest scope in my possession. ;) A good thing about waiting for a donor scope is having spare parts/boards if something else is broken. Or parts to sell once this one works - that could perhaps pay for the majority or the whole thing in the end.

To end on a positive note, this does give me time to order caps and recap the A5/A2A1/A3 boards. :)


Edit: I think the seller must have known, since he mentioned the tube might need replacing, and suspect that he dropped it. Oh well, he did warn me..
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on October 24, 2016, 09:04:24 pm
Well, there's your problem.. And, sometimes you win, sometimes you lose.

How are my chances that nothing else is damaged from this broken tube? Everything else looks totally undamaged and in excellent condition. After all, it has been turned on with the tube in this state.

Been there, done that, ended up with: https://entertaininghacks.wordpress.com/2016/03/09/rescuing-a-broken-tektronix-465-crt/ (https://entertaininghacks.wordpress.com/2016/03/09/rescuing-a-broken-tektronix-465-crt/)

Quote
Tubes from 2445, 2445A, 2445B, 2465, 2465A, 2465B,2430, 2430A, 2432, 2432A and 2440 are all suitable, right?

See http://www.reprise.com/host/tektronix/reference/crt.asp (http://www.reprise.com/host/tektronix/reference/crt.asp)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on October 25, 2016, 05:49:40 am
Wow, that's a hell of a mess. Obviously the seller did drop it, or it fell off a bench. I'm sure he knows exactly what happen and doesn't want to admit it. And it's hard to say if there's other damage until after you install a replacement CRT.

But it is neat to see Tek's innovative and at the time leading edge process that combined a ceramic bell of the CRT with the glass gun and faceplate. As far as I know no else attempted that. But I did read somewhere that Tek shared some of their CRT technology with Sony which directly influenced the design of the Trinitron CRT.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on October 25, 2016, 07:39:37 am
But it is neat to see Tek's innovative and at the time leading edge process that combined a ceramic bell of the CRT with the glass gun and faceplate. As far as I know no else attempted that. But I did read somewhere that Tek shared some of their CRT technology with Sony which directly influenced the design of the Trinitron CRT.

Tektronix started using ceramic CRT envelopes in 1962 with the 561A (http://w140.com/tekwiki/wiki/561A) and this also allowed marking the graticule on the inside removing parallax error.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on October 25, 2016, 05:56:22 pm
What a bummer  |O, really sorry to hear that cheeseit.  :'(

Please, once you have the replacement tube, share your journey here please, that will be really interesting.

PS : The broken tube, have you dump it yet ? I really love to own it if you're going to toast it, as the gun and metal parts inside looks artistic, at least to my eyes. I will pay for the shipping cost.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on October 25, 2016, 06:23:25 pm
... the gun and metal parts inside looks artistic, at least to my eyes.

And mine.

I was lucky to have access to a glass bandsaw. If I hadn't I would have had to experiment with heated nichrome wires.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: cheeseit on October 25, 2016, 08:16:48 pm
Been there, done that, ended up with: https://entertaininghacks.wordpress.com/2016/03/09/rescuing-a-broken-tektronix-465-crt/ (https://entertaininghacks.wordpress.com/2016/03/09/rescuing-a-broken-tektronix-465-crt/)

I had seen that before and it was the second thing that came to mind after pulling only the top half out of the scope, right after "#&!$ hell". :D It looks awesome!

I've been emailing with the seller and he insists that it was not dropped and he does sound sincere. He called it his dear scope and talks about how he would hate to see it trashed and that he really hope I will try to find a replacement tube. I don't know, seems implausible that it would snap in two without an external force so maybe it happened in transit and something else is arcing too.. :-DD Whatever it is, it needs a new tube now so time will tell if it holds any other surprises.

Such a tube is a technical marvel IMHO and deserves to be displayed, though SWMBO had the ".. yes, very cool.."-look on her face when I showed her. ::)

PS : The broken tube, have you dump it yet ? I really love to own it if you're going to toast it, as the gun and metal parts inside looks artistic, at least to my eyes. I will pay for the shipping cost.

I feel the same about its looks so I hope you can find another tube somewhere. :) Any ideas for making something of the envelope funnel? And sure, I will update once I make some progress.

----

I didn't realize that the tube I linked to was on sale and that the sale ended a few hours ago. So, having spent some time searching for scopes and tubes that was reasonably priced I wrote the seller asking if there was a chance that I could get the 12% off sale price. There was and the tube will be on its way in a couple of days. They say it is an 8 on a scale from 0 (dead) to 10 (brand new) so I figured that it was worth it, especially considering the 30-day warranty. The seller even gave me a 15% discount instead.
Now I just need to decide whether to try the tube in the scope in its current condition, or order new caps and recap it first. I'm leaning towards testing it before recapping, in case something else is damaged.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: cheeseit on November 07, 2016, 07:51:28 pm
My new tube has finally arrived and is still in one piece. Qservice (http://www.qservice.eu/default.asp) had packeged it real good using loads of bubble wrap, foam and tape. It came in a cardboard box with British American Tobacco Group logos. Wonder if that triggered an inspection or x-raying along the way.. ;D
(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=268441;image)

Date code is from week 15 in 1993 and it looks good, with no soot but that could of course just have been cleaned off. I trust the seller though and hope it is as good as the service he provided.
(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=268443;image)

I have decided to just recap it before installing the tube as it seemed likely that the only problem was the broken tube. I ordered caps from Mouser late last week which is scheduled to arrive tomorrow so hopefully this lovely scope will be up and running soon once time permits. Should be later this week or the next.

This is my first time replacing a CRT but I'm guessing that I will likely have to do some or all of the adjustments outlined in the "CRT Adjustments"-section of the SM, right?


Edit: this is the old tube, disregard the light specs and what looks like (and is) a brush stroke. That Lichtenberg-looking burn, does that perhaps indicate that the tube was powered when it had its catastrophic failure?
(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=268447;image)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on November 07, 2016, 10:08:54 pm
This is my first time replacing a CRT but I'm guessing that I will likely have to do some or all of the adjustments outlined in the "CRT Adjustments"-section of the SM, right?

Yes and the horizontal and vertical deflection will probably need to be adjusted as well.  The transient response may be affected but if you do not have a suitable signal source, leave it alone.

Quote
Edit: this is the old tube, disregard the light specs and what looks like (and is) a brush stroke. That Lichtenberg-looking burn, does that perhaps indicate that the tube was powered when it had its catastrophic failure?

That is what happens when debris gets lose inside the CRT envelope (no surprise here) and contacts the phosphor which is very delicate.  It is a bad idea to move or store CRTs face down.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on November 08, 2016, 03:24:02 am
cheeseit, readying pop corn to watch your journey, please share it here along with photos, thanks in advance.  :popcorn:  :clap:
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Fateh Singh on November 10, 2016, 05:00:30 pm
I have been reading the messages on this topic and find them enlightening.
On my own machine -2465B- I have  changed the capacitors as already advised by many experts here, and has the supply
voltages are under specs. For a few days , I was confounded by  very high voltages on all lines, when PSU was powered outside
the machine. Then somewhere, I read that the supplies have to be loaded to be tested. On loading the supplies settled OK.
Now, the machine has the following problems-  It shows   Fail Test 05 -44.  Presumeably,  the DAC312 and the Comparator 311 on A5 has something wrong.
The 311- pin 7 output shows fluctuating 0.8V when the test is looping.  Grid bias is active. Focus is acive. Intensity pot has no effect. Beam find brings the beam into a small rectangle in the screen center. Otherwise the beam is off screen with only spots on screen. I will continue the search for faults, because i want this wonderous machine to help me in my many projects.
Kindly help with your questions and suggestions. I would like to post a small video of what the screen looks like, but just now, i dont know how.
Many thanks .
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on November 11, 2016, 01:37:58 am
Now, the machine has the following problems-  It shows   Fail Test 05 -44.  Presumeably,  the DAC312 and the Comparator 311 on A5 has something wrong.

If this fail occurred after you replaced the caps and reassembled the scope go back and check the ribbon cables that plug on the underside of the top plate. It is very easy to plug them one pin off or they aren't fully seated. We've all done it and it causes those trigger level fails.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Fateh Singh on November 11, 2016, 02:49:36 pm
The ribbon cable is on A5 and it is going to many front panel switches. Did you mean this? It seems very secure. I have not touched it.
I have another scope, and will look into the signals from Comp311, and will revert. Meanwhile , the status quo. Error test 05  44.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on November 11, 2016, 08:04:45 pm
Just as a double cre you positive the voltages are in spec and you have checked for ripple using another scope. Can do funny things when not in spec.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Fateh Singh on November 12, 2016, 10:50:06 am
I am checking with  TDS7104- dig. scope- using it first time. The trace appears a bit noisy- unlike smooth lines in analog scopes.
Supplies + _5V, +_15V appear OK. 42V and 87V  not seen yet.
On A5 board  Test pin wave forms  1 , 2 , 4  appear OK.  no. 3 on U2540 hex inverter pin 10 , is not there ( remains high ) pin 11 is remains low.
So this chip is innocent.
The comparator 311, appears to give out on pin 7-  some pulses longer than others.Why?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on November 12, 2016, 11:12:36 am
What do you mean the 42v and 87v are not seen?. Are the voltages not present or you haven't measured.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Fateh Singh on November 13, 2016, 10:12:43 am
Mr Bryan,  I have checked the 87V and 42V supplies with scope. They look OK. DMM measures only 15 mv ripple.
On checking the high voltage A9 card- I find an anamoly. The sinewave oscillation  on Pin7 ,T1970- is not a steady amplitude
+_150V AC.  Its amplitude is modulated- the oscillation builds up and dies down.Each cycle is 5-6 waves. The behavior is the same at  pins 5 and 6.
Because the oscillator is under feedback control with U1956, trying to stabilise -1900V- the IC pin7 has the same modulation at low amplitude.
R1973 is listed as 16K, but actually it was 120K. The layout seems different here, and i am trying to see if any C or R is open /short/out of specs.
My suspicion is on U1956- dual op amp. Its supplies are ok.    -300V supply from doubler fed by pin 7 T1970 is OK- possibly due to filtering
and low load. But this behavior from pin7 must be doing funny things to Control grid voltage and the -1900 V cathode bias.
Thanks for your interest in my woes.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on November 13, 2016, 10:32:23 am
Fateh:  Do you have the comprehensive service manual for the scope. Sounds like there is some issues with the scope and the A9 board is definitely a area that I am not familiar with. I can send you a copy if you do not have one. You may want to join the Yahoo group Tekscopes. This is where all the experts in teak scopes hang out, if they can't help no one can<g> Takes a couple days to join as the memberships are moderated.

https://groups.yahoo.com/neo/groups/TekScopes/info (https://groups.yahoo.com/neo/groups/TekScopes/info)

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Fateh Singh on November 13, 2016, 12:15:53 pm
Bryan, I have one downloaded copy with me- and I have all circuit schematics in A3 and A2 sizes.
I am reasonably good at trouble shooting electronic equipment. It is my hobby and my profession now.
We are designing an EV motor and and Inverter. Stuck with the inverter, that requires 4 isolated 20 V /0.5A
supplies. Hence the requirement of good quality Oscilloscopes.
Please send your copy of the service manual by mail-  fs_monder@yahoo.com.

Many thanks.
Fateh
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on November 14, 2016, 10:27:21 am
E-mail sent
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Fateh Singh on November 15, 2016, 06:28:02 am
Bryan,

We have got it RIGHT, after much hair splitting. The error message  Fail  Test 05  44   passed after change R2013. I dont know stable or accurate
that is.  The HV control system loop oscillation, went away,  after some prying  about U1956. I tried putting another capacitor across pins 1 and 2 . No change except a little lower modulation frequency.  Possibly, some dry solder point got set right.

Now, all four channel traces are on screen , and they can be moved about. Intensity control OK. Focus OK. Checking calibration can wait.
Replacing electrolytics on A1 card can also wait. It looks like a difficult maneuver just  now. May be NV RAM data transfer to another compatible
chip later on. Breathe easy now.

Thanks everybody here, especially about clearing doubts about DAC functioning.

Fateh
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on November 15, 2016, 06:45:49 am
That is good news that you got it fixed, or at least hope so. One thing I would do as a priority is get the Dallas NVRAM changed sooner than later or risk losing your calibration data. The battery on the chip is probably close to 25-30 years old by now. Lot's of threads on how to replace.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: cheeseit on November 15, 2016, 09:40:37 pm
It's alive! No more arcing and now with squiggly lines on the tube! ;D
(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=270676;image)

Apart from the missing adjustment everything seems to work as far as I can tell. (?) The image looks a bit more fussy than IRL but it definitely needs adjustment - I assume that it is possible to adjust it to a much sharper image? ATM this is the best I can achieve using the front panel adjustments.

The PS has been recapped and I replaced the single electrolytic and the fuse on the HV-board. Two 15R resistors (R1010 and R1019) on the regulator board were replaced with beefier ones. One measured open and had visible cracks, and the other measured 68K and had tiny scorch marks, both out of circuit.

Handling and installing the tube was a bit scary since this is the most expensive single part I have ever replaced, and of course, because of the fragile glass. The tube also didn't line up to the holes in the shield as well as the old one did. The ground pin was so crooked that it was impossible to use so I had to pull the tube out again and straighten the pin with flat nose pliers. I took great care not to bend it and just hope that I didn't damage the seal but it was unfortunately necessary.

No error codes on boot and the battery is healthy at 3.56V measured on the SRAM supply pins so calibration is safe for the time being. I already bought a new battery and will be replacing the current one. 15592 hours on and 2619 power cycles logged.

I'm not sure how to proceed with the adjustments but will study the relevant parts of the SM and try to figure out what exactly needs to be done and what my options are, given the equipment I have and my limited budget. I will return once I make further progress and/or if (when) I need help. Thanks so far. :)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on November 15, 2016, 11:14:09 pm
I'm not sure how to proceed with the adjustments but will study the relevant parts of the SM and try to figure out what exactly needs to be done and what my options are, given the equipment I have and my limited budget.

Congratulations, and that's the right attitude :)

I presume you replaced those blasted (pun intended) mains filter caps.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: cheeseit on December 13, 2016, 09:39:17 pm
I was searching for higher bandwidth probes for my 2465B above and ended up buying another (working) 2465B on my local craigslist. :D The seller obviously didn't really know what he was selling since his reply to me asking for probes was "please explain what probes are and where I can find them". :P Turned out that it included four P6137 400MHz probes and a single P6105A 100MHz. He also had a manual, quick start guide and a few other bits. He was asking for €270, I courageously (since others were interested too) offered him €148, and got it for €161. Total cost including shipping €180, which to me is a score considering that sold listings on ebay shows the P6137 selling for about €60 a piece plus shipping. >:D

This is what I got:
(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=277824;image)

It looks like it has been stores upright somewhere dirty, or for a very long time. I know that it is trivial to reset but only 3454 hours on and 658 power cycles so I'm hoping that it has just been stored for a long time. Perhaps the inside will give some clues. The three probe instruction sheets I got have revision dates from 1991 to '93 so the scope likely is from this period.
All the probes appear to work. The tube has no burns and is very bright. The 2nd and 4th channel (I think) did show a bit of noise when the scope was cold but that went away after warming up. The readout and traces shimmers a tiny bit randomly from time to time. Otherwise everything appears to work fine but I haven't yet done much testing.
(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=277828;image)

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=277826;image)

I will open it up tomorrow and see what it looks like inside and what needs to be done but PSU and A5 is likely to need work I would guess. I seem to recall that recapping the PSU has solved issues similar to the shimmer I'm seeing. I'll post once I have opened it and had a look around. :)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on December 13, 2016, 11:13:53 pm
That is one heck of a good score!  :clap: :-+
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on December 14, 2016, 12:34:12 am
I got similar deals on a Tektronix 2440 and 7854 which apparently sat in storage for many years and were in excellent condition.  Later I hunted down a front cover for the 2440 so it remains clean and protected.

The 2nd and 4th channel (I think) did show a bit of noise when the scope was cold but that went away after warming up.

Warming up usually results in better performance from aluminum electrolytic capacitors so this might indicate that they are at the end of their useful life.

I am fussy on exactly which 2465 series oscilloscopes had problems with leaky surface mount aluminum electrolytic capacitors but I do not think the early and late ones did but it is still worth checking.

Quote
The readout and traces shimmers a tiny bit randomly from time to time. Otherwise everything appears to work fine but I haven't yet done much testing.

Check to see if this is just an artifact of the beam multiplexing needed to display the readout by disabling the readout.  Sometimes the readout will momentarily synchronize with the sweep to produce visible artifacts.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: razberik on December 14, 2016, 08:35:18 am
The seller obviously didn't really know what he was selling since his reply to me asking for probes was "please explain what probes are and where I can find them". :P
Use word "cables". ;D "Cable" is more explaining that "probe".
Quite funny in situations where "cables" are more valuable than the instrument itself.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: cheeseit on December 14, 2016, 09:33:41 pm
I got similar deals on a Tektronix 2440 and 7854 which apparently sat in storage for many years and were in excellent condition.  Later I hunted down a front cover for the 2440 so it remains clean and protected.

The 2nd and 4th channel (I think) did show a bit of noise when the scope was cold but that went away after warming up.

Warming up usually results in better performance from aluminum electrolytic capacitors so this might indicate that they are at the end of their useful life.

I am fussy on exactly which 2465 series oscilloscopes had problems with leaky surface mount aluminum electrolytic capacitors but I do not think the early and late ones did but it is still worth checking.

Quote
The readout and traces shimmers a tiny bit randomly from time to time. Otherwise everything appears to work fine but I haven't yet done much testing.

Check to see if this is just an artifact of the beam multiplexing needed to display the readout by disabling the readout.  Sometimes the readout will momentarily synchronize with the sweep to produce visible artifacts.
I was thinking electrolytic caps warming up too so great that you mention this. And this one unfortunately does have leaky surface mount caps but it still haven't caused that much damage.
I will look into the part about beam multiplexing and synchronization. Thank you!

The seller obviously didn't really know what he was selling since his reply to me asking for probes was "please explain what probes are and where I can find them". :P
Use word "cables". ;D "Cable" is more explaining that "probe".
Quite funny in situations where "cables" are more valuable than the instrument itself.
Cables might have made more sense to him but I would expect him to answer that there is a power cord included.. :D I don't know about the probes being more valuable than the instrument but it sure was a nice bonus having a working 2465B thrown in when purchasing probes. I'm thinking of selling it once refurbed and perhaps use the money to finally buy a modern scope. I've been wanting a Rigol 1054Z for a while.

Update:
Just a few images for now since I'm of to bed but I've taken the case of and it looks both good and bad. Good because it is really clean, and bad because the surface mount caps have leaked. The damage is not that bad and some scrubbing with alcohol and a brush should take care of it. This is my first time removing corrosion like this so I will have to read up on it using this thread. I thinking replacing the affected resistors and caps, or what? I will at least remove the other components to scrub thoroughly.

I have some side-by-side images of this 1993 next to my 1989 vintage, if anyone is interested? There are a few differences, besides the obvious A5 boards, like different bodges and such.

Corrosion:
(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=278027;image)

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=278029;image)

The U800 has a strange concave and roughed up mark. Is this a sign that its been cooked? I hope not and would think that it would be convex and not working if so, judging by its looks.
(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=278031;image)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on December 24, 2016, 06:52:25 pm
Taking a scope break –

While still curious about where the upper frequency limit is, I’ve had daydreams of actually seeing 500 MHz displayed.   The 2465B is rated for 400 MHz, which is quite respectable.   But the scope spec’s say it will display 500 MHz!

To find that upper limit, thought I would use my Baofeng handheld radio as a signal source.   This is one of the many slightly different variations of the well known UV-5R which is spec’d up to 520 MHz.   Tested this one to find the upper limits and was pleased to see it top out at 570 MHz.   So that should do well in finding the upper limit of the scope.

The connection was made by simply hooking the scope probe onto the insulated antenna and pressing the transmit button.

Plan was to start out at 570 MHz, then reduce the frequency until the scope was able to lock on to it.   But the scope locked on to the first test at 570 MHz.   And everything was very stable at that frequency.   Wow!

Next test was to see how the frequency readouts worked.   Pressing the delta V & delta T buttons displays the vertical cursor lines that indicate frequency.   For this test the cursors were spread over 10 cycles which read 57 MHz, which = 570 MHz for the waveform.   And again, all was stable and reading correctly.   See photos below.

Repeated the test using the 10x button and adjusted the cursor to cover just one cycle.   And again, everything was stable and accurate.

Then I let the scope determine the frequency by pressing the lower red “HELP” button followed by the channel 1 button.   And as can be seen in the 3rd photo, it easily read out the frequency as 576.9 MHz, while the Baofeng can be seen indicating570.000 MHz on the top indicated frequency, which amounts to a 1% error.   Wow again!

While these frequencies are impressive, they say nothing about the voltage levels that have rolled off quite significantly.   And the scope probe I used was only rated for 100 MHz.   But the same argument could be made for signals at 400 MHz where the scope gain has rolled off by 3 DB, plus probe losses.

The only bad news here is that I still don’t know where the upper frequency limit is.   But, that’s ok, I’ll take what is until I find a higher frequency signal source.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: cheeseit on December 30, 2016, 12:24:51 am
Taking a scope break –

Very interesting - I hope you find a higher frequency source!

Update

Now that Christmas is over I finally found some time to continue work on my second 2465B. It cleaned up real nice, except for the BNC's. I took the front panel out and disassembled it and then washed the face plate in warm water and soap. The buttons were washed and then whitened with hydrogen peroxide. The image below doesn't really do it justice but they are gray now, not that brownish-gray like before.
As a pleasant surprise both the implosion shield and the blue filter cleaned up nice too and has hardly any scratches, only a few tiny ones that are only barely visible when viewed from certain angles and in the right light. Combined with the generel cleanliness inside and lack of dust on the fan and on the boards, I'm inclined to believe that the low number of hours on and power cycles are indeed true and haven't been reset.
(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=281758;image)

What unfortunately didn't just clean up is the badge, which is a minor annoyance for now, and the BNC's. It looks like the plating on the BNC's have been eaten through by corrosion. They of course work no problem but their appearance bothers me. The image below is after polishing them once. I would like the scope looking mint if I resell it, so, I've found a source for somewhat cheap (NOS I think) BNC's but am wondering if desoldering and replacing them will affect anything? It's heating up the associated components twice after all. Or are they salvageable, and if so, using what? I've used what I had, which is a product called Silvo, that has worked fine before.
(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=281760;image)

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=281762;image)

I've started recapping the power supply with the components I had in stock using my new ZD-915 - what a joy it is to finally have a desoldering station. My TL866 has arrived so now I await the arrival of an order from Mouser so I can finish recapping and replace the DS1225Y with FRAM.
Doing this I found some more corrosion, this time under the four 250µF 20V caps on the A3 board. All four have some black gunk around the positive lead but it fortunetly didn't spread that far and cleaned up nicely using a glass fiber brush, alcohol and q-tips. No visible damage after it has been removed.
(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=281764;image)

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=281766;image)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on December 30, 2016, 03:26:47 am
Very nice looking scope cheeseit!   Thanks for sharing.   It's amazing what a little soap & water or other cleaners can do.   Certainly increases the perceived value.

My scope arrived very clean inside and out, except for the BNC's that are tarnished.   like yours, they all work just fine, but some cleaning would help the appearance.   You said you used Silvo to clean the BNC's.   Is that a silver polishing compound?

Interesting that you used hydrogen peroxide on the knobs which might brighten mine up too.   Never heard of using it for that.

Your BNC's appear to be pitted, which probably means there is nothing that can be done to fill in the pits.   Appears that your scope may have been stored in a higher humidity environment.

Also have been wanting to suggest that you replace the 4 electrolytic caps on the A5 board ASAP, because they leak, as yours are just starting too.   C 2965 appears to be corroding the adjacent screw head.   Mine was worse and an adjacent IC, U2890, had absorbed the acid which caused it to fail.   Thought those IC's were totally sealed, but this one had a corroded interior when I opened it up, along with signs of corrosion on the exterior solder connections.   So where the corrosive gases migrate to, can be a challenge to forecast.   Other board connections were thinned, but still ok.   Also replaced several other suspected components adjacent to those cap's.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: lordvader88 on December 30, 2016, 04:09:35 am
why does this thread have some many views/replies for some random scope ?

Anyways I own a Tektronix 2430A, got it for a decent price (I guess) on fleabay, but as it turns out CH1 has a big problem in the vertical gain. But all and all good enough for now.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on December 30, 2016, 04:36:22 am
@ cheeseit and Old-E
There's some good restoration tips in this sticky thread including polishing BNC's.
https://www.eevblog.com/forum/repair/vintageclassic-renovation-techniques/ (https://www.eevblog.com/forum/repair/vintageclassic-renovation-techniques/)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: cheeseit on December 30, 2016, 11:26:06 am
@ cheeseit and Old-E
There's some good restoration tips in this sticky thread including polishing BNC's.
https://www.eevblog.com/forum/repair/vintageclassic-renovation-techniques/ (https://www.eevblog.com/forum/repair/vintageclassic-renovation-techniques/)

Thanks, don't know why I forgot about that sticky and I remember seeing robrenz fantastic results and thinking that would come in handy sometime. I will try to find what he used but what about replacing the BNC's, I know how to do it but will it affect anything?

why does this thread have some many views/replies for some random scope ?

Because it is a great scope. :)

My scope arrived very clean inside and out, except for the BNC's that are tarnished.   like yours, they all work just fine, but some cleaning would help the appearance.   You said you used Silvo to clean the BNC's.   Is that a silver polishing compound?

Yes it's primarily for silver polishing but also works on gold, aluminium and chrome. I once gave it a try on some BNC's that were tarnished and it worked great. I'll try some other products but they do appear pitted and had green oxide spots so I think they are too far gone for just polishing.

Interesting that you used hydrogen peroxide on the knobs which might brighten mine up too.   Never heard of using it for that.

It works wonders. Google whiten yellow plastic and you'll find many guides but it's basically about submersing it in a 3%-10% solution and exposing it to UV. Many just place it out in the sun but I've found that using a desk lamp lowered down over the glass jar that I use works great. The LED bulb I use and the little heat from it is enough. I just stir it vigorously from time to time to remove the bubbles that form and rinse it once it looks nice. The aluminium inserts in some of the knobs on the 2465 is not a problem in a low solution but other metals very much react in hydrogen peroxide so remember to remove the set screws.
Some suggest using a UV-sealant afterwards might be a good idea.

Also have been wanting to suggest that you replace the 4 electrolytic caps on the A5 board ASAP, because they leak, as yours are just starting too.   C 2965 appears to be corroding the adjacent screw head.   Mine was worse and an adjacent IC, U2890, had absorbed the acid which caused it to fail.   Thought those IC's were totally sealed, but this one had a corroded interior when I opened it up, along with signs of corrosion on the exterior solder connections.   So where the corrosive gases migrate to, can be a challenge to forecast.   Other board connections were thinned, but still ok.   Also replaced several other suspected components adjacent to those cap's.

I have new caps on the way for exactly that and plan to desolder the adjacent passives and IC's and clean it using brushes, white vinegar, water and alcohol. I'll replace the passives where the solder looks dull and perhaps a few of the 7400 logic IC's but the damage doesn't look that bad so I hope that a thorough cleaning is good enough.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on December 30, 2016, 07:58:09 pm
@ cheeseit and Old-E
There's some good restoration tips in this sticky thread including polishing BNC's.
https://www.eevblog.com/forum/repair/vintageclassic-renovation-techniques/ (https://www.eevblog.com/forum/repair/vintageclassic-renovation-techniques/)

Thanks, don't know why I forgot about that sticky and I remember seeing robrenz fantastic results and thinking that would come in handy sometime. I will try to find what he used but what about replacing the BNC's, I know how to do it but will it affect anything?
That would be up to you. Sure if you want her looking like new then replace them, personally I wouldn't bother.
Grab the part # and have a search in Sphere's stock:
http://www.sphere.bc.ca/test/tekparts.html#catalog (http://www.sphere.bc.ca/test/tekparts.html#catalog)

Why I say I wouldn't bother is because when I tried to find BNC replacements that are an exact physical match it can be hard work but the one for this Tek could be a common part and easy to find.
BUT then you have to install them......maybe the scope has to come into many pieces to gain access to the solder joints............nah if they're functional I'd leave them be.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: cheeseit on December 30, 2016, 09:48:38 pm
Thanks again. I will try polishing it some more, this time using another polishing agent and some buffs on my Proxxon. I already have ordered some BNC replacements though, at €9 a pair, just in case polishing isn't good enough and I can't live with it. I take it that replacing them doesn't pose any problems, apart from quite possibly being a bit laborious.

Man, that Sphere site just takes you back to the bad old days of mid 90's internet.. ;D  |O They do however have a lot of great stuff.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on December 30, 2016, 10:08:17 pm
I take it that replacing them doesn't pose any problems, apart from quite possibly being a bit laborious.
It could be worse than just laborious, especially the Gnd connection pins. If the Gnd plane is substantial, as it likely will be as to not fuse if a connection is made that makes a Gnd loop, then desoldering the BNC Gnd pins will require an iron with good thermal mass. These can be tricky but not impossible with a good iron and is one of the reasons why I said if they are functional just leave them be.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on January 01, 2017, 10:19:07 pm
lordvader 88
"why does this thread have some many views/replies for some random scope ?"

How many analog scopes are there that have all these features, and can display more than 570 MHz?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Michael Lloyd on February 01, 2017, 11:56:57 pm
I have a number of Tek scopes, including a 2465B and 2467. My favorite is a 545B but that's another era. The 2467 is in storage and the 2465B is on the rack and I use it. How concerned should I be about the battery?, tant's and, electrolytics?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on February 02, 2017, 12:24:10 am
I have a number of Tek scopes, including a 2465B and 2467. My favorite is a 545B but that's another era. The 2467 is in storage and the 2465B is on the rack and I use it. How concerned should I be about the battery?, tant's and, electrolytics?

The infamous mains X/Y film caps can be "entertaining" when they fail; in my 2465 a series resistor rapidly dissociated itself and took some of the PCB prepreg with it.

The control board caps are also infamous for venting their spleen over nearby components. Seen that in my 2445B.

A protection against battery failure would use the test routine to examine the nonvolatile memory's contents, and to make a video as you step through each location. Then, if necessary, you could reprogram another memory with the old calibration constants.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Michael Lloyd on February 04, 2017, 02:02:33 pm
I have a number of Tek scopes, including a 2465B and 2467. My favorite is a 545B but that's another era. The 2467 is in storage and the 2465B is on the rack and I use it. How concerned should I be about the battery?, tant's and, electrolytics?

The infamous mains X/Y film caps can be "entertaining" when they fail; in my 2465 a series resistor rapidly dissociated itself and took some of the PCB prepreg with it.

The control board caps are also infamous for venting their spleen over nearby components. Seen that in my 2445B.

A protection against battery failure would use the test routine to examine the nonvolatile memory's contents, and to make a video as you step through each location. Then, if necessary, you could reprogram another memory with the old calibration constants.

I've been hesitant to touch the 2465B and 2467 but I'm thinking about recapping the PSU as a precautionary measure. Maybe the control board too (now). I'll look into running the test routine
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on February 04, 2017, 04:14:28 pm
I have a number of Tek scopes, including a 2465B and 2467. My favorite is a 545B but that's another era. The 2467 is in storage and the 2465B is on the rack and I use it. How concerned should I be about the battery?, tant's and, electrolytics?

The infamous mains X/Y film caps can be "entertaining" when they fail; in my 2465 a series resistor rapidly dissociated itself and took some of the PCB prepreg with it.

The control board caps are also infamous for venting their spleen over nearby components. Seen that in my 2445B.

A protection against battery failure would use the test routine to examine the nonvolatile memory's contents, and to make a video as you step through each location. Then, if necessary, you could reprogram another memory with the old calibration constants.

I've been hesitant to touch the 2465B and 2467 but I'm thinking about recapping the PSU as a precautionary measure. Maybe the control board too (now). I'll look into running the test routine


I recommend you consider recapping the PSU. I recently did my 1985 vintage 2465 DMS and it fixed a drifting issue with the DMM and Counter/Trigger option boards due to a low +5VDC that originated from the Inverter board. This voltage was not part of the group that can be checked on the main board at J119. The attached chart from the Tek Yahoo Group lists all the caps that should be replaced.

If your A5 Control boards are SMD you should seriously consider changing the caps. They are known leakers and will damage the board. The older pin thru hole boards (such as mine) are much less prone to issues and in fact mine is all original.

 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Michael Lloyd on February 05, 2017, 02:07:18 am
Thanks for the parts list. Everything is ordered. $30-ish for a little peace of mind.

Quote
A protection against battery failure would use the test routine to examine the nonvolatile memory's contents, and to make a video as you step through each location. Then, if necessary, you could reprogram another memory with the old calibration constants.

I haven't found a test routine that shows the NVRAM contents. It passes the tests I ran with the ?T/?V menu selection but no data is displayed. From what I've read the battery doesn't warn you when it dies...
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on February 05, 2017, 02:23:31 am
Quote
I haven't found a test routine that shows the NVRAM contents. It passes the tests I ran with the ?T/?V menu selection but no data is displayed. From what I've read the battery doesn't warn you when it dies...

I believe it is Exercisor 2 test that displays the calibration data.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Michael Lloyd on February 05, 2017, 03:23:43 am
Much appreciated. I checked the service manual and was able to figure out how to retrieve the cal data. I video'd it and put it on YouTube. I don't know if it's useful for anyone else. If it is I'll post a link.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old-E on February 05, 2017, 05:24:29 am
Mic. L.
There has been some fairly detailed entries in this thread, over the past year or two, on saving and transferring the digital calibration data for your scope.   it would be good to publish your experiences here too for all those interested.   Many of these improvements / restorations are laborious.   But the scope one ends up with is quite good.   
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on February 05, 2017, 06:22:45 am
Thanks for the parts list. Everything is ordered. $30-ish for a little peace of mind.

Quote
A protection against battery failure would use the test routine to examine the nonvolatile memory's contents, and to make a video as you step through each location. Then, if necessary, you could reprogram another memory with the old calibration constants.

I haven't found a test routine that shows the NVRAM contents. It passes the tests I ran with the ?T/?V menu selection but no data is displayed. From what I've read the battery doesn't warn you when it dies...


Good deal.  :-+ When you get ready to replace the caps on the Regulator and Inverter boards do NOT do a mass remove then go back and do a mass install. There are minor differences between the 2465, 2465A, and 2465B. Plus there are discrepancies with the board lettering and the schematics which Tektronix never fixed. Doing a mass replace then install will result in aggravation and magic smoke. Do one or two caps at a time and compare value, orientation, and voltage rating as you replace them. Granted that's inefficient but it will be accurate.

Also you'll notice that C1110, 1111, 1113, 1114, 1115, 1116 have all been "upgraded" to 330uf. I followed that recommendation and everything works fine.   
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on February 05, 2017, 11:26:40 am
Much appreciated. I checked the service manual and was able to figure out how to retrieve the cal data. I video'd it and put it on YouTube. I don't know if it's useful for anyone else. If it is I'll post a link.

Wish I ran the test and recorded the data before replacing my Dallas. Something went wrong and I lost all the calibration data. @#$*$*($. Why don't you go ahead and post the link
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on February 05, 2017, 11:31:21 am
Quote
Good deal.  :-+ When you get ready to replace the caps on the Regulator and Inverter boards do NOT do a mass remove then go back and do a mass install. There are minor differences between the 2465, 2465A, and 2465B. Plus there are discrepancies with the board lettering and the schematics which Tektronix never fixed. Doing a mass replace then install will result in aggravation and magic smoke. Do one or two caps at a time and compare value, orientation, and voltage rating as you replace them. Granted that's inefficient but it will be accurate.

Also you'll notice that C1110, 1111, 1113, 1114, 1115, 1116 have all been "upgraded" to 330uf. I followed that recommendation and everything works fine.   

Good advice and take lot's of pictures of your board before recapping. There is either a error on the Tek schematics or a error on the board silkscreen for one of the caps and the polarity is reversed. Can't remember which cap, but best to replace one at a time so you don't miss it. Also note that some boards have one extra bi-polar electrolyte's where the replacement list only shows one. Think it's the later revisions, so best to order a extra or two.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: peter-h on March 15, 2017, 09:32:17 pm
Hello everyone!

I have a 2465B which I bought about 10 years ago, refurbished by a firm which used to sell new and used Tek gear - Hesing Technology in the UK (disappeared some years ago).

It's been working great until a few days ago. The front panel has basically packed up. The LEDs are mostly illuminated although many appear at a low brightness. The rotary switches work fine, pressing the buttons which activate what sounds like range switching relays does create the right relay clicking noises, so it almost looks like it is just the LEDs which are not being driven correctly. But I also notice that the AC/GND/DC/GND/DC selection on each channel doesn't seem to work, so some of the momentary buttons seem to have also acquired only a partial functionality.

I have been doing hardware/software development since the 1970s and have download the service manual mentioned in this thread. And I have read hopefully all of this great thread but can't see this issue mentioned. So while I can start with the service manual, to get me started faster, has anyone here come across this issue before?

I do have another scope - a cheap 25MHz DSO - and various DVMs I can use.

Page 461 (front panel troubleshooting flow chart) seems relevant. I entered the Exerciser 01 mode and all the switches and pots are getting picked up. However, I can't find anything in the manual on the switch codes referred to on that page. Also the four 2-digit hex values seem to change in a funny way. Hard to describe without doing a movie but pressing a given switch once registers on the switch code display (in the first two groups), pressing it again registers too (this time in the second two groups) and subsequent presses don't change anything. This may well be right but it's not what I would expect from a keypad scanned in the usual matrix way. Why the two button presses?

But definitely every switch and every pot does work, so maybe the input mode selector issue is either imaginary (the CRT display doesn't show everything) or there is a separate issue.

The LEDs clearly don't work. I will have to check the items referenced there. The attached image shows that nearly all the LEDs are lit up to some extent.

Has anyone come across this before?

Many thanks for any input!

EDIT: I found table 6-17 for the switch codes. It doesn't suggest that pressing a switch twice should change anything on the switch code display...
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: james_s on March 15, 2017, 10:06:06 pm
The first thing I would do is check all of the power supply rails. A dead or off-spec output can cause all kinds of issues.

I hadn't seen this thread yet but those are some great pics. That scope, like most Tek gear is a work of art. I have a lot of respect for the guys who designed this stuff. Wonder if those hybrids could be replicated by modern SMD components on a small PCB?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 15, 2017, 10:11:41 pm
...
Page 461 (front panel troubleshooting flow chart) seems relevant. I entered the Exerciser 01 mode and all the switches and pots are getting picked up. However, I can't find anything in the manual on the switch codes referred to on that page. Also the four 2-digit hex values seem to change in a funny way. Hard to describe without doing a movie but pressing a given switch once registers on the switch code display (in the first two groups), pressing it again registers too (this time in the second two groups) and subsequent presses don't change anything. This may well be right but it's not what I would expect from a keypad scanned in the usual matrix way. Why the two button presses?
...
Take a look at page 6-15.  It describes the format of the line and the codes that show up for Exerciser 01.

As james_s recommends, definitely start with power supply checks, and I would pay particular attention to the A5 board.

If the flowcharts don't get you anywhere, you could look at the LED DATA and LED CLK signals.

Do changes to the vertical and horizontal knobs show up on the readout?


EDIT:  Also, let us know if your serial number is <=B049999 or >=B050000 so we can play along with the right set of schematics.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Michael Lloyd on March 15, 2017, 10:51:22 pm
Much appreciated. I checked the service manual and was able to figure out how to retrieve the cal data. I video'd it and put it on YouTube. I don't know if it's useful for anyone else. If it is I'll post a link.

Wish I ran the test and recorded the data before replacing my Dallas. Something went wrong and I lost all the calibration data. @#$*$*($. Why don't you go ahead and post the link

The video turned out to be crap. The  numbers are out of focus or over exposed, I'm not sure which. I'll leave the link anyway. I'll shoot another video when I get home

https://youtu.be/iHlCVdnBvBQ
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on March 15, 2017, 11:13:37 pm
Wonder if those hybrids could be replicated by modern SMD components on a small PCB?

Apparently one of the hybrids was. I believe the U800 I think...for awhile could be returned to a company in Japan that was able to fix them.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: peter-h on March 16, 2017, 07:16:48 am
S/N is not on the back! See pic: http://peter-ftp.co.uk/screenshots/2017-03-16_071429.jpg (http://peter-ftp.co.uk/screenshots/2017-03-16_071429.jpg)

It says B057050 on the front.

There isn't a fan on the back but there is a very noisy one inside.

I will open it up in the next day or two.

I did find that switch code table - thank you. I reckon there is something wrong with the switches. As I posted, pressing a button once shows up as a change in the four 2-digit values (only the left two change) and pressing it again shows up as another change (only the right two change). Subsequent presses don't change anything. I would be amazed if that was right. Can anyone confirm this? I can do a little video later.

It would be fairly common to use the same lines as are used to scan the switches for driving (multiplexed) LEDs. In fact I am using an ST LED display driver chip right now which does exactly that.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on March 16, 2017, 09:05:09 am
I did find that switch code table - thank you. I reckon there is something wrong with the switches. As I posted, pressing a button once shows up as a change in the four 2-digit values (only the left two change) and pressing it again shows up as another change (only the right two change). Subsequent presses don't change anything. I would be amazed if that was right. Can anyone confirm this? I can do a little video later.

It would help if you would relate your observations to the definition in the service manual p6-15 and p6-15, viz:

POTS AND SWITCHES (Exerciser 01). This routine displays the values that the Microprocessor detects asvarious digitized pots and switches are activated. Thehalf of the top line of the display appears after turningpot. The right half of the top line of the CRT display appears after pressing a switch. The top line of the CRT display has the following format:
AA BB CC DEEE FF GG HI JJ KL

The format is defined as follows:

"AA" is the code of the most-recently-activated potentiometer (see Table 6-9 for definition of pot codes).

"BB" is the current value (in hexadecimal) of pot AA. See Table 6-9 for the approximate range of codes for the CCW  (counter clockwise) and CW (clockwise) potentiometer rotations.

"CC" is the previous value (in hexadecimal) of pot AA.

"0" is the DAC Multiplexer code used to select pot AA (see Table 6-9).

"EEE" is the 12-bit DAC value (in hexadecimal) associated with pot AA. See Table 6-9 for the
approximate range of codes for the CCW (counter clockwise) and CW (clockwise) potentiometer rotations.

"FF" is the code of  the previously-activated potentiometer (see Table 6-9).

"GG" is the row code of the most-recently-activated switch (see Table 6-10 for definition of row codes).

"H" is the switch-position code: 0 for open; C for closed.

"I" is the column code of the most-recently-activated switch (see Table 6-10).

"JJ" is the row for for the previously-activated switch.

"K" is the switch-position code: 0 for open; C for closed.

"L" is the column code for the previously-activated switch.


Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 16, 2017, 02:22:01 pm
...
It would be fairly common to use the same lines as are used to scan the switches for driving (multiplexed) LEDs. In fact I am using an ST LED display driver chip right now which does exactly that.
It's not the case on this scope.  Take a look at schematic <3>.  There are 6 cascaded 74F164 shift registers that drive the LEDs directly and are loaded by LED CLK and LED DATA.

I'm not ignoring the other symptoms you're stating with the subsequent presses.  If the flowcharts don't help, I'm suggesting picking one obvious symptom that's easy to track backwards or forwards in relation to the processor.  There aren't that many other things involved in controlling the front panel LEDs, so that would seem to be the simplest choice.

You said everything was working and now it's not.  So it's likely we're looking at one failure somewhere.  Find the problem with the LEDs and you're probably going to find the explanation for all the issues.

When you get the lid off, examine A5 closely for signs of cap leakage.  This era of 24xxA/B scope is notorious for leaking caps which corrode and eventually sever PCB traces.

Some people will have you replace ALL the caps immediately even if everything looks fine.  (Wait for it....)  I'd recommend the approach of finding the actual problem and then deciding from there whether wholesale cap replacement is warranted.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: peter-h on March 16, 2017, 08:55:35 pm
As a quick interim reply, tggzzz's explanation is clearly what I am seeing, so the switches seem OK.

I need to fix the LEDs. If they are driven from a shift register that should be easy, though I don't see how you could get them all lit up at some low brightness unless you are either clocking garbage data fast, or you have lit up the lot and there is a power issue (a low supply rail).

Thank you for the time taken to reply. This is a brilliant forum! I go back many years to sci.electronics.design and comp.arch.embedded but this is much better!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 16, 2017, 11:27:10 pm
It's hard to judge in the photo, but if they are that dim then it could be a power issue somewhere.  Low supply rail, or could also be a bad ground.  Check Vcc and Gnd potentials directly on the chip pins in case a trace got eaten somewhere.

I'd highly encourage you to read the theory section and maintenance section of the service manual before tackling anything.  It's among the best ever written (at least in my opinion).  There are descriptions on how the LEDs and switch/pot scanning are implemented.

Good luck and let us know what you find...
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on March 17, 2017, 10:45:53 am
Wonder if those hybrids could be replicated by modern SMD components on a small PCB?

Apparently one of the hybrids was. I believe the U800 I think...for awhile could be returned to a company in Japan that was able to fix them.

Thomas Lafay did that here -> http://www.davmar.org/TE/Tek2465/lafay.html (http://www.davmar.org/TE/Tek2465/lafay.html)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on March 18, 2017, 08:59:07 pm
Just dropping this link to another thread where a member has seemed to overcome a U800 issue.
https://www.eevblog.com/forum/repair/2467b-with-a-strange-horizontal-issue-video-link/ (https://www.eevblog.com/forum/repair/2467b-with-a-strange-horizontal-issue-video-link/)
Title: Tektronix 2465B oscilloscope overhaul
Post by: Satbeginner on March 19, 2017, 02:15:29 pm
Hi All,

I recently got my 2465B through ePay from Italy, and it arrived safely.
I asked the seller to carefully pack it, surrounded by soft foam, and he did. Kudo's to him for that!!

Last week I started working on it.
It has the "all SMD" A5 board with the Dallas chip, and it started with no beam and stopped it selftest with the "ADD" light lit.

As it turned out, I could see the 05 FAIL 44 after I tweaked the GRID Bias.

I went to look for the 4x SMD caps, and yes, they all had been leaking and all of their values were down in the 10-30 nF range... ;-)
After replacing these (not really nice, because there were PCB-tracks eaten away as well) it still gave the same message.
It turned out the R2013 (10kOhm, part of the front panel DAC reference divider) was up to 35kOhm, this explained the "high voltage" error.
Somehow this type of 0,1% resistors are more susceptible to the electrolytes than the normal SMD ones?

I replaced it with a new 10kOhm et voila, problem solved!! :-+

BTW, some people report this being a 0,1% resistor for accuracy, but I replaced it with a normal 1% metal film resistor. (true, I selected one of 10,002 kOhm with my Keithley 2000)
In my humble opinion this reference is "only" used to select the front panel settings, and not for measurements, so I think it is not really super critical.
It is true it must be stable, to not unwillingly change scope settings based on temperature changes...

Note: feedback I got from the Tekscopes group at Yahoo indicates my assumptions about the use of this DAC divider are not completely true. It appears this DAC -and so the divider!- are involved in measurement, so also in accuracy. At least a check of the calibration is necessary, so maybe a calibration as well.

Today I decided -after reading ALL of this thread!! and nothing else to do on a sunny Sunday- to go all the way, and recap all the electrolytic's and also replace the Dallas chip.
so I ordered the caps, heat sink, socket and Dallas chip at Mouser Europe, and now I have to wait.... (last time I ordered at Mouser Europe, they still shipped from the US, but no tax/customs issues though..)

Yes, although my scope has a Tek U800 thats is not getting hot, I will put an heatsink on it.
I ordered a few of these to see if they will fit:  http://www.mouser.es/search/ProductDetail.aspx?r=532-507222B00 (http://www.mouser.es/search/ProductDetail.aspx?r=532-507222B00)

Mine was build in Holland, Heerenveen, the serial-number starts with H706xxx, so in a way, it found its way back home.
(Not really, although I am Dutch, I do live in Spain.... ;-)

Will keep you all posted,

Un saludo,

Satbeginner (Leo)
Title: Re: Tektronix 2465B oscilloscope overhaul
Post by: BravoV on March 19, 2017, 04:55:59 pm

Will keep you all posted,


Hi Leo, welcome to the club  :-+ and thanks for the info.

About the damaged PCB traces caused by leaking electrolytic caps, did you take any close up any photos on that part ?  That will be a great addition to this thread.  :-+

Looking forward to see your work on this gem, post lots of photos documentation please if you don't mind
Title: U800 mounting & securing weakness ?
Post by: BravoV on March 20, 2017, 11:04:57 am
With this thread -> https://www.eevblog.com/forum/repair/2467b-with-a-strange-horizontal-issue-video-link/ (https://www.eevblog.com/forum/repair/2467b-with-a-strange-horizontal-issue-video-link/) , the OP demonstrated that the two over tightened nuts that are securing the U800 were making horizontal problem, sort of stressing out physically the U800 chip. And we're not talking about the thermal cycle that poor chip endures with that two nuts yet.  :'(


Which brings out again, my observation at earlier post at the beginning regarding this securing method on this poor U800.


This U800 shots was the originally assembled, untouched since it was left from Tektronix factory, just look on how they sandwiched the chip's tab with washers. Also its obvious at standard DIP package, when the pins are soldered properly, the bottom of IC's body should not and will never touch the board, even without the washer.

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=301061;image)


Bottom view of U800, which is clearly the only heat path to dissipate the generated heat.

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=301059;image)


This is the board where U800 is located, that big exposed pad definitely is not touching the IC's bottom part.

(https://www.eevblog.com/forum/testgear/tek-24xx-series-u800-heatsink-diy/?action=dlattach;attach=84028;image)
Both last two photos are courtesy of Kirby from -> https://www.eevblog.com/forum/repair/tektronix-2445-repair/ (https://www.eevblog.com/forum/repair/tektronix-2445-repair/)

Now its clear, no matter how strongly we fastened those two nuts, it wont improve "significantly" the heat transfer from the chip to the bolt thru that little metal tab since it has washers, let alone transfer it to the pcb big pad right below the chip, which will never happen anyway especially its installed with the two washers at the bottom.

And if the U800 is soldered, I think it doesn't need that two nuts from the beginning right ?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Satbeginner on March 20, 2017, 01:41:12 pm
I couldn't help myself, I just bought a second 2465B to repair... :palm: :palm: :palm:
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on March 20, 2017, 03:16:13 pm
I couldn't help myself, I just bought a second 2465B to repair... :palm: :palm: :palm:

No ... not that face palm ... infact its good and good news only, no bad news at all.  ::)

Now, visit here for the stress relief amongst brother & sisterhood of -> TEA ...  (https://www.eevblog.com/forum/chat/test-equipment-anonymous-(tea)-group-therapy-thread/)  >:D
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on March 20, 2017, 03:41:20 pm
I couldn't help myself, I just bought a second 2465B to repair... :palm: :palm: :palm:

No ... not that face palm ... infact its good and good news only, no bad news at all.  ::)

Now, visit here for the stress relief amongst brother & sisterhood of -> TEA ...  (https://www.eevblog.com/forum/chat/test-equipment-anonymous-(tea)-group-therapy-thread/)  >:D

That thread relieves stress in the same way that a persistent itch is relieved by a good scratch => better in the short term, but worse in the long term.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tecman on March 20, 2017, 08:25:31 pm
Question for all of you restorers.  I am waiting to receive a 2467 I grabbed off ebay.  All appears to be functional, based on the listing info.  I do plan to ra-cap the unit.  It has the same basic HW as the 2465A.  As for the RAM, it has the "Keeper" Li battery.  I plan to replace it with a socket and a CR123 Li cell.  I did the same on my Tek AFG 5101 function generator.  My issue is if the RAM data is still being maintained, I may be able to use an external source to keep the data while I perform the battery surgery.

My question is what happens if you lose RAM data ?  If you do a CAL procedure (steps in the manual), will this refresh the BB RAM and generate a checksum ?

Since there is no way to remove the RAM to read the contents, without losing the data, there must be a method for the scope to "restore" itself from a dead battery.

Any insight is appreciated.

paul
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on March 20, 2017, 11:47:47 pm
It has the same basic HW as the 2465A.

1984 - 2445 and 2465
1987 - 2445A, 2455A, 2465A, and 2467
1989 - 2445B, 2455B, 2465B, and 2467B

Quote
As for the RAM, it has the "Keeper" Li battery.  I plan to replace it with a socket and a CR123 Li cell.

The A5BT2570 is a "Keeper II" part number LTC-7P which is a 3.6 volt LiSOCl2 cell.  Tektronix must have liked these; they used them in other instruments as well.  Just be sure to replace it with a 3.6 volt cell or the oscilloscope will probably return a low battery warning.  Interestingly enough, the oscilloscope will return a different fault (High battery?  I forget.) if the battery voltage is too high like with 3xAA cells.

Quote
My question is what happens if you lose RAM data ?  If you do a CAL procedure (steps in the manual), will this refresh the BB RAM and generate a checksum ?

Yes, doing the external calibration procedure will restore the calibration data and write a new checksum but the calibration procedure is not trivial like on a 2440 series.

Quote
Since there is no way to remove the RAM to read the contents, without losing the data, there must be a method for the scope to "restore" itself from a dead battery.

This might be possible through the GPIB interface; I do not remember.  One of the 2465 series experts will know.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tecman on March 21, 2017, 12:20:06 am
David:

Thanks for the info.  I was planning to do a full cal on the unit.

 Based on the photo and s/n it looks like a mid 2467.  The service manual lists 2465a and 2467 as both covered by the same manual.  I looked for a reference site that might cross the s/n to a date (B011907), but no luck.  It does have the PBs instead of the flip switched for mode setting, a'la the 2465a.  When it comes in I will look for date codes.

paul
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 22, 2017, 01:15:37 am
Since there is no way to remove the RAM to read the contents, without losing the data, there must be a method for the scope to "restore" itself from a dead battery.

This might be possible through the GPIB interface; I do not remember.  One of the 2465 series experts will know.
I don't know about the 2565A/2467, but the EAROM in the 2456 can dumped via GPIB.  By examining the EPROMs on the GPIB board I was able to figure out the following.  It may be extensible to other models.

First, you have to enable the "special" commands:

  key 0

Then you can dump the EAROM with the following command:

  earom? <address to dump>[,<address to dump>,<...>]

This allows reading out of multiple locations in one command.  For example, to dump the first 10 addresses:

  earom? 0,1,2,3,4,5,6,7,8,9

Then the next 10:

  earom? 10,11,12,13,14,15,16,17,18,19

And so on, until address 199.  The first 100 locations are the EAROM on the main board, and the second 100 is the EAROM on the buffer board.  This is the same as in the exerciser.  The values should match.

The above commands return a line in the form (from the above example 0 to 9):

  EAR 0:84,1:1993,2:10102,3:1893,4:10091,5:1798,6:1494,7:1420,8:9608,9:1431;

The return format is <address>:<value> and everything is in decimal.  You can set an EAROM value by using the same format:

  earom <address>:<value>

Trying to write multiple values in one line didn't work for me and crashed my scope.  YMMV.

It would be interesting if someone could try this on a model other than a 2465(plain).

WARNING!!   If you want to play with any of this, be careful not to overwrite overwrite the EAROM values until you've saved them with a screen capture!  On my 2465 it DOES NOT MATTER if you have the the cal jumper set to off.  These commands are surely hidden for a reason!


If you're even braver, there's another hidden query I've discovered called "BYTE?".  It takes one argument and dumps that number of bytes from somewhere.  I can't figure out what it's dumping, and I can't make it repeat itself except after a reboot.  Eventually after several hundred bytes it causes my 2465 to reboot.  I'm mentioning it because maybe that command will be useful on other models without EAROMs.


If anyone decides to try anything, please post your results.  Obviously this needs a GPIB interface.  I haven't found any equivalent method to write EAROM/NVRAM values from the screen, although now that I found it via GPIB it makes me suspect it's possible.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Satbeginner on March 23, 2017, 09:37:49 pm
Hi all,

Today my Mouser shipment with the replacement parts arrived, so i started with the recap of the power supply.

There was the error in the board layout in the manual where the caps C1115 en C1132 were mixed up, but I used the existing population on the board as leading.
I also found this thread where the error in the doc is described: https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/475/ (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/475/)

I used the 2465B Recap Modified parts list that is floating around (attached with this message) to order at Mouser, and I found 2 points of attention:

The 2 big caps ordered as 330uF 250V need to be axial for proper mounting, and
On my PS there are 3pcs 1uF 50V non polarised caps instead of 2pcs.C1274, C1291 AND C1292!!

Anyway,

The PS part is done, and I really think the minor trembling of the readout is gone now, so, I consider it a succes.

Now I want to improve the cooling of U800 and replace the Dallas chip.
That will be something for tomorrow, I think.
Tomorrow I will also put some pictures of the result of the PS and also my A5 board.

Un saludo,

Satbeginner (Leo)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on March 23, 2017, 10:45:25 pm
Now I want to improve the cooling of U800 and replace the Dallas chip.

I am not convinced the U800 needs to cooled, yes it gets hot, but I am sure Tek took this into account when engineering. I suspect failures are due to a fan that stops working or the cooling vents at the bottom are plugged with lint, or maybe it's used in a environment that is beyond it's ambient temperature specs.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on March 24, 2017, 01:22:05 am
Now I want to improve the cooling of U800 and replace the Dallas chip.

I am not convinced the U800 needs to cooled, yes it gets hot, but I am sure Tek took this into account when engineering. I suspect failures are due to a fan that stops working or the cooling vents at the bottom are plugged with lint, or maybe it's used in a environment that is beyond it's ambient temperature specs.

If it's the Tek manufactured die typically found in the 2465 I would agree. The Maxim die typically found in the 2465A & B has been proven to be more prone to heat failure.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bryan on March 24, 2017, 04:04:52 am
I thought the Maxim dies were not specific to the U800 but for the other custom chips, U400's maybe
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Satbeginner on March 24, 2017, 11:58:22 am
Hi all,

here again some progress on my 2465B revival.

I will share my info on the steps I took so far:

- Recap Power Supply & tests of the old Caps afterwards... ;-)
- Repair/replacement of the Delayed Time Base lever inside the front-panel
- Removal of the Dallas and placement of a socket so it can be replaced when I get my programmer
- Cooling of my Tek U800 and how
- Pictures of the previous replacement of the four caps on the A5 board

Although I am a big fan of "If it ain't broken, don't try to fix it..." I do think this 2465B could be the scope I will use till I die, so I decided to do the recap.
Mainly because when Tek build this thing, they made sure all new components were up to spec, so now, after more than 25 years, I thought it could be useful to renew the old parts that are known to age.

So yesterday I did a full recap of the Power Supply, that job took me a few hours, but all-in-all, not too bad.
I just replaced everything, but I sure was curious about how necessary it actually was, so today I did a quick capacity and ESR test with one of these small all-in-one testers.

As it turned out, more than half of the capacitors were in fact OK!?
Even so, I am happy knowing all parts are now new and "future-proof".

The caps that were bad were:

3,3uF, 350V
10uF, 160V
10uF, 100V
47uF, 25V
4,7uF, 35V
Tantalum 4,7uF

and funny enough, one of the 15 Ohm resistors went up to 4968 Ohm!! without any markings or change of color.

When I got my 2465B, the VAR knob inside the Time Base was missing, and as it turned out, the pull to delayed time base was not working either.
When I looked in to this the little lever that operates the slide switch inside was broken, so that had to be replaced. (I am not a great fan of glue...)
Qservice in Greece had this part, so that was an easy fix.

Next, the Dallas chip.
Almost all the parts have a 90-ties datestamp  on them, so this means the Dallas is -still working- in almost 16 year of extra time!
I choose to go for the original, so today I removed my Dallas and put a socket on the board.
Reading and copying must wait till I receive my programmer, but at least the soldering bit is done today.
I used a simple push-and-release manual tin-sucker that worked OK on all pins but pin 14. (because of the ground-plane inside the board)
I removed the tin from the holes, and then, using a small pointed pair of pliers, I wiggled the pins one by one from left to right, to make sure they were loose inside the holes before pulling on the chip.
To remove the Dallas I applied the soldering iron to pin 14 while carefully pulling the Dallas out.

After that I placed a socket on the board, I choose the double action flat surface type of socket, because they seem to work a bit better with pins of unequal thickness. (tin residue on the used Dallas)
After that, the moment of truth was, will it still have calibration info in it??? Yes!! (I am a happy bunny right now!)

And now the final part: cooling of the U800.
The consensus seem to be, that the TekTronix made chips are "better" in terms of failing on the long term.
Mine is not getting hot, but it may have to do whem touching the chip is is just doing almost nothing?
Maybe when the scope is running on a very high frequency with a high repetition rate, it may get hot due to more capacitive load??

Anyway, I decided to help this little chip a bit.
What I did was, I removed the nut where the metal tab from under the chip is, and made a brass (for thermal conductivity) bushing the same height as the remaining part of the chip.
So basically, I try to guide the heat through this bushing to the top, and there transfer it to a cooling element.
I also put some thermal conductive grease on top of the chip, although this may be of little effect.
The cooling I found at Mouser's, it is a double to-220 part.

I will start adding pictures to show what I did.

Un saudo,

Satbeginner (Leo)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on March 24, 2017, 01:36:00 pm
And now the final part: cooling of the U800.
The consensus seem to be, that the TekTronix made chips are "better" in terms of failing on the long term.
Mine is not getting hot, but it may have to do whem touching the chip is is just doing almost nothing?
Maybe when the scope is running on a very high frequency with a high repetition rate, it may get hot due to more capacitive load??

Anyway, I decided to help this little chip a bit.
What I did was, I removed the nut where the metal tab from under the chip is, and made a brass (for thermal conductivity) bushing the same height as the remaining part of the chip.
So basically, I try to guide the heat through this bushing to the top, and there transfer it to a cooling element.
I also put some thermal conductive grease on top of the chip, although this may be of little effect.
The cooling I found at Mouser's, it is a double to-220 part.

I will start adding pictures to show what I did.

Un saudo,

Satbeginner (Leo)

Be careful. The studs that secure U800 are NOT at ground potential. I may be mistaken but I think each stud is at a different potential. So you could easily cause a short. The heatsink modifications I've seen for U800 are glued to the top of the chip away from the studs. So check what you've done very carefully or you might have magic smoke.   
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on March 24, 2017, 01:39:46 pm
I thought the Maxim dies were not specific to the U800 but for the other custom chips, U400's maybe

I've read that when Tek stopped manufacture of their own custom dies Maxim took over and that includes U800. If I'm wrong someone correct me.   
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on March 24, 2017, 01:47:33 pm
and funny enough, one of the 15 Ohm resistors went up to 4968 Ohm!! without any markings or change of color.

Leo, which resistor is that ?

No markings ? You still have it ? Photo please.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on March 24, 2017, 01:50:37 pm
Be careful. The studs that secure U800 are NOT at ground potential. I may be mistaken but I think each stud is at a different potential. So you could easily cause a short. The heatsink modifications I've seen for U800 are glued to the top of the chip away from the studs. So check what you've done very carefully or you might have magic smoke.

That studs (or embedded bolts ?) is -5 (negative five) volts.

Posted this at -> post #2 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg70295/#msg70295) at the beginning of this thread, yep, I measured it with DMM.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Satbeginner on March 24, 2017, 03:05:52 pm
Be careful. The studs that secure U800 are NOT at ground potential. I may be mistaken but I think each stud is at a different potential. So you could easily cause a short. The heatsink modifications I've seen for U800 are glued to the top of the chip away from the studs. So check what you've done very carefully or you might have magic smoke.

That studs (or embedded bolts ?) is -5 (negative five) volts.

Posted this at -> post #2 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg70295/#msg70295) at the beginning of this thread, yep, I measured it with DMM.

Sorry, my bad, wrong post!!


Just one of the 1/4W resistors used at the line input filter
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Satbeginner on March 24, 2017, 03:09:48 pm
And now the final part: cooling of the U800.
The consensus seem to be, that the TekTronix made chips are "better" in terms of failing on the long term.
Mine is not getting hot, but it may have to do whem touching the chip is is just doing almost nothing?
Maybe when the scope is running on a very high frequency with a high repetition rate, it may get hot due to more capacitive load??

Anyway, I decided to help this little chip a bit.
What I did was, I removed the nut where the metal tab from under the chip is, and made a brass (for thermal conductivity) bushing the same height as the remaining part of the chip.
So basically, I try to guide the heat through this bushing to the top, and there transfer it to a cooling element.
I also put some thermal conductive grease on top of the chip, although this may be of little effect.
The cooling I found at Mouser's, it is a double to-220 part.

I will start adding pictures to show what I did.

Un saludo,

Satbeginner (Leo)

Be careful. The studs that secure U800 are NOT at ground potential. I may be mistaken but I think each stud is at a different potential. So you could easily cause a short. The heatsink modifications I've seen for U800 are glued to the top of the chip away from the studs. So check what you've done very carefully or you might have magic smoke.

Hi,

thanks for your response, in the picture you can see this cooler stays far away from any surrounding part, I also have like 8-9 mm from the case.
Although my U800 stayed cool, I just wanted to help it a little by conducting heat away from the chip.
The spring washers are no good in doing this, but -my thoughts- a solid brass ring might help, and also cooling the chip -although plastic- itself a bit.

I never liked glue and heatsinks, in my book they always end up somewhere loose in the device... ;-)

Un saludo,

satbeginner (Leo)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Satbeginner on March 24, 2017, 03:14:16 pm
and funny enough, one of the 15 Ohm resistors went up to 4968 Ohm!! without any markings or change of color.

Leo, which resistor is that ?

No markings ? You still have it ? Photo please.

Hi,

it was just one of the 1/4W resistors used in the line input filter.

Un saludo,
Satbeginner (Leo)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: cheeseit on March 24, 2017, 06:25:38 pm
Must be either R1010 or R1019. Both were bad in one of my 2465B, one was open and the other measured 68K, but both had visible signs although not that easy to see.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on March 24, 2017, 06:44:12 pm
Must be either R1010 or R1019. Both were bad in one of my 2465B, one was open and the other measured 68K, but both had visible signs although not that easy to see.

The problem in my 2465 was R1016. It was easy to determine, since it was missing. So was a circular patch of PCB pre-preg, and C1016 was not a cuboid.

Tektronix designers thoughtfully provided a big pointer to this, in the form of an irregular large black marking on the PCB and a smoke signal that was visible from outside the case.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Satbeginner on March 24, 2017, 08:23:53 pm
Must be either R1010 or R1019. Both were bad in one of my 2465B, one was open and the other measured 68K, but both had visible signs although not that easy to see.

It was R1010, now this one and R1019 both replaced with 2W ceramic ones.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Satbeginner on March 25, 2017, 10:41:23 am
And now the final part: cooling of the U800.
The consensus seem to be, that the TekTronix made chips are "better" in terms of failing on the long term.
Mine is not getting hot, but it may have to do whem touching the chip is is just doing almost nothing?
Maybe when the scope is running on a very high frequency with a high repetition rate, it may get hot due to more capacitive load??

Anyway, I decided to help this little chip a bit.
What I did was, I removed the nut where the metal tab from under the chip is, and made a brass (for thermal conductivity) bushing the same height as the remaining part of the chip.
So basically, I try to guide the heat through this bushing to the top, and there transfer it to a cooling element.
I also put some thermal conductive grease on top of the chip, although this may be of little effect.
The cooling I found at Mouser's, it is a double to-220 part.

I will start adding pictures to show what I did.

Un saludo,

Satbeginner (Leo)

Be careful. The studs that secure U800 are NOT at ground potential. I may be mistaken but I think each stud is at a different potential. So you could easily cause a short. The heatsink modifications I've seen for U800 are glued to the top of the chip away from the studs. So check what you've done very carefully or you might have magic smoke.

Hi,

thanks for your response, in the picture you can see this cooler stays far away from any surrounding part, I also have like 8-9 mm from the case.
Although my U800 stayed cool, I just wanted to help it a little by conducting heat away from the chip.
The spring washers are no good in doing this, but -my thoughts- a solid brass ring might help, and also cooling the chip -although plastic- itself a bit.

I never liked glue and heatsinks, in my book they always end up somewhere loose in the device... ;-)

Un saludo,

satbeginner (Leo)

I found this message thread in the Tekscopes Yahoo group.
Does make you think...

https://groups.yahoo.com/neo/groups/TekScopes/conversations/topics/120573 (https://groups.yahoo.com/neo/groups/TekScopes/conversations/topics/120573)

It appears there are 2 main causes for a U800 to die:
- heat, and as a result of that the internal separation of the chip and the substrate (therefor also torque is very important!), and
- internal arcing of the tube...

Well, I hope if the scope and the tube are old, the tube will be properly conditioned so the arcing will be gone by now.

In that thread I also found some people who did the same kind of cooling as I did.

Un saludo,

Satbeginner (Leo)

 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on March 25, 2017, 02:40:52 pm
You can't view that link to the Tek Yahoo group unless you are a member. I was a member but for reasons that I will keep to myself I left the group. With one exception I found the blog to be more helpful in fixing issues with my 2465. And perhaps that's due to most of my issues were with the DMS version that has Counter/Trigger and DMM options which I'm finding are not that common.

U800: Opinions range from there is no issue to the sky is falling. My take....depends if you are dealing with Tek die or Maxim die and you must be proactive in keeping the cooling system serviced. Make sure all vent holes are clear and the fan is operating properly. I tend to fall into the position that if it ain't broke, leave it alone. In my case it's been there since 1985 and works fine. Would an additional heatsink help? I'm sure it would but there are risks. Once risk I see is accidentally applying an uneven torque to the mounting studs. And as far as I know the service manual does not list a torque spec for those studs. Too risky IMHO especially if the prime failure seems to be die separation. But I certainly won't fault anyone who want's to go this route.   
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: peter-h on March 28, 2017, 09:52:50 pm
I have open up mine at last. Some chips are date coded 1997. The battery backed up SRAM is 1995.

I believe this scope was "overhauled" in some way about 10 years ago, by the refurbish company which I bought it from.

Some pics here - the site crashes when I try to upload anything sizeable.

http://peter-ftp.co.uk/screenshots/2017-03-28_225205.jpg (http://peter-ftp.co.uk/screenshots/2017-03-28_225205.jpg)
http://peter-ftp.co.uk/screenshots/2017-03-28_225239.jpg (http://peter-ftp.co.uk/screenshots/2017-03-28_225239.jpg)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on March 28, 2017, 10:30:23 pm
I have open up mine at last. Some chips are date coded 1997. The battery backed up SRAM is 1995.

I believe this scope was "overhauled" in some way about 10 years ago, by the refurbish company which I bought it from.

Some pics here - the site crashes when I try to upload anything sizeable.

http://peter-ftp.co.uk/screenshots/2017-03-28_225205.jpg (http://peter-ftp.co.uk/screenshots/2017-03-28_225205.jpg)
http://peter-ftp.co.uk/screenshots/2017-03-28_225239.jpg (http://peter-ftp.co.uk/screenshots/2017-03-28_225239.jpg)
You're constrained by the forum 1Mb file size limit, compress the size of your pics to under 1 Mb and much less unless great detail is needed. In most cases 100Kb is plenty big enough.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on March 29, 2017, 02:01:05 am
I have open up mine at last. Some chips are date coded 1997. The battery backed up SRAM is 1995.

I believe this scope was "overhauled" in some way about 10 years ago, by the refurbish company which I bought it from.

Some pics here - the site crashes when I try to upload anything sizeable.

http://peter-ftp.co.uk/screenshots/2017-03-28_225205.jpg (http://peter-ftp.co.uk/screenshots/2017-03-28_225205.jpg)
http://peter-ftp.co.uk/screenshots/2017-03-28_225239.jpg (http://peter-ftp.co.uk/screenshots/2017-03-28_225239.jpg)

Interesting, your Maxim U800 date code is 95 ? Manufactured in 1995 ?

Anyone know approx. when Tek stopped producing 2465B/2467B scopes ?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: peter-h on March 29, 2017, 06:42:53 am
"There are 6 cascaded 74F164 shift registers that drive the LEDs directly and are loaded by LED CLK and LED DATA."

These are not on the CPU board and are probably quite hard to get to. I have dismantled the "easy" covers...

The capacitors look OK
http://peter-ftp.co.uk/screenshots/2017-03-29_073937.jpg (http://peter-ftp.co.uk/screenshots/2017-03-29_073937.jpg)
http://peter-ftp.co.uk/screenshots/2017-03-29_074006.jpg (http://peter-ftp.co.uk/screenshots/2017-03-29_074006.jpg)

The scope shows 1995 all over the place
http://peter-ftp.co.uk/screenshots/2017-03-29_074103.jpg (http://peter-ftp.co.uk/screenshots/2017-03-29_074103.jpg)
but there are some 1997 chips in there. So maybe it was built up from modules sitting on the shelf.

Now I need to find out where to check the supply voltages, and how to get to the shift registers that drive the display. It appears that to get access to the front panel PCB one has to peel off the front label (there seem to be screws under it) which is going to be awfully messy.

Thanks for the 1MB image size input. For now I am using screenshots on my FTP site, which should not go missing because I use it for various other stuff.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on March 29, 2017, 07:01:46 am
Now I need to find out where to check the supply voltages,

The J119 for all voltage rails.

Don't forget to get a big fan to blow the whole A1 board while you're working on it, remember those poor hybrids.

(https://www.eevblog.com/forum/testgear/2467-no-power/?action=dlattach;attach=58502;image)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: peter-h on March 29, 2017, 07:40:55 am
Super many thanks!
All are in spec except the +10V which is 9.987V - verified with two meters one of which is a HP3468A which has been checked against a 0.01% reference.

http://peter-ftp.co.uk/screenshots/2017-03-29_084017.jpg (http://peter-ftp.co.uk/screenshots/2017-03-29_084017.jpg)
The missing minus sign on the last line of that pic is my mistake :)

(http://peter-ftp.co.uk/screenshots/2017-03-29_084017.jpg)

The hybrid chips didn't get particularly warm - I would estimate +45C. And the big plastic one with the two screws was not warm at all.

The 74F164 chips are indeed on the front panel PCB - A6

(http://peter-ftp.co.uk/screenshots/2017-03-29_085119.jpg)

Now I am trying to find the clock and data signals going to the front panel, without having the dismantle the front panel which is obviously complicated.

Would it be around here?

(http://peter-ftp.co.uk/screenshots/2017-03-29_085740.jpg)

Obviously I am hoping the fault is with the clock and data rather than after the shift registers.

(http://peter-ftp.co.uk/screenshots/2017-03-29_090527.jpg)

I found the LED clock on the CPU board as pin 16 J652

(http://peter-ftp.co.uk/screenshots/2017-03-29_094447.jpg)

but can't find the LED DATA signal.

Anyway, U2550 (HC138) has +5V on pin 14 which is the LED CLOCK, so definitely there is no clock signal to the LEDs. Other outputs are waggling OK. I will try changing this chip.

EDIT: I found there is indeed no clock unless the front panel is operated. Then I do see pulses, so the clock is OK. I just need to find where the LED data is... The troubleshooting flow chart refers to P652 pin 13 and pin 5 (for LED clock and data) but thise don't correspond to the circuit. Also the IDC connectors on the CPU board can't be probed; one has to find the signals on a chip.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 29, 2017, 02:19:45 pm
...
but can't find the LED DATA signal.
When you say you "can't find" it, do you mean there's no signal or you can't locate it on the schematic?  LED DATA is on the snippet you posted; outlined below.

When checking signals, make sure they are true TTL, low < 0.7V and high > 2.1V.  If you're having a power issue or a chip somewhere without power, it can lead to strange logic levels.  In this case, LED CLOCK and DATA are coming from HCT series chips (CMOS TTL) so they should be very near 0V for low and 5V for high.

Maybe you could share some screen captures?

You can see in the snippet that CONT DATA (control data) signal is the same as LED DATA.  CONT DATA, among other things, is used to control the attenuator relays.  Can you hear the relays clicking if you cycle through the V/div settings?  That would be a good indication CONT DATA, and therefore LED DATA, is ok as far as U2210.

I would also check for continuity from GND to J652.19, and from +5V to J652.20 to make sure the front panel is getting power (or at least getting to J652).  Use the power connector where you measured the incoming voltages as your reference points.

As you're poking around, keep in mind a lot of failures in these circa scopes is caused by bad PC traces.  Don't assume that if a signal or power is ok in one place, then it's ok everywhere.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: peter-h on March 29, 2017, 02:33:38 pm
Mark - many thanks.

"When you say you "can't find" it, do you mean there's no signal or you can't locate it on the schematic?  LED DATA is on the snippet you posted; outlined below."

I did find the likely LED DATA signal later :) Pin 5 J652. I need to probe it on pin 2 U2210.

Is the LED clock definitely pin 16 J652?

"Maybe you could share some screen captures?"

Stand by - in a few hours.

"You can see in the snippet that CONT DATA (control data) signal is the same as LED DATA.  CONT DATA, among other things, is used to control the attenuator relays.  Can you hear the relays clicking if you cycle through the V/div settings?  That would be a good indication CONT DATA, and therefore LED DATA, is ok as far as U2210."

Yes the buttons seem to work for clicking various relays e.g. the input AC or DC or GND mode. So it has to be the clock - or something actually on the front panel.

"I would also check for continuity from GND to J652.19, and from +5V to J652.20 to make sure the front panel is getting power (or at least getting to J652).  Use the power connector where you measured the incoming voltages as your reference points."

How do you get to the front panel? I can see some screws on the bottom, but there are many buttons etc to remove. At that point I would rather pay someone who has done this before, a couple of hundred GBP... I am in the UK.

"As you're poking around, keep in mind a lot of failures in these circa scopes is caused by bad PC traces.  Don't assume that if a signal or power is ok in one place, then it's ok everywhere."

Sure... OK. The internals all seem very clean on this one.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 29, 2017, 03:00:05 pm
Is the LED clock definitely pin 16 J652?
I think so.  I would believe the schematic before the troubleshooting chart.  The J652.13 referenced in the chart is already spoken for as ROW 0 at the bottom right corner of schematic <2>.

You could unplug J652 and do a quick continuity check from J652.16 to U2550.14 to confirm.

Quote
How do you get to the front panel? I can see some screws on the bottom, but there are many buttons etc to remove. At that point I would rather pay someone who has done this before, a couple of hundred GBP... I am in the UK.
There are step-by-step instructions starting on page 6-28 in the maintenance section.  I've never had the privilege of needing to remove the front panel.  If there are any tricks to it perhaps someone who has done it can post.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: peter-h on March 29, 2017, 05:35:24 pm
I do get 0V to +5V transitions on the clock and data.

Regarding the continuity check, where is pin 1 of J652? :) I assumed pin 1 is the coloured conductor on the ribbon cable. There is continuity OK.

So the LED signals seems OK, which is bad news.

I am pretty sure what I am seeing on the LEDs is that they are all dimly lit but that is intentional - it is a form of backlighting. Then, the selected mode is illuminated brightly, and that is what is not happening.

I have been trying to scope it with a TDS2004B which is a really horrible digital scope and it is really difficult to get it to show any low duty cycle signals. I just don't know how to use it. It was used purely as an FFT display on a vibration analyser. So I am using the 2465B to probe itself and that works. All the front panel switches and modes seem to work, although of course one cannot see the one selected; one has to go to the top of a column with lots of presses and then e.g. (on the trig mode) press 3 times to get NORM :)

So the front panel will need dismantling... I am not sure I have the enthusiasm for that.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: james_s on March 29, 2017, 05:56:31 pm
It sounds like some noise is getting into the shift register clocking to the LEDs. You should be able to capture a run of the clock and data lines with the DSO and see pretty clearly which LEDs should be on, the data is shifted out as a chunk of 48 bits, so you should clearly see groups of 48 clock pulses with the data line transitioning high or low for each LED lit. If you force the LED data line either low or high, all LEDs should either light full brightness or go out. I don't think the dim glow is normal, none of my Tek scopes do that.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Satbeginner on March 29, 2017, 06:02:15 pm
I recently removed my front panel to replace one of the plastic extension shafts.

I had to remove the surrounding plastic front trim by removing the screws all around the scope.

After that I removed the two flatcables who plug into the A5 board.

Now you can slide out the entire control unit.

That can be divided into the two boards by removing the 4 screws.
Watch out you do not damage the fragile flatcables.

Succes,

Satbeginner
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: peter-h on March 29, 2017, 06:41:03 pm
So... one should be able to access the front panel electronics without having to remove all the buttons? In that case I will give it a go.

There are definitely not 48 pulses - unless there are long gaps between some of them. I will try to capture it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Satbeginner on March 29, 2017, 06:44:16 pm
It comes out as a separate unit, see in this picture.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 29, 2017, 06:48:38 pm
My 2465 doesn't have dimly lit indicators either.  If you examine the schematic, the LEDs should be completely off since they are each driven by a single output of the 74F164's

Can you get the TRIG'D LED to light with normal brightness?  It shares the +5VD with the other LEDs but is driven to ground by a separate signal line.

Maybe the 74F164's are without a ground connection?  Just a guess.  It has to be something in common to all the LEDs.  james_s has an interesting suggestion to try to force all the LEDs on.

To capture the entire 48 bit sequence, you should be able to trigger on the LED CLOCK with the TDS2004B set to single.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 29, 2017, 07:02:54 pm
Actually, in looking more closely at your front panel photo in :

  https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1161319/#msg1161319 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1161319/#msg1161319)

Would it be accurate to say that *some* of the LEDs are normal brightness?  For example, Ch1 and Ch2 "50ohm DC", all of the MODE LEDs, trigger READY, x10 MAG, plus some others.

Many of the LEDs share pullups to +5VD.  This is ok in normal operation since not more than one is expected to be on at a time in some of the groups.  But in this failure, if all LEDs are on via the 74F164's, some groups will appear dimmer since they're wired to a single pullup.

The LEDs I've named above have their own dedicated pullup, so if they are on they should be normal brightness.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: peter-h on March 29, 2017, 07:54:20 pm
"Can you get the TRIG'D LED to light with normal brightness?  It shares the +5VD with the other LEDs but is driven to ground by a separate signal line."

Yes indeed I can; the manual says this one is driven directly.

If I bang the front panel, the brightness of the LEDs all changes. So it does look like a ground or some such has come off somewhere.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: james_s on March 29, 2017, 07:57:19 pm
Download the manual for the DSO and sit down for an hour to learn to properly use it, that is time well spent and will make your life much easier. At least work out how to take single shot captures and set up the triggering. The TDS2004B is not particularly high bandwidth but it's still a very capable instrument that is well worth having and once you are proficient with it you will be able to sit down and use pretty much any other Tek DSO. Single shot captures are fantastic, you can use them to check the rise time and overshoot of power rails at turn-on, capture transient events, capture and analyze bitstreams like the LED data we are looking at here, once you learn how to do that you'll wonder how you ever got by without it.

Edit:
Just saw your latest reply. If tapping on the panel has an effect then something is definitely loose. Pop off the bezel and pop out the whole panel, usually there's a clip you push in on the side and it just pops out. Poke around with an insulated stick and see if you can find a cracked solder joint. I think you're very close to a solution here.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: peter-h on March 29, 2017, 08:23:50 pm
I got the panel off

(http://peter-ftp.co.uk/screenshots/2017-03-29_211816.jpg)

but to pull off the PCB so I can access the components on top of it I need to use an allen key on the large knobs. I have that but can't get the large (timebase) knob off even if I remove the grub screw completely.

If you look closely at that PCB you can see somebody has been there before, resoldering a row of joints along the centre of it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Satbeginner on March 29, 2017, 08:25:14 pm
My time base knob has two Allen bolts......
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: james_s on March 29, 2017, 08:28:18 pm
You may not need to get the board off, look closely for cracked solder joints, start at the header where the ribbon cable plugs in and then follow the clock and data lines to the shift register. I suspect the clock is floating and picking up noise, randomly clocking at a much higher rate.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: peter-h on March 29, 2017, 08:37:41 pm
I am stuck with the two smaller knobs (volts/div). They need Imperial allen keys which I don't have. So I made one by grinding down a metric one.

(http://peter-ftp.co.uk/screenshots/2017-03-29_213604.jpg)

I should be able to plug these two PCBs into the processor board, presumably :) I hope they don't need additional grounding.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: peter-h on March 29, 2017, 08:44:48 pm
Well, I did that

(http://peter-ftp.co.uk/screenshots/2017-03-29_214423.jpg)

and while the pots and switches work, the LEDs are all dark.

A quick check shows ground continuity to the 74F164s but their +5V is not joined to the +5V of the HCT chips on the CPU board. There is about 200 ohms between those two +5V rails. Maybe that's intentional.

I need to be very careful now. One slip-up with the thing powered and it will likely be a write-off.

For some reason I can't find the schematic of this PCB... My scope is B057050.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: peter-h on March 29, 2017, 09:21:08 pm
I think I found something:

The two +5V rails ARE supposed to be the same one

(http://peter-ftp.co.uk/screenshots/2017-03-29_221959.jpg)

but there is about 1k between them. That is pin 20 of P652, and even across the cable itself it is broken.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: peter-h on March 29, 2017, 09:32:21 pm
JOB DONE

(http://peter-ftp.co.uk/screenshots/2017-03-29_223117.jpg)

You can see the yellow wire bringing the +5V from the CPU board, in the top right.

Now I have to put this damned thing together :)

THANK YOU ALL!

I must confess to reading the RTB2004 thread but the pricing is crazy. I also really love analog scopes. Mostly I have used Iwatsu which just keep on going... like this logic analyser

(http://peter-ftp.co.uk/screenshots/2017-03-29_223424.jpg)

which was purchased new for about GBP 8k c. 1985. The two probes were stolen but I got the schematic of it and built new ones which plug into the IDC connector in the front.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 29, 2017, 10:10:08 pm
You can see the yellow wire bringing the +5V from the CPU board, in the top right.

Now I have to put this damned thing together :)
Great; glad you got it working!

But did you find the actual break or is the jumper your final solution?

If you haven't found the break, I'd really recommend that you do.  If it's the ribbon cable then replace it, or if it's a broken trace somewhere you should find out why it's broken.  Murphy says it will come back to get you at the most inopportune time.

You had mentioned previously that the AC/GND/DC/GND/DC push buttons didn't seem to work.  Are they ok now too?  Once you reach the front panel, the buttons are electrically separate from the LEDs.  The ribbon cable is one thing in common.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: peter-h on March 29, 2017, 10:43:56 pm
The break was within the ribbon cable. It was at one end or the other; the IDC connection was obviously marginal (as they often are). It was not a PCB track break. I probed it on the cable itself and it was totally open. So the front panel was getting some current into its +5 rail via the other signals!

I don't have a spare 20 way cable so I just put in that +5V wire.

It is all working, including the AC/GND/DC/GND/DC push buttons. They were working all along; just very confusing without the LED indication.

One unrelated thing: is there any adjustment for the focus between the upper and lower part of the CRT? This photo doesn't show it too well but the upper stuff is less focused

(http://peter-ftp.co.uk/screenshots/2017-03-29_234003.jpg)

I doubt there is. In the 1970s I built some oscilloscopes, using ancient ex-mil CRTs and finally with a Mullard scope tube, PDA, and solid state deflection plate drivers. I recall using the uA733 differential video chip, which still exists! More than about 20MHz was nontrivial though. But there was never any control over the focus, although in principle one could modulate the focus voltage according to the Y deflection plate drive. I think TVs did that but they used very wide deflection angles.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: james_s on March 29, 2017, 11:00:08 pm
Just make a new cable, you can buy the connectors for very little and a piece of ribbon cable, I use a bench vise to crimp them, takes just a few minutes to make a cable. Glad to hear you tracked down the problem though.

Yeah DSOs are expensive, but I was under the impression you already had the TDS scope? I've always been an analog scope guy myself but since acquiring a really good older Tek DSO it has become my primary scope. Being able to capture and examine waveforms is just incredibly useful.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 29, 2017, 11:04:40 pm
One unrelated thing: is there any adjustment for the focus between the upper and lower part of the CRT? This photo doesn't show it too well but the upper stuff is less focused
There's some interplay between the front panel ASTIG and FOCUS controls.  I would try those first.

There's also a number of internal adjustments that are described starting on page 5-7, including an Edge Focus control which may help.

But be aware that messing with some of the CRT adjustments can alter where the beam lands in relation to the graticule.  Once you reach an optimum display there are later cal steps that recenter everything if needed.  I would carefully mark everything with a fine Sharpie before moving any adjustments in case you need to get back to the beginning.

Almost all the adjustments interact with each other.  It will drive you crazy trying to get it perfect.  I know it took me a couple of hours until it was "good enough".
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on March 30, 2017, 02:01:16 am
One unrelated thing: is there any adjustment for the focus between the upper and lower part of the CRT? This photo doesn't show it too well but the upper stuff is less focused

The 2465 has an edge focus adjustment so at the least it should be possible to even the focus out somewhat.  The focus also tracks the intensity and there is an adjustment for that but I do not think it is adjusted for beam position because that would be difficult to do at such a high bandwidth.  The theory section in the service manual should say.

Yeah DSOs are expensive, but I was under the impression you already had the TDS scope? I've always been an analog scope guy myself but since acquiring a really good older Tek DSO it has become my primary scope. Being able to capture and examine waveforms is just incredibly useful.

I have always understood the advantages of a DSO but would rather have a reliable instrument that I understand well than a list of questionable features marketing checked off that I can do without so my go-to DSO is a 2230/2232 unless I need higher bandwidth.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: peter-h on March 30, 2017, 05:58:32 am
"Just make a new cable, you can buy the connectors for very little and a piece of ribbon cable, I use a bench vise to crimp them, takes just a few minutes to make a cable. Glad to hear you tracked down the problem though."

I have put it back together now, but the problem is that IIRC that cable is soldered at the front panel end, and with a PTH board there is a very high risk of pulling off a pad on the topside, unless one can melt all 20 at the same time. I have a turret mill and could machine up a copper block with 20 holes on a 0.1" grid... :) Anyway next time I will know where to look. You people have been incredibly helpful. I co-run a forum too (EuroGA) and it isn't an easy job!

"Yeah DSOs are expensive, but I was under the impression you already had the TDS scope? I've always been an analog scope guy myself but since acquiring a really good older Tek DSO it has become my primary scope. Being able to capture and examine waveforms is just incredibly useful."

The TDS scope is horrible. The user interface is slow. You turn a knob and it takes close to a second before anything happens. This applies to the commonly used stuff like vertical position. Who designed this (I've been doing HW and SW since ~ 1975) should be shot. Maybe it uses a 4004 running Java? And it wasn't that cheap - about GBP 1000. It was bought for vibration measurement in a light aircraft - http://peter2000.co.uk/aviation/vibration/index.html (http://peter2000.co.uk/aviation/vibration/index.html) - where I wanted a portable scope but the battery powered ones (well, the ones which wer not near-useless) cost a lot more. Also the screen resolution is rubbish so narrow pulses show up as a line of pixels hanging down from 5V, sometimes all the way down to 0V and sometimes halfway down, with the latter indicating that there is a short or bus contention etc. It's a toy... I hoped it would be generally usable but it isn't.

If I was buying a DSO it would have to be 200MHz at least and have a really high-res display. The RTB2004 looks like it would be nice but who knows whether the UI is fast.

Of course the storage aspect of a DSO is great. But then I see the way they load up the price if you want data analysis options :) This is off topic now - there is the long RTB2004 thread. I wonder if that one can be bought as a base model and hacked to 300MHz?

BTW does anybody want hi-res (15MB) photos of the innards of my Tek scope before I put the covers on it tonight? I can put them on a FTP site, permanently.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: peter-h on March 30, 2017, 07:29:51 am
One more Q: is the fan temperature controlled? It is very noisy. The supply voltage was measured at 9V so it is a 12V Nippon fan, but still very noisy. I routinely replace fans in PCs with lower noise versions, and the old HP/Tek gear all had very noisy fans.

The fan used is 80mm standard size but slightly unusual being 20mm thick (today most are 15 or 25mm).
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: james_s on March 30, 2017, 03:53:56 pm
It sounds like you have the DSO set to a low horizontal rate or a high capture rate, this will reduce the waveform rate so the waveform on the screen does not update until the next capture is ready to be displayed. There should be a small indicator on the edge that moves in real time though, then the waveform will appear in the new location on the next update. This is just how these scopes work, it's fine once you understand why it behaves the way it does. Mine is 1GHz but honestly most of the time 60MHz would be enough. It's way more than enough for diagnosing things like the LED problem you just dealt with. If you really don't like the DSO I would happily take it off your hands :D

Yeah I forget sometimes that not everyone has good desoldering gear. I use a Hakko 808 vacuum gun for this sort of thing and it makes it trivial to desolder stuff like that. I could pull that ribbon cable in under a minute with very little risk of damage but it's the sort of thing that is expensive if it isn't something you would use frequently.

I'm not sure about that particular scope, but none of the Tek gear I've worked with has temperature controlled fans. I suspect you'd be just fine replacing it *if* you are certain you get something that moves as much air. Those scopes are full of fancy hot-running hybrid ICs that are made of pure unobtanium.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: peter-h on March 30, 2017, 04:54:18 pm
The fan in my scope is a Nidec D08A [D08A-12TH] and the data sheet is here: http://www.nidec.com/en-Global/product/fan/category/F010/G070/P2000261/ (http://www.nidec.com/en-Global/product/fan/category/F010/G070/P2000261/)

The spec is actually not bad at all, for noise and airflow. I guess it is noisy because it is mounted directly to the metal chassis without any vibration isolation.

I will happily have a play with the DSO - thanks :)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: james_s on March 30, 2017, 04:59:44 pm
It's possible the fan is making more noise that it should be. Have a close look at the blades for built up crud, I've seen fans get so much dust and grime collected that it throws off the balance and they vibrate.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: peter-h on March 30, 2017, 05:14:24 pm
Well, guess what? I found the fan is broken. One of the three plastic "legs" which hold the motor in place was cracked. Something hit it, perhaps in transit. Easy to repair with epoxy.

Would Tektronix have used a Japanese fan which is still in production today, 22 years later? I reckon somebody changed it. This scope has been repaired. Somebody has resoldered the joints to the three shaft encoders / multiposition rotary switches. I paid GBP 2k for this scope some 10-15 years ago. The cosmetic condition was (and is) as new and the internals are spotless.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: james_s on March 30, 2017, 06:31:55 pm
I'm not sure what fan Tek used in the 2465B but my TDS300 and TDS400 series scopes all have a Japan Servo "DC Centaur" CUDC12D4 fan. The service manual for the 2465B probably lists the part number.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: peter-h on March 31, 2017, 09:41:47 pm
With a repaired fan, and the fan retaining plate modded (by bending) so it doesn't push against the fan hard (that pushes the fan motor against the scope chassis) the fan is much quieter. The motor was rubbing against the chassis.
Title: U800 chips and A1 board layers view
Post by: BravoV on May 19, 2017, 06:07:59 pm
Mined some gems lately ....  :-DD

I just leave these few close up shots here, hopefully will aid someone, someday that who want to desolder, replace or do some surgery at their U800 gem chip or A1 board repair.

Minor notes, from the cut view, A1 board is clearly a 4 layers board.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on May 19, 2017, 06:45:32 pm
Obviously you have some junk units laying around. By any chance do you have a 2465 Buffer board with Option 01 (DMM) and any combo of options 06, 09, 10? Tek P/N 670-7830-05 or 670-7830-09. I'd salvage the EAROM off it to try to fix a checksum error on mine.

Probably not...it's not very common but I figured I'd ask.  :-+ 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on May 20, 2017, 12:06:42 pm
Obviously you have some junk units laying around. By any chance do you have a 2465 Buffer board with Option 01 (DMM) and any combo of options 06, 09, 10? Tek P/N 670-7830-05 or 670-7830-09. I'd salvage the EAROM off it to try to fix a checksum error on mine.

Probably not...it's not very common but I figured I'd ask.  :-+

Wish I have that, sorry.  :-//

No, I'm not the one who butchered those A1 boards, no way in hell I would do that.  :'(

Actually they're sort of "souvenir" gift from a friend who visited abroad, and brought me these as he aware of the U800 obsession, at least me as a 2465B owner.  :palm:
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on May 20, 2017, 05:05:45 pm
Obviously you have some junk units laying around. By any chance do you have a 2465 Buffer board with Option 01 (DMM) and any combo of options 06, 09, 10? Tek P/N 670-7830-05 or 670-7830-09. I'd salvage the EAROM off it to try to fix a checksum error on mine.

Probably not...it's not very common but I figured I'd ask.  :-+

Wish I have that, sorry.  :-//

No, I'm not the one who butchered those A1 boards, no way in hell I would do that.  :'(

Actually they're sort of "souvenir" gift from a friend who visited abroad, and brought me these as he aware of the U800 obsession, at least me as a 2465B owner.  :palm:

No problem, appreciate the response. I've been experimenting with different schemes in an attempt to fix the checksum error. One experiment was to provide standby power to the EAROM when the scope is powered off. It was partially successful in that I was able to get the scope to pass all tests consistently upwards of 6 hours rather than for approx 10 minutes after performing the DC balance check which clears the checksum in both the A5 board and the Buffer board. But it was inconsistent. Sometimes it wouldn't clear at all.

As I've mentioned in prior entries in this thread I've noticed no negative effects with the checksum problem on the Buffer board. It clears when I press the A/B/Menu switch. And the DMM and Counter options calibrated with no issues. It's just a minor annoyance.

I keep an eye on E-bay but so far nothing has shown up.     
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on May 20, 2017, 05:13:59 pm
Yeah, those option boards alone are rare as hen's teeth as Dave said, wish you good luck.  :-+
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SeanB on May 21, 2017, 07:32:55 pm
At least with the sawn board you can be sure the U800 is not a fake chip with more certainty, but the bigger question is if they work still, and if not if they are repairable with new package and leadwires after they are decapped.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on May 22, 2017, 08:49:40 am
At least with the sawn board you can be sure the U800 is not a fake chip with more certainty, but the bigger question is if they work still, and if not if they are repairable with new package and leadwires after they are decapped.

Yep, I'm curious too, its just my current U800 is working fine.
Title: Tektronix U800 Pads
Post by: BravoV on May 22, 2017, 08:53:55 am
More on the U800 pads and traces as references.

Beware these two photos are in original size, and managed to manually adjust their compression level up to the forum limitation while still have enough details (1 MB each and 2MB total max per post).  >:D

PS : Pardon for few lints as I was running out of lint free wiper.   :P
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on May 22, 2017, 08:59:15 am
Another proof that the U800 cooling design is sort of half baked  ::), the two star rings basically lift the whole IC from the big cooling pad below it, and the only cooling path only thru the other rings at the tab (not pictured here).  :palm:

Second shot is the close up of U800 ( Tektronix 155 0241 02 ) bottom (this is Maxim's one) , the chip die location is obvious.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on May 22, 2017, 11:21:01 am
When I saw how Tektronix mounted these parts, I concluded that somewhere they screwed up the engineering.  The shoulder of the pins prevents the DIPs from sitting flush and even if they did not, DIP leads do not allow enough strain relief for good reliability.  DIP packages designed for heat sink attachment have a very different configuration.  What I think might have worked is a thermally conductive spacer between the package and the board and the right kind of low profile collet socket.

Maybe what they did was sufficient though.  What was the failure rate for these parts while under warranty?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: grumpydoc on May 22, 2017, 11:28:39 am
When I saw how Tektronix mounted these parts, I concluded that somewhere they screwed up the engineering.  The shoulder of the pins prevents the DIPs from sitting flush and even if they did not, DIP leads do not allow enough strain relief for good reliability.  DIP packages designed for heat sink attachment have a very different configuration.  What I think might have worked is a thermally conductive spacer between the package and the board and the right kind of low profile collet socket.

Maybe what they did was sufficient though.  What was the failure rate for these parts while under warranty?
I read somewhere that the original intent was to have the tab in contact with the PCB to provide heatsinking but this didn't work given the stand-off provided by the DIP leads.

Has anyone tried thermal pads under U800?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on May 22, 2017, 11:48:03 am
When I saw how Tektronix mounted these parts, I concluded that somewhere they screwed up the engineering.  The shoulder of the pins prevents the DIPs from sitting flush and even if they did not, DIP leads do not allow enough strain relief for good reliability.  DIP packages designed for heat sink attachment have a very different configuration.  What I think might have worked is a thermally conductive spacer between the package and the board and the right kind of low profile collet socket.

Maybe what they did was sufficient though.  What was the failure rate for these parts while under warranty?

I read somewhere that the original intent was to have the tab in contact with the PCB to provide heatsinking but this didn't work given the stand-off provided by the DIP leads.

Has anyone tried thermal pads under U800?

The funny part though is that they did not even try this.  Using lockwashers as spacers is the last thing I would have considered.

One of the common problems with flange mounted packages is that the base gets bent with the ends being pulled down and any thermal compound pushing up in the center which breaks the die attachment.  This would go double for a narrow DIP package with the fasteners at the ends and its relatively thin base.

The solution is to use a clip which pushes down on the center of the package but that would have worked poorly in this case because of the soldered DIP leads holding the package rigidly in place.  Still, I think it would have been better than the lockwashers although they would have needed to find another way to electrically attach the tabs.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on May 23, 2017, 04:55:09 am
While I agree that the U800 is an unorthodox and possibly flawed design I suspect that the root cause of many failures is improper maintenance of the cooling system. I've done several checks and experiments on the 2465 cooling system design to understand how it functions for reasons that I'll explain later. Here is some of what I've found:

It is important that the ventilation slots on the bottom of the case be kept clear. Those slots are more or less directly below U800. I performed an experiment with smoke to gauge the amount of air drawn into those slots by the cooling fan and it is considerable. For maximum effectiveness I would recommend that the scope always be up on the tilt bail rather than down on it's feet. And certainly not stacked with other hot equipment below it.

Directly in front of the bottom ventilation slots there is a large black heatsink bonded to the outside of the case. This may be a feature of only fully optioned 2465's with the DMM and Counter. I'm not sure. You guys who have non-optioned 2465's would have to chime in. But I did see a 2465 DMS for sale on E-bay where the heatsink was missing and you could clearly see that it was once there.

I wanted to get an idea of how warm the rear metal panel got after several hours operation. So I attached a thermocouple to the panel just opposite the power supply. I applied a 1ns rise time 1Mhz square wave to channel 1 to give the sweep circuits a good workout. The results in the following picture. After 2 hours the temperature rose from 72 degrees F ambient to 97 degrees F and stabilized and rose no higher. Not bad.



The most important part of the cooling system is the fan itself. The 2465 uses a Siemens hall effect sensor motor with a squirrel cage impeller (See pix).  The 2465A and B use a more conventional computer type fan which is easy to service.       

Rear plastic panel removed to show impeller


The Siemens motor is prone to develop screeches and rattles over time. There is a rebuild procedure to install new bushings that is ridiculously complex due to the design of the motor. And replacement motors are unobtainium. See this link for the rebuild procedure.

http://antiqueradios.com/forums/viewtopic.php?f=8&t=235478 (http://antiqueradios.com/forums/viewtopic.php?f=8&t=235478)

My Siemens motor does have a loud rattle. But luckily only for about 20 minutes after power on then it settles down and is whisper quiet. For now it's going to remain in place but I'm sure one of these days it's going to crap out. So I have designed and built a replacement fan assembly ready to install should that happen. It uses a conventional 80 x 80 fan and will totally replace the Siemens assembly. This is the reason for performing the above measurements. It's a set of baseline data that I can use to make appropriate adjustments if I have to install the new fan.

If anyone is interested in seeing the replacement fan design let me know and I'll post it. 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Ed Bray on July 17, 2017, 07:58:55 pm
I bought a 2455B today on ebay, it will arrive tomorrow, there does not seem to be a lot about this model, loads about the 2445B and 2465B.

Got it for a good price (£124 delivered) so hopefully it is not a anchor, the seller states he will take returns so if it does turn out to be bad I'll only lose the shipping costs.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on July 18, 2017, 12:06:37 am
Welcome aboard and also to the forum Ed.

Yeah, that model is rarely seen in the wild, please share few of it's internal photo shoots during your inspection teardown.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Ed Bray on July 18, 2017, 03:47:43 pm
Thanks for the welcome.

The 2455B arrived this afternoon and although it powers up and seems to go through a startup regime there is nothing on the CRT. No trace, no display, nada!

So it's already back in its packaging waiting to be collected for it's journey back. Ah well, back to my IWATSU.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: USMC_Spike on August 18, 2017, 07:33:49 am
My 2465a is not so pristine.
I will be reading intently for some time.

Thank you.

USMC_Spike
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: cvavr on September 18, 2017, 03:35:53 pm
Hello

It is my first post on this forum.
Just bought an old 2467 on ebay and now I am thinking on upgrading it with option 06 CTT.
I have found an A20 670-7830-13 buffer board and an A27 670-7997-01 CTT board.
The problem is that the 2467 requires an A27 670-7997-07 or A27 670-7997-09 CTT board.
The 670-7997-01 is for the 2465. The 2467 is similar to the 2465A.
Looking at the schematics of both -01 and -07 I've notticed that they are identical.
So most likely the difference is the firmware in the U5930 EPROM.
Maybe somebody has the binary image of the U5930 for the CTT boards A27 670-7997-07 or A27 670-7997-09.
Many thanks in advance.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: WastelandTek on October 16, 2017, 04:38:29 pm
Whelp, I just got gifted a vanilla 2445, thankfully in relatively good working order.  There does seem to be something a little wonky in the input coupling relays.  looks like I have some work ahead of me curating this.  Only just started reading but just with a cursory assay of the literature;

>electrolytic and some film caps

>some resistors

>heatsink U800

>construct interface and read out cal data

>develop strategy for eventual memory replacement and reprogramming

>keep eye out for later model rear panel to facilitate eventual fan replacement

have I missed anything obvious?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on October 16, 2017, 05:08:59 pm
Whelp, I just got gifted a vanilla 2445, thankfully in relatively good working order.  There does seem to be something a little wonky in the input coupling relays.  looks like I have some work ahead of me curating this.  Only just started reading but just with a cursory assay of the literature;

>electrolytic and some film caps

The mains input filter caps, definitely. http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf (http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf)

Otherwise I suggest only as necessary (i.e. short circuit tants or too much ripple on voltage rails). Depending on whether you have a 2445/2445a/2445b, it may be beneficial to replace some SMD electrolytics on the control board.

Quote
>heatsink U800

Opinions vary. Be aware some say that it is easy to mechanically damage the IC when fitting a heatsink. I suggest not touching it until necessary.

Quote
>construct interface and read out cal data
>develop strategy for eventual memory replacement and reprogramming

My technique is to make a video of the screen while using the screen controls to step through the memory. Make sure you can read all the values, and store the video safely.

If/when a problem occurs, transcribe the memory contents. My plan with my 2465 or 2455B is then to create a replacement for whatever memory has become deceased, probably using an arduino-class MCU and programming to with bit-banged i/o simulating the real memory. Obviously I haven't done that, so the feasibility is unproven.

Don't forget to run the self-tests detailed in the manual.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Knack on October 28, 2017, 11:44:58 pm
I have just pulled my 2465B out of storage to use it after almost 30 years. I had forgotten that I even had it. As I was the original purchaser and the only user, I know when I last used it, it worked flawlessly.

So I am in the process of getting her cleaned up a bit before hitting the on button. I have 4 of the original probes, 2 of which are still in the factory sealed pouches. Plus the ops manual, the Polaroid camera shroud, and the added reticules.

I'll love getting her back to operating condition. Thanks for starting this thread, it will come in handy.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on October 29, 2017, 12:19:02 am
I have just pulled my 2465B out of storage to use it after almost 30 years. I had forgotten that I even had it. As I was the original purchaser and the only user, I know when I last used it, it worked flawlessly.

So I am in the process of getting her cleaned up a bit before hitting the on button. I have 4 of the original probes, 2 of which are still in the factory sealed pouches. Plus the ops manual, the Polaroid camera shroud, and the added reticules.

I'll love getting her back to operating condition. Thanks for starting this thread, it will come in handy.

Looking forward to see it awake from it's long Rip Van Winkle slumber. Post pictures!  :-+

And welcome to the forum! 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Knack on October 29, 2017, 12:34:20 am
Thanks med, will do.  8)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tazdog on December 10, 2017, 10:19:09 pm
All:
This has been a very informative thread with lots of good information and I was wondering if anyone has had this issue...

I purchased my 2465B from eBay with a known issue thinking that it could be fixed with the "known issue fixes" in this thread but not yet.  |O
I received it with Tektronix cal stickers in place so I thought "BONUS! no one has tinkered with it". So I went through the normal procedures and replaced PS caps and A5 board caps and carefully cleaned the electrolytic mess made by those. I also replaced the cal RAM. Then I noticed that the CAL/NO CAL jumper was in the CAL position?? Being a noob with the 2465 I didn't realize that the bottom row displayed "..." between settings. Why was it in the CAL position?? The only explanation is that someone sent the scope to TEK for repair and for one reason or another the customer didn't want it fixed. So TEK sent the scope back with CAL in place that way it could still be used albeit in a limited fashion.

So, what is the issue I hear you say??...

The scope will not DC balance on ch 1 & 2. Auto DC BAL routine (pressing both upper coupling buttons of CHs 1 & 2 simultaneously) does not balance the channels. You can flip through the input level settings and the trace moves all over the place.

Things that I have looked at...

1. After initiating the procedure and it completes there are no LIMIT errors.
2. Checking the Trigger pick-off of both ch. 1 and 2 during the procedure I see the scope has initiated +/- voltage switching of various potentials and i believe then the processor checks the TSO for when the Display Sequencer detects a trigger and I do see activity on this line. TLA of U500 goes to a high level but TLB shows a ramp so I think the processor is using this to detect the trigger level for the procedure.
3. If I use some of the the CAL data files uploaded to this thread and burn them to my RAM, the DC balance is close to what it needs to be but as soon as I run the DC balance procedure it goes right back to being bad.

Maybe I'm just  :horse:

Any Thoughts???
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tazdog on January 03, 2018, 04:49:16 am
Ok in case anyone is still interested I found the issue. The unit has a bad A&B Trigger chip - 155-0239-02
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on January 03, 2018, 12:48:15 pm
Ok in case anyone is still interested I found the issue. The unit has a bad A&B Trigger chip - 155-0239-02

Good deal! Were you able to confirm that with a replacement part?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tazdog on January 04, 2018, 04:56:52 am
Yes, replacing the part fixed the issue  :). I must say that when I was testing the scope, the low level trigger wasn't working properly. At 50mV vertical sensitivity or lower, I could get the trigger light to indicate a trigger condition but the scope display was unstable. This further led me to believe that the issue was the trigger chip.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: sekess on January 04, 2018, 05:18:46 pm
Hey guys.  I'm new here.
Just came across this thread.  Excellent info.

From reading through this thread, I think it's time for me to change out my Dallas RAM.  I think I'll go with the FM16W08.  But, I have a question about sourcing an adapter pcb.  The one that I saw used here was this Aries adapter from Digikey:

https://www.digikey.com/product-detail/en/aries-electronics/28-650000-10/A320-ND/123761 (https://www.digikey.com/product-detail/en/aries-electronics/28-650000-10/A320-ND/123761)

This one goes for close to $19.  Does anyone have a source of a less expensive one that is still decent quality with the thin round pins?

  Thanks,
    Steve 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: boro on January 15, 2018, 04:20:10 pm
Hi everybody! This is my first post and I wanted to thank you all for this great and informative thread!

I have a 2445A that lost tha calibration data due to the Keeper battery age...
I had the first warnings a few months ago, but by the time I was able to purchase a new Keeper, via a friend Down Under, because their shipping is forbidden to Italy, I got to the dreaded Test 04 fail error...
I don't need a super calibrated scope, I just use it for some basic troubleshooting and I only got a (cheap) signal generator and a (cheap) DMM.
I went through all the pages of the thread but it's still not clear what are my options at this point. Calibrating it would set me back some 150€ plus shipping. I might even think of doing so but I wondered whether once the machine underwent through all the calibrating steps, and putting back the nocal jumper, the scope would retain the data. Dumb question I know...  ::)

Thank you all for any advice/info you'll want to provide me, it'll be much appreciated!

B.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: pquadrat on February 17, 2018, 10:08:14 am
Hi everyone,

very good thread about the 2465B Scope. I got mine some years ago from ebay, a 2465BDV, which hat some options included (01, 05, 06, 09, 10), TV triggering, CTT, Word Recognizer Probe, DVM, GPIB). It came frome a production site, a lot of opreation hours, very few on/off cycles.
Just replaced all caps in the power supply, and the Dallas chip and the already leaking electrilytics on the A5 boards. Without this thread, I would never have noticed that, thanks!
I bought a Dallas chip from china, which was an old one with reprinted date code. And then one from a local distributor, which was fresh.

Because there were no pics of a BDV in this thread ( I think), I will post some:

Next post will be about my new scope, a 2445B.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: pquadrat on February 17, 2018, 10:10:08 am
more...
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: pquadrat on February 17, 2018, 10:22:55 am
Now to my new scope, a 2445B (same as a 2465B except bandwith), Serial below 050000, so it has the old-style A5 board without SMD and without the leaking caps.
It looks almost like new, has below 900h of operation, came from a broadcasting station (sfb, Sender Freies Berlin) here in Germany.  I did the bandwith "hack" on the A1 board (seems to work very close to my 2465B).

But it has a focus problem: When cold, it is extremely out of focus (and astig as well), it takes 5 to 10 minutes to get a sharp image. My other 2465BDV is perfect from the first second.

I did replace all caps in the power supply. But I am not sure if this problem was there before the re-cap, because this was one of the first things to do after getting the scope.

Any suggestions? I did check the supply voltages (J119 on Board A1), all stable from the beginning.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on February 17, 2018, 11:10:21 am
Hi everyone,

very good thread about the 2465B Scope. I got mine some years ago from ebay, a 2465BDV, which hat some options included (01, 05, 06, 09, 10), TV triggering, CTT, Word Recognizer Probe, DVM, GPIB). It came frome a production site, a lot of opreation hours, very few on/off cycles.
Just replaced all caps in the power supply, and the Dallas chip and the already leaking electrilytics on the A5 boards. Without this thread, I would never have noticed that, thanks!
I bought a Dallas chip from china, which was an old one with reprinted date code. And then one from a local distributor, which was fresh.

Because there were no pics of a BDV in this thread ( I think), I will post some:

Next post will be about my new scope, a 2445B.

Welcome to our group of Tek 24XX users. I'm glad you found all the information you needed to get yours up and working, especially in reference to the specific issues with the SMD A5 board. I have an older 2465 DMS which has the same features as yours but has the older pin thru hole A5 board. I'm sure you found getting the scope apart to re-cap the power supply very challenging as I did. All those option boards have to come out and then reassembly can be frustrating.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on February 17, 2018, 11:11:30 am
Any suggestions? I did check the supply voltages (J119 on Board A1), all stable from the beginning.
Focus (excuse the pun) investigations on componentry in the EHT supply for the CRT, that's where these sorts of problems are normally found IME.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on February 17, 2018, 11:24:19 am
Now to my new scope, a 2445B (same as a 2465B except bandwith), Serial below 050000, so it has the old-style A5 board without SMD and without the leaking caps.
It looks almost like new, has below 900h of operation, came from a broadcasting station (sfb, Sender Freies Berlin) here in Germany.  I did the bandwith "hack" on the A1 board (seems to work very close to my 2465B).

But it has a focus problem: When cold, it is extremely out of focus (and astig as well), it takes 5 to 10 minutes to get a sharp image. My other 2465BDV is perfect from the first second.

I did replace all caps in the power supply. But I am not sure if this problem was there before the re-cap, because this was one of the first things to do after getting the scope.

Any suggestions? I did check the supply voltages (J119 on Board A1), all stable from the beginning.

Attached is a partial schematic of the 2465 focus/astig circuit. The 2445 should be similar. The first thing I would check is that -300V to Q1851 and Q1852. With the scope "cold" and power off hang your probe on that supply and see what it does as the scope powers up and warms up. Of course be VERY CAREFUL working around the high voltage supply. It can really hurt.  :scared:
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: pquadrat on February 17, 2018, 01:06:41 pm
Now to my new scope, a 2445B (same as a 2465B except bandwith), Serial below 050000, so it has the old-style A5 board without SMD and without the leaking caps.
It looks almost like new, has below 900h of operation, came from a broadcasting station (sfb, Sender Freies Berlin) here in Germany.  I did the bandwith "hack" on the A1 board (seems to work very close to my 2465B).

But it has a focus problem: When cold, it is extremely out of focus (and astig as well), it takes 5 to 10 minutes to get a sharp image. My other 2465BDV is perfect from the first second.

I did replace all caps in the power supply. But I am not sure if this problem was there before the re-cap, because this was one of the first things to do after getting the scope.

Any suggestions? I did check the supply voltages (J119 on Board A1), all stable from the beginning.

Attached is a partial schematic of the 2465 focus/astig circuit. The 2445 should be similar. The first thing I would check is that -300V to Q1851 and Q1852. With the scope "cold" and power off hang your probe on that supply and see what it does as the scope powers up and warms up. Of course be VERY CAREFUL working around the high voltage supply. It can really hurt.  :scared:

I checked all voltages around Q1851 and Q1852, all very stable from the beginning. -300V is stable.  Focus can also be bad if other voltages of the tube are wrong, so I have to look elsewhere.

There is a test point "74" with a warm-up voltage raising from zero to 15V (around U1890), I will try to understand what is done with this circuit.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on February 17, 2018, 01:57:45 pm
Now to my new scope, a 2445B (same as a 2465B except bandwith), Serial below 050000, so it has the old-style A5 board without SMD and without the leaking caps.
It looks almost like new, has below 900h of operation, came from a broadcasting station (sfb, Sender Freies Berlin) here in Germany.  I did the bandwith "hack" on the A1 board (seems to work very close to my 2465B).

But it has a focus problem: When cold, it is extremely out of focus (and astig as well), it takes 5 to 10 minutes to get a sharp image. My other 2465BDV is perfect from the first second.

I did replace all caps in the power supply. But I am not sure if this problem was there before the re-cap, because this was one of the first things to do after getting the scope.

Any suggestions? I did check the supply voltages (J119 on Board A1), all stable from the beginning.

Attached is a partial schematic of the 2465 focus/astig circuit. The 2445 should be similar. The first thing I would check is that -300V to Q1851 and Q1852. With the scope "cold" and power off hang your probe on that supply and see what it does as the scope powers up and warms up. Of course be VERY CAREFUL working around the high voltage supply. It can really hurt.  :scared:

I checked all voltages around Q1851 and Q1852, all very stable from the beginning. -300V is stable.  Focus can also be bad if other voltages of the tube are wrong, so I have to look elsewhere.

There is a test point "74" with a warm-up voltage raising from zero to 15V (around U1890), I will try to understand what is done with this circuit.

Yep, that circuit is the grid bias to the CRT. If that's not correct it will affect the focus. Section 5-4 of the Service Manual describes the adjustments. If you have a slowly rising voltage at the output of that Op-amp concurrent with better focus I would check for leaky capacitors in that area.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: pquadrat on February 18, 2018, 10:53:08 am

Yep, that circuit is the grid bias to the CRT. If that's not correct it will affect the focus. Section 5-4 of the Service Manual describes the adjustments. If you have a slowly rising voltage at the output of that Op-amp concurrent with better focus I would check for leaky capacitors in that area.

I charged and discharged the C1990 an was able to bring the voltage at the output of the op-amp to 0v or 15V, without affecting the focus much.
Grid bias adjustment was done exactly as written in the adjustment section. I will check testpoints 72, 73 next.

I checked the Output of the High Voltage Module U1830, pin 4, which should be -900V, according to the schematics. It is only -617V.

The focus pot is near the end of the adjustment range when in focus, and I can never get it as sharp as my other 2465B.

But now I have to wait an hour or so until the bad focus is back. Cooling the HV board with cooling spray does not help, so I think it is not heat related.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: pquadrat on February 18, 2018, 12:11:48 pm
Tthe Output of the High Voltage Module U1830, pin 4 is also 617V on my other 2465B, so I think 900V is an error in the schematics.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on February 18, 2018, 12:38:36 pm
Thinking out loud....try swapping the HV supplies between the 2 scopes. I believe they are the same part number. I've never pulled the supply in a 24XX so I don't know how difficult it would be.

If that doesn't fix it you basically only have one thing left. The CRT itself. If it were "gassy" (loosing it's vacuum) or has low emission it could cause an extended warm up time. 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: pquadrat on February 18, 2018, 04:16:38 pm
Thinking out loud....try swapping the HV supplies between the 2 scopes. I believe they are the same part number. I've never pulled the supply in a 24XX so I don't know how difficult it would be.

If that doesn't fix it you basically only have one thing left. The CRT itself. If it were "gassy" (loosing it's vacuum) or has low emission it could cause an extended warm up time.

Swapping the A9 (HV) boards did not change anything. 2465B sharp as ever, 2445B sharp 10 minutes from start. And it takes about one hour  switched-off to get it fully out of focus again.

I have never heart of a bad 2465 CRT up to now. And it is bright from the first moment.

I will check the power supply again, because I think it was not having this problem before i replaced the caps in it, or at least not so bad. I think I would have noticed that.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on February 18, 2018, 05:14:37 pm
Thinking out loud....try swapping the HV supplies between the 2 scopes. I believe they are the same part number. I've never pulled the supply in a 24XX so I don't know how difficult it would be.

If that doesn't fix it you basically only have one thing left. The CRT itself. If it were "gassy" (loosing it's vacuum) or has low emission it could cause an extended warm up time.

Swapping the A9 (HV) boards did not change anything. 2465B sharp as ever, 2445B sharp 10 minutes from start. And it takes about one hour  switched-off to get it fully out of focus again.

I have never heart of a bad 2465 CRT up to now. And it is bright from the first moment.

I will check the power supply again, because I think it was not having this problem before i replaced the caps in it, or at least not so bad. I think I would have noticed that.

I've never heard of a bad 24XX CRT either, other than ones broken due to shipping damage or falling off a bench.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on February 18, 2018, 08:54:20 pm
...
I will check the power supply again, because I think it was not having this problem before i replaced the caps in it, or at least not so bad. I think I would have noticed that.
If you're not already doing so, use a scope in addition to a DMM to make sure there's nothing strange happening on any of the supplies.  (Maybe something with the +87V supply?  It supplies CRT ANODE #1 directly.)

I think your experiment with C1990 was a good idea, and also checking the ASTIG and FOCUS outputs to the CRT.  I would try monitoring ALL the voltages going into the CRT to see what (or if) anything is changing over the warm up.  And compare those to your working 2465B over a warm up.

If you get desperate enough as a last resort, there's always swapping in the good CRT for a test.  The procedure is not too bad but it does take a couple of hours.  The 14kV acceleration anode holds a charge for a LONG time (speaking from experience - Ouch! is all I have to say).
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: korlatos on March 12, 2018, 12:30:43 am
Since there is no way to remove the RAM to read the contents, without losing the data, there must be a method for the scope to "restore" itself from a dead battery.

This might be possible through the GPIB interface; I do not remember.  One of the 2465 series experts will know.
I don't know about the 2565A/2467, but the EAROM in the 2456 can dumped via GPIB.  By examining the EPROMs on the GPIB board I was able to figure out the following.  It may be extensible to other models.

First, you have to enable the "special" commands:

  key 0

Then you can dump the EAROM with the following command:

  earom? <address to dump>[,<address to dump>,<...>]

This allows reading out of multiple locations in one command.  For example, to dump the first 10 addresses:

  earom? 0,1,2,3,4,5,6,7,8,9

Then the next 10:

  earom? 10,11,12,13,14,15,16,17,18,19

And so on, until address 199.  The first 100 locations are the EAROM on the main board, and the second 100 is the EAROM on the buffer board.  This is the same as in the exerciser.  The values should match.

The above commands return a line in the form (from the above example 0 to 9):

  EAR 0:84,1:1993,2:10102,3:1893,4:10091,5:1798,6:1494,7:1420,8:9608,9:1431;

The return format is <address>:<value> and everything is in decimal.  You can set an EAROM value by using the same format:

  earom <address>:<value>

Trying to write multiple values in one line didn't work for me and crashed my scope.  YMMV.

It would be interesting if someone could try this on a model other than a 2465(plain).

WARNING!!   If you want to play with any of this, be careful not to overwrite overwrite the EAROM values until you've saved them with a screen capture!  On my 2465 it DOES NOT MATTER if you have the the cal jumper set to off.  These commands are surely hidden for a reason!


If you're even braver, there's another hidden query I've discovered called "BYTE?".  It takes one argument and dumps that number of bytes from somewhere.  I can't figure out what it's dumping, and I can't make it repeat itself except after a reboot.  Eventually after several hundred bytes it causes my 2465 to reboot.  I'm mentioning it because maybe that command will be useful on other models without EAROMs.


If anyone decides to try anything, please post your results.  Obviously this needs a GPIB interface.  I haven't found any equivalent method to write EAROM/NVRAM values from the screen, although now that I found it via GPIB it makes me suspect it's possible.

I can confirm that you can dump the 2465A SRAM calibration data using GPIB and the earom? command exactly as described in MarkL's post above.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mahwe on March 19, 2018, 11:51:52 pm
Thanks for the nice teardown Photos.
sorry for my bad englisch.
I have an Tek2445B since 10 jears and i was reallly happy with it, till yesterday.
It works fine the Problem is, that my scope crt Signal Position start to jump, when i try to change the horiz./vertical Position from every Cannel(1,2,3,4) , also the mesurment (delta V delta t) jumps.
So that it makes no fun to use it :-BROKE :-// :scared: .
Does annybody have had the same Problem?
First i tested the different Voltages from the Power supply but they are ok(agilent34410A tested).
If it wold be only one Funktion, than i would clean the Potys from the front pannel, but so i think it must be something on the Control /readout/Buffer Board( SMD Version 671-0965 05   P9-0247B-04 (Tektronix chip1991)).
The Signals  on the CRT seem to be ok, also the Nummbers and Letters only the Signal moved non linear up an down and the Measurment Lines. |O
thanks
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Satbeginner on March 20, 2018, 04:58:56 am
Check the TL074 OpAmps on the A5 board, I had several of these acting like that.

Good hunting,

Leo
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 20, 2018, 03:34:40 pm
The analog front panel controls on the 2445B, like almost all of them in this series, are converted from analog to digital, processed by the microprocessor, and then output again as an analog signal.

Since you have multiple controls suddenly showing instability, it's probably something in common that has failed or is intermittent (including connectors).

Before digging into the control board, I would first take a look at Exerciser routine 01.  This utility displays the reading on all the front panel switches and pots in hexadecimal.  Examine the readout values of the pots that are misbehaving to see if they're stable.  This will at least divide your problem into either an input issue or an output issue.  How to access the Exerciser is described in the service manual in the "Maintenance" section.

Of possible interest are also those microprocessor controlled pots which are *not* showing instability.  That could help you narrow down what *is* working.

It might also help if you could post a short video demonstrating the problem.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mahwe on March 21, 2018, 07:54:45 pm
First thanks for your help here a small Video

https://youtu.be/MUbJ79MrbwM

the next days i will test the scope
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tazdog on March 22, 2018, 02:48:02 pm
All, just a tip for anyone working on the A5 board due to capacitor leakage, don't forget to check R2010 20K trim pot. Mine was reading close to 30K so that's a big difference!!! They are easy to get from DigiKey.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 22, 2018, 04:58:21 pm
First thanks for your help here a small Video
...
the next days i will test the scope
Thanks, that was a great video of the problem.  It wasn't too clear because your hand was blocking the control, but it looks like the Intensity control is also affected.  That would be consistent with the issue on the other controls.

I think running the exerciser 01 as previously described would be a good next step.


In many of parts of your video you can see the output DAC stepping towards a final and stable value.  At the moment that makes me think it could be an input issue.  Running the exerciser 01 will say for sure.

The input "ADC" is actually comprised of a DAC, a comparator, and some analog MUXes to select which pot to read.  How this operates is in the Theory section under "Front-Panel Scanning and Analog Controls", and specifically "Pot Scanning".  I'd suggest reading that section if you haven't already done so.

Also note that to make troubleshooting more complicated, they use the same DAC for the output as well, which feeds an array of sample and hold circuits.

Do you have the GPIB option on this scope?  It appears you don't, given the lack of GPIB LEDs above the screen, but I want to make sure.  The GPIB interface on some scopes in this family have separate ADC/DAC circuitry that intercepts some of the analog controls, but I don't know for sure on the 2445B.

Which brings me to...  I can't find a schematic specifically for the 2445B.  If you (or anyone) knows of one, please post a link.  There are plenty of 2445B service manuals out there, but for some reason the schematic section has been omitted from all that I could find.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tazdog on March 23, 2018, 12:05:36 am
If you can't find a free manual, http://artekmanuals.com (http://artekmanuals.com) has them. Good scan's and they are searchable.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tazdog on March 23, 2018, 03:05:42 am
OK, google is your friend, right from the source - https://www.tek.com/manual/2445-service-manual (https://www.tek.com/manual/2445-service-manual) - if you don't mind giving up your email address  :)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 23, 2018, 03:27:19 am
OK, google is your friend, right from the source - https://www.tek.com/manual/2445-service-manual (https://www.tek.com/manual/2445-service-manual) - if you don't mind giving up your email address  :)
Thanks, but that's for the 2445.  We need the schematics pages for the 2445B, emphasis on the B.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on March 23, 2018, 07:12:44 am
All, just a tip for anyone working on the A5 board due to capacitor leakage, don't forget to check R2010 20K trim pot. Mine was reading close to 30K so that's a big difference!!! They are easy to get from DigiKey.

What was the problem/symptom before you fix that ?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: z01z on March 23, 2018, 07:15:37 am
Thanks, but that's for the 2445.  We need the schematics pages for the 2445B, emphasis on the B.
You could use the manual for the 2465B, the 45s are said to be mostly the same as the 65s. Search for the filename: 070-6873-00_2465bSvc_Sep89.pdf
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: grumpydoc on March 23, 2018, 10:05:17 am
Thanks, but that's for the 2445.  We need the schematics pages for the 2445B, emphasis on the B.
You could use the manual for the 2465B, the 45s are said to be mostly the same as the 65s. Search for the filename: 070-6873-00_2465bSvc_Sep89.pdf
There might be other differences but, from memory, the firmware limits the fastest timebase slightly in the '45 and there is some filtering on the input to the final Y amp - after the delay line, to limit bandwidth slightly. At least some of the implementation is with PCB traces to form inductors.

Some unscrupulous vendors have, in the past, been known to bypass this and sell the result on eBay claiming it to be a 2465.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tazdog on March 23, 2018, 02:36:53 pm
The "2445" manual should be good enough for the issue he is experiencing.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: casinada on March 23, 2018, 05:20:55 pm
http://www.ko4bb.com/getsimple/index.php?id=manuals&dir=Tektronix (http://www.ko4bb.com/getsimple/index.php?id=manuals&dir=Tektronix)
 :-//
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 23, 2018, 05:48:14 pm
http://www.ko4bb.com/getsimple/index.php?id=manuals&dir=Tektronix (http://www.ko4bb.com/getsimple/index.php?id=manuals&dir=Tektronix)
 :-//
Been there.  In the 2445B directory, right?  Like I said previously, the service manual is there, and in many other places around the net, but they are all missing the schematics.

The suggestion to get a complete service manual from Artek is probably the way to go.  They have the 2445B.

Strictly speaking, I agree it's not necessary and you can probably get away using the schematics from one of the close relatives of this scope.  But if it were me and I never fixed one of these before, I'd want something accurate for now and to keep as a future reference.  It's certainly up to user mahwe.  I'm just trying to provide some troubleshooting hints.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tazdog on March 24, 2018, 04:38:59 am
I agree. start with the free one and if that doesn't have enough info then purchase a manual.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Orange on March 24, 2018, 09:02:50 am
If you need a free 2465B manual with schematics, have a look at the Bitsavers site. It is there. It has reasonable readable diagrams.
Link of the mirror site:
http://bitsavers.informatik.uni-stuttgart.de/test_equipment/tektronix/scope/ (http://bitsavers.informatik.uni-stuttgart.de/test_equipment/tektronix/scope/)

Follow MarkL his suggestion
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Orange on March 24, 2018, 09:17:17 am
I just uploaded a better scanned 2465B service manual to the http://www.ko4bb.com/ (http://www.ko4bb.com/) site

It is a 1993 manual, with schematics on one page, good quality, 35 Megs
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on March 24, 2018, 09:22:00 am
I just uploaded a better scanned 2465B service manual to the http://www.ko4bb.com/ (http://www.ko4bb.com/) site

It is a 1993 manual, with schematics on one page, good quality, 35 Megs

Thanks.  :-+

Can't download it yet as its still in unchecked upload area.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Orange on March 24, 2018, 10:10:32 am
Try to set-up an ftp to ftp.ko4bb.com. User is manualuploads, pw is also manualuploads.

There are two manuals  ;)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on March 24, 2018, 10:26:42 am
Thanks, got it !  :-+

Found an interesting date in there, highlighted in red.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Orange on March 24, 2018, 10:32:34 am
Thanks, got it !  :-+

Found an interesting date in there, highlighted in red.
Even better, did not even noticed this
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on March 24, 2018, 10:36:45 am
Thanks, got it !  :-+

Found an interesting date in there, highlighted in red.
Even better, did not even noticed this

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=16703;image)

Yeah, cause all this times I've been wondering about my fan's date code, and was keep suspecting whether its originally installed from factory, I guess this confirmed it.

Again, thanks a lot for your contribution.  :clap:


Edit : Also already uploaded to TiN's xdevs.com documents server, hope you don't mind.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on March 29, 2018, 01:54:51 am
You guys made me curious about the numbers of hours on my Tek 2445B. Check this out.
I replaced the electrolytic caps only in the PS and HV, the FRAM is on its way, I saved the content of the NVRAM and installed a socket. Do you think I should change the caps on the main board? It works fine.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: james_s on March 29, 2018, 04:47:29 am
IMHO if it works fine leave it alone, there's always some risk inherent in taking the thing apart.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on March 30, 2018, 10:22:02 am
There is a bit of a vertical jitter in the readout on some horizontal ranges and the tube goes out of focus if I go all the way up with the intensity but I guess this is mostly related to the aging of the tube?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on April 04, 2018, 02:31:24 am
I've got my FRAM FM6W08 from ebay and it doesn't work. I can program it with Xeltek SP5000, it passes verification, but once inserted in the scope I get TEST 04 FAIL 11. It's either a faulty rejected chip, I wouldn't be surprised considering it was only $4.39, or maybe it doesn't work in 2445B. I would expect the addressing mode to be identical between 2445, 2465, 2467. Any experience?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on April 04, 2018, 01:53:17 pm
There is a bit of a vertical jitter in the readout on some horizontal ranges and the tube goes out of focus if I go all the way up with the intensity but I guess this is mostly related to the aging of the tube?
A little bit of jitter is normal.  There are adjustments to tweak the vertical and horizontal readout jitter, R805 and R618.  It's in the service manual in the "DC Balance, And X-Y Phase Differential" section.

The de-focusing with increased brightness is called "blooming" and you're right, it gets worse as the tube ages.  You may be able to partially compensate for it by going through the CRT adjustment procedures in the service manual, particularly the High Drive Focus.  Some of these adjustments may change the position of how the beam lands on the graticule and the display (and just the display) may become uncalibrated.

Hint: Mark the current position of any pots with a good Sharpie before you move them in case you need to put them back.   The CRT adjustments have a lot of interaction between them and can drive you crazy trying to get them just right.  Unless the jitter and focus really bothers you, I would probably leave everything alone.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on April 04, 2018, 02:04:07 pm
I've got my FRAM FM6W08 from ebay and it doesn't work. I can program it with Xeltek SP5000, it passes verification, but once inserted in the scope I get TEST 04 FAIL 11. It's either a faulty rejected chip, I wouldn't be surprised considering it was only $4.39, or maybe it doesn't work in 2445B. I would expect the addressing mode to be identical between 2445, 2465, 2467. Any experience?
No experience, but one thing you could do is use Exerciser 02 to scroll through the calibration data you programmed into the FRAM.  As discovered in another thread, RAM locations 0x1e00 - 0x1fff should be the 16-bit calibration constants visible through the exerciser, big endian.

Maybe the values (or lack of) would provide some clues.

Is that part number right?  Did you mean FM16W08?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on April 05, 2018, 12:46:13 am
Unless the jitter and focus really bothers you, I would probably leave everything alone.

That's exactly what I'll do, it is very usable as is.  :-+

No experience, but one thing you could do is use Exerciser 02 to scroll through the calibration data you programmed into the FRAM.  As discovered in another thread, RAM locations 0x1e00 - 0x1fff should be the 16-bit calibration constants visible through the exerciser, big endian.

Maybe the values (or lack of) would provide some clues.

Is that part number right?  Did you mean FM16W08?

Yes, I meant FM16W08. The problem is that the scope keeps rebooting so I have a hard time running the exerciser. I managed to do it once and all the locations were 00. I removed it and read it with the programmer and other than the very last address and one somewhere in the middle of the calibration space they were all there.
What I suspect is that it is a part that failed in production. I works in the programmer, probably it is programmed at low speed, but once it is addressed at full speed, it doesn't keep up. Don't know.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on April 05, 2018, 02:29:54 pm
What I suspect is that it is a part that failed in production. I works in the programmer, probably it is programmed at low speed, but once it is addressed at full speed, it doesn't keep up. Don't know.
Seems like a good theory.  The cycle time of the 2445B and others in the series is a leisurely 800ns, so the FRAM must be in pretty bad shape to not work at that speed.  Either that or some setup/hold times are on the edge since it works some of the time.  It might be better to get a fresh, known good FRAM from Digikey or Mouser before investing more time in it.

You might already be familiar with this paper that talks about using FRAM in a 2465B successfully:

  http://worldphaco.com/uploads/TEKTRONIX_2465b_OSCILLOSCOPE_CALIBRATION___REPOWERING_THE_DS1225.pdf (http://worldphaco.com/uploads/TEKTRONIX_2465b_OSCILLOSCOPE_CALIBRATION___REPOWERING_THE_DS1225.pdf)

The 2445B should be the same as far as the SRAM concerned.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: james_s on April 05, 2018, 05:24:32 pm
It's possible that it's a fake that is not even a real FRAM inside. It could even be something like a microcontroller paired with a serial EEPROM, you never know with random Chinese parts. I got several Dallas SRAM modules that were obvious fakes.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on April 05, 2018, 11:14:37 pm
It's possible that it's a fake that is not even a real FRAM inside. It could even be something like a microcontroller paired with a serial EEPROM, you never know with random Chinese parts. I got several Dallas SRAM modules that were obvious fakes.

It is possible but I would think is too much trouble, does it even make economic sense? I'll give it an X-Ray one day to see how many dies are inside.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on April 06, 2018, 09:33:01 am
It's possible that it's a fake that is not even a real FRAM inside. It could even be something like a microcontroller paired with a serial EEPROM, you never know with random Chinese parts. I got several Dallas SRAM modules that were obvious fakes.

It is possible but I would think is too much trouble, does it even make economic sense? I'll give it an X-Ray one day to see how many dies are inside.

I've read somewhere but forgot where, for those dodgy ones especially Maxim/Dallas BBSRAM products, actually they're genuine, but re-cycled and re-labelled.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: james_s on April 06, 2018, 09:26:42 pm


I've read somewhere but forgot where, for those dodgy ones especially Maxim/Dallas BBSRAM products, actually they're genuine, but re-cycled and re-labelled.

I've seen both, old parts that have been relabeled, and counterfeit copies, confirmed by xray followed up by grinding into the thing. The copies had a completely different internal layout.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: usergen on April 07, 2018, 06:55:34 pm
hi all and hope not to be OT, could anybody suggest how to remove the front panel knobs not having screws? I tried to pull them out with my fingers but they seem very tight and I'm afraid to break something if applying more force. thanks.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: usergen on April 08, 2018, 08:01:12 pm
any feedback from you guys?  :(
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on April 08, 2018, 09:43:53 pm
any feedback from you guys?  :(
They do just pull off, but maybe after being on there for so long they are stuck.

Maybe warm the knob up a little (like with hair dryer, not a heat gun) before pulling on it?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: usergen on April 08, 2018, 10:12:29 pm
tnx a lot MarkL, even for the picture!!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on April 09, 2018, 09:34:51 am
Also be warned, as sometimes not all knobs can flushed completely, like mine here.  ::)

(https://www.eevblog.com/forum/beginners/asking-about-tektronix-2465b-any-experienced-tek-tech-or-lovers-jump-in-please/?action=dlattach;attach=16291;image)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: usergen on April 09, 2018, 02:28:23 pm
Hello BravoV, I haven't tried to remove any yet but I'm a bit confused now, does it mean your knobs can't be entirely pulled off or do they can't be pulled in further? thanks a lot.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: cheeseit on April 09, 2018, 06:34:34 pm
Its the latter and the same on my scopes with about 1-2 mm distance from knob to face.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: usergen on April 09, 2018, 07:00:18 pm
all the knobs safely removed, thanks again guys.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: gregariz on April 09, 2018, 07:06:32 pm
any feedback from you guys?  :(
They do just pull off, but maybe after being on there for so long they are stuck.

Maybe warm the knob up a little (like with hair dryer, not a heat gun) before pulling on it?

My advice after learning the hard way is that Tektronix knobs are really not meant to be removed. Really they are a weak point in an otherwise classic cro. They clip onto that inner plastic sheath and with a bit of age the clips in the knobs become very brittle and can break. If that happens often the only thing to do is to apply some glue and glue them back on - hoping you never need to remove them again. Some years back a fellow on the net bought up the old Tektronix stock and was charging a fairly heavy price per knob, but once you've broken a few you know why he did it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: james_s on April 10, 2018, 02:30:42 am
It's possible that the plastic shrinks slightly in addition to becoming brittle. That's a fairly common and rather annoying trait of plastic. It wouldn't take much shrinkage for a knob to get stuck on a shaft.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on April 10, 2018, 03:05:55 am
Although I haven't tried on mine, just thinking out loud on the idea about applying some plastic friendly grease before putting back the knob, but not making it too loose that they falling out by it self during use.  :-//
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on April 11, 2018, 01:22:25 am
It's possible that it's a fake that is not even a real FRAM inside. It could even be something like a microcontroller paired with a serial EEPROM, you never know with random Chinese parts. I got several Dallas SRAM modules that were obvious fakes.

It is possible but I would think is too much trouble, does it even make economic sense? I'll give it an X-Ray one day to see how many dies are inside.

I've read somewhere but forgot where, for those dodgy ones especially Maxim/Dallas BBSRAM products, actually they're genuine, but re-cycled and re-labelled.

Ok, I have the X-Ray. It seems to be one die inside, no evidence of MCU and EEPROM. It's either a crappy part or 2445 cannot work with FRAM. I'm inclined towards the first.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: pquadrat on April 12, 2018, 07:51:35 am
Hi,

I've got another 2445B (with new style A5 board), defective, no trace or anything on the CRT, but otherwise it is working fine, all buttons/LEDs working, triggering on signals etc.

After swapping some boards with another 2554B, I could locate the fault on the A1 mainboard. Removing the horizontal and vertivcal deflection cables did not give an image, so my guess was, that the error could only be the Z (intensity) control. And it was U950, which is the Z axis control chip. With the U950 from the other 'scope, all works fine.

Does anyone here has a working U950 (155-0242-01) chip for sale? Preferred in Europe?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on April 12, 2018, 07:58:56 am
Does anyone here has a working U950 (155-0242-01) chip for sale? Preferred in Europe?
At the foot of this page there's a link to a 27 MB cross ref file of Tek parts.
http://www.sphere.bc.ca/test/tekequiv.html (http://www.sphere.bc.ca/test/tekequiv.html)

It might be commonly available so check what it is.  ;)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: pquadrat on April 12, 2018, 08:17:59 am
Does anyone here has a working U950 (155-0242-01) chip for sale? Preferred in Europe?
At the foot of this page there's a link to a 27 MB cross ref file of Tek parts.
http://www.sphere.bc.ca/test/tekequiv.html (http://www.sphere.bc.ca/test/tekequiv.html)

It might be commonly available so check what it is.  ;)

It is one of the custom Tek chips.

And I was able to get one here in Germany, so no longer looking for one.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: neo on April 18, 2018, 09:53:54 pm
Anyone know what it means when a 2465B bleeps its front lights? Fan's running and it starts up like normal until it starts that, the blinking of it's front light i mean.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on April 19, 2018, 12:06:42 am
Anyone know what it means when a 2465B bleeps its front lights? Fan's running and it starts up like normal until it starts that, the blinking of it's front light i mean.

Start with the basics and work from there. Make absolutely certain all your supply voltages are within spec as far as voltage and ripple. J119 on the main board is a convenient location to check them. I don't have the manual in front of me at the moment so I can't tell you what page it's on. 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: neo on April 19, 2018, 02:45:33 am
Anyone know what it means when a 2465B bleeps its front lights? Fan's running and it starts up like normal until it starts that, the blinking of it's front light i mean.

Start with the basics and work from there. Make absolutely certain all your supply voltages are within spec as far as voltage and ripple. J119 on the main board is a convenient location to check them. I don't have the manual in front of me at the moment so I can't tell you what page it's on.

So then, the blinking points to nothing specific then, therefore the long way it is. Thank you that is exactly what i wanted to know, the 70s were easier to work on  :-DD

https://www.eevblog.com/forum/repair/tektronix-2465b-repair/ (https://www.eevblog.com/forum/repair/tektronix-2465b-repair/)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: andy2000 on May 04, 2018, 02:45:37 pm
I recently started working on my late model 2445B.  It had the usual leaking caps on the A5 board, plus some open traces.  I've taken care of those problems, and it's basically working, but there's one peculiarity. 

If I use auto scale, or any of the auto measurements, it momentarily blanks the trace (I assume this is normal), but when it's done, the trace is either very dim, or invisible.  I can get the trace back by turning up the intensity, but the same thing happens again if I repeat the auto operation.  After enough times, it needs to be near maximum to get a visible trace.  Reducing the intensity control to minimum, and turning it up restores its normal range.  I assume this isn't normal. 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on May 04, 2018, 02:50:35 pm
I recently started working on my late model 2445B.  It had the usual leaking caps on the A5 board, plus some open traces.  I've taken care of those problems, and it's basically working, but there's one peculiarity. 

If I use auto scale, or any of the auto measurements, it momentarily blanks the trace (I assume this is normal), but when it's done, the trace is either very dim, or invisible.  I can get the trace back by turning up the intensity, but the same thing happens again if I repeat the auto operation.  After enough times, it needs to be near maximum to get a visible trace.  Reducing the intensity control to minimum, and turning it up restores its normal range.  I assume this isn't normal.

It happens on my 2445B. I have presumed it is because it doesn't "know" how bright to set the beam, and so adopts a conservative value.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: pquadrat on May 04, 2018, 04:35:58 pm
I recently started working on my late model 2445B.  It had the usual leaking caps on the A5 board, plus some open traces.  I've taken care of those problems, and it's basically working, but there's one peculiarity. 

If I use auto scale, or any of the auto measurements, it momentarily blanks the trace (I assume this is normal), but when it's done, the trace is either very dim, or invisible.  I can get the trace back by turning up the intensity, but the same thing happens again if I repeat the auto operation.  After enough times, it needs to be near maximum to get a visible trace.  Reducing the intensity control to minimum, and turning it up restores its normal range.  I assume this isn't normal.

I tested it on a late 2465B and a late 2445B, both set the intensity to the same intensity as adjusting the intensity knob to the mid-position. On one this is fine, on the other it is to dark. But both are equal to the mid-position if adjustet by hand.

Re-adjusting grid bias and the other intensity adjustments (see the service manual) so that mid-position of the intensity pot gives a "normal" intensity will help.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on May 04, 2018, 06:09:09 pm
If I use auto scale, or any of the auto measurements, it momentarily blanks the trace (I assume this is normal), but when it's done, the trace is either very dim, or invisible.  I can get the trace back by turning up the intensity, but the same thing happens again if I repeat the auto operation.  After enough times, it needs to be near maximum to get a visible trace.  Reducing the intensity control to minimum, and turning it up restores its normal range.  I assume this isn't normal.

This is completely normal and how the 4 channel 2247A series work as well.

After the oscilloscope sets the intensity to nominal, it requires you to turn the intensity control through that setting before it will allow manual control of the intensity again.  This prevents the zero or offset of the manual control from shifting which could be a little confusing.

Modern oscilloscopes use an infinite turn control so this would not be an issue for them because the zero or offset is always relative anyway but Tektronix used a 300 degree potentiometer for digital control; rotary encoders were very expensive back when these oscilloscopes were made.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on May 04, 2018, 07:10:37 pm
go through this alot...  but it acts exactly as you describe. It's just kind of strange. The 2467B also has the added annoying "feature" of blanking or reducing the intensity to nearly nothing as a protection to the CRT from burns, every 90 seconds or so. Irritating. This really only helps those who don't use the intensity knob to lower the level when leaving a high intensity trace on the screen. The rest of us suffer. :--
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: GerryBags on May 04, 2018, 08:58:56 pm
Hi all, just received a very clean 2465B with a perennial problem: Start-up proceeds right up until the ADD led comes on and it stops. A/B TRIG brings about normal front-panel operation but no display or trace on the CRT, but it is glowing. So I have a look at A5 around the DAC area and look what I find! Green pins, and one corroded torx bolt are the only real evidence of electrolyte release, but thankfully I took pictures, and I'll lay ten-to-one that that resistor there has opened, or one near-by.

One question I have: does anyone know when these SMD control boards first started failing? This machine was last cal'd (by Tek, no less, it was owned by Sony Europe) in '09, when this particular A5 board was already 19 years old. Considering SMD hadn't been around that long in 1990 that's really not bad going.

With any luck that will be the only issue (apart from the dreaded cracked Rifas of course) this baby has!

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: GerryBags on May 04, 2018, 09:03:07 pm
This may be a redundant question, but would you guys change the Dallas NVRAM while you had the board off. I'm really hoping someone is going to say: "No, Gerry, you don't need to learn how to read and program cal data just yet." Anyone?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: GerryBags on May 04, 2018, 09:36:10 pm
Anyone know what it means when a 2465B bleeps its front lights? Fan's running and it starts up like normal until it starts that, the blinking of it's front light i mean.

Start with the basics and work from there. Make absolutely certain all your supply voltages are within spec as far as voltage and ripple. J119 on the main board is a convenient location to check them. I don't have the manual in front of me at the moment so I can't tell you what page it's on.

So then, the blinking points to nothing specific then, therefore the long way it is. Thank you that is exactly what i wanted to know, the 70s were easier to work on  :-DD

https://www.eevblog.com/forum/repair/tektronix-2465b-repair/ (https://www.eevblog.com/forum/repair/tektronix-2465b-repair/)

i think I might have found a clue for you, Neo. Having just built a dim-bulb tester recently I was keen to use it to power up the 2465B I mention above. It didn't like it. The bulbs brightened, fans on, the leds on the 'scope all came on, then all went off, fan off, then it tries to do it again. It starts as normal (barring the missing display) when plugged directly into the mains. I'm thinking that the cold resistance of the filaments in series with the inrush current limiters, which are NTC thermistors, is stopping the switching psu from starting, and that may be the issue that is affecting your 'scope.

On my 2467B the larger thermistor (RT1010) had drifted high and the resistor in parallell (R1010) with it had opened. If your R1010 has drifted high rather than opened it could be having a similar effect to my dim-bulb tester and not allowing enough current through to get the switcher started.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on May 04, 2018, 11:33:26 pm
Anyone know what it means when a 2465B bleeps its front lights? Fan's running and it starts up like normal until it starts that, the blinking of it's front light i mean.

Start with the basics and work from there. Make absolutely certain all your supply voltages are within spec as far as voltage and ripple. J119 on the main board is a convenient location to check them. I don't have the manual in front of me at the moment so I can't tell you what page it's on.

So then, the blinking points to nothing specific then, therefore the long way it is. Thank you that is exactly what i wanted to know, the 70s were easier to work on  :-DD

https://www.eevblog.com/forum/repair/tektronix-2465b-repair/ (https://www.eevblog.com/forum/repair/tektronix-2465b-repair/)

i think I might have found a clue for you, Neo. Having just built a dim-bulb tester recently I was keen to use it to power up the 2465B I mention above. It didn't like it. The bulbs brightened, fans on, the leds on the 'scope all came on, then all went off, fan off, then it tries to do it again. It starts as normal (barring the missing display) when plugged directly into the mains. I'm thinking that the cold resistance of the filaments in series with the inrush current limiters, which are NTC thermistors, is stopping the switching psu from starting, and that may be the issue that is affecting your 'scope.

On my 2467B the larger thermistor (RT1010) had drifted high and the resistor in parallell (R1010) with it had opened. If your R1010 has drifted high rather than opened it could be having a similar effect to my dim-bulb tester and not allowing enough current through to get the switcher started.

An SMPS, unlike a selenium rectifier, will attempt to deliver constant output power. If the input voltage is abnormally low, the input current will be abnormally high - and that can cause "problems".
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: andy2000 on May 05, 2018, 01:33:19 pm

I tested it on a late 2465B and a late 2445B, both set the intensity to the same intensity as adjusting the intensity knob to the mid-position. On one this is fine, on the other it is to dark. But both are equal to the mid-position if adjustet by hand.

Re-adjusting grid bias and the other intensity adjustments (see the service manual) so that mid-position of the intensity pot gives a "normal" intensity will help.

It's good to know it's normal.  I'll readjust it to provide usable intensity at mid range.  It seems strange that it couldn't just remember the previous intensity value and recall it when it's done. 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: andy2000 on May 05, 2018, 01:46:05 pm
Hi all, just received a very clean 2465B with a perennial problem: Start-up proceeds right up until the ADD led comes on and it stops. A/B TRIG brings about normal front-panel operation but no display or trace on the CRT, but it is glowing. So I have a look at A5 around the DAC area and look what I find! Green pins, and one corroded torx bolt are the only real evidence of electrolyte release, but thankfully I took pictures, and I'll lay ten-to-one that that resistor there has opened, or one near-by.

One question I have: does anyone know when these SMD control boards first started failing? This machine was last cal'd (by Tek, no less, it was owned by Sony Europe) in '09, when this particular A5 board was already 19 years old. Considering SMD hadn't been around that long in 1990 that's really not bad going.

With any luck that will be the only issue (apart from the dreaded cracked Rifas of course) this baby has!

I started seeing numerous problems with leaking SMD caps in consumer devices as long ago as the mid 90's.  I'm not sure when these started to leak, but I would guess they had been leaking for many years before symptoms started to show up.  I doubt they even opened your scope when they calibrated it if it met specs when they tested it. 

I don't think I've ever seen an SMD electrolytic made before the late 90's that wasn't bad.  My suspicion is that the seals in the early SMD caps couldn't take the heat from the reflow oven.

You'll have to look carefully for open traces.  I had to remove the DAC to inspect underneath, and verify the continuity of all traces in the affected areas with an ohm meter.  I ended up finding about 5 open, or nearly open traces.

Definitely backup your Dallas NVRAM ASAP.  Mine failed a few days after I started working on it.  Unfortunately, I can't find the backup I thought I made when I first bought the scope a couple of years ago! 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on May 05, 2018, 04:26:32 pm

I tested it on a late 2465B and a late 2445B, both set the intensity to the same intensity as adjusting the intensity knob to the mid-position. On one this is fine, on the other it is to dark. But both are equal to the mid-position if adjustet by hand.

Re-adjusting grid bias and the other intensity adjustments (see the service manual) so that mid-position of the intensity pot gives a "normal" intensity will help.

It's good to know it's normal.  I'll readjust it to provide usable intensity at mid range.  It seems strange that it couldn't just remember the previous intensity value and recall it when it's done.

The previous value might be invalid, since the signal and hence timebase may have significantly changed.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: cheeseit on May 05, 2018, 10:39:01 pm
This may be a redundant question, but would you guys change the Dallas NVRAM while you had the board off. I'm really hoping someone is going to say: "No, Gerry, you don't need to learn how to read and program cal data just yet." Anyone?

Most definitely. At the very least get a backup of your cal data, either by using the exerciser and record the data or by reading its content. That will be far easier than going through calibration if you lose your data. You'll find all the info you'd need on how to do it in this very thread.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: GerryBags on May 05, 2018, 10:59:24 pm
I ordered the little TL866 mini programmer about half an hour ago and have just finished watching Dave's review.  :-+ this thread has already come in handy a couple of times, so a big thanks to all the people who've contributed to it!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on May 05, 2018, 11:11:19 pm
This may be a redundant question, but would you guys change the Dallas NVRAM while you had the board off. I'm really hoping someone is going to say: "No, Gerry, you don't need to learn how to read and program cal data just yet." Anyone?

Most definitely. At the very least get a backup of your cal data, either by using the exerciser and record the data or by reading its content. That will be far easier than going through calibration if you lose your data.
I was always to chicken to get one of these great scopes (and part of me would still like one) for the risk of losing the Cal data but the above is excellent advice.  :-+
Make some record, any record is better than none so when the Dallas battery dies you're not left totally high and dry.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on May 06, 2018, 08:08:20 am
One question I have: does anyone know when these SMD control boards first started failing? This machine was last cal'd (by Tek, no less, it was owned by Sony Europe) in '09, when this particular A5 board was already 19 years old. Considering SMD hadn't been around that long in 1990 that's really not bad going.

There is post few pages back, similar to your problem, that the leaked liquid from the electrolytic cap also ruined the PCB traces and pins under and surrounding components  :(, here is the affected board photo and the description, just beware.

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=137900;image)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on May 06, 2018, 08:27:27 am
I was always to chicken to get one of these great scopes (and part of me would still like one) for the risk of losing the Cal data but the above is excellent advice.  :-+

Still waiting you to join the club Rob.  :P
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on May 06, 2018, 08:40:45 am
I was always to chicken to get one of these great scopes (and part of me would still like one) for the risk of losing the Cal data but the above is excellent advice.  :-+

Still waiting you to join the club Rob.  :P
Once upon a time (fairy tale starting  ::)) I did relish fixing scopes but the demands of what I do now takes away all that spare time.  :(
TBH I probably never will as there's only a few months now to wait for something new in an entirely different league.
If I'm real lucky I'll get one to beta test but probably not.  :(
Anyways, I've started saving for it.......

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on May 06, 2018, 08:44:33 am
All,
  My scope is currently fully assembled, so I could not look at the inverter board. However, I did consult my 2445B manual (also covers 2455B) and saw the same component size mismatch as shown in previous posts. I also have a copy of the service manuals for the 2445 and the 2465. Those have the diagrams with the physical size correct, but positioned slightly different. According to all three manuals I have, the parts list C1114 and C1115 as the same value. When looking at the 2445 board layout, the physical size of both C1114 and C1115 are the same, with C1132 being physically smaller. According to what I see in my manuals, C1132 is supposed to be 10uf@160v, C1115 is supposed to be 250uf@20v.

Mitch

It may be that only the "B" versions are affected judging from your layouts.

As stated before, the BOM and schematics are correct. Here are annotated uncorrected and corrected versions of fig 10-13 from service manual 070-6863-01

Uncorrected:
(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=426241;image)

Corrected:
(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=426247;image)

Re quoting Howardlong's post #475 (HERE (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg645469/#msg645469)) above as I think this is important one, but with this forum's local attachment as these images are currently hosted at Photobucket.com, my browser can't view it.

Re-attaching the photos here below and also edited Howardlong's post above with the images from the attachments below.

Just worry if someday photobucket.com change their business, as like other problems we've encountered in this forum at images hosted externally that are gone forever.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: GerryBags on May 06, 2018, 05:28:47 pm
One question I have: does anyone know when these SMD control boards first started failing? This machine was last cal'd (by Tek, no less, it was owned by Sony Europe) in '09, when this particular A5 board was already 19 years old. Considering SMD hadn't been around that long in 1990 that's really not bad going.

There is post few pages back, similar to your problem, that the leaked liquid from the electrolytic cap also ruined the PCB traces and pins under and surrounding components  :(, here is the affected board photo and the description, just beware.

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?

action=dlattach;attach=137900;image)

Yes, that was what made me go back and look at the green pins on mine. I can only see a couple of other affected components nearby, none of the ICs have any corrosion on their pins but I will check the continuity of all the traces in that area. Mine looks like a much milder case, fortunately.

I saw a YT video last night of a guy fixing up a TDS540 with no display, and it was caused by exactly the same thing: corroded pins on components and ICs near SMD electrolytics that look normal but have green pins. It looks like heat is causing the caps to break their seals while still working, as the caps aren't dead short after removal but the capacitance drifts with applied voltage. Electrolyte vapor is going to affect the highest current pins near it in that scenario I think (please correct me if not) which seems to fit with the observed damage.

I've ordered some of that Quik-Chip SMD removal alloy, 2 gold pin sockets and 2 Maxim DS1225Y-200IND+, as I may as well do the A5 on my 2467B at the same time. I thought I'd finished re-capping the PSU on that.... until I saw one little, cracked, RIFA on A3 right between the honking great transistor on its own heatsink and transformer T1050 that I'd put off due to its gittish location. I could have sworn I bought Y2 2200pF caps but could not find them anywhere, so it is still in bits waiting for parts.... the 2465B will need the same caps changing out anyway. I had some caps that were close in value, also safety caps, but as these're doing EMI filter duty on the Inverter I thought the value was going to be more critical than, say, bypass caps. Am I right? Better safe than sorry?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: cheeseit on May 06, 2018, 06:03:03 pm
At first I thought my A5 didn't look too bad but upon close examination I ended up removing quite a few components, followed by careful cleaning of both components, traces and pads before putting all the components back again. I used lots of alcohol, solderwick and a glass fiber brush for cleaning. Attached image shows what needed cleaning and I believe I reflowed a bunch of components around the areas as well.

Edit: oh, and vias too, don't forget those.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: GerryBags on May 06, 2018, 06:18:21 pm
Seeing that the top one of the two connectors inside your red boundary brings in the power from A5, checking that thoroughly will be vital, thanks! i hadn't even twigged that that might be an issue but, of course, it is in the airflow path from those caps and has plenty of potential for electrolysis.

I'm thinking that power-down might be the point when the most damage is caused. My theory goes: While the 'scope is running the SMD caps heat up and start off-gassing their electrolyte, but the fan will be pulling air from the main board on the bottom and chucking it through the port at the top of A5 where the ribbon cable comes through. Once the power is turned off, the fan stops straight away, but the caps will still be off-gassing and the PSU filter caps will ensure there is still charge on some of the pins. I wonder, if the fan ran on for a few minutes after power off, whether this would have mitigated the issue? Obviously the caps were still going to fail at some point, but they might not have caused so much... collateral damage when they did.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on May 06, 2018, 07:05:16 pm
GerryBags, appreciate if you can share & post the close up photos of the damages if any, or any other new findings on that cap problem here, hopefully not.

So many victims of these damned caps.   :(
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: GerryBags on May 06, 2018, 07:32:57 pm
Bravo-V, here's a crop of one I took on first opening. I'll make sure to document the repair, as I'm bound to make plenty of mistakes which others can learn from - although I'm going to try my damnedest not to. I'll post the pics here.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: cheeseit on May 06, 2018, 07:42:35 pm
I think more than those with arrows need attention, like the cap to the left of the upper tantalum. And possibly those rows of three vias in the upper left, some of them looks corroded.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on May 06, 2018, 07:50:44 pm
I think more than those with arrows need attention, like the cap to the left of the upper tantalum. And possibly those rows of three vias in the upper left, some of them looks corroded.

Agree, any nearby vias to the leaking caps also could act as pipe for leaking/sipping the liquid to the other side, and also the black tantalum, I would de-solder it just to inspect the trace under it, its way too close to that cap above it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: GerryBags on May 06, 2018, 08:04:45 pm
Thanks guys, I'm ratcheting up my sensitivity to the green-ness now, I'd rather exceed the affected area with my repair than have to revisit it.  I will also investigate the DAC adjust pot (R2010) very thoroughly. I've read blog posts from a couple of people who have had issues with that, maybe as it's raised off the board.

Will boiling flux keep the oxides out of the solder if those exposed pins with slight corrosion are reflowed, do you think?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on May 12, 2018, 05:01:57 pm
This may be a redundant question, but would you guys change the Dallas NVRAM while you had the board off. I'm really hoping someone is going to say: "No, Gerry, you don't need to learn how to read and program cal data just yet." Anyone?

Yes, I did. I saved a copy years ago but just last month I changed it. I tried to use an FM16W08 from ebay but it didn't work for me so I ordered a DS1225AD. Programmed it with my TL866 and all is well.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: GerryBags on May 12, 2018, 05:19:11 pm
I carried out the SMD cap replacement on the A5 of my 2467B (same as 2465B) as this one didn't appear to be in bad condition at all. As pointed out earlier by someone, appearances can be deceptive! The two uppermost (closest to the camera), a 10uF and a 33UF had both eaten their pads. For the 10uF (on the left in the pic) had only left half a via to solder to, hence the monstrosity you see extending past the via. Getting a pair of lock tweezers on that extension was the only way I could sink it to stop it moving when the cap went on top. It works anyway, the last shot is of the 'scope after I put it back together.

I tried to desolder the first cap, but there is not enough access to the negative pad, until you cut away the plastic seat, so for the other three I cut the plastic seat, snipped off the cap away from its pads, then desoldered the pads. By the last cap I'd gotten the hang of it, isn't that always the way?  :)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: GerryBags on May 13, 2018, 01:44:16 am
It seems that I have issues with U500, the A/B trigger hybrid. The readout got fainter as I put the 'scope through its paces, and I found that the A/B trigger button wasn't working properly.

Now I get no readout at all apart from a brief flash on start-up telling me it has failed "Test 05  40", which is the main board, a positive peak that is too positive, possibly a problem with the line trigger, but definitely something to do with U500. The readout issue may be related, as the trigger hold-off time or time spent waiting for a trigger event is used (2nd priority, I think) to display the readout, or completely separate. The main board is implicated in the readout troubleshooting chart at one point, but I can't get to that point without a scope to check for a 425mV sine wave. I'll let everyone know what I find, as all this is applicable to the 2465B.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on May 13, 2018, 02:53:15 am
In order to expand and preserve the knowledge base on the 24XX series in one place without attempting to cross post please refer to the Test Equipment Anonymous (TEA) thread pages 422 to 424. My saga of scoring a pristine 2465 for the pauper's sum of $60 USD.  :-/O 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on May 13, 2018, 05:13:01 am
It seems that I have issues with U500, the A/B trigger hybrid. The readout got fainter as I put the 'scope through its paces, and I found that the A/B trigger button wasn't working properly.

Now I get no readout at all apart from a brief flash on start-up telling me it has failed "Test 05  40", which is the main board, a positive peak that is too positive, possibly a problem with the line trigger, but definitely something to do with U500. The readout issue may be related, as the trigger hold-off time or time spent waiting for a trigger event is used (2nd priority, I think) to display the readout, or completely separate. The main board is implicated in the readout troubleshooting chart at one point, but I can't get to that point without a scope to check for a 425mV sine wave. I'll let everyone know what I find, as all this is applicable to the 2465B.

If U500 took a dump you may be SOL finding one. But don't they plug onto the board? I think they do and I thought I read somewhere that they can develop contact resistance. Try reseating it and see what happens. It's worth a shot.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: GerryBags on May 13, 2018, 06:06:02 am
I've seen a couple for sale for around $40-60, but i shall make sure it is that first. I'll definitely try cleaning the contacts (Thanks!), and I also have a 2465B that I can swap the hybrids with to see if there is any change. I'm also going to check J119's voltages, to see what is too positive and whether the +/-5 V rail that supplies U500 and the 10 V reference are within tolerance. I'm not too hopeful that it will be as simple as cleaning contacts, the way it got got worse over a couple of hours. No readout or display at all by the end. I'll open her up again once I've had some sleep and see what I can find.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on May 13, 2018, 08:02:45 am
In order to expand and preserve the knowledge base on the 24XX series in one place without attempting to cross post please refer to the Test Equipment Anonymous (TEA) thread pages 422 to 424. My saga of scoring a pristine 2465 for the pauper's sum of $60 USD.  :-/O

Could you provide links to the specific start/end messages, please. That thread only has 213 pages in it - see screenshot.

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=431732)

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on May 13, 2018, 08:07:58 am
In order to expand and preserve the knowledge base on the 24XX series in one place without attempting to cross post please refer to the Test Equipment Anonymous (TEA) thread pages 422 to 424. My saga of scoring a pristine 2465 for the pauper's sum of $60 USD.  :-/O

Could you provide links to the specific start/end messages, please. That thread only has 213 pages in it - see screenshot.

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=431732)
Entirely depends of your forum view settings for posts/page.  ;)
For me TEA is 400+ pages.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on May 13, 2018, 08:31:36 am
Just mention the post number instead of page number.

Still not fool proof though, if someone deleted their post before and screw up the sequence number.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on May 13, 2018, 11:28:08 am
Just mention the post number instead of page number.

Still not fool proof though, if someone deleted their post before and screw up the sequence number.

Oops, sorry...didn't think about some having different screen views. It starts at post 10542 and ends at post 10594.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: cheeseit on May 13, 2018, 02:22:11 pm
It seems that I have issues with U500, the A/B trigger hybrid. The readout got fainter as I put the 'scope through its paces, and I found that the A/B trigger button wasn't working properly.

Did you run the scope for extended periods without a fan keeping everything cool while the case was off? If so that may explain any issues with the hybrids but hopefully it's just a bad contact.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: GerryBags on May 14, 2018, 02:58:24 am
Did you run the scope for extended periods without a fan keeping everything cool while the case was off? If so that may explain any issues with the hybrids but hopefully it's just a bad contact.

Hi Cheesit, no I didn't run it all with the cover off, until just now to check the voltages on J119, because I'd been warned about hot hybrids, U800 in particular with its poor thermal connection to the board. The voltages are all well within spec, with the 10V reference being spot on. Given the "positive level too positive" note on a 4X fail I was thinking it might be something I'd done in the PSU, but I'm also not getting more than a few mV ACV reading on the the test points (my only way of checking the ripple without a working scope).

Next step is to swap out the U500 for one that I don't even know is ok. Not ideal, as the other 'scope is show the same LED code on the front! :D I'm really hoping that the blown caps and corrosion on the A5 board around the DAC ref is the cause of that one, but for all I know that U500 could be shagged too. This is going to cost me £40-£50 whether it works or not.... at least if it works I'll know, won't I?  :phew:

Edit to add: No joy. Swapped out the U500 hybrids and get exactly the same behavior as before. The A/B Trig button won't clear the error state (add LED illuminated) immediately, it takes a couple of goes to do it which, coupled with the failure to switch to the B Trig menu, makes me think it is an issue with the control board, as it involves the readout, display and the A/B trigger.  :-//

Another edit to add: I think I've narrowed it down to the area around the DAC on A5, the affected electro caps, and the ones near it are on the +/-15 V rails for the DAC and a load of op amps in the analog control section, and also one on the Vref for the DAC. It seems that most of the problems others have had with similar symptoms have all traced back there, and the fact I had to bodge up pads for one of the caps shows that the corrosion was worse than it looked on the surface (this was the "OK" board out of the two!  :-DD) and I think that the slow onset was down to a corroded trace opening once it had warmed up. At least now I'm pretty sure where I am in the schematics (1, 2 & 12) and what's doing what so I can start probing and see what I can find.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: santosp on May 29, 2018, 04:06:58 pm
Hello.
Does anyone have available a copy of the eproms for the 2465 oscilloscope?  I need specific the 160-162..-06 version, as to verify with mine originals.

Thank you.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: santosp on May 29, 2018, 08:29:09 pm
Just for the history this is the firmware dump from my scope.  :)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: emece67 on June 13, 2018, 04:49:50 pm
.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on June 13, 2018, 05:08:43 pm
Just bought this really nice 2465B, in excellent cosmetic condition and with only 750 working hours. It works superb. Being in such good cosmetic shape and working so flawlessly, I'm a bit reluctant to open it for a recap

If it is working, there are three principal issues: the RIFA mains filter caps, the three SMD electrolytic caps on the board containing the NVRAM, and the general electrolytic caps in the PSU.

Particularly on 240V, I'd always replace the RIFA caps. One detonated on my 2465, and the series resistor removed a 1cm diameter of the PCB's prepreg (and spread carbon elsewhere). This requires normal desoldering skill.

I'd replace the three SMD caps before they leak and mess up other components - as happened on my 2445B. This requires some skill with removing/replacing individual SMD components.

I wouldn't replace the electrolytic caps in the PSU unless you measure excessive ripple on any of the supplies. (OTOH, I have done just that on my 2465 :) Inconsistent? Me?)

Quote
and cal RAM refreshment, what do you think about postponing such maintenance? Serial is 134xxx.

I've recorded a video with the cal data thru EXER 02, is this enough to recover the cal data in an eventual backup battery drain?

My attitude is to record the data and replace the NVRAM iff it fails. But I haven't verified that is sufficient strategy.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on June 13, 2018, 05:32:45 pm
...
I've recorded a video with the cal data thru EXER 02, is this enough to recover the cal data in an eventual backup battery drain?

My attitude is to record the data and replace the NVRAM iff it fails. But I haven't verified that is sufficient strategy.

The EXER 02 dump is sufficient to restore the cal constants.  It was verified by someone on the Yahoo groups.io Tekscopes group a couple of months ago.  What EXER 02 doesn't do, however, is capture the various vertical, sweep, and other stored settings.  So you would lose any presets you've saved, but that's usually not of any consequence.


EDIT: I keep forgetting Tekscopes was moved from Yahoo to groups.io about 6 months ago: https://groups.io/g/TekScopes
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: cheeseit on June 13, 2018, 05:40:02 pm
I very much agree with what tggzzz suggests but would like to add that the PSU in one of my 2465B's had a few caps that were starting to leak electrolyte. It wasn't critical, nor visible before I pulled the caps, but there were a bit of corrosion. I don't think PSU caps leaking is a common problem though.

Neither have I performed the procedure but one or more in this thread verified that restoring cal data from a recording was working so you should be safe. On the other hand, if you do work on the A5 and have the board out, you might as well get it over with IMHO. Then you're safe for a dozen or more years and don't risk having it die some day when you need to use it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on June 14, 2018, 01:47:43 am
About a month ago I picked up this 2465 (sitting on top my 2465 DMS). It is in excellent condition and it appears to have low usage/hours. (The 2465 doesn't have EXER5 so can't verify the hours). I verified the supply voltages to be in spec. But despite all that I've decided to re-cap the Inverter/Regulator boards anyway. The caps are on order from Mouser and should arrive tomorrow. Next month I have to take a week furlough from work that's when I'll perform the surgery.     
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: emece67 on June 14, 2018, 08:39:25 am
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Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on June 14, 2018, 10:56:21 am
Thanks to all that answered my question.

So, well, I'll open it and perform the update, focusing on the RIFAs, PSU and the three electrolytic ones. Recently I updated the battery backed Dallas RAM in some hp54600 scopes (that was easy. All they were suffering from the vertical deflection cap syndrome), so I will also try to update it. Once opened there's no big reason to not to try a more ample overhaul, maybe including some heatsink for the U800. I'm wondering if Berillyum Copper may be a good choice for such custom made heatsink.

Thanks again and regards.

Buried in this thread you'll find the chart that lists all the caps you'll need for the Inverter/Regulator boards. But for your convenience I'll post it again. It originally came from the Tek Yahoo Group. I used it successfully 2 years ago to re-cap the 2465 DMS.

As I mentioned previously I will be re-capping the PSU on this recently purchased 2465. I plan on doing it the week of July 8-14 and I will do a full pictorial of the process. So if you can wait until that time it will give you a better idea on completing the job successfully. There are pitfalls to watch out for....like mistakes in the service manual...which can lead you to a dead instrument and magic smoke. I've been down that path before so I know how to avoid these issues.

U800. Be very cautious here. Your 2465B has a Maxium chip which is known to have issues. My take on it is that it's been in there 30 years, leave it alone. Don't operate the scope for long periods without the case installed and make sure the fan operates properly. But if want to install a heatsink make it one that just epoxies to the top of the chip. DO NOT under any circumstances mess with the screws or nuts that secure the chip to the board. Chances are you'll cause uneven torque and the chip will fail. And also be aware that those screws are not at ground potential.         
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on June 14, 2018, 11:55:37 am
Once opened there's no big reason to not to try a more ample overhaul, maybe including some heatsink for the U800.

The U800 in my 2465 is cool to the touch. There's no way I will fool with it, given the reports I've seen about how easy it can be to introduce problems.

"If it works, leave it alone".

As for which capacitors to use, there's currently a long discussion about it on the TekScopes group - including a couple of lists of capacitors.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: emece67 on June 14, 2018, 08:37:58 pm
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Title: Re: Tektronix 2465B oscilloscope teardown
Post by: vik on June 20, 2018, 12:10:33 am
Hi all,

Thanks for everyone who contributed to this thread, I have found it invaluable. I owned a 2465A for nearly 10 years but lately I've started to worry about the 30+ years old battery dying one day, taking my calibration data with it. After reading the part of this thread about backing up the memory using exerciser 02 or GPIB, I have built my own cheap GPIB adapter and backed up the data. Please allow me to share some findings.

First, a really cheap GPIB interface can be built from an Arduino Mega (or possibly an Uno even), a pack of jumper leads, a 26 pin ribbon cable cut in half and a rather plasticy but functional 26 pin Centronics to ribbon cable connector from Ebay / Hong Kong. I used this library: https://github.com/mathiashelsen/agipibi. I have forked it and added another Python program that lets you send commands directly:  https://github.com/viktorradnai/agipibi/blob/master/python/gpib_console.py

I have also accidentally discovered that the 'earom? f' command prints the entire contents of the memory at once:

vik@cygnus:~/priv/projects/arduino/gpib/agipibi/python$ ./gpib_console.py
2018-06-20 00:21:47,795 WARNING No reponse to ping, you should reset the board
2018-06-20 00:21:47,795 INFO Get instrument ID
2018-06-20 00:21:48,044 INFO ID: ID TEK/2465A,V81.1,SYS:FV06,BB:FV01,GPIB:FV02;

agipibi> key 0
agipibi> earom? f
EAR 0:11,1750,9930,1717,9906,9954,10102,10039,1822,9963,1718,647,8837,8838,644,8855,8828,648,8842,651,8868,97,31,31,8225,32,15820,7198,7459,15645,16295,16290,8111,16290,16310,8759,8759,565,570,7907,15667,7474,8192,16328,8099,8105,8111,8138,744,747,743,8933,2144,2134,10331,10314,10301,10328,10301,8298,2140,10334,10324,10310,2137,2108,110,842,823,837,1648,1627,1700,9834,696,8915,6238,11894,11795,1828,1819,566,583,302,8492,2042,10238,1435,9028,9025,830,9018,827,827,8883,8883,9935,1359,9018,8897,707,827,832,9020,832,8903,713,8885,8381,205,173,65312,65280,65298,254,631,511,32893,65282,65344,767,2303,63752,65344,32512,65280,16895,8703,255,255,65408,65280,47872,65280,255,255,65280,57120,255,254,255,255,65280,65282,48896,61328,222,2265,32991,32895,57104,65280,32963,39135,63232,32008,57088,64832,16831,229,254,255,65280,65280,65280,48896,255,255,65296,64256,9610,255,255,239,65280,65296,48916,47969,4319,33014,763,253,49026,65296,239,255,29440,65280,61184,65296,32891,239,255,191,65280,65280,65280,65280,255,255,65280,65280,255,33023,255,255,65288,65352,64802,65296,4351,16503,4792,16575,65280,65296,8959,255,65280,30464,65024,63360,9182,6399,511,255,65280,65280,65280,65280,255,255,65280,65280,255,127,8447,255,65280,65281,63232,32672,127,6399,127,16582,61188,65288,4351,37119,13104,32256,5376,40704,8005
agipibi> ^C
vik@cygnus:~/priv/projects/arduino/gpib/agipibi/python$

It also seems like the 2465A only has entries from 0-254. 255 is zero and from 256 onwards the values wrap around. Is that enough to back up all of my calibration data?

I don't feel like experimenting with restoring the settings, but I'm happy to write another script that does this over GPIB in one go if someone is willing to test.

I have looked around in my scope and it was surprisingly clean and dust free. I did not see many electrolytic caps and the couple I've found seemed OK. Is there anything else I would be advised to do to future-proof the scope? The guides I've seen about cap replacement, etc, were mostly for the 2465B.

Regards,
Vik
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: emece67 on June 20, 2018, 07:40:44 am
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Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on June 20, 2018, 01:53:05 pm
...
It also seems like the 2465A only has entries from 0-254. 255 is zero and from 256 onwards the values wrap around. Is that enough to back up all of my calibration data?

I don't feel like experimenting with restoring the settings, but I'm happy to write another script that does this over GPIB in one go if someone is willing to test.
...
The 256 values should match what you see in EXER 02, in which case, yes, it has all of your calibration data.

Putting the calibration data back via GPIB works on a 2465(plain), but I haven't heard of anyone trying it yet on an A or B.  There's no reason to think it would operate differently, but until someone tries it I guess we don't know for sure.  I've been watching for an A or B junker on ebay for some time now to do this experiment.

Nice find on the "f" option to the EAROM command, thanks!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: vik on June 20, 2018, 03:11:09 pm
The 256 values should match what you see in EXER 02, in which case, yes, it has all of your calibration data.
A spot check of a few memory locations (including the start and end) indicates that the data does match up.

Putting the calibration data back via GPIB works on a 2465(plain), but I haven't heard of anyone trying it yet on an A or B.

I would try this if I could only find someone near me (around London, UK) who can re-calibrate the scope (for a sensible price) in the event of the experiment going wrong.

Also I'd like to replace the Keeper battery at some point but I cannot find a source for it on this side of the pond. There is an LTC-7PN sold on Ebay UK (https://www.ebay.co.uk/itm/EVE-EF651625-LTC-7PN-Size-750mAh-Lithium-Battery-Cell-3-6V-PCB-Pin-232542/142821167102 (https://www.ebay.co.uk/itm/EVE-EF651625-LTC-7PN-Size-750mAh-Lithium-Battery-Cell-3-6V-PCB-Pin-232542/142821167102)) under a (rather convincingly named) brand called EVE or "Energy Very Endure". Has anyone used one of them? Looks like the difference is that the casing is metal rather than plastic. The US sellers I've looked at either won't ship overseas or charge an arm and leg.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: z01z on June 21, 2018, 07:53:09 pm
Also I'd like to replace the Keeper battery at some point but I cannot find a source for it on this side of the pond. There is an LTC-7PN sold on Ebay UK (https://www.ebay.co.uk/itm/EVE-EF651625-LTC-7PN-Size-750mAh-Lithium-Battery-Cell-3-6V-PCB-Pin-232542/142821167102 (https://www.ebay.co.uk/itm/EVE-EF651625-LTC-7PN-Size-750mAh-Lithium-Battery-Cell-3-6V-PCB-Pin-232542/142821167102)) under a (rather convincingly named) brand called EVE or "Energy Very Endure". Has anyone used one of them? Looks like the difference is that the casing is metal rather than plastic. The US sellers I've looked at either won't ship overseas or charge an arm and leg.
Yes, the availability of the original battery in Europe is limited. Mouser sells it, sadly only in the US.
I did manage to get one from ebay a few years back, as you've mentioned it's not urgent for you, so you could wait and see if one appears.
Btw, these other brands can be had from retailers, for example Conrad sells the one you've found. These might be just as good as the original, but you never know. Unless you buy one and use it for 30 years :).
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: james_s on June 22, 2018, 04:34:11 pm
Is there space to install a holder for something else? How about a CR2032? They're dirt cheap and readily available. I don't know how much the capacity of the originals is.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on June 25, 2018, 03:02:13 am
I've got my 2445B few years ago and it was waiving like crazy. I knew there must be something wrong with the PS and I found this http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf. (http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf.) I recapped the power supply with the exception of the two big Sprague 290uF and the Rifa caps. Last week I ordered two 330uF Nichicon PW and the Rifa caps (well most of them, I missed two) and I opened it up to replace them. To my surprise, the Sprague ESR was better than the new Nichicon, 25mOhm Sprague and 100mOhm Nichicon so I didn't replace them. Sure enough, the Rifa caps were all micro cracked.
One relatively annoying issue that I have is that I can see a small flicker, a tiny fluctuation of the intensity. Do you know where it can come from? It has over 40K hours so I may need to recap the main board?
Also, the intensity knob is cracked. Do you know where I can get one without having to sell the scope to buy it?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: z01z on June 25, 2018, 05:34:16 am
Also, the intensity knob is cracked. Do you know where I can get one without having to sell the scope to buy it?
You could check Qservice (https://www.qservice.tv/vpasp/), they sell various Tek parts. No affiliation, just a happy customer.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: pquadrat on June 25, 2018, 09:03:36 am
I've got my 2445B few years ago and it was waiving like crazy. I knew there must be something wrong with the PS and I found this http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf. (http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf.) I recapped the power supply with the exception of the two big Sprague 290uF and the Rifa caps. Last week I ordered two 330uF Nichicon PW and the Rifa caps (well most of them, I missed two) and I opened it up to replace them. To my surprise, the Sprague ESR was better than the new Nichicon, 25mOhm Sprague and 100mOhm Nichicon so I didn't replace them. Sure enough, the Rifa caps were all micro cracked.
One relatively annoying issue that I have is that I can see a small flicker, a tiny fluctuation of the intensity. Do you know where it can come from? It has over 40K hours so I may need to recap the main board?
Also, the intensity knob is cracked. Do you know where I can get one without having to sell the scope to buy it?

I think the light flicker is normal and part of the design. All of my three scopes have it, one has only 800 hours of operation. Also the flickering of the LEDs on the front panel when You press buttons seems to be normal. Did not change with replacing all caps in the power supply at all.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on June 25, 2018, 09:18:57 am
I've got my 2445B few years ago and it was waiving like crazy. I knew there must be something wrong with the PS and I found this http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf. (http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf.) I recapped the power supply with the exception of the two big Sprague 290uF and the Rifa caps. Last week I ordered two 330uF Nichicon PW and the Rifa caps (well most of them, I missed two) and I opened it up to replace them. To my surprise, the Sprague ESR was better than the new Nichicon, 25mOhm Sprague and 100mOhm Nichicon so I didn't replace them. Sure enough, the Rifa caps were all micro cracked.
One relatively annoying issue that I have is that I can see a small flicker, a tiny fluctuation of the intensity. Do you know where it can come from? It has over 40K hours so I may need to recap the main board?
Also, the intensity knob is cracked. Do you know where I can get one without having to sell the scope to buy it?

I think the light flicker is normal and part of the design. All of my three scopes have it, one has only 800 hours of operation. Also the flickering of the LEDs on the front panel when You press buttons seems to be normal. Did not change with replacing all caps in the power supply at all.

Mine does that too.

Read this somehere that its common for B model (2445B & 2465B), to have that annoying whole panel's faint LEDs flickering everytimes when any button was pressed.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on June 25, 2018, 09:24:55 am
I've got my 2445B few years ago and it was waiving like crazy. I knew there must be something wrong with the PS and I found this http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf. (http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf.) I recapped the power supply with the exception of the two big Sprague 290uF and the Rifa caps. Last week I ordered two 330uF Nichicon PW and the Rifa caps (well most of them, I missed two) and I opened it up to replace them. To my surprise, the Sprague ESR was better than the new Nichicon, 25mOhm Sprague and 100mOhm Nichicon so I didn't replace them. Sure enough, the Rifa caps were all micro cracked.
One relatively annoying issue that I have is that I can see a small flicker, a tiny fluctuation of the intensity. Do you know where it can come from? It has over 40K hours so I may need to recap the main board?
Also, the intensity knob is cracked. Do you know where I can get one without having to sell the scope to buy it?

I think the light flicker is normal and part of the design. All of my three scopes have it, one has only 800 hours of operation. Also the flickering of the LEDs on the front panel when You press buttons seems to be normal. Did not change with replacing all caps in the power supply at all.

Mine does that too.

Read this somehere that its common for B model (2445B & 2465B), to have that annoying whole panel's faint LEDs flickering everytimes when any button was pressed.
Now there's a nice little challenge for you !
Is more front panel bulk capacitance needed for the LED supply rails or is it a digital glitch affecting the the switching for the LEDs ?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on June 25, 2018, 09:25:19 am
I've got my 2445B few years ago and it was waiving like crazy. I knew there must be something wrong with the PS and I found this http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf. (http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf.) I recapped the power supply with the exception of the two big Sprague 290uF and the Rifa caps. Last week I ordered two 330uF Nichicon PW and the Rifa caps (well most of them, I missed two) and I opened it up to replace them. To my surprise, the Sprague ESR was better than the new Nichicon, 25mOhm Sprague and 100mOhm Nichicon so I didn't replace them. Sure enough, the Rifa caps were all micro cracked.
One relatively annoying issue that I have is that I can see a small flicker, a tiny fluctuation of the intensity. Do you know where it can come from? It has over 40K hours so I may need to recap the main board?
Also, the intensity knob is cracked. Do you know where I can get one without having to sell the scope to buy it?

I think the light flicker is normal and part of the design. All of my three scopes have it, one has only 800 hours of operation. Also the flickering of the LEDs on the front panel when You press buttons seems to be normal. Did not change with replacing all caps in the power supply at all.

Mine does that too.

Read this somehere that its common for B model (2445B & 2465B), to have that annoying whole panel's faint LEDs flickering everytimes when any button was pressed.

My 2465 DMS does it but strangely my no option 2465 does not.  :-//
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on June 25, 2018, 09:31:54 am
I've got my 2445B few years ago and it was waiving like crazy. I knew there must be something wrong with the PS and I found this http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf. (http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf.) I recapped the power supply with the exception of the two big Sprague 290uF and the Rifa caps. Last week I ordered two 330uF Nichicon PW and the Rifa caps (well most of them, I missed two) and I opened it up to replace them. To my surprise, the Sprague ESR was better than the new Nichicon, 25mOhm Sprague and 100mOhm Nichicon so I didn't replace them. Sure enough, the Rifa caps were all micro cracked.
One relatively annoying issue that I have is that I can see a small flicker, a tiny fluctuation of the intensity. Do you know where it can come from? It has over 40K hours so I may need to recap the main board?
Also, the intensity knob is cracked. Do you know where I can get one without having to sell the scope to buy it?

I think the light flicker is normal and part of the design. All of my three scopes have it, one has only 800 hours of operation. Also the flickering of the LEDs on the front panel when You press buttons seems to be normal. Did not change with replacing all caps in the power supply at all.

Mine does that too.

Read this somehere that its common for B model (2445B & 2465B), to have that annoying whole panel's faint LEDs flickering everytimes when any button was pressed.
Now there's a nice little challenge for you !
Is more front panel bulk capacitance needed for the LED supply rails or is it a digital glitch affecting the the switching for the LEDs ?

Its the digital glitch, as pquadrat pointed above, and also again read it somewhere (damn, I forgot where ? maybe years ago at old Tek yahoo group ? :palm:) that modding or improving the bulk cap at the panel's rail doesn't fix it.

Challenge ? Don't have the gut yet and I guess this will involve heavy use on logic analyzer.  :P
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on June 25, 2018, 12:18:13 pm
It is not front panel LED flicker, it is CRT flicker. Tiny but noticeable and random, not following a pattern. I did recap all of the power supply with the exception of the two big blue Sprague caps which are OK.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on June 25, 2018, 12:34:24 pm
It is not front panel LED flicker, it is CRT flicker. Tiny but noticeable and random, not following a pattern.
How can they be one in the same ?  :-//
Sounds like a power rail issue to me......tantalums sputtering maybe ?

We well know Tek wasn't conservative with tant voltage ratings so I wonder now many are running close to their rated voltages in 24** scopes ?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on June 25, 2018, 02:12:36 pm
One relatively annoying issue that I have is that I can see a small flicker, a tiny fluctuation of the intensity. Do you know where it can come from? It has over 40K hours so I may need to recap the main board?

Is the flicker still there when the readouts are turned off, i.e. the readout control in the central position? The readouts "steal" time from the main trace, and that can cause intensity variations depending on the sweep time.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on June 25, 2018, 06:48:14 pm
I think the light flicker is normal and part of the design. All of my three scopes have it, one has only 800 hours of operation. Also the flickering of the LEDs on the front panel when You press buttons seems to be normal. Did not change with replacing all caps in the power supply at all.

Mine does that too.

Read this somehere that its common for B model (2445B & 2465B), to have that annoying whole panel's faint LEDs flickering everytimes when any button was pressed.

Now there's a nice little challenge for you !
Is more front panel bulk capacitance needed for the LED supply rails or is it a digital glitch affecting the the switching for the LEDs ?

Like the 4 channel 22xx series oscilloscopes, the LEDs are controlled through 74164 style shift registers which lack a registered output so every time the shift register data is clocked, the LEDs flicker as their data is reloaded.  In a way this is advantageous albeit annoying because it shows that the shift registers are being accessed.

Technically since the shift registers driving the LEDs have their own independent clock, they only need to be accessed when the LED outputs are updated but for whatever reason, Tektronix updates them on certain events even when their data is not changed.

One relatively annoying issue that I have is that I can see a small flicker, a tiny fluctuation of the intensity. Do you know where it can come from? It has over 40K hours so I may need to recap the main board?

Is the flicker still there when the readouts are turned off, i.e. the readout control in the central position? The readouts "steal" time from the main trace, and that can cause intensity variations depending on the sweep time.

Exactly, the beam is multiplexed to produce the readout while traces are being drawn resulting in trace flicker.  Shut all of the readout off by centering the readout intensity control to see if the flicker stops before assuming that there is a problem.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on June 26, 2018, 01:37:19 am
Also, the intensity knob is cracked. Do you know where I can get one without having to sell the scope to buy it?
You could check Qservice (https://www.qservice.tv/vpasp/), they sell various Tek parts. No affiliation, just a happy customer.

Thanks, I will think about it $7.99+$9=16.99. I may try to repair mine first.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on June 26, 2018, 01:44:04 am
One relatively annoying issue that I have is that I can see a small flicker, a tiny fluctuation of the intensity. Do you know where it can come from? It has over 40K hours so I may need to recap the main board?

Is the flicker still there when the readouts are turned off, i.e. the readout control in the central position? The readouts "steal" time from the main trace, and that can cause intensity variations depending on the sweep time.

Yes, it is still there with the readout off....but....I don't think it is the scope. Since I don't have much use for it these days I connected my Dutchtronix scope clock just for fun. It is that thing that flashes I think. Probably the internal processing makes it miss some scan cycles.
Looks like a square wave from the Feeltech FY6600 doesn't flicker. I will check more tomorrow, I'm too tired tonight. Thank you all for your suggestions!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on July 08, 2018, 11:38:20 pm
The subject of this several part post will be a road map for re-capping the PSU Regulator/Inverter boards in the 2465, 2465A, and 2465B. It will not cover known issues with the A5 board which went under considerable change through out the 24XX series. I think most of what will be discussed here will also apply to the 2445 but I'm not totally sure. If someone knows that answer go ahead and chime in.

The candidate: The top 2465. The bottom 2465 DMS had it's PSU re-capped 2 years ago by me.

(https://imagizer.imageshack.com/v2/xq90/923/3Y2ptB.jpg) (https://imageshack.com/i/pn3Y2ptBj)

What I know about this 2465: I purchased it 2 months ago. Appears to have a build date of 1983. It was owned by IBM. I suspect it has low hours judging by it's condition which is very good. (The 2465 does not have EXER05 which logs the hours so I can't be absolutely sure). No errors on power up and all critical parameters appear to be in spec. I had it apart about a month ago and measured the supply voltages at J119 and they were all in spec. The supply caps are all original hence the re-cap. But no leakers were observed.

Tools required: All the fasteners in the 24XX are torx. So you will need a suitable driver. Also refer to post #1069 where I attached the cap replacement chart used. All the caps were purchased from Mouser.


Upon removal of the rear cover if you have a 2465 you will encounter this cage fan. The 2465A and B use a conventional computer type fan which requires no additional attention. This cage fan is notorious  for becoming very noisy and rattling. The one in this 2465 is whisper quiet, which gives me additional evidence that this scope has low hours. The cage fan in my 2465 DMS rattles like hell for about a half hour and then settles down to quiet. I do have a replacement computer fan built up and ready to be installed if required but will require modification to the rear cover. The cage fan is driven by a Siemens motor which is unobtanium as a replacement and ridiculously complex to rebuild as shown by this link:

http://antiqueradios.com/forums/viewtopic.php?f=8&t=235478 (http://antiqueradios.com/forums/viewtopic.php?f=8&t=235478)

(https://imagizer.imageshack.com/v2/xq90/921/2ItFA5.jpg) (https://imageshack.com/i/pl2ItFA5j)

Remove the center nut on the fan. Spray some Deoxit into the center hub to act as a lubricant. Now the fun begins. VERY CAREFULLY start to pry the fan off the shaft. If you are lucky the fan and center collet will come off in one piece. The other alternative is that the fan will come off and the center collet will remain on the shaft. That's also OK. But what most likely will happen is the collet will snap in half with part on the shaft and part inside the fan. But don't worry, it can be epoxied back together. This happen to me when I pulled it apart a month ago but didn't happen this time. And you are not alone here, it happens to just about all of them.

(https://imagizer.imageshack.com/v2/xq90/921/NoOgvO.jpg) (https://imageshack.com/i/plNoOgvOj)

The fan successfully removed from the motor shaft.

(https://imagizer.imageshack.com/v2/xq90/921/vhCz6P.jpg) (https://imageshack.com/i/plvhCz6Pj)

And now to the top cover. This 2465 has no options so just remove all the fasteners and pull it off. But if you have any options such as GPIB, Counter/Trigger, Probe Power, etc things are a little more complex. There will be a buffer board attached to the underside of the cover and additional wiring interconnects, including to the PSU. Note where everything goes and take additional pictures if necessary. If you have a 24XX with the DMM option you have to totally remove that board before you can even access the top cover. And wiring interconnects running all over. And it's a nightmare to put put back together. The 2465 DMS is that nightmare.

(https://imagizer.imageshack.com/v2/xq90/923/C7WBa5.jpg) (https://imageshack.com/i/pnC7WBa5j)

Once the cover is removed the supply is now accessible. Part 2 will remove it and get it ready for re-cap.

(https://imagizer.imageshack.com/v2/xq90/924/cM5HkJ.jpg) (https://imageshack.com/i/pocM5HkJj)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on July 09, 2018, 12:54:28 am
Part 1 got the scope torn down to access the PSU. Part 2 here will get the supply out and the Regulator and Inverter boards separated to perform the re-cap.

Remove the ribbon cable from the A5 board.

(https://imagizer.imageshack.com/v2/xq90/922/QWdqRa.jpg) (https://imageshack.com/i/pmQWdqRaj)

Remove the plastic cover from the line filter. If your mains voltage is 240V you should consider changing the line filter. There have been reports of magic smoke release from 240V but not from 120V. My mains is 120V so I'm leaving it. Remove the jumpers from the line filter and fuse holder to the PSU. Same for voltage selector switch under it. Remove the 2 white wire connectors in the center of the board. The boards are secured by 2 fasteners on the back panel and 3 fasteners on the lower heatsink. Once they are removed the board can be pulled out.

(https://imagizer.imageshack.com/v2/xq90/924/XFU7BR.jpg) (https://imageshack.com/i/poXFU7BRj)

The PSU on the bench, ready to be disassembled. Take lots of pictures from multiple angles on how it goes together.

(https://imagizer.imageshack.com/v2/xq90/924/BmMTYw.jpg) (https://imageshack.com/i/poBmMTYwj)

There are 4 clips....2 on top, 2 on the bottom. Carefully pry them off.   

(https://imagizer.imageshack.com/v2/xq90/923/2NFRI6.jpg) (https://imageshack.com/i/pn2NFRI6j)

There are 4 of these interconnects. Release the tab and carefully pull them up completely. Do not bend them or you'll have a hard time in reassembly.

(https://imagizer.imageshack.com/v2/xq90/924/V8ZgAQ.jpg) (https://imageshack.com/i/poV8ZgAQj)

Disassemble and pull the Regulator board off the Inverter board. Set the Inverter board aside. The Regulator board will be done first.

(https://imagizer.imageshack.com/v2/xq90/922/oR8B8F.jpg) (https://imageshack.com/i/pmoR8B8Fj)

The Regulator board is now ready for re-cap.

(https://imagizer.imageshack.com/v2/xq90/924/YEg6Uz.jpg) (https://imageshack.com/i/poYEg6Uzj)

I strongly recommend you do one capacitor at a time. Do NOT do a mass remove then mass install. Folks that have done that have run into issues. There is a famous mistake in the service manual, specifically on the parts diagram that reverses C1132 and C1115 resulting in a low voltage cap in a high voltage circuit. You know the result.

Follow the value/rating you remove with what you install. One by one. Yes, it takes a lot longer. But it will be accurate. And note that the replacement chart DOES have some upgrades to higher value. That is OK and will work fine. Tomorrow we'll complete the re-cap of both boards and re-install.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on July 09, 2018, 09:09:23 am
Wow .. thanks for sharing med6753 !  :-+  :clap:

PS : All your images are saved, just in case Imageshack acting up in the future, hope you don't mind.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on July 09, 2018, 09:29:14 am
Wow .. thanks for sharing med6753 !  :-+  :clap:

PS : All your images are saved, just in case Imageshack acting up in the future, hope you don't mind.

Don't mind at all!  :-+

(Busy re-capping  :-DD)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on July 10, 2018, 01:21:52 am
This is Part 3 of the PSU re-cap. In this section we'll get both boards re-capped and reassembled.


Here is the Regulator board re-cap complete. No leakers or bulging caps were found. But the one RIFA cap did have it's typical internal cracking which indicated impending failure.

(https://imagizer.imageshack.com/v2/xq90/923/QGdj2e.jpg) (https://imageshack.com/i/pnQGdj2ej)

Next is the Inverter board. Remove the metal shield. If you have a 2465A or B chances are the right side of the board looks very different. (I've not seen one so I'm assuming). That assembly contains the fan motor, which only the 2465 has, and  C1021 and C1022.

(https://imagizer.imageshack.com/v2/xq90/921/HvdJWm.jpg) (https://imageshack.com/i/plHvdJWmj)

Remove that cover to expose the capacitors and the fan motor.

(https://imagizer.imageshack.com/v2/xq90/922/8CJytt.jpg) (https://imageshack.com/i/pm8CJyttj)

Remove the fan motor and put it aside. Now this is where things get a little muddy and confusing. As you can see the original capacitors are axial lead. The replacement capacitors are radial lead. This presents a fitment issue. I ran into this issue when I re-capped the 2465 DMS 2 years ago and I had to modify the assembly to get the capacitors to fit properly. I've since learned that these particular capacitors almost never fail. I tested these two capacitors and they are OK. So I've made the decision to NOT replace them. You have to decide if you want to leave them or replace them.

(https://imagizer.imageshack.com/v2/xq90/923/iSeF4X.jpg) (https://imageshack.com/i/pniSeF4Xj)

Regardless of what you decide to do with C1021 and C1022 you have to lift one lead from the board and remove that assembly to gain access to 2 capacitors underneath mounted to the board.

(https://imagizer.imageshack.com/v2/xq90/924/wCnBe4.jpg) (https://imageshack.com/i/powCnBe4j)

Once those capacitors are replaced re-install the assembly and re-solder C1021 and C1022. Install the fan motor then replace the top piece. Then continue with the rest of the re-cap of the board.

(https://imagizer.imageshack.com/v2/xq90/924/lcIUki.jpg) (https://imageshack.com/i/polcIUkij)

The re-cap of the Inverter board is now complete. Again, no leaking or bulging caps were found but 3 RIFA caps had internal cracking.

(https://imagizer.imageshack.com/v2/xq90/921/fneR4N.jpg) (https://imageshack.com/i/plfneR4Nj)

Install the shield back onto the board.

(https://imagizer.imageshack.com/v2/xq90/921/8JVvDX.jpg) (https://imageshack.com/i/pl8JVvDXj)

Re-assemble the Inverter and Regulator boards back together. They are now ready to install. Part 4 will do the install and power up.

(https://imagizer.imageshack.com/v2/xq90/922/9VpXDR.jpg) (https://imageshack.com/i/pm9VpXDRj)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on July 10, 2018, 01:58:56 am
OK, here is Part 4 of the PSU re-cap and the moment of truth. Will it power up?

Here is the PSU installed. The plastic shield back over the line filter and if you have a 2465 the cage fan is installed in the back. Then install the top cover. And if you have options make sure all interconnects are seated.

(https://imagizer.imageshack.com/v2/xq90/923/dpmlab.jpg) (https://imageshack.com/i/pndpmlabj)

Here it is. Power up and boot with no errors! Whew!  :phew:

(https://imagizer.imageshack.com/v2/xq90/923/e5oYmH.jpg) (https://imageshack.com/i/pne5oYmHj)

One final check. Allow the scope to stabilize for about 5 to 10 minutes then check J119, pin 4. That is the reference voltage. It should be between +9.99V and +10.01V. If it's out of spec adjust the pot on the Regulator board. Then verify all the voltages at J119 as per the service manual. But keep in mind that if you have options some of them derive their supply voltages from the Inverter board. The DMM option does this to insure isolation between common and ground. So if one of your options is not working properly you may need to check it's supply voltages.

Don't run the scope outside the case any longer than necessary. The case insures proper airflow to those expensive hybrids and the unobtanium U800.   

(https://imagizer.imageshack.com/v2/xq90/924/dGusEC.jpg) (https://imageshack.com/i/podGusECj)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: jkn on July 30, 2018, 04:21:33 pm
Hi all
    I have just now (finally!) joined this forum, prompted by a need/desire to do a bit of work on my Tek 2465 scope (no B or anything).

I plugged it in after many months idle a week or so ago and got a dreaded bang and puff of smoke... Having read through some of the wonderful teardown info here, from a visual inspection it looks like one of my X2 mains caps has gone (the scope still worked, even as I was powering it off quickly). But I'm taking advantage to do a few other things whilst replacing those.

One thing I am nervous about though - this removal of the fan/mandrel. Are there any other tips anyone can give apart from 'go gently and glue back up if you have to'? I've read elsewhere that you can also push a bit on the mandrel, after loosening the nut a little. I also wondered about making some sort of jug to apply pressure in the right place. Can anyone give me advice or reassurance here?

Thanks a lot from the UK

Jon N


Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on July 31, 2018, 12:18:37 am
One thing I am nervous about though - this removal of the fan/mandrel. Are there any other tips anyone can give apart from 'go gently and glue back up if you have to'? I've read elsewhere that you can also push a bit on the mandrel, after loosening the nut a little. I also wondered about making some sort of jug to apply pressure in the right place. Can anyone give me advice or reassurance here?

Thanks a lot from the UK

Jon N

Your concern about the fan assembly is certainly understandable. If you apply pressure incorrectly you could break the fan itself. That would be a difficult repair.

I haven't heard about pushing the assembly forward slightly and I'm not sure if it would help because the mandrel is tapered. And all those years assembled has resulted in the fan and the mandrel "cold fusing" together. That's where the deoxit or some other penetrating oil would help. A long thin pair of needle nose pliers against the rear hub and carefully pry forward seems to be the best method that I found. The point is....don't be afraid of it....just work carefully and chances are it will come apart.     
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: james_s on July 31, 2018, 12:46:41 am
I wonder why they used such a complex fan instead of just putting a muffin fan in the panel like practically every other instrument out there.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on July 31, 2018, 09:28:54 am
I wonder why they used such a complex fan instead of just putting a muffin fan in the panel like practically every other instrument out there.

Apparently some over zealous Tek engineer thought that the 2465 required a complex variable speed fan as shown in this schematic. And apparently later on it was discovered that a standard $20 computer type fan would do the job just as effectively. 

(https://imagizer.imageshack.com/v2/xq90/922/0Mv3Zw.jpg) (https://imageshack.com/i/pm0Mv3Zwj)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: jkn on July 31, 2018, 12:12:11 pm
One thing I am nervous about though - this removal of the fan/mandrel. Are there any other tips anyone can give apart from 'go gently and glue back up if you have to'? I've read elsewhere that you can also push a bit on the mandrel, after loosening the nut a little. I also wondered about making some sort of jug to apply pressure in the right place. Can anyone give me advice or reassurance here?

Thanks a lot from the UK

Jon N

Your concern about the fan assembly is certainly understandable. If you apply pressure incorrectly you could break the fan itself. That would be a difficult repair.

I haven't heard about pushing the assembly forward slightly and I'm not sure if it would help because the mandrel is tapered. And all those years assembled has resulted in the fan and the mandrel "cold fusing" together. That's where the deoxit or some other penetrating oil would help. A long thin pair of needle nose pliers against the rear hub and carefully pry forward seems to be the best method that I found. The point is....don't be afraid of it....just work carefully and chances are it will come apart.     

Thanks for the info.

I think the idea about pushing is to push the screw (which is part of the mandrel?) back against the case, and separate the mandrel and fan that way. I guess you would best do this by supporting the rest of the fan with a thin spacer, or otherwise you'd put strain on the motor shaft and bearings.

Your idea about the thin pliers ... so you are suggesting levering the mandrel part of the rear of the fan? This is, what 1/2" across?

I have never seen a good picture of the fan & mandrel (removed), I am not sure I have got it right in my head.

Thanks, Jon N
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on July 31, 2018, 01:33:38 pm
Here's the best picture I have of the fan removed. I was mistaken when I said you could pry from the back hub. You can't. The hub of the fan extends internal to the case. But the thin needle nose can get between the case and the shaft piece and carefully pull forward. What you call a mandrel and I call a collet you can barely see extending slightly out from the end of the fan. When you tighten the nut it pulls forward and compresses against the motor shaft and also tightens it against the fan itself.

(https://imagizer.imageshack.com/v2/xq90/921/vhCz6P.jpg) (https://imageshack.com/i/plvhCz6Pj)   
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Satbeginner on July 31, 2018, 02:14:02 pm
It is similar how a bicycle steer is fixed.

To loosen: undo the nut a few turns, before any pulling!!, slightly tap the nut inwards, this will loosen the collet and the fan from the shaft.
Now pull the fan from the shaft.


To tighten: place the fan on the shaft, carefully tighten the nut. (A bit)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on July 31, 2018, 02:24:43 pm
I wonder why they used such a complex fan instead of just putting a muffin fan in the panel like practically every other instrument out there.

Apparently some over zealous Tek engineer thought that the 2465 required a complex variable speed fan as shown in this schematic. And apparently later on it was discovered that a standard $20 computer type fan would do the job just as effectively. 

Later they did replace them with standard tubeaxial fans which were noisier and lower performance.  It is difficult to improve on a centrifugal fan and their tubeaxial version was really good also.

Tektronix used that custom brushless fan motor and circuit for a long time going back to at least the 1970s.  Based on the various fan options in the 76xx series which used a shaded pole motor, I suspect they had issues with flux leakage from the fan motor interfering with the CRT until they settled on their own proven design.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on July 31, 2018, 02:50:36 pm
It is similar how a bicycle steer is fixed.

To loosen: undo the nut a few turns, before any pulling!!, slightly tap the nut inwards, this will loosen the collet and the fan from the shaft.
Now pull the fan from the shaft.


To tighten: place the fan on the shaft, carefully tighten the nut. (A bit)

That is an excellent suggestion.  :-+
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: jkn on July 31, 2018, 02:53:13 pm
Here's the best picture I have of the fan removed. I was mistaken when I said you could pry from the back hub. You can't. The hub of the fan extends internal to the case. But the thin needle nose can get between the case and the shaft piece and carefully pull forward. What you call a mandrel and I call a collet you can barely see extending slightly out from the end of the fan. When you tighten the nut it pulls forward and compresses against the motor shaft and also tightens it against the fan itself.

(...Image URL elided)

Yes, I saw that nice picture, thanks. I'm happy to call that a collet ;-). IIUC that part is separate from the fan moulding, in theory at least - is that right?

Quote
I was mistaken when I said you could pry from the back hub. You can't. The hub of the fan extends internal to the case.
I'm not sure I fully understand you here...

Quote
But the thin needle nose can get between the case and the shaft piece and carefully pull forward.

OK, I think.

Also see the post from 'Satbeginner' below:

Quote
To loosen: undo the nut a few turns, before any pulling!!, slightly tap the nut inwards, this will loosen the collet and the fan from the shaft.
Now pull the fan from the shaft.

That makes sense to me (I understand the 'quill' arrangement on a bike), but this approach doesn't seem to be mentioned much and I do wonder how slight a 'slight tap' really means... Is there a need to protect the motor shaft from the knock that you are trying to give the ... collet?

Sorry if I am seeming uncharacteristically cautious, I only have one of these scopes!

Cheers, Jon N

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: jkn on July 31, 2018, 05:00:04 pm
Update - managed it!

Well, more or less. I packed some cardboard between the rear of the fan and the chassis, then got a small-ish hanner and tapped the screw head of the collet.

It took a bit more force than I was expecting but then it loosened and I was able to remove the fan.

The collet was still holding inside the fan assembly; I wanted to get it out and may have made a slight error there. I turned the collet and it started coming out; however now that I have it out I see that it has a break in the middle, just where the metal screw stops. I am guessing this is a common place for it to break; it is not all the way through and I am pretty confident that a bit of epoxy resin will hold it OK once I have degreased the thing.

So now I am on with the next stage. I just have to puzzle out how to remove the black plastic mains shield. That should be easy, but...

Cheers, J^n
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on July 31, 2018, 06:04:21 pm
Update - managed it!

Well, more or less. I packed some cardboard between the rear of the fan and the chassis, then got a small-ish hanner and tapped the screw head of the collet.

It took a bit more force than I was expecting but then it loosened and I was able to remove the fan.

The collet was still holding inside the fan assembly; I wanted to get it out and may have made a slight error there. I turned the collet and it started coming out; however now that I have it out I see that it has a break in the middle, just where the metal screw stops. I am guessing this is a common place for it to break; it is not all the way through and I am pretty confident that a bit of epoxy resin will hold it OK once I have degreased the thing.

So now I am on with the next stage. I just have to puzzle out how to remove the black plastic mains shield. That should be easy, but...

Cheers, J^n

Good deal!    :-+    And yes, that's where they all seem to break. Epoxy will fix it.

And removing the mains shield is easy once you closely examine it.

Edit...and since you are in the UK and have 240V mains you should consider changing the line filter.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: siggi on July 31, 2018, 09:48:40 pm
Apparently some over zealous Tek engineer thought that the 2465 required a complex variable speed fan as shown in this schematic. And apparently later on it was discovered that a standard $20 computer type fan would do the job just as effectively. 

I replaced the "complex variable speed fan" with a "$20 computer type fan" in my 2465 because the bearings were worn and the motor squealed like <insert wounded animal here>. After suffering this abomination for a couple of months, I took the trouble to find a NOS motor to reverse the mod. I'm also fortunate enough to own a 2467, so I've had occasion to compare the two kinds of fans.

So, from experience, the 2465 is as near silent as makes no difference - as is my 485, which has the same kind of fan. The 2467, by comparison, while perhaps not as loud as a 747 at takeoff, is annoyingly loud enough that it's only turned on at need.

All this to say that I take umbrage at the "do the job just as effectively" statement, and I'd wager you haven't had the opportunity to compare the two.
I'd also guess the squirrel cage fan design goes back a ways (witness the 485, introduced in 1972), and so was inherited by the 2465 as a tested design. There was plenty of other innovation in that scope for its time, and perhaps the "$20 computer type fan" wasn't all that common or inexpensive back in 1984 when the 2465 was introduced.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: james_s on July 31, 2018, 10:16:02 pm
I suspect that any sort of retrofit is likely to be sub-optimal compared to designing the scope around an off the shelf fan in the first place. The large 4" fans used in many other instruments are not terribly noisy and some of them move a good deal of air. There also exist squirrel cage type brushless self contained fans although I don't know how common they were when this scope was made. I can certainly see some advantages to the fan they used, however I would have done it differently and at least used some kind of standard off the shelf motor.

Overall it's a small nag though and forgivable next to all the amazing engineering that Tek has done over the years. They have really gone the extra mile in many cases to make their instruments as good as they can possibly be. The fact that so many 30-40+ year old Tektronix scopes are still in regular use is a testament to that.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on August 01, 2018, 12:18:58 am
Apparently some over zealous Tek engineer thought that the 2465 required a complex variable speed fan as shown in this schematic. And apparently later on it was discovered that a standard $20 computer type fan would do the job just as effectively. 

I replaced the "complex variable speed fan" with a "$20 computer type fan" in my 2465 because the bearings were worn and the motor squealed like <insert wounded animal here>. After suffering this abomination for a couple of months, I took the trouble to find a NOS motor to reverse the mod. I'm also fortunate enough to own a 2467, so I've had occasion to compare the two kinds of fans.

So, from experience, the 2465 is as near silent as makes no difference - as is my 485, which has the same kind of fan. The 2467, by comparison, while perhaps not as loud as a 747 at takeoff, is annoyingly loud enough that it's only turned on at need.

I have a 2465 DMS with the cage fan that does the same shenanigans for about 20 minutes to about a half hour after initial power on. Then it calms down but is never whisper quiet and it makes itself known but isn't annoying. I do have a conventional fan built up and ready to go in if it gets worse. But for now it's going to remain in place. The cage fan in my other 2465 is always whisper quiet and I sometimes have to check to make sure it's still running.  ;D
   
All this to say that I take umbrage at the "do the job just as effectively" statement, and I'd wager you haven't had the opportunity to compare the two.
I'd also guess the squirrel cage fan design goes back a ways (witness the 485, introduced in 1972), and so was inherited by the 2465 as a tested design. There was plenty of other innovation in that scope for its time, and perhaps the "$20 computer type fan" wasn't all that common or inexpensive back in 1984 when the 2465 was introduced.

Your umbrage is misplaced. I'm only speaking from a historical perspective and reality. When the 2465A was introduced the cage fan was dropped in favor of a conventional design. If the Tek engineers felt it wouldn't do the job they would have continued with the cage fan.   
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on August 01, 2018, 12:16:33 pm
Your umbrage is misplaced. I'm only speaking from a historical perspective and reality. When the 2465A was introduced the cage fan was dropped in favor of a conventional design. If the Tek engineers felt it wouldn't do the job they would have continued with the cage fan.

I think it more likely that the Siemens motor they were using was discontinued.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: siggi on August 01, 2018, 01:09:05 pm
I have a 2465 DMS with the cage fan that does the same shenanigans for about 20 minutes to about a half hour after initial power on. Then it calms down but is never whisper quiet and it makes itself known but isn't annoying.
My 485's fan did the same thing. Before you replace the motor, try flushing it with IPA, then lubricating it with something like 5W-30 synthetic motor oil. It might be enough to silence it for a couple of more decades :). This is a bit of a pain to do, as if memory serves, you need to desolder the motor from the PCB it's mounted on to gain access to the thrust bearing screw. Once that's out, you can pour IPA through the motor a couple of times to flush out the gunked up old dust-in-oil.

Your umbrage is misplaced.
Maybe umbrage is the wrong word, I just feel my 2467 is unreasonably loud in comparison to the 485 and the 2465.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on August 02, 2018, 02:23:46 am
What an excellent resource this thread is on 24xx scopes. I always wanted to get a 2465B, but shunned it a bit mostly to the part of having to deal with the Dallas RAM module replacement, and reading/programming it, etc. I am very experienced in electronics, but have not done much memory chip programming, so this will be pretty new to me. Now thanks to this great post I am very close to having all the info I need to go ahead and get one of these great scopes, and a list of all the post-purchase things that need to be taken care of. I currently have a Tek 2247A 100MHz as my main scope and I am very happy with it, I did all the required/recommended internal update work when I got it back in 2012. But.. of course one cannot have too many scopes, right?  :-X (I also have a 222 and a 2013A).

I have been reading this post now for several hours straight from page 1 and been taking tech notes, so far I'm only up to page 20, but decided to jump ahead here to post a quick question. I have my eyes on a friend's-friend 2465BCT (SN 59xxx) and last callibrated in 2015 which he apparently no longer needs and I am told it is in good shape, although I have not seen it personally yet. My question is, what are the differences of the BCT version over the plain B type? I see that both are 400MHz, but I am not sure what the advantage would be to get this BCT type. I understand the CT part means "Counter Timer" (?). Does that mean that I can take automatic frequency/Time readings on any waveform in the same way I do it with my 2247A (as well as voltage readings, etc) which I find extremely useful features and would hate not to have them available on a 2465B (or BCT variant) scope.

Could one of you very knowledgeable members please explain what are the advantages or disadvantages of the BCT over the plain B version? The scope would see mainly hobby bench usage, but I would definitively want to know what I would be getting into to ultimately help make up my purchase decision. I looked around for a manual of the 2465BCT but so far only managed to find OM/SM manuals for the 2465B and 2467B in PDF format.

Thanks to all the people that have already contributed to this post over something like 6 years now. Simply amazing!

Well, its back to page 21.  :P

-Alex
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on August 02, 2018, 09:43:17 am
The 2465BCT has Option 09, which is the Counter/Trigger. See attached. This is from the 1986 Product Catalog and it's the 2465 Option 09 but the 2465B is essentially the same. I have this option on my 2465 DMS and it comes in quite handy.

(https://imagizer.imageshack.com/v2/xq90/921/bg6cEK.jpg) (https://imageshack.com/i/plbg6cEKj)

I have a copy of the 2465B Options Operating Manual in PDF if you want it. Send me an e-mail at seanfinn999@gmail.com. I don't have a copy of the 2465B Options Service Manual but Artek Manuals does have it for sale.   
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on August 02, 2018, 05:04:42 pm
Thanks Med, the picture is getting clearer now about the BCT variant. I grabbed the JPG and that should be enough for now. I will contact you via email later on if I need the PDF doc.

But from what I now read this option 09 just -increases- the accuracy of the frequency and time measurement of the displayed waveform by using crystal-controlled reference. So my question here is, how does the plain 2465B take time/freq measurements without option 09? What kind of reference does it use? Or is the plain B not capable of taking frequency readings and display them on screen? I'm probably wrong but cannot understand why a sophisticated instrument like a 2465B does not have an internal high precision crystal-controlled reference to begin with. I understand the frequency counter on the B version is good up to 150-200MHz, so if its not going to be very accurate it does not make much sense to display the measurement numerically on screen.

As a comparison, in my 2247A everything time/frequency measurement based is related to the 10MHz internal oscillator, with an option to connect an external high precision 10MHz (Rubidium, etc) signal to substitute the internal one. By doing just two button presses I get dead on frequency (or time) measurements shown numerically on screen with 6 decimal places from a displayed waveform even it is only maybe half a division in amplitude, and up to 100MHz. Granted the internal 10MHz is not a OCXO and takes about 30 min to fully stabilize, but will be rock solid after that.

Does the 2465B also do frequency measuring like this?


The 2465BCT has Option 09, which is the Counter/Trigger. See attached. This is from the 1986 Product Catalog and it's the 2465 Option 09 but the 2465B is essentially the same. I have this option on my 2465 DMS and it comes in quite handy.

I have a copy of the 2465B Options Operating Manual in PDF if you want it. Send me an e-mail at seanfinn999@gmail.com. I don't have a copy of the 2465B Options Service Manual but Artek Manuals does have it for sale.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on August 02, 2018, 05:39:46 pm
But from what I now read this option 09 just -increases- the accuracy of the frequency and time measurement of the displayed waveform by using crystal-controlled reference. So my question here is, how does the plain 2465B take time/freq measurements without option 09? What kind of reference does it use? Or is the plain B not capable of taking frequency readings and display them on screen? I'm probably wrong but cannot understand why a sophisticated instrument like a 2465B does not have an internal high precision crystal-controlled reference to begin with. I understand the frequency counter on the B version is good up to 150-200MHz, so if its not going to be very accurate it does not make much sense to display the measurement numerically on screen.

As a comparison, in my 2247A everything time/frequency measurement based is related to the 10MHz internal oscillator, with an option to connect an external high precision 10MHz (Rubidium, etc) signal to substitute the internal one. By doing just two button presses I get dead on frequency (or time) measurements shown numerically on screen with 6 decimal places from a displayed waveform even it is only maybe half a division in amplitude, and up to 100MHz. Granted the internal 10MHz is not a OCXO and takes about 30 min to fully stabilize, but will be rock solid after that.

Does the 2465B also do frequency measuring like this?

You are actually asking something I have wondered about but nobody has been able to answer.  I have a 2247A and more recently acquired a 2445B so I can only answer part of your question.

The 2247A has the normal A and B triggers but also a C trigger and universal timer/counter IC which is used to make voltage and timing measurements continuously in real time.  The 2445B does the same thing using its A or B trigger (so the display blanks during measurement) and some form of microprocessor control which results in equally good voltage measurements but much lower resolution timing measurements and measurements are *not* made in real time with continuous updates; it makes a single measurement and then displays it along with the sweep.

I have no idea how the timer/counter variants of the 2465B series operate other than providing higher resolution and I have never seen a video showing them in operation.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on August 02, 2018, 05:48:34 pm
Thanks for the input David. Lets hope one of the Tek gurus on this post can answer our question.

BTW, don't you love your 2247A? I know I do!  (Disclaimer: no intention on hijacking this thread, not that it would even be possible) ;-)


But from what I now read this option 09 just -increases- the accuracy of the frequency and time measurement of the displayed waveform by using crystal-controlled reference. So my question here is, how does the plain 2465B take time/freq measurements without option 09? What kind of reference does it use? Or is the plain B not capable of taking frequency readings and display them on screen? I'm probably wrong but cannot understand why a sophisticated instrument like a 2465B does not have an internal high precision crystal-controlled reference to begin with. I understand the frequency counter on the B version is good up to 150-200MHz, so if its not going to be very accurate it does not make much sense to display the measurement numerically on screen.

As a comparison, in my 2247A everything time/frequency measurement based is related to the 10MHz internal oscillator, with an option to connect an external high precision 10MHz (Rubidium, etc) signal to substitute the internal one. By doing just two button presses I get dead on frequency (or time) measurements shown numerically on screen with 6 decimal places from a displayed waveform even it is only maybe half a division in amplitude, and up to 100MHz. Granted the internal 10MHz is not a OCXO and takes about 30 min to fully stabilize, but will be rock solid after that.

Does the 2465B also do frequency measuring like this?

You are actually asking something I have wondered about but nobody has been able to answer.  I have a 2247A and more recently acquired a 2445B so I can only answer part of your question.

The 2247A has the normal A and B triggers but also a C trigger and universal timer/counter IC which is used to make voltage and timing measurements continuously in real time.  The 2445B does the same thing using its A or B trigger (so the display blanks during measurement) and some form of microprocessor control which results in equally good voltage measurements but much lower resolution timing measurements and measurements are *not* made in real time with continuous updates; it makes a single measurement and then displays it along with the sweep.

I have no idea how the timer/counter variants of the 2465B series operate other than providing higher resolution and I have never seen a video showing them in operation.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on August 03, 2018, 01:14:07 am
Thanks for the input David. Lets hope one of the Tek gurus on this post can answer our question.

BTW, don't you love your 2247A? I know I do!  (Disclaimer: no intention on hijacking this thread, not that it would even be possible) ;-)


But from what I now read this option 09 just -increases- the accuracy of the frequency and time measurement of the displayed waveform by using crystal-controlled reference. So my question here is, how does the plain 2465B take time/freq measurements without option 09? What kind of reference does it use? Or is the plain B not capable of taking frequency readings and display them on screen? I'm probably wrong but cannot understand why a sophisticated instrument like a 2465B does not have an internal high precision crystal-controlled reference to begin with. I understand the frequency counter on the B version is good up to 150-200MHz, so if its not going to be very accurate it does not make much sense to display the measurement numerically on screen.

As a comparison, in my 2247A everything time/frequency measurement based is related to the 10MHz internal oscillator, with an option to connect an external high precision 10MHz (Rubidium, etc) signal to substitute the internal one. By doing just two button presses I get dead on frequency (or time) measurements shown numerically on screen with 6 decimal places from a displayed waveform even it is only maybe half a division in amplitude, and up to 100MHz. Granted the internal 10MHz is not a OCXO and takes about 30 min to fully stabilize, but will be rock solid after that.

Does the 2465B also do frequency measuring like this?

You are actually asking something I have wondered about but nobody has been able to answer.  I have a 2247A and more recently acquired a 2445B so I can only answer part of your question.

The 2247A has the normal A and B triggers but also a C trigger and universal timer/counter IC which is used to make voltage and timing measurements continuously in real time.  The 2445B does the same thing using its A or B trigger (so the display blanks during measurement) and some form of microprocessor control which results in equally good voltage measurements but much lower resolution timing measurements and measurements are *not* made in real time with continuous updates; it makes a single measurement and then displays it along with the sweep.

I have no idea how the timer/counter variants of the 2465B series operate other than providing higher resolution and I have never seen a video showing them in operation.

I'm afraid I can't answer many of your questions either. I'm just a hobbyist who happen to get real lucky and stumble across 2- 2465's real cheap (1 was $0, the other $60) this past 3 years. They are way more scope than I'll ever need and I've hardly scratched the surface of their features and capabilities. My speed is more like a 465 which I currently have on my bench undergoing restoration.  :D But I will answer what I know for sure.

The 2465 does not have the capability to tie in an external reference like your 2247A. And I doubt the 2465A & B have that capability either.

I do use the Counter display on the 2465 DMS when measuring waveforms. It's accuracy is right on par with my 2 frequency counters. And yes, on the 2465 it's supposedly only good out to 150MHz.

The other trigger features I have not used.

Again I'll offer the 2465B Options Operation Manual if you want it. You can study the theory and circuit description to see if it meets your needs. I can also send you the vanilla 2465 Ops manual too if you want to determine what sort of reference it uses. I don't have a copy of the vanilla 2465B Ops manual but it should be similar.

 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on August 03, 2018, 03:23:21 pm
The 2465 does not have the capability to tie in an external reference like your 2247A. And I doubt the 2465A & B have that capability either.

Option 1E on an oscilloscope with timer/counter option 06 or 09 adds an external reference input which accepts any of 1.000000, 3.579545, 4.433185, 5.000000, or 10.000000 MHz as a reference.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on August 03, 2018, 04:14:28 pm
The 2465 does not have the capability to tie in an external reference like your 2247A. And I doubt the 2465A & B have that capability either.

Option 1E on an oscilloscope with timer/counter option 06 or 09 adds an external reference input which accepts any of 1.000000, 3.579545, 4.433185, 5.000000, or 10.000000 MHz as a reference.

OK, that must apply to the 2465A or B. I have the complete option list for the 2465 and Option 1E is not listed. 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on August 03, 2018, 05:30:08 pm
Option 1E on an oscilloscope with timer/counter option 06 or 09 adds an external reference input which accepts any of 1.000000, 3.579545, 4.433185, 5.000000, or 10.000000 MHz as a reference.

OK, that must apply to the 2465A or B. I have the complete option list for the 2465 and Option 1E is not listed.

I do not see it either and the timer/counter option for the 2445/2465 was added in 1985 and they were only produced for three years from 1984 to 1986.  I also do not see it for the 2445A/2455A/2465A/2467 in 1987 but the external reference is listed in the 1988 catalog so it became available part way through the 2465A series.

Oh, I did resolve one thing.  I found comment that the display update rate for the timer/counter in automatic resolution mode is twice per second or every four sweeps so it does update continuously like the 2247A timer/counter does.  So that answers my question; the 2465/A/B series timer/counter updates continuously but unlike the 2247A, the other measurements do not.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on August 03, 2018, 06:09:44 pm
I see answers so far have been mainly focusing on the external reference input BNC option 1E. But that still leaves the real question unanswered as to why a sophisticated instrument like the 2465 (inc A&B) did not come with a high precision internal reference to begin with (not to mention a standard external input), but instead the buyer had to add options 06 and or 10 to get a higher degree of accuracy.

I wonder if it is possible Tektronix was mainly focusing on developing a higher bandwidth scope, and not so much on other (useful in my opinion) features that could have been easily added? Which features? again, take a look at the 2247A real-time on-screen measurements (frequency, time, volts, etc).

If this is the case, I for one am a bit disappointed. I only rarely push my scope bandwidth needs beyond 100MHz, but I was instead looking forward that getting a 2465B would be (or almost) like a 2247A on steroids with 400MHz bandwidth and a somewhat nicer updated front panel functionality and design. Seems now to me that this is not quite the case, so unless someone can maybe disprove this, and with all due respect to the 2465, but I think I rather stay with my 2247A for now. No dying NVRam, no Hot deflection hybrid, and virtually no unobtanium parts. Oh, and no leaking SMD caps either.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on August 03, 2018, 11:30:25 pm
I see answers so far have been focusing on the external reference input BNC option 1E. But that still leaves the real question unanswered as to why a sophisticated instrument like the 2465 (inc A&B) did not come with a high precision internal reference to begin with (not to mention a standard external input), but instead the buyer had to add options 06 and or 10 to get a higher degree of accuracy.

I wonder if it is possible Tektronix was mainly focusing on developing a higher bandwidth scope, and not so much on other (useful in my opinion) features that could have been easily added? Which features? again, take a look at the 2247A real-time on-screen measurements (frequency, time, volts, etc).

Part of the answer is that the 2247A series and the 2465 series were designed by different groups at Tektronix and intended for different markets.  The 2247A is more for the service market and the faster 2465 series was more for the design market.

The release dates are also instructive:

2235/2236   1984   *
2445/2465   1984
2245/2246   1987
2445A/2455A/2465A/2467   1987   *
2245A/2246A/2247A   1989   *
2445B/2455B/2465B/2467B   1989

The custom timer/counter IC was first used in the 2236 and then the 2445A/2455A/2465A/2467 and then even later the 2245A/2246A/2247A.  So the 2445A/2455A/2465A/2467 had it before the 2247A and the 2247A is just a 2246A with the timer/counter option.

That timer/counter is also pretty good.  It includes a 100MHz phase locked VCO with random modulation to prevent errors from synchronous sources and it is a reciprocal counter so it delivers a constant number of digits independent of input frequency.  For some reason Tektronix never used it in an independent universal timer/counter.

Quote
If this is the case, I for one am disappointed. I only rarely push my scope bandwidth needs beyond 100MHz, but I was instead looking forward that getting a 2465B would be (or almost) like a 2247A on steroids with 400MHz bandwidth and a somewhat nicer updated front panel functionality and design. Seems now to me that this is not quite the case, so unless someone can maybe disprove this, and with all due respect to the 2465, but I think I rather stay with my 2247A for now. No dying NVRam, no Hot deflection hybrid, and virtually no unobtanium parts.

The 2246 and 2247A that I have also have a brighter and sharper CRTs than my 2445B.  Maybe that is just due to hours of operation but the CRT designs are very different to support their respective bandwidths.

I do not like the dying NVRAM issue either especially given how difficult the calibration is and as you note, there was a physical design issue with the big DIP hybrid packages.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on August 10, 2018, 12:25:26 pm
Does anybody know why some 24xx scopes don't seem to have the blue filter installed over the screen? Was the filter an option, or is it removable? If I get a scope without the blue filter, is it easy to get one and reinstall it? Personally I think the filter helps quite a bit, and don't understand why anyone would remove it to use a scope without it being present.

Still looking for my future 24xx...

Thanks.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on August 10, 2018, 04:05:38 pm
Its removeable easily and installation too, not a big deal, just read the service manual, there is a graphical illustration.

I guess on those that removed, prolly they were badly scratched or cracked as its just sort of acrylic blue thingy.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: james_s on August 10, 2018, 04:14:56 pm
Perhaps it worked better with a scope camera to not have the filter? Seems like the filter is easily removable on my 465 too, looks better with it on though.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on August 13, 2018, 08:12:28 am
Perhaps it worked better with a scope camera to not have the filter? Seems like the filter is easily removable on my 465 too, looks better with it on though.

To my eyes, on camera its better with filter on, shot this while ago.

(https://www.eevblog.com/forum/beginners/oscilloscope-training-class-(long)/?action=dlattach;attach=22223;image)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on August 19, 2018, 01:38:58 pm
Guys I have still no idea, even with the possibility of the filter not allowing good pictures etc, why so many of these scopes out there seem to be missing the blue filter. Or is it perhaps that the scope picture taking crowd is/was larger than one would think? I have to agree the screen looks so much better with the filter attached, so why would anyone remove it (ok besides scratched/broken which i would think is just a minority of the cases (?). Anyhow I am glad it would be an easy fix, maybe someone out there would have one to sell. But first is first, getting a scope to go with the filter, or ideally not needing to look for one to begin with.

Also wanted to ask, would a 2465A low SN under 50K (~10000) have SMD boards, or would the components be through hole? In this same model would there also be the possibility of having the dreaded cap rot on the A5 board, and a dying NVRam module? I'm asking because I read that some of these scopes do not have these problems.

Is there a reference table out there somewhere that would help to have a better idea of the innards of the scope in relation to its model/version/serial number?

Thanks.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: james_s on August 19, 2018, 05:36:44 pm
Maybe the filter was an optional accessory that not everyone chose to purchase? You can get sheets of colored gel at camera and theatrical shops in a wide range of shades, there may be one that's a good match for the blue filter if anyone is looking to add one.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Satbeginner on August 19, 2018, 05:44:51 pm
Many of the filters just got lost, like the front covers.
Especially the front covers, they all seem to end up as pencil cases in some deskdrawer.
The filters were designed for an easy removal in the case of a film scope-camera.


Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tkamiya on August 19, 2018, 05:52:42 pm
I have a 2465BCT with Dallas chip that is toast.  All cal data is GONE.  Would anyone be so kind to point me to a right direction?  I really don't want to cal this scope as I don't need that kind of precision.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on August 19, 2018, 06:07:25 pm
Especially the front covers, they all seem to end up as pencil cases in some deskdrawer.

Maybe we need to start using different search terms on ebay, like "Blue Pencil Tray" or "holder". Some time ago, just to see what came up, I tried looking for a 2465 front cover, but not one positive result came back.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Satbeginner on August 19, 2018, 06:15:20 pm
I have a 2465B with option 06 (I believe that is the CT).
When I revived my unit -A5 capacitor leaking- I also replaced the Dallas and calibrated my scope.
I can send you my Dallas contents, but you need to replace and program the Dallas.
I put my Dallas in a socket, so it was easy to backup the data after calibration using a programmer.

All pins can be cleared using a sucker, only pin 14 needs to be removed while putting a soldering iron on it, because of the ground plane it needs a bit more heat.
To remove the Dallas, I remove the tin around a pin, then I wiggle each pin using a small pair of pliers a bit so I see the pin is loose, before pulling, this to protect the vias in he PCB.

Obviously there is no guarantee that your scope will be close to it's normal function when you use my caldata.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on August 19, 2018, 07:35:03 pm
Maybe we need to start using different search terms on ebay, like "Blue Pencil Tray" or "holder". Some time ago, just to see what came up, I tried looking for a 2465 front cover, but not one positive result came back.

The sellers often do not know which instrument the cover goes to or do not list them all.

When I was cover shopping, I had the dimensions which sellers often list and just did a search for Tektronix and oscilloscope covers.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tkamiya on August 19, 2018, 08:26:40 pm
I have a 2465B with option 06 (I believe that is the CT).
Obviously there is no guarantee that your scope will be close to it's normal function when you use my caldata.


If you don't mind, I'd love to have what you have.  tkamiya9(at)yahoo.com please!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Satbeginner on August 19, 2018, 08:45:35 pm
Message send
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tkamiya on August 19, 2018, 08:50:38 pm
Received.  Thank you!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Satbeginner on August 19, 2018, 08:57:54 pm
Perhaps it worked better with a scope camera to not have the filter? Seems like the filter is easily removable on my 465 too, looks better with it on though.

To my eyes, on camera its better with filter on, shot this while ago.

(https://www.eevblog.com/forum/beginners/oscilloscope-training-class-(long)/?action=dlattach;attach=22223;image)

The camera used in that case is a camera that was directly positioned over the CRT, where the little groove is for.
Polaroid and Kodak made the films I believe.
Often used in old school labs where stuff was mostly Single Shot, like short laser pulses etc.

Like these:

https://www.google.de/search?biw=1745&bih=892&tbm=isch&sa=1&ei=K9l5W5ONO4_uaYKbrsgF&q=tektronix+crt+camera&oq=tektronix+crt+camera&gs_l=img.3...0.0.0.7878.0.0.0.0.0.0.0.0..0.0....0...1c..64.img..0.0.0....0.FDak53Igd1A (https://www.google.de/search?biw=1745&bih=892&tbm=isch&sa=1&ei=K9l5W5ONO4_uaYKbrsgF&q=tektronix+crt+camera&oq=tektronix+crt+camera&gs_l=img.3...0.0.0.7878.0.0.0.0.0.0.0.0..0.0....0...1c..64.img..0.0.0....0.FDak53Igd1A)

Un saludo,

satbeginner (Leo)

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tkamiya on August 19, 2018, 09:30:09 pm
Now I need to buy a programmer.  Purchases never end.  Shrinking budget never stops.   until it reaches zero.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Satbeginner on August 19, 2018, 09:44:14 pm
I used this one:

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on August 20, 2018, 02:07:21 am
Perhaps it worked better with a scope camera to not have the filter? Seems like the filter is easily removable on my 465 too, looks better with it on though.

To my eyes, on camera its better with filter on, shot this while ago.

(https://www.eevblog.com/forum/beginners/oscilloscope-training-class-(long)/?action=dlattach;attach=22223;image)

The camera used in that case is a camera that was directly positioned over the CRT, where the little groove is for.
Polaroid and Kodak made the films I believe.
Often used in old school labs where stuff was mostly Single Shot, like short laser pulses etc.

Like these:

https://www.google.de/search?biw=1745&bih=892&tbm=isch&sa=1&ei=K9l5W5ONO4_uaYKbrsgF&q=tektronix+crt+camera&oq=tektronix+crt+camera&gs_l=img.3...0.0.0.7878.0.0.0.0.0.0.0.0..0.0....0...1c..64.img..0.0.0....0.FDak53Igd1A (https://www.google.de/search?biw=1745&bih=892&tbm=isch&sa=1&ei=K9l5W5ONO4_uaYKbrsgF&q=tektronix+crt+camera&oq=tektronix+crt+camera&gs_l=img.3...0.0.0.7878.0.0.0.0.0.0.0.0..0.0....0...1c..64.img..0.0.0....0.FDak53Igd1A)

Un saludo,

satbeginner (Leo)

Leo, that photo was shot using plain cheap dslr.  :P

Here is how the setup looks like :

(https://www.eevblog.com/forum/beginners/oscilloscope-training-class-(long)/?action=dlattach;attach=22215;image)

No hood nor special tool was used, I shared this little trick while ago, read the details -> HERE (https://www.eevblog.com/forum/beginners/oscilloscope-training-class-(long)/msg98176/#msg98176).
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on August 20, 2018, 02:38:24 am
So getting back to my other question, what do you guys think about an early serial (under 50K)  2465A version scope, possibly showing an error message on screen at power up, but that otherwise seems to properly display traces and cursors, a bit dusty on the outside but no broken shafts or missing knobs buttons, or any other obvious damage, etc, no front cover or probes, but yes it has the blue screen filter. I have not had a chance to see it personally, but this is what i have so far been able to glean into the situation, and I am still haggling with the owner over a compromise price given probable problems. Just like trying to buy a car without even test driving it first, so how much trouble could I possibly get into....? Ha!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on August 20, 2018, 03:28:39 am
So getting back to my other question, what do you guys think about an early serial (under 50K)  2465A version scope, possibly showing an error message on screen at power up, but that otherwise seems to properly display traces and cursors, a bit dusty on the outside but no broken shafts or missing knobs buttons, or any other obvious damage, etc, no front cover or probes, but yes it has the blue screen filter. I have not had a chance to see it personally, but this is what i have so far been able to glean into the situation, and I am still haggling with the owner over a compromise price given probable problems. Just like trying to buy a car without even test driving it first, so how much trouble could I possibly get into....? Ha!

To answer your prior question from earlier. The A5 board in the 2465A is pin thru hole. At least that's what the service manual shows. Could later S/N's be SMD? Wouldn't surprise me.

What is the error message? Can you get the seller to tell you?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on August 20, 2018, 01:38:52 pm
I am asking him to send me a picture of the error message, but he really doesn't know much about scopes. I am not sure of the procedure to bring up the error message myself, but I assume telling him to just turn on the scope and then taking a picture of the first screen he will see would be enough to capture the error message? Thanks for the input.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on August 20, 2018, 03:26:35 pm
I am asking him to send me a picture of the error message, but he really doesn't know much about scopes. I am not sure of the procedure to bring up the error message myself, but I assume telling him to just turn on the scope and then taking a picture of the first screen he will see would be enough to capture the error message? Thanks for the input.

Yes, when you press power on the scope will boot and then stop at the error message. It will be displayed across the bottom of the screen.

Edit....here's an example:
(https://imagizer.imageshack.com/v2/xq90/924/4hisOg.jpg) (https://imageshack.com/i/po4hisOgj)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on August 20, 2018, 03:54:40 pm
OK got it, that was very helpful. I was thinking the error message would be displayed more towards the middle of the screen, where I saw something on an earlier picture but it was way too blurry to be readable because of unsteadiness of the camera. Is there any other type of message that would come up at some point in or around the center of the screen? Thanks.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on August 20, 2018, 05:11:06 pm
Another useful bit of information at this point while looking for a 246x scope would be if there is an error code specific to an instrument that has lost its calibration constants? Is there such error message, or is there anything else I would need to look out for to know for sure that the calibration is gone? Thanks.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on August 20, 2018, 08:00:39 pm
I bought a Canon SX150 just for taking oscilloscope photographs and use it freehand well enough in ambient room lighting but you can also make a camera mount to use the existing bezel mount on these oscilloscopes:

http://glydeck.blogspot.com/2011/03/motorola-mystery.html (http://glydeck.blogspot.com/2011/03/motorola-mystery.html)
https://www.amplifier.cd/Technische_Berichte/Photographie_Oszilloskop/Foto_Halterung.html (https://www.amplifier.cd/Technische_Berichte/Photographie_Oszilloskop/Foto_Halterung.html)

There used to be one here but it is gone:

http://www.cembreros.jazztel.es/camerascope/camscope_en.htm (http://www.cembreros.jazztel.es/camerascope/camscope_en.htm)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on August 20, 2018, 09:22:13 pm
Another useful bit of information at this point while looking for a 246x scope would be if there is an error code specific to an instrument that has lost its calibration constants? Is there such error message, or is there anything else I would need to look out for to know for sure that the calibration is gone? Thanks.

You can download a copy of the 2465A service manual here...

https://elektrotanya.com/tektronix_2465a_2467.pdf/download.html

Starting at section 6-10 it lists all the diagnostic routines.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: emece67 on September 03, 2018, 04:29:52 pm
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Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on September 03, 2018, 05:25:46 pm

But it is the Lithium cell what worries me. Its timestamp is from 1988Q1, so it has more than 30 years on it. Its voltage is now 3.67 V.

Does anybody changed this battery not losing the battery cal. data? I'm thinking on powering the RAM from an external battery; remove the old one; solder a pair of wires to the PCB holes of the removed battery; and connect a new battery to such wires, in case I need to replace the battery again in the future. Comments on this? Any other EEVblog-approved procedure?

Also, the battery (a Eagle-Picher Keeper LPC-7P) seems to be unobtanium in EU, any replacement?

Thanks a lot & regards.

Yes, that's been done. A backup voltage provided while the battery is changed out. If I recall correctly that procedure is buried somewhere way back in this thread. Got a few hours to do some reading/searching?  :-DD
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on September 03, 2018, 05:30:08 pm
Thanks Med! Been kind of busy with other stuff lately and didn't have much time to check back in here until today. Downloading manual now.

Another useful bit of information at this point while looking for a 246x scope would be if there is an error code specific to an instrument that has lost its calibration constants? Is there such error message, or is there anything else I would need to look out for to know for sure that the calibration is gone? Thanks.

You can download a copy of the 2465A service manual here...

https://elektrotanya.com/tektronix_2465a_2467.pdf/download.html

Starting at section 6-10 it lists all the diagnostic routines.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: cheeseit on September 03, 2018, 05:35:02 pm
How-to here (http://jestineyong.com/tektronix-2465a-dv-oscilloscope-memory-backup-battery-replacement/) and battery here (https://www.conrad.com/ce/en/product/650799/EVE-EF651625-Non-standard-battery-LTC-7PN-U-solder-pins-Lithium-36-V-750-mAh-1-pcs?queryFromSuggest=true)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on September 03, 2018, 05:37:14 pm

But it is the Lithium cell what worries me. Its timestamp is from 1988Q1, so it has more than 30 years on it. Its voltage is now 3.67 V.

Does anybody changed this battery not losing the battery cal. data? I'm thinking on powering the RAM from an external battery; remove the old one; solder a pair of wires to the PCB holes of the removed battery; and connect a new battery to such wires, in case I need to replace the battery again in the future. Comments on this? Any other EEVblog-approved procedure?

Also, the battery (a Eagle-Picher Keeper LPC-7P) seems to be unobtanium in EU, any replacement?

Thanks a lot & regards.

Yes, that's been done. A backup voltage provided while the battery is changed out. If I recall correctly that procedure is buried somewhere way back in this thread. Got a few hours to do some reading/searching?  :-DD

Yes I saw it somewhere back in those 46 previous pages. As I recall that in essence the procedure is that the yellow tantalum capacitor next to the battery is temporarily removed, and the leads of a 2xAA cell battery holder is soldered in place on the capacitor pads, and be sure to watch correct polarity. The two AA batteries will power the RAM chip while you exchange the Lithium battery. Once done verify everything looks good, remove the 2xAA battery holder leads, and reinstall the tantalum capacitor.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: james_s on September 03, 2018, 05:53:15 pm
Why remove the capacitor? Can't you just tack solder some wires to the pads with the capacitor in place?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on September 03, 2018, 06:02:38 pm
Why remove the capacitor? Can't you just tack solder some wires to the pads with the capacitor in place?

Not sure, maybe its easier (possibly also more secure) to firmly solder the wires of the battery holder on the pads on the component side when the capacitor is removed, so as to keep those wires out of the way, while one would be working on the foil side to exchange the Lithium cell. I have never done the procedure, but I think it would make sense. Tack soldering wires sometimes work themselves loose. Please feel free to correct me if I am wrong.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: james_s on September 03, 2018, 06:07:56 pm
I think it's worth looking closely for the best method, something you have to be careful about is accidentally shorting the two nodes together which will result in a power glitch that will likely corrupt the memory. I would be nervous about the possibility of shorting something with the soldering iron while trying to remove and reinstall that part.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: cheeseit on September 03, 2018, 06:16:49 pm
Removing it is unnecessary, and reduces the risk of lifting pads or damaging the board. With proper and careful solder work (use flux) nothing works itself lose, provided you don't yank the wires or throw the board around. You can use kapton tape to secure the wires to the board, and perhaps to shield the areas around the solder points. See the guide I provided, it is pretty easy.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: emece67 on September 04, 2018, 10:01:27 pm
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Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tkamiya on September 05, 2018, 12:21:38 am
Replaced my memory chip with Dallas compatible with socket.  Somehow, in the process, something got knocked lose and it won't even boot.  Took it apart and put it together, got back to where it was before.  04 11 error again.  I guess someone else's cal data wasn't close enough.  I'm somewhat encouraged that someone managed to cal it close enough with even an analog function generator.


Why can't I have TEN working scopes?  Waaaaaaaaa!  (I feel better now)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: emece67 on September 13, 2018, 06:43:34 pm
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Title: Re: Tektronix 2465B oscilloscope teardown
Post by: emece67 on September 17, 2018, 12:23:43 pm
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Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on September 17, 2018, 07:12:33 pm
Hi again,

Finally managed to fix it. As there was no image at all, but the controls seem operative, I decided to check the HV board. Soon noticed that all HV voltages were dead, because the HV oscillator was also dead, as the unregulated -15 V tension was not present. Such voltage comes from the A2A1 regulator board via the J121 connector in the center of the image.

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=525008)

The problem was that I inserted the connector badly, in such a way that pin 1 from the PCB (the unregulated -15 V) was not inside the plastic connector, but below it  |O, where it cannot be seen . This was possible (apart for my clumsiness) because pin 2 is not present, so it is possible to push the connector slightly tilted, so pin 1 goes outside its place.

The unregulated -15 V source seems not to be used in any place, but in the HV oscillator, and it is also not monitored by the processor, so the remaining circuitry worked flawlessly and all tests passed OK.

It's working now, waiting for the AA sized Li-SOCl2 cell I will use to replace the PCB mounted RAM backup battery.

Regards.


More proof that 9 times out of 10 when you discover a new problem after any work you have done, it's time to carefully inspect the work. Has happened to me more than once on 2467B work. Pulled out a hidden connector while lifting out the Option 06 PCBA (Counter/Timer/Trigger), took a while to find that one.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on September 18, 2018, 12:49:04 am
Hi again,

Finally managed to fix it. As there was no image at all, but the controls seem operative, I decided to check the HV board. Soon noticed that all HV voltages were dead, because the HV oscillator was also dead, as the unregulated -15 V tension was not present. Such voltage comes from the A2A1 regulator board via the J121 connector in the center of the image.


The problem was that I inserted the connector badly, in such a way that pin 1 from the PCB (the unregulated -15 V) was not inside the plastic connector, but below it  |O, where it cannot be seen . This was possible (apart for my clumsiness) because pin 2 is not present, so it is possible to push the connector slightly tilted, so pin 1 goes outside its place.

The unregulated -15 V source seems not to be used in any place, but in the HV oscillator, and it is also not monitored by the processor, so the remaining circuitry worked flawlessly and all tests passed OK.

It's working now, waiting for the AA sized Li-SOCl2 cell I will use to replace the PCB mounted RAM backup battery.

Regards.

Good deal on finding your issue. Once you get your battery issues sorted out I strongly recommend re-capping the PSU. While I'm typically the type that takes the path "if it ain't broke, don't fix it" in the case of the 2465 PSU I'd rather be proactive. Troubleshooting those boards installed as they are can be a real PITA. And you can't power them outside the scope unless you build a load rack. So prevention seems to make sense. I think you mentioned before that your 2465B has low power on hours. That's fine but in the life of a capacitor you have to think in terms of total elapsed time. In this case we are talking 25-30 years which is old.

I've done two 2465's without any real issues. The last one I did I documented the entire process starting at post 1091. If you work slowly and carefully the most your scope will be out of action is 2 days. And it was totally worth the effort.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on September 18, 2018, 07:10:43 am
See http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf (http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on September 18, 2018, 11:39:59 am
See http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf (http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf)

I ran across that article years ago after getting the 2465 DMS and started searching for information. I also joined the Tek Yahoo Group. It was clear from that article plus what I learned in the group that re-capping the PSU in the 24XX series was a smart investment. It certainly worked for me in that the 2465 DMS has not had any sort of crap out since re-capping (Knock on wood :-DD). And since getting the 2nd 2465 earlier this year I've done the same. 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: emece67 on September 18, 2018, 09:22:44 pm
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Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on September 22, 2018, 04:11:23 am
Hi all,

Just started to open my pristine 2465B for a recap and cal. backed memory update, just to discover that mine has the old style A5 board (insertion components) that, to hold the cal. data, has a separate RAM chip and a PCB mounted Lithium battery, as seen here:


Interesting, what serial number range is your scope? That would probably the best option to look for.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on October 01, 2018, 02:12:16 am
This latest teardown will cover the heavily optioned 24XX such as the 2465 DMS which have options such as DMM and Counter/Trigger. It is a supplement and an addition to the vanilla 2465 teardown I documented in this thread back in July. My reasons for this supplement are two fold. First, the teardown of these beasts to either re-cap to PSU or service the fan motor is much more complex. And second, the fan motor in my 2465 DMS has developed a death screech and I need to pull the motor and service it.

The candidate. The lower 2465 DMS. The top 2465 was the subject of the teardown in July for the PSU. The PSU in the 2465 DMS was done 2 years ago and at that time the fan motor was sometimes noisy but usually quieted down after about 20 minutes or so. In retrospect I should have serviced it then because now I have no choice but to rip it apart again. But the benefit is others will see how it's done and how much more complex it is. This 2465 DMS has the following options:

Option 01: 4.5 digit DMM
Option 09: Counter/Trigger/Timer with 17-bit Word Recognizer
Option 10: GPIB Interface

(https://imagizer.imageshack.com/v2/xq90/923/3Y2ptB.jpg) (https://imageshack.com/i/pn3Y2ptBj)

On the surface it doesn't seem like a lot but in reality there is a lot of additional circuit boards and interconnects as this teardown will reveal. After all, we are dealing with 1980's technology with much less device density which results in higher component count. So the first section we'll start with the cage fan and DMM board removal. Section 2 will deal with the top plate removal and all the interconnects. Section 3 will deal with the fan motor itself and reassembly.


Once the covers are removed the first order of business is the cage fan if you have an older 2465. Newer 2465A and B have a computer type fan so you can skip this part. For more complete info on how to remove this cage fan see here:

https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1658102/#msg1658102 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1658102/#msg1658102)

(https://imagizer.imageshack.com/v2/xq90/924/yN4HAJ.jpg) (https://imageshack.com/i/poyN4HAJj)

Here's an example of the inner collet snapping in half when attempting to pull the fan off the shaft. It's no big deal. Either epoxy or cyanoacrylate (super glue) will fix it right up.
(https://imagizer.imageshack.com/v2/xq90/924/bha5FI.jpg) (https://imageshack.com/i/pobha5FIj)

The DMM Board must be completely removed. Remove the 2 screws on the left side.
(https://imagizer.imageshack.com/v2/xq90/922/WetDfL.jpg) (https://imageshack.com/i/pmWetDfLj)

Now swing the board completely to the right. The white cable is to the beeper on the front panel that will unplug as you swing the board over.
(https://imagizer.imageshack.com/v2/xq90/924/Yeafht.jpg) (https://imageshack.com/i/poYeafhtj)

Pull the connector on the far right.
(https://imagizer.imageshack.com/v2/xq90/924/XbBJxq.jpg) (https://imageshack.com/i/poXbBJxqj)

Remove ribbon cable from top plate.
(https://imagizer.imageshack.com/v2/xq90/924/MX0dzH.jpg) (https://imageshack.com/i/poMX0dzHj)

Pull connectors off front banana jacks. Unbolt ground wire from board. Now the DMM Board can be removed.
(https://imagizer.imageshack.com/v2/xq90/921/NCPu6G.jpg) (https://imageshack.com/i/plNCPu6Gj)

The top plate is now accessible. Looks innocent enough, doesn't it? The real fun is yet to begin in Part 2.
(https://imagizer.imageshack.com/v2/xq90/923/84OT0G.jpg) (https://imageshack.com/i/pn84OT0Gj)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: xrunner on October 01, 2018, 02:18:26 am

The top plate is now accessible. Looks innocent enough, doesn't it? The real fun is yet to begin in Part 2.


Something scary must be underneath there. I can't wait.  :popcorn:
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on October 01, 2018, 03:43:47 am
Part 2. Top plate removal. Remove all the fasteners around the perimeter of the top plate. There are 2 additional fasteners that secure the plate to the PSU underneath.

(https://imagizer.imageshack.com/v2/xq90/923/84OT0G.jpg) (https://imageshack.com/i/pn84OT0Gj)

Carefully and slowly start pulling straight up on the plate. It will be tight because there are 2 large pin connectors that interface to the PSU underneath. But don't pull too far yet. Maximum of about 2 inches.


On the A5 board side remove these 2 connectors from the top plate.
(https://imagizer.imageshack.com/v2/xq90/922/5hYJ4z.jpg) (https://imageshack.com/i/pm5hYJ4zj)

On the front pull the ribbon cable.
(https://imagizer.imageshack.com/v2/xq90/924/JHWOvg.jpg) (https://imageshack.com/i/poJHWOvgj)

Underneath that ribbon cable are 2 additional ribbon cables that need to be removed. VERY IMPORTANT. Note how they are oriented with red stripe to the left. And don't mix them up. Ask me how I know this? No....don't ask.

(https://imagizer.imageshack.com/v2/xq90/923/8SQUpc.jpg) (https://imageshack.com/i/pn8SQUpcj)

On the left side by the CRT remove these 3 connectors.
(https://imagizer.imageshack.com/v2/xq90/921/ULQtvb.jpg) (https://imageshack.com/i/plULQtvbj)

Same side in the rear remove the GPIB interface cable.
(https://imagizer.imageshack.com/v2/xq90/923/ikictB.jpg) (https://imageshack.com/i/pnikictBj)

In the rear, down that rabbit hole that the camera didn't pick up are the connectors for probe power, if that feature is installed.
(https://imagizer.imageshack.com/v2/xq90/921/tlwGSv.jpg) (https://imageshack.com/i/pltlwGSvj)

Now start pulling straight up. On the left side by the CRT there will be an additional connector to the Counter/Trigger board.
(https://imagizer.imageshack.com/v2/xq90/924/fTTakP.jpg) (https://imageshack.com/i/pofTTakPj)

Now the top plate can be removed. And this is what you have. Attached to the plate itself is the Buffer Board. Plugged into that is the Counter/Trigger Board and behind it the GPIB board. You are probably thinking “that wasn't too bad”. Just wait, putting it all back together is the fun part.
(https://imagizer.imageshack.com/v2/xq90/921/53KEm2.jpg) (https://imageshack.com/i/pl53KEm2j)

So now the PSU is exposed and can be removed. I STRONGLY recommend if a re-cap hasn't been done do it now. Reference here for details:

https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1658219/#msg1658219 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1658219/#msg1658219)

(https://imagizer.imageshack.com/v2/xq90/921/pOAD8V.jpg) (https://imageshack.com/i/plpOAD8Vj)

Part 3 will deal with the fan motor and then the reassembly.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on October 01, 2018, 06:18:07 am
Part 3 will deal with the fan motor and then the tedious task of reassembly.

Here's the PSU on the bench. The fan motor is behind that black assembly on the right.
(https://imagizer.imageshack.com/v2/xq90/923/Ery7Js.jpg) (https://imageshack.com/i/pnEry7Jsj)

Once free unplug the connector..
(https://imagizer.imageshack.com/v2/xq90/923/WRINnr.jpg) (https://imageshack.com/i/pnWRINnrj)

Unsolder it from the circuit board.
(https://imagizer.imageshack.com/v2/xq90/924/g4remI.jpg) (https://imageshack.com/i/pog4remIj)

The method I chose to use for repair was the one proposed by user Siggi in this post:

https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1715741/#msg1715741 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1715741/#msg1715741)

But my motor had an unexpected surprise. There was no retaining screw. Just a hole over the rear bushing. And a small amount of a black substance which appeared to be ground up bushing. The area was greasy and gummy, including the spacer. It appears that someone has been in here before but I'm not sure. But I decided to forge ahead with a repair anyway. (Don't have any pictures. Seems my phone “ate” them...sorry) I cleaned everything with 100% IPA. Once dry I used a Q-tip soaked in synthetic motor oil and forced it into the hole. (I suppose light machine oil would be a better choice and I don't have any). I then set the motor in the vertical position with the rear bushing up overnight to insure the oil soaked in. Then another cleaning on the exterior with IPA. Resoldered to the circuit board then reinstalled into the PSU.

Here's it reinstalled into the PSU.
(https://imagizer.imageshack.com/v2/xq90/923/8fC0cw.jpg) (https://imageshack.com/i/pn8fC0cwj)

And the PSU reinstalled into the scope.   
(https://imagizer.imageshack.com/v2/xq90/924/0WPud1.jpg) (https://imageshack.com/i/po0WPud1j)

Reassembly of the Top Plate: No pictures since it's basically a reversal of the disassembly. But some things to be aware of. First, if you re-capped the PSU it is imperative that you reassembled it correctly. If it isn't you'll never get the PSU and Top Plate to align properly. Second, there isn't a lot of slack in some of the cables and trying to get everything connected while having the room to get your fingers where needed can be extremely frustrating. Work slow and carefully. Once all the cabling is done insure the plate is aligned with the pin connectors to the PSU and carefully push it down into place. If done correctly all the perimeter screw holes will align. If they don't something is wrong and you need to find the cause.

Once you're confident the plate is properly aligned install the fasteners. Then reinstall the DMM board and the cage fan. Then you are ready for the smoke test. Hopefully there isn't any.

What were my results? The fan motor for the first time since I've owned this scope is totally silent. So far the repair has worked and I've run it several hours. Will it last? Hard to say. I think this motor is potentially on it's last legs. But so far it's a thumbs up.  :-+
(https://imagizer.imageshack.com/v2/xq90/924/pdDyaY.jpg) (https://imageshack.com/i/popdDyaYj)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on October 01, 2018, 06:43:36 am
med6753, gorgeous machine  :clap: and thanks for sharing the nicely shot detail photos.  :-+

Is there any reason you don't use the forum's attachment instead of hosting them at imageshack ?

Really worry if someday imageshack acting up, all of this great photos with details will be lost, as we already have few valuable post that had photos gone at earlier posts in this thread alone.  :'(

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on October 01, 2018, 07:40:43 am
med6753, gorgeous machine  :clap: and thanks for sharing the nicely shot detail photos.  :-+

Thanks for the flowers  :-+

Is there any reason you don't use the forum's attachment instead of hosting them at imageshack ?

Personal preference I guess.

Really worry if someday imageshack acting up, all of this great photos with details will be lost, as we already have few valuable post that had photos gone at earlier posts in this thread alone.  :'(

Yes, it's a risk. I was a victim of the Photobucket asshattery but I did go back and fix all my pictures, including in this thread. I think the other image services such as Imageshack took note of what happen to Photobucket and I'm hoping they learned from it. And I also to pay a nominal fee to Imageshack so I think we're safe.   
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: kcbrown on October 01, 2018, 08:02:37 pm
What were my results? The fan motor for the first time since I've owned this scope is totally silent. So far the repair has worked and I've run it several hours. Will it last? Hard to say. I think this motor is potentially on it's last legs. But so far it's a thumbs up.  :-+

Totally silent because it's not turning at all?   ;D

Sorry, just had to ask.   >:D

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mnementh on October 02, 2018, 01:28:58 am
Awesome pictorial med... good detail and the angles are actually useful.  :-+

My recommendation is specifically synthetic motor oil; I used 0W-30 or 5W-30 in the motor on my 2230 a decade ago and still quiet.

The collet-clamp on the fan in these are a total pud to get off without them cracking just like yours. My experience is that this is a losing battle... even ones I know I got free without breaking a few years ago were discovered broken in-use later. I tried the CA thing; it just broke again on one side or the other of the glue joint.  :palm:

IIRC, the fan on my 2230 (or maybe it was one of my 2465s) is just held on by friction; I discovered after using it for a couple years that it had been that way all along; there was no threaded shaft/nut at all.

When I reassembled, I just put the the cone portion onto the shaft and pressed the fan in place with moderate force while holding the can of the motor inside the 'scope. I tried pulling it off and it was on there much tighter than the press-fit most such fans are equipped with; and so far, it has not worked loose YET after many years. Lets just call it an ongoing experiment; whichever scope it's still on. ;)

(https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=533949;image)   I keep telling myself I'm going to find one of these that fits the taper (https://www.towerhobbies.com/cgi-bin/wti0001p?&I=GPMQ4965&) of the fan; but alas, so far I couldn't be arsed to carry through with that plan.  :palm:

I'll post my detail of actually servicing the motor itself here in retaliation... not gonna let you get off scott-free. ;)

mnem
*Nukular*
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mnementh on October 02, 2018, 01:50:43 am
2465 Blower Motor Service

We've all seen a number of articles on rebuilding the 24xx SMPS, and as those who own a 2465 (or any of several other models of this vintage) know, the Seimens canister brushless motor in them can be a bit of a hairball to service when it dries out and starts to squeal/chirp.

Many of us are aware of this article outlining the COMPLETE "Refurbishment" of one such motor that had knackered bushings (http://antiqueradios.com/forums/viewtopic.php?f=8&t=235478), but for many of us (hopefully MOST who are still into these old beasts) the damage is not nearly so bad, and none of us want to volunteer for THAT level of dismantling.  :scared:

Here is the process I've arrived at over the years for servicing the actual motor; as always YMMV, DQMOT, WTFBBQ? DILLIGAF?!? (take your pick) applies...

DISASSEMBLY:


(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=536634;image)

I start out with desoldering the driver PCB because I've seen enough other disassembly tutorials on the SMPS itself; including a good one by med6753 just a few posts above this one.  I don't feel a need to recurse those articles yet again.


(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=536640;image)

Before we start disassembling, take note of the endplay on the motor shaft. If your motor is mostly healthy, it'll be pretty small. Your fingers are a pretty good judge of what is reasonable, but if you feel a need to mic it out, look for 0.5-0.8mm. If it's really loose then you have other problems, like med there who found a big open hole in the back of his motor.  :o


(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=536646;image)

This is what you SHOULD find on your endbell; a little hole sealed up with the ubiquitous Silastic cement. If it's not all dark brown & hard, your motor probably didn't get run dry for too long.  :-+


(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=536652;image)

The Silastic will pick out easily in most cases...


(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=536658;image)

But watch out; those German engineers left a booby-trap in there for ya that COULD kill your motor if you're careless. So don't be. ;)


(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=536664;image)

Once you have the pooky all picked outta the hole, the set screw comes out with very little force. It's not a proper threaded hole; more like the kind where the screw cuts its own threads into ridges molded into the hole like those old fashioned tuning coils from the dawn of electronics. The great wheel never stops turning. ;)

There's really only a few grams of thrust force here as long as you aren't abusing the thing; it doesn't really need much thread to hold. This is what a healthy set screw/thrust bearing looks like; a mirror smooth surface. I wouldn't worry about a little dimple in the surface either; but if it has been run dry a long time, that screw could be chowdered up pretty bad.


(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=536670;image)

This is where the crunk hits the air circulation device; cleaning the dried out oil remains so the bushings can... bush... again. I've seen some that were really bad; it looked like it had caught fire in there. Another that actually had some form of bacteria growing in/on the plastic body.  :scared:

Use your preferred plastic-safe degunker here; I prefer CRC # 03040 Food Safe Industrial Silicone Spray Lube (https://smile.amazon.com/CRC-03040-Silicone-Lubricant-Weight/dp/B00192D0TQ). It tastes like it has an alcohol carrier and the SMDS lists some stuff ending in ane, so probably some kind of plastic that it's not safe on... however I've been using the stuff as contact & control cleaner (especially nice on pots & faders) for over a decade and haven't found it yet.

From the Q&A on the product page above:

Quote from: Amazon Q & A
Four items totaled are listed on the can. (1) Hydrotreated light naphtha is a light petroleum. (2) 1,1Difuorethane is a propellant listed as safe to use by the EPA for food. (3) Polydmethylsiloxane is a type of silicone. (4) n-Hexane 110-54-3 is a crude oil product that evaporates very quickly into the air and is used to extract vegetable oils from crops like soybeans. I use this product on my Cabela's meatgrinder after I've cleaned it, dried it, and before I put it away. It keeps away the rust while keeping the product lubricated between uses. Also never use this product near an open flame as it is very flammable.

So anything naphta will dissolve might be a problem... not sure. I'm sure Cerebus will be along any minute now to correct me. ;)

Bottom line is it dries quickly, leaving only a thin silicone lubricant film behind.


(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=536676;image)


(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=536682;image)

Chuck up the shaft gently; just barely tight with your fingertips. Hold the motor can lightly and run the drill on high speed to work your degunker through the bushings. Spray, run drill, spray again until the backwash runs clear and it looks clean inside the bushing holes.

Play it safe; put the motor somewhere with good ventilation, preferably warm, and let it dry overnight.

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=536688;image)

You wanna wipe the outside of the motor can down with alcohol before you put her to bed for the night; that silly-cone spray does make holding her a wee bit like handling an eel.

And finally... I'm gonna end this segment with...


(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=536697;image)

Yes, they are relevant. I promise.

Cheers,

mnem
Why is the mouse when it spins?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mnementh on October 02, 2018, 01:55:31 am
Thrust Bearing Service:

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=536703;image)

Once you've cleaned the motor, the next step is to service the thrust bearing. If your set screw/thrust bearing is chowdered up from being run dry, you'll need to find a way to get a smooth flat or domed surface for the motor shaft to ride against.

This is offered as an alternate repair method to that in the article on antiqueradios.com I linked to earlier; (http://antiqueradios.com/forums/viewtopic.php?f=8&t=235478)  I don't know many people who would want to take on building a jig and hand-lapping a thrust bearing surface that way.  :palm:

The ball needs to be close to the exact size of the hole to prevent chattering; this will still leave 3-4 turns of thread for the set screw behind the ball. If the hole in your motor isn't tight enough to install the set screw on top of a ~3mm ball, you can omit the set screw altogether and fill the hole with epoxy, or you may want to touch up the thrust surface on the set screw instead.

If your set screw/thrust bearing is in good condition, ignore this step and move on to oiling/reassembly.


(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=537087;image)


Another tactic for repairing a chowdered surface is to chuck the set screw up in a drill (use moderate force or you'll damage the threads) and dress the end against the flat of a fine stone or cut-off wheel on a Dremel with the drill running at the same time as seen here. This is a poor man's "precision ground surface".  >:D

I use this tactic quite often to repair the ends of "special screws" that have been started crooked and damaged the threads on the end. A little chamfer once the bad threads are ground away and that screw is saved.  :-+

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=537093;image)

This is what this screw looks like right after being ground on the flat of the cut-off wheel; I wouldn't be afraid to use this as-is, quite honestly. Took a couple minutes including setting up drill and Dremel. If followed by dragging across 600-800 grit emery cloth with the drill running, it is surprisingly quick and effective.

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=537099;image)

This is what it looks like after running it in the drill with a few quick passes on one of my wife's discarded fingernail buffing blocks. These are NOT emery boards (which my wife steals from me all the time... grrr...  :rant: ) but final polishing abrasives on a dense foam brick. As you can see here, moderate pressure when chucking up in the drill resulted in no damage to the threads.

It actually took me longer to get three decent pics than it did to refinish the end of this m3 set screw from my parts bin.    ;)

Again; if your set screw/thrust bearing is in good condition, ignore these steps and move on to oiling/reassembly.


(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=536709;image)

OILING AND REASSEMBLY:

My preferred lubricant for small motors is full synthetic 0W-30 or 5W-30 motor oil recovered by allowing "empty" oil bottles from an oil change in my car to drain into an old pill bottle like this one overnight.

I use a ~ 2mm wide blade-tip screwdriver as a precision applicator; dip it in the bottle then quickly apply 2-3 drops right on the shaft and let it sit for several minutes in an upright position before doing the same on the opposite end. Repeat for both ends, and repeat again if it appears to just suck the oil in. There is felt batting around the bushings; you are trying to re-saturate it with fresh oil.

This is a brushless motor; the worst that can happen is some oil mess. Of course, use some common sense... a big puddle of oil in your 24xx later could become a big hassle.  ::)

Let the motor sit overnight after oiling if you can; this will give the oil plenty of time to soak into the batting, and you'll be reasonably sure it's not gonna drip after you reinstall it.

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=536715;image)

Reinstall the set screw/thrust bearing. Just turn it in a few turns; don't tighten it.


(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=536721;image)
Sorry for the fuzzy pic; it was the best one of several and the motor's all back together now.

Adjust endplay so it feels the same as when you first disassembled the motor. Your fingers are a pretty good judge of what's reasonable endplay. If you feel a need to mic it out, or if your set screw was chowdered up or missing obviously this will be way off; look for 0.5-0.8mm.  :-+


(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=536727;image)

Use your sealant of choice to close up the hole and lock the set-screw in place. I prefer silicone RTV sealant as it is eazy to remove if needed.

DON'T FORGET THE PLASTIC SPACER when you reassemble the motor to the driver PCB.


(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=536733;image)

TESTING:

A healthy motor will start at around 8V with a 30mA draw; set your power supply with current limited accordingly for initial test. The shaft is hard as hell and mirror-finished; a mark with a Sharpie will make it a lot easier to see when it starts turning. Let it run a few minutes, checking resistors and driver IC to be sure they get no more than warm.


(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=536739;image)

Here we're going to put the fan on temporarily for performance tests. Just press it onto the collet cone; it will hold. No sense to risk breaking it by tightening the nut.


(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=536745;image)

Here we're running at 12V; it's drawing approx 60mA. Fan is running just above idle. Note location of thermistor and pinout of 0.100" power header.

Dont forget to test/replace that electrolytic cap seen on the upper right corner by the motor. It is prehistoric too. ;)


(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=536751;image)

Idling at 8V; drawing ~40mA.


(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=536757;image)

Idling at 12V; drawing ~55mA


(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=536763;image)

And here's the last step; testing the thermal speed control.  Place your soldering iron CLOSE to the thermistor, but don't make contact. The fan motor should start to ramp up speed in a few seconds. You'll need to up the current limit on your power supply if you haven't already.

Do several cycles of "apply heat, fan speeds up / remove heat, fan slows down" and observe the motor; it should still be pretty much dead silent at these low voltages. IIRC, it runs on 18-20V in situ.  Remember to keep checking resistors and driver IC for overheating while testing.

If it runs cool and quiet, time to put it back in... unless you haven't let it sit overnight since oiling it.

You REALLY should take the time, just to be sure of no oily puddles.  :-+

Cheers,

mnem
The higher the faster, of course.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on October 02, 2018, 03:10:05 am
Mnem...great write up!  :-+ If my motor takes a dump again I may try this procedure. Or just scrap it and install a computer fan. I already have one built up and modeled and ready to install if required.

I also used synthetic motor oil.....5W-30 to be exact.

Yes Kcbrown, the fan is running.  :-DD
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on October 09, 2018, 07:24:38 pm
Finally bit the bullet and took the plunge on a 2465B SN 55xxx with what seems good front panel cosmetics on the advertised pictures, including the storage pouch and... A FRONT COVER (!), AC cable but sadly no probes. All for less than $200 plus a bit of S/H. Seller was in same state so shipping went dramatically down, and that certainly gave me some extra legroom towards my willingness on how far to go on the final purchase price given the "As-Is" clause and reported condition (see bellow).

Now for the finer details... sounds to me this scope has the typical symptoms of bad DAC ref voltage due to leaking cap corrosion problem on the A5 board (I hope that's all it is!!). Seller said the scope shows a TEST 05 FAIL 40 upon power up, and that subsequently the traces show quite a bit of jitter and after a while they wander off-screen towards the bottom. Well I guess at least there are live traces present, one fewer problem to deal with, and hopefully the cal constants are still intact.

But in spite of this somewhat risky sounding error and obvious less than ideal condition, after weeks of reading so many very detailed descriptions on how other people, many with little or almost no previous knowledge on these great scopes (just like myself), managed to successfully pull trough their restoration projects. So I decided that it was time and also felt ready to take my chances. This thread alone speaks volumes about how reassuring it is to be in good company when it comes to so many like-minded 246x scope enthusiasts out there, and the great pool of resources that has been built up so far because of so many people posted their detailed experiences. I probably expect to have more questions than answers, but in the end hope to be able to contribute a tiny bit as well towards adding more useful information to this thread for the next newcomer.

So now I'm off to start working on the parts purchase list. Guess I start focusing first on the A5 restoration, and then move on to recap the power supplies as needed. I have seen numerous references to capacitor lists with Mouser (and/or Digikey?) part numbers.

I've attached a picture of the new acquisition, hope to get it in about 2 weeks or so.
More pictures of teardown to follow.

Any comments and suggestions will of course be very welcomed.

PS. Does anybody know what Option 46 is? Can't remember off hand, and its not on my Options short list I had hand compiled, nor is it mentioned in the service manual (section 7.1)
Picture attached of rear panel as well.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on October 19, 2018, 01:48:49 am
I said...

...
It also seems like the 2465A only has entries from 0-254. 255 is zero and from 256 onwards the values wrap around. Is that enough to back up all of my calibration data?

I don't feel like experimenting with restoring the settings, but I'm happy to write another script that does this over GPIB in one go if someone is willing to test.
...
The 256 values should match what you see in EXER 02, in which case, yes, it has all of your calibration data.

Putting the calibration data back via GPIB works on a 2465(plain), but I haven't heard of anyone trying it yet on an A or B.  There's no reason to think it would operate differently, but until someone tries it I guess we don't know for sure.  I've been watching for an A or B junker on ebay for some time now to do this experiment.

Nice find on the "f" option to the EAROM command, thanks!

I finally got a junker to try this on.  $70 on ebay for a 2445A with DVM option, CTT, and GPIB.  I bought it for parts, but the only thing wrong with it was a bad INTENSITY pot.  No fun at all.

So the answer is "yes".  If you push the values displayed via EXER 02 back via GPIB, it works.  You'll need to convert from the hex on EXER 02 to decimal for the GPIB commands.

To repopulate the NVRAM contents you can also directly replay the output of the GPIB NVRAM read data, providing an easy backup method.

This should also work fine on the "B" series since the NVRAM operation is essentially the same.

If you've completely lost your NVRAM, the scope will come up with random and bizarre settings.  Put the NVRAM contents back via GPIB and then power cycle it.  The settings will still be random because the GPIB writes only put back the calibration data (and not the settings).  I couldn't find a "factory default" setting, but if you exercise all the controls to make the settings sane again, all will be ok.

For reference, here's the post that describes the GPIB commands:

  https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1167050/#msg1167050 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1167050/#msg1167050)

If anyone wants it, attached are the NVRAM contents from the 2445A from both the EXER 02 and the GPIB interface.  They are the same.  Obviously this cal data is specific to this scope.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: 0culus on October 19, 2018, 03:22:51 am
I recently got my Tek 2465B and love it. Amazing piece of kit. I ended up finding a pretty good deal on a freshly refurbished and calibrated one (also got a P6137 10x probe and a P6101 1x with it) just the basics as far as options go. This thread helped me decide to pull the trigger because I feel confident that I too can learn how to work on this scope down the road.

Since I recently acquired an RF signal generator (HP 8657A) that goes to 1040 MHz, I wanted to test out the upper limits of bandwidth on the 2465B. I was able to acquire an accurate frequency measure with the cursors at 800 MHz, +130 dBf. Obviously it is heavily attenuated and a bit noisy. Probably not useful in practice, but you can't touch any modern digital scopes with that bandwidth for less than $1000 US. 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on October 19, 2018, 08:29:19 am
I've had my Tek 485 display a stable >1GHz signal. Not bad for a 350MHz scope :)

The limitation wasn't the frequency, but the amplitude of the signal; the limit was set when the amplitude fell to <0.2 divisions. That is a good illustration of the quality of Tek's tunnel diode trigger circuits.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on October 19, 2018, 08:40:35 am
I've had my Tek 485 display a stable >1GHz signal. Not bad for a 350MHz scope :)

The limitation wasn't the frequency, but the amplitude of the signal; the limit was set when the amplitude fell to <0.2 divisions. That is a good illustration of the quality of Tek's tunnel diode trigger circuits.

When it comes detective works, especially on hunting down spurious high freq > 400 MHz oscillation, combined with my 2465B 400MHz limitation just to see the signal, then I used 3GHz spectrum analyzer + 2.5 GHz RF probe to catch them for the amplitudes and span, a resource limited hobbyist grade HF probing technique.  :P
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: 0culus on October 19, 2018, 09:12:44 pm
I've had my Tek 485 display a stable >1GHz signal. Not bad for a 350MHz scope :)

The limitation wasn't the frequency, but the amplitude of the signal; the limit was set when the amplitude fell to <0.2 divisions. That is a good illustration of the quality of Tek's tunnel diode trigger circuits.

Wow! What probes did you use for that?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on October 26, 2018, 03:35:11 am
Scope arrived, finally.

This is a 2465B SN 55K off ebay, very good cosmetics, and insides are very clean, almost no dust anywhere. Has a TEK U800, and NVRAM has a date code 9020. Most chips are also 1990's. I attached some general pictures. More detailed pictures to follow.

Plugged in, power on, but no trace or readout on screen. Self test stops at the "ADD" label, which means a Test 05 Error of some kind. Seller's description stated that the scope was showing an Error 05 Fail 40, which means "Positive Level too positive", and I assumed most probably due to corrosion on the A5 board due to well known leaky caps, which now is already confirmed ->detailed pictures of clean-up to follow as well. Seller also stated that trace had a lot of vertical jitter, and after a while it would move off screen towards the bottom. Not sure how long ago this scope still had a visible trace upon power up.

Anybody has any ideas/suggestions on why there is no trace?

Oh, and yes, I will definitively check all the voltages at J119 once I get the mess cleaned up on A5.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on October 26, 2018, 03:55:23 am
Decided to keep on going tonight with the leaky caps removal and pad clean-up, so here are some pictures of the process. I followed the recommendation of a very knowledgeable member of the Tek Scopes group to not attempt to lift the caps in one piece, as it is very easy to damage or lift the pads off the board, but rather to chop them up to pieces and get down to the pads before trying to desolder what was left. Also, while desoldering not to pull up, but rather to slide to the side any remains of the caps connecting leads. Well I actually desoldered the single cap on the other corner in a conventional way and all went well, but decided against it where the other 3 caps are very close together.

The pads of the caps cleaned up quite well, not much damage due to corrosion or any eaten away traces that I could spot. But as one can see there is a wide area of other affected parts that will need to be cleaned (affected IC legs), or replaced in the case of caps and resistors. Once all those other affected SMD parts have been removed, the other recommendation is to wash the affected areas with water, dish soap and a soft toothbrush to get rid as much of possible of any remaining electrolyte left over from the leaking caps. Then put the board into a convection oven to dry.

Here are some before and after pictures of the repair in the area of the 3 caps.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on October 26, 2018, 04:02:26 am
Here is the other affected area on the A5 board where the remaining single leaky cap was located. Quite a bit to clean up and replace as well around that area. Apologies for the almost duplicate pictures, but I couldn't quite get the right camera angle that would show all the places with greenish or dull spots.

Comments and suggestions welcomed.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on October 26, 2018, 04:28:46 am
AMR Labs, congrats on the score !  :clap:

Also thanks for sharing the photos, really appreciate it.  :-+

About the leaky caps, suggesting to check if the surrounding thin traces for continuity as it seems like they're corroded too, also reflowing the solder at the surrounding components as their solder joints look tarnished, not shiny as neighboring solder that are far away from the leaky caps.

Put few example highlighted points by arrows on the affected traces.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on October 26, 2018, 08:33:21 am
I've had my Tek 485 display a stable >1GHz signal. Not bad for a 350MHz scope :)

The limitation wasn't the frequency, but the amplitude of the signal; the limit was set when the amplitude fell to <0.2 divisions. That is a good illustration of the quality of Tek's tunnel diode trigger circuits.

Wow! What probes did you use for that?

None! BNC coax, 50ohm termination in the scope. 

The 485 has two attenuators, one 50ohm and one 1Mohm. None of this "stuff a 50ohm resistor across the 1Mohm//20pF input and call it 50ohm" crap :)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: grbk on October 26, 2018, 02:22:08 pm
Plugged in, power on, but no trace or readout on screen. Self test stops at the "ADD" label, which means a Test 05 Error of some kind. Seller's description stated that the scope was showing an Error 05 Fail 40, which means "Positive Level too positive", and I assumed most probably due to corrosion on the A5 board due to well known leaky caps, which now is already confirmed ->detailed pictures of clean-up to follow as well. Seller also stated that trace had a lot of vertical jitter, and after a while it would move off screen towards the bottom. Not sure how long ago this scope still had a visible trace upon power up.

Anybody has any ideas/suggestions on why there is no trace?

Oh, and yes, I will definitively check all the voltages at J119 once I get the mess cleaned up on A5.

Your scope sounds almost exactly like mine. The problem is almost certainly just the DAC circuit on A5 due to the capacitor corrosion. That DAC circuit is used for controlling pretty much everything in the scope. ADD being illuminated also suggests you have a DAC problem. Fix A5 and you'll be good to go.

I say this from experience -- a couple weeks ago I purchased a SN005xxxx 2465B, datecodes ~1990, with no trace (advertised as "HV collapses") for not much money. Finished fixing it the other day (have not recapped the power supply or replaced the NVRAM yet; those are next on the list). I haven't yet gotten around to writing it up for this thread and posting my pictures, but here's the abridged version for you & posterity.

My issues checked out almost identically to yours. No trace. Startup checks left ADD illuminated, indicating some kind of Test 05 failure.

I could turn grid bias up all the way and at least get a readout, but no visible trace; at least now I could see that the error was Test 05 Fail 44. I checked the reference voltages generated by the A5 DAC. From memory, I think they're supposed to be +1.36V and -1.25V, but they were way low. You can also probe these at some of the front panel pots (e.g. intensity). I also ran the front panel control exerciser routine (EXER01) which showed limited range for many of the front panel controls, again due to the missing reference voltages (they're used as the positive and negative supplies for many? of the front panel pots).

I replaced all of the SMT caps and a good chunk of the DAC circuit resistors on A5. My procedure was roughly this:

If you turned up grid bias during the debugging phase, you'll probably want to turn it down again before powering up. You'll also want to run through the CRT adjustment procedure if you tweaked grid bias. It's pretty easy and does not affect your other calibration steps.



Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on October 27, 2018, 04:18:54 am
@BravoV

Thank very much for the pointers. Yes next step I plan to undertake an extensive cleaning effort of the affected areas to remove any traces of capacitor electrolyte left on the board and in between components, and of course replace well known suspect parts. I am planning on putting together a purchase list of all the parts in the DAC area, including the reference resistors, capacitors, as well as the adjustment trimmer which frequently also seems to go bad in these cases. I wonder if anyone out there has the Mouser PNs of these parts? That would make it so much easier to order them.

Should be posting more pictures as I make progress, hopefully soon. This forum thread has already become a must read reference for any 2465 enthusiast, so I think the more information is added the better it will be getting over time to help others that follow. It certainly got me started. Thanks again for the arrows!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on October 27, 2018, 04:55:55 am
Plugged in, power on, but no trace or readout on screen. Self test stops at the "ADD" label, which means a Test 05 Error of some kind. Seller's description stated that the scope was showing an Error 05 Fail 40, which means "Positive Level too positive", and I assumed most probably due to corrosion on the A5 board due to well known leaky caps, which now is already confirmed ->detailed pictures of clean-up to follow as well. Seller also stated that trace had a lot of vertical jitter, and after a while it would move off screen towards the bottom. Not sure how long ago this scope still had a visible trace upon power up.

Anybody has any ideas/suggestions on why there is no trace?

Oh, and yes, I will definitively check all the voltages at J119 once I get the mess cleaned up on A5.

Your scope sounds almost exactly like mine. The problem is almost certainly just the DAC circuit on A5 due to the capacitor corrosion. That DAC circuit is used for controlling pretty much everything in the scope. ADD being illuminated also suggests you have a DAC problem. Fix A5 and you'll be good to go.

I say this from experience -- a couple weeks ago I purchased a SN005xxxx 2465B, datecodes ~1990, with no trace (advertised as "HV collapses") for not much money. Finished fixing it the other day (have not recapped the power supply or replaced the NVRAM yet; those are next on the list). I haven't yet gotten around to writing it up for this thread and posting my pictures, but here's the abridged version for you & posterity.

Excellent write up grbk, thank very much for the information. Your case being so similar really encourages me to think I will be solving the display problems with an A5 repair as well.

Quick question: what would you say are the easiest access points to check on the +1.36V and -1.25V DAC reference voltages? Wanted to do a quick "1-2-3" check on that to see at what level those voltages are actually now, before and after the board wash of the two separate affected areas. And eventually after the required parts are replaced. Kind off to keep track of those voltages, mostly out of curiosity. Are there any easy access test points on the A5 board itself, or maybe some pins on one of the on board connectors? I do have the service manual but have been kind of overwhelmed a bit between some lack of time and all the huge amount of technical information in there, so at times one tends to loose track of what is where. Guess it will get better after I have gone through it enough times to familiarize myself with the content on a greater extent.

BTW by any chance do you (or anyone else out here) would have handy an already made list of specific Mouser PNs of the usual parts that need to be replaced in the DAC area? I've come across a list with Digikey PNs for some of the caps and resistors, which is a start but would also like to order the DAC trimmer resistor as well, just in case. And for several reasons, including the above and beyond easy and friendly quality user experience, my preferred go to parts place for years now has always been Mouser.

Thanks again for the great write up. I will send in some more updates of progress on the board wash hopefully in the next couple of days, as time and other occupations pressing for attention as well do permit.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: 0culus on October 27, 2018, 04:58:44 am
I've had my Tek 485 display a stable >1GHz signal. Not bad for a 350MHz scope :)

The limitation wasn't the frequency, but the amplitude of the signal; the limit was set when the amplitude fell to <0.2 divisions. That is a good illustration of the quality of Tek's tunnel diode trigger circuits.

Wow! What probes did you use for that?

None! BNC coax, 50ohm termination in the scope. 

The 485 has two attenuators, one 50ohm and one 1Mohm. None of this "stuff a 50ohm resistor across the 1Mohm//20pF input and call it 50ohm" crap :)

D'oh, of course!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: grbk on October 27, 2018, 06:09:32 am
Quick question: what would you say are the easiest access points to check on the +1.36V and -1.25V DAC reference voltages? Wanted to do a quick "1-2-3" check on that to see at what level those voltages are actually now, before and after the board wash of the two separate affected areas. And eventually after the required parts are replaced. Kind off to keep track of those voltages, mostly out of curiosity. Are there any easy access test points on the A5 board itself, or maybe some pins on one of the on board connectors? I do have the service manual but have been kind of overwhelmed a bit between some lack of time and all the huge amount of technical information in there, so at times one tends to loose track of what is where. Guess it will get better after I have gone through it enough times to familiarize myself with the content on a greater extent.

BTW by any chance do you (or anyone else out here) would have handy an already made list of specific Mouser PNs of the usual parts that need to be replaced in the DAC area? I've come across a list with Digikey PNs for some of the caps and resistors, which is a start but would also like to order the DAC trimmer resistor as well, just in case. And for several reasons, including the above and beyond easy and friendly quality user experience, my preferred go to parts place for years now has always been Mouser.

Thanks again for the great write up. I will send in some more updates of progress on the board wash hopefully in the next couple of days, as time and other occupations pressing for attention as well do permit.
I’m out of town for the weekend so unfortunately I can’t provide specifics or take a picture of the schematic where I circled my test points for the reference voltage. However they should be straightforward to find if you compare the schematic and layout view. On the SMT A5 board, there are no explicit test points for the reference voltage, but they are easy to access on component terminals, I just don’t remember which components. First find the reference voltages in the analog control schematic (they’re labeled clearly), then identify which components have those voltages on them (for each there should be an op amp and probably an analog mux and maybe a capacitor). Then identify the components on the layout diagram. The voltages are also available on some of the front panel pots — intensity for sure, don’t remember which others. The schematic is clear on this though. They are undoubtedly on some headers/cable assemblies as well but I don’t know which and I didn’t investigate carefully.

As far as I can tell the original R2010 trimmer is no longer made. However it looks like a standard 20K cermet trimmer so I ordered Bourns PN PVG3A203C01R00 which should have the same footprint and otherwise be equivalent. However I didn’t end up installing it since the original one measured ok, so your mileage may vary.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on October 27, 2018, 02:07:08 pm
Maybe this has already been done before, but I compiled a composite picture of my actual board with superimposed component labels, and also differentiated which parts are directly related to the DAC, and others near by that are not directly related, but also show signs of corrosion. In my mind this should make it easier to positively identify all the critical parts that set the DAV reference voltage (current).

Wanted to add the DAV reference voltage testing points as well, but not yet sure where they are. Will add once I located these.

There is also one additional part shown with a red label that does not match the location as seen on the service manual parts layout for this area, but it seems more to the left. Maybe board changes that where only documented in later service manuals. I am using service manual PN 070-6863-00 last revision Sept 1989.

If I made any mistakes, please let me know so they can be corrected.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: cheeseit on October 27, 2018, 05:14:01 pm
Try to find 070-6863-01 which is newer, preferably the searchable version.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on October 27, 2018, 07:20:12 pm
Board wash!

Took quite a bit to get the crud around the 3-4 most affected resistors, had to repeat with several wash cycles.

Done gently with dish soap and a soft toothbrush.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on October 27, 2018, 07:35:29 pm
Ok dried the board for a while and popped in temporary elco subs for the removed leaky caps so I could take some measurements around the DAC. Please see attached image with schematic of the DAC input resistor network. All voltages in red taken with a HP974A DMM. I have not checked yet any of the resistor values, which I assume cannot be checked in-circuit anyhow.

Not sure if anyone has records of what the correct voltages should be around these nodes so as to compare and try to figure out which ones are probably bad without having to pull one by one to test them. For me once a SMD part out it will probably stay out and a new replacement will go in instead. So i rather will try to keep as many as possible of the undisturbed originals and try to deduce which might be bad with these voltage measurements.

The +1.36V out at the + side of C2420 only measures a mere +0.25V or so (all measurements where a bit jumpy and dance around 0.1-0.2V). Likewise the -1.25V output has only 0.23V (at pin 13 of IC2420).

Anyone out there that has done these same measurements on a good scope?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on October 27, 2018, 07:42:46 pm
Try to find 070-6863-01 which is newer, preferably the searchable version.

Turns out I actually had the -01 version, but had chosen the other one because it has a very handy page navigation side bar that makes it so much easier to land on the right page, for example 6-10 instead of the page number that the Acrobat reader shows. But the -01 is definitively much more up to date and will use it from now on. Thanks.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on October 28, 2018, 07:59:09 am
So I build a simulation of the resistor divider of the DAC input with 5% resistors on a protoboard so I could make some voltage reading comparisons. I am assuming that the two DAC reference inputs are high impedance and do not account for much if any change on the actual resulting voltages (please correct me if I am wrong on this). I also adjusted the 10V input voltage to match the 9.988V actually seen on the scope, and adjusted the wiper of the 20K trimmer to match 5.51V as seen on the scope as well. The results are on the attached picture.

The total series resistance of this network measured roughly about 38~39K (I left out the 15uF C2010 capacitor on purpose to be able to measure this resistance). I measured about 268uA current flowing through the divider, which I calculated taking the voltage across  the 1K R2016 resistor, the upper leg of the divider, which is 9.988v - 9.72v = 268mV / 1K = 268uA. Again, these are 5% resistors, so readings will be slightly off here and there, but should definitively be good enough for a general comparison.

Now going back to my original readings on the scope (I re-posted the picture showing those readings as well), the voltage difference on the 1K R2016 resistor is only 9.988-9.926 = 62mV, which if I assume the 1K resistor is still within its value, there are only 62uA of current flowing into the resistor network. Way too low. This I would think would mean that one or more resistors have gone high (or open). My first suspect would be R2012 10K, as the voltage on pin 15 of the DAC (-Ref) is more than twice as high as expected, and this resistor is the lower leg of the voltage divider. Then again, maybe R2013 has gone high (or open), as the +Ref voltage is about 2.25v low compared to my simulation.

I could try to further tweak my breadboard simulation to see if I can find a combination that would arrive at the actual voltages read on the scope. That would of course only be practical if one assumes that only one or maybe two resistors have sustained damage, but given that more than two might be bad, it might be a futile exercise.

Time now for a break, get some Zzzzs.... its almost 4am.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: grbk on October 29, 2018, 12:50:14 am
Ok dried the board for a while and popped in temporary elco subs for the removed leaky caps so I could take some measurements around the DAC. Please see attached image with schematic of the DAC input resistor network. All voltages in red taken with a HP974A DMM. I have not checked yet any of the resistor values, which I assume cannot be checked in-circuit anyhow.

Not sure if anyone has records of what the correct voltages should be around these nodes so as to compare and try to figure out which ones are probably bad without having to pull one by one to test them. For me once a SMD part out it will probably stay out and a new replacement will go in instead. So i rather will try to keep as many as possible of the undisturbed originals and try to deduce which might be bad with these voltage measurements.

The +1.36V out at the + side of C2420 only measures a mere +0.25V or so (all measurements where a bit jumpy and dance around 0.1-0.2V). Likewise the -1.25V output has only 0.23V (at pin 13 of IC2420).

Anyone out there that has done these same measurements on a good scope?

Before I replaced the resistors, my reference voltages measured +0.27V and -0.25V which lines up well with your measurements. I didn't measure any of the other node voltages, sorry.

So I build a simulation of the resistor divider of the DAC input with 5% resistors on a protoboard so I could make some voltage reading comparisons. I am assuming that the two DAC reference inputs are high impedance and do not account for much if any change on the actual resulting voltages (please correct me if I am wrong on this). I also adjusted the 10V input voltage to match the 9.988V actually seen on the scope, and adjusted the wiper of the 20K trimmer to match 5.51V as seen on the scope as well. The results are on the attached picture.

The total series resistance of this network measured roughly about 38~39K (I left out the 15uF C2010 capacitor on purpose to be able to measure this resistance). I measured about 268uA current flowing through the divider, which I calculated taking the voltage across  the 1K R2016 resistor, the upper leg of the divider, which is 9.988v - 9.72v = 268mV / 1K = 268uA. Again, these are 5% resistors, so readings will be slightly off here and there, but should definitively be good enough for a general comparison.

Now going back to my original readings on the scope (I re-posted the picture showing those readings as well), the voltage difference on the 1K R2016 resistor is only 9.988-9.926 = 62mV, which if I assume the 1K resistor is still within its value, there are only 62uA of current flowing into the resistor network. Way too low. This I would think would mean that one or more resistors have gone high (or open). My first suspect would be R2012 10K, as the voltage on pin 15 of the DAC (-Ref) is more than twice as high as expected, and this resistor is the lower leg of the voltage divider. Then again, maybe R2013 has gone high (or open), as the +Ref voltage is about 2.25v low compared to my simulation.

I could try to further tweak my breadboard simulation to see if I can find a combination that would arrive at the actual voltages read on the scope. That would of course only be practical if one assumes that only one or maybe two resistors have sustained damage, but given that more than two might be bad, it might be a futile exercise.

Time now for a break, get some Zzzzs.... its almost 4am.

This is an interesting exercise and if you're inclined to continue I would be interested to hear the results. Even if you find that all resistors except one or two measure okay, I would still recommend you replace all of the ones with visible corrosion to prevent any future problems, so long as you think you can remove them easily without damaging the board. I believe the precision 10K ones do tend to go high or open.

Edit: I can't spell.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on October 29, 2018, 08:55:42 pm
Progress!

So I went to try and test the DAC reference resistors in-circuit to try and determine which ones would be more suspect. To start I measured across the two 10.0K resistors, and one was measuring around 160K and the other was even higher around 300K I think it was, so they had to be bad. A good start would be to pull those out, one at a time. I pretty much routinely solder 1206 SMD parts by hand with a fine tip for one of my commercial projects that uses a few of these on the board, done with a T7 fine tip and a Weller 25W pencil iron "dimmed down" with a light dimmer to reduce somewhat the tip temperature. First I scraped a bit the dull solder on both ends of the resistors, and then added a bit of fresh solder, and after doing this on both ends the resistors would stand up on one end almost like it wanted to come off with the tip and without almost any effort at all. Luckily these parts don't seem to be held onto the the board other than with the two solder junctions, no other additional bonding stuff as it sometimes happens. So minimal stress to the board pads.

Went first to pull R2012 10.0K, but by mistake ended up pulling R2016. Ooops. Even tough it initially had some serious crud on the ends, turns out it appeared to be still ok, a quick check measured  1.001K, so not far off if anything but now that it is out will definitively replace it. Next I went to get R2012, one of the 10.0K resistors, which this time was the correct one, and came out very easily as well. But this one measured completely open. Same was the case of R2013, the other 10.0K resistor. Two for two, so far so good. So I figured now that I have these 3 resistors out of the network I could probably make some in-circuit tests of the remaining ones. R2011 a 4.75K resistor measured very close at 4.749K, so leave that one alone for now. R2015 the 82.5K one measured 60.6K, and R2014 221K measured 64.2K across it. Since both these resistors are connected together as well as to R2010 the 20K trimmer, it would be expected those readings to be way off their actual value. But where they still correct? So I took my previously "protoboarded" 5% resistor network simulator and pulled out the two 10K and the 1K resistor, and measured across the 220K, and it measured 60K, and the 82K resistor measured at 63K. That is very close to what I am getting on the A5 board so for now will not disturb them. BTW R2520 and R2521 which are 681-ohm 0.1% resistors used to convert the output current of the DAC to a voltage, in circuit measured 687 and 691 ohms respectively, so for now I will consider them good enough as well, and at least no opens.

So getting back to my project that uses 1206 resistors, by chance it happens to use some 10K and 1K units as well, and I had plenty of them in the parts drawers. Only thing these are 5% tolerance, but I though, what the heck, just for temporary testing purposes they are certainly better than an open resistor. So in went two 10K and one 1K 5% (I hope nobody pukes, probably the nice purist guys at Tekgroup probably would at least cringe at this, so maybe for now will keep it my little secret). Also reinstalled the temporary leaded elco filter caps (pulled from an old board, but checked for ESR and value) and back in went the A5 board. See attached picture of the reworked board with the temporary resistors and caps.

Before power up I held the tip of the DMM on the the +1.36V test point (I found a convenient location to be at the positive end of C2420). At initial power up it was still showing the same +0.26V as before, -oh crap no progress at all. But then 1-2 seconds later the screen readout came to life! I measured again and I now was getting +1.3848V, not exactly "on-spec" but close enough for now. And the -1.25V ref voltage (measured at pin13 of U2420) was at -1.2688. Wahooo!

On startup the scope cycles through all the test steps lighting up the front panel indicators in sequence, and at the end no errors are shown.

So, looks like I made some progress after all! Calibration will for now obviously be way off, but I am not going to mess with the +1.36V setting until I put in the proper tolerance resistors. No sense disturbing that setting at this point. On the last picture (ITS ALIVE!!! - remember the movie Young Frankenstein 1974?), for purely academic reasons I set the timing Alpha time cursors centered onto 2 divisions, and with the time base set at 500nS its obvious the resulting 973nS reading (which should have been exactly 1000nS) tells it all. But for now, today was a good day and I am happy with this progress. Will be placing the A5 parts order at Mouser tonight!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on October 29, 2018, 09:30:13 pm
@AMR Labs
Wouldn't you just measure a few of your 5% resistors on hand to find some that fall within a 1% tolerance and use those ?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on October 29, 2018, 10:44:15 pm
@AMR Labs
Wouldn't you just measure a few of your 5% resistors on hand to find some that fall within a 1% tolerance and use those ?

Well, the 10.0K resistors have to be 0.1% tolerance, the rest 1%. But I figured this was just a test exercise to see if the screen would come  to life once the DAC ref voltages were back in the ballpark, or if there might be other problems. Now I know for sure. I'm planning to order the proper resistors anyhow, so I just did not see the need to do any close matching if the strictly test results where probably going to be pretty much the same. I would have used leaded 5% 1/4Wresistors if I didn't have these 1206 SMDs handy. The resistors I end up using where checked, tough. One was 10.01K and the other 9.98K, even being from the same batch next to each other on the tape. Don't remember now the 1K, but it was also quite close. Then there is also the temperature coefficient and long term stability to take into account, which are qualities of metal film, and mine are just "film" resistors so not really suitable candidates even if a very close match would have been found.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on October 30, 2018, 01:08:37 am
EXER O5 DATA

HRS ON: 365
PWR ON/OFF: 125

Does this sound real for an early 90's scope? Or perhaps these counters might have been reset at some point?

Also copied EXER 02 RAM calibration data, took a video while scrolling through from address 00 to FF, and wrote them down by hand as well, just in case.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on October 30, 2018, 01:23:52 am
My 2465B bought in 2011 had 292 on hours & and on/off counter at 349, I guess that depends on previous owner usage, but yours look pretty low count, assuming its not tampered.

(https://www.eevblog.com/forum/beginners/asking-about-tektronix-2465b-any-experienced-tek-tech-or-lovers-jump-in-please/?action=dlattach;attach=16425;image)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on October 30, 2018, 02:56:48 am
My 2465B bought in 2011 had 292 on hours & and on/off counter at 349, I guess that depends on previous owner usage, but yours look pretty low count, assuming its not tampered.

I guess that must be the scope that started this thread? I saw you also got lucky that the front cover and a storage pouch where included, mine came with those as well, but no probes. Very hard to get those accessories included nowadays on a low or even mid priced 2465x on ebay, specially the front cover. I have seen these sold separately for $100, just for the cover. And you also have a TEK made U800. In what serial number group is yours? Mine is 55xxx and most chips inside have a 1990 date code, including the NVRAM. From the inscriptions and labels on the front cover and on one side, this might have been a field unit that was not really taken out that much, and who knows maybe even less once the problems created by the leaky caps started to show up. The inside is almost pristine, very little dust only in a few places, if any at all. No signs of anyone tampering inside either.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on October 30, 2018, 09:59:54 am
My 2465B bought in 2011 had 292 on hours & and on/off counter at 349, I guess that depends on previous owner usage, but yours look pretty low count, assuming its not tampered.

I guess that must be the scope that started this thread? I saw you also got lucky that the front cover and a storage pouch where included, mine came with those as well, but no probes. Very hard to get those accessories included nowadays on a low or even mid priced 2465x on ebay, specially the front cover. I have seen these sold separately for $100, just for the cover. And you also have a TEK made U800. In what serial number group is yours? Mine is 55xxx and most chips inside have a 1990 date code, including the NVRAM. From the inscriptions and labels on the front cover and on one side, this might have been a field unit that was not really taken out that much, and who knows maybe even less once the problems created by the leaky caps started to show up. The inside is almost pristine, very little dust only in a few places, if any at all. No signs of anyone tampering inside either.

Yes, thats the only one I have, wish I have more especially the 2467B one.  :P

Really like the blue front cover, as its made from a really-really strong & thick plastic, even the whole scope can stand on it's front panel safely with that thing attached, like photos at the 1st post, and its really convenient for minor repair or inspection job at the scope.  :-+

My 2465B was built at Guernsey UK, with unique "G" prefix at the serial G150XXX.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on October 30, 2018, 04:51:38 pm
Yes the 2467B is nice, but since they are in great demand prices are through the roof, compared to the 2465B. Lots of people looking to get one, but waiting for the right/fair price.

I agree the front cover is very important to have, more so to get it with the scope in the first place, and yes definitively makes it easier to rest the scope on its face upside down to safely remove the back panel. I was even feeling a bit apprehensive of buying a scope like this without the front cover, as it is a very effective layer of protection against bent/broken controls due to shoddy packaging or in-transit mishandling. More than a few horror stories out there of mangled front panels.

Was going back to page one and looking at your pictures of the scope, very nice indeed. Which reminds me, at some point I will probably have to check on the power supply caps, and wrestle with those two boards to get them out.

BTW looking at you options sticker in the back, mine is a bit different, and the only option marked on this one is numbered 46, which I still have not been able to figure out what it is. Do you (or anyone ) know what option 46 is for? Asked before but no answers, so give it another try.

So from the origin of your scope I assume you are located on the other side of the "pond". Bet you never thought about this thread lasting so many years.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on October 30, 2018, 05:03:03 pm
Updated A5 DAC area parts layout, and Ref voltage test points. Wish I had this info when I first started. Hope it helps the next 2465B owner(s) down the line.

Mouser parts order to rebuild the A5 DAC resistors and caps almost ready to be sent out. I am also ordering one DS1225AD-150 to have it handy, even tough I eventually want to go the FM16W08 way. Still have to buy a programmer as well. From what I read so far, the GQ-4X programmer is the one to get, as I understand it is compatible with both the DS1225 and FM16W08.

Not sure what 28-DIP socket to order tough, Mouser is only showing me one from 3M (PN 517-4828-3004-CP) with dual leaf type compression contacts, which I assume will be fine for the DS1225, but I wonder if down the line it will also handle the pins on the SOIC28-DIP28 converter PCB needed for the FRAM.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: cheeseit on October 30, 2018, 06:45:05 pm
Actually that kind of socket fits the DS1225 poorly, at least the ones I have, but the pins on the converter (standard pin headers) fits very well. They may damage the socket because of sharp edges but I don't plan on removing it again so no problem. The same is true for machined sockets I believe.

GQ-4X is a nice programmer and will work.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on October 30, 2018, 07:05:47 pm
Actually that kind of socket fits the DS1225 poorly, at least the ones I have, but the pins on the converter (standard pin headers) fits very well. They may damage the socket because of sharp edges but I don't plan on removing it again so no problem. The same is true for machined sockets I believe.

Can you by any chance recommend a better socket, and possibly a source?

Thanks for the input.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on October 30, 2018, 07:31:18 pm
Yes the 2467B is nice, but since they are in great demand prices are through the roof, compared to the 2465B. Lots of people looking to get one, but waiting for the right/fair price.

I agree the front cover is very important to have, more so to get it with the scope in the first place, and yes definitively makes it easier to rest the scope on its face upside down to safely remove the back panel. I was even feeling a bit apprehensive of buying a scope like this without the front cover, as it is a very effective layer of protection against bent/broken controls due to shoddy packaging or in-transit mishandling. More than a few horror stories out there of mangled front panels.

Was going back to page one and looking at your pictures of the scope, very nice indeed. Which reminds me, at some point I will probably have to check on the power supply caps, and wrestle with those two boards to get them out.

BTW looking at you options sticker in the back, mine is a bit different, and the only option marked on this one is numbered 46, which I still have not been able to figure out what it is. Do you (or anyone ) know what option 46 is for? Asked before but no answers, so give it another try.

So from the origin of your scope I assume you are located on the other side of the "pond". Bet you never thought about this thread lasting so many years.

Good deal on getting your DAC issues straightened out.  :-+ And yes, recapping the Regulator and Inverter boards should be next on the agenda. You can follow my post back in July on getting those boards out with minimal hassle.

Edit, starts at reply 1091.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: macboy on October 30, 2018, 11:39:43 pm
I normally wouldn't clutter a technical thread with such stuff, but since this is the definitive 2465 thread, I'll mention I've posted a probe pouch and a front cover over in the buy/sell forum:
https://www.eevblog.com/forum/buysellwanted/fs-(canada)-tek-2465-2467-front-cover-and-probe-pouch/ (https://www.eevblog.com/forum/buysellwanted/fs-(canada)-tek-2465-2467-front-cover-and-probe-pouch/)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on October 30, 2018, 11:58:58 pm
I normally wouldn't clutter a technical thread with such stuff, but since this is the definitive 2465 thread, I'll mention I've posted a probe pouch and a front cover over in the buy/sell forum:
https://www.eevblog.com/forum/buysellwanted/fs-(canada)-tek-2465-2467-front-cover-and-probe-pouch/ (https://www.eevblog.com/forum/buysellwanted/fs-(canada)-tek-2465-2467-front-cover-and-probe-pouch/)

Already have 2 probe pouches and while I'd really like to have a front cover for my 2465 I think $76 USD plus shipping is a little (no, a lot) too much.   :-- (And yes, I understand they are rare and sell at a premium which is why mine will remain naked)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on October 31, 2018, 12:13:29 am
Good deal on getting your DAC issues straightened out.  :-+ And yes, recapping the Regulator and Inverter boards should be next on the agenda. You can follow my post back in July on getting those boards out with minimal hassle.
Edit, starts at reply 1091.

Thanks for the heads up Med, will certainly take a look at it! The traces seem a bit fuzzy under certain conditions, specially while using the 10x horizontal magnification, and most probably recapping the PS might help cleaning up the traces. On the other hand, it really helps using the 20MHz BW limit, it makes the traces much sharper. That tells me there must be HF noise probably creeping in through the power supply.

Here is a pic of the scope still triggering on a 800.000MHz signal, even tough at this point the trace looks quite fuzzy due to the vertical input amp gain running way out of bandwidth (the input signal was 400mV). The automatic counter would only read up to 650MHz. But in general the counter doesn't seem to be very accurate, always seems to be off by 10% or so. Even with an accurate 10MHz signal the 2465B was showing a counter best reading at something like 10.173 MHz. I guess that is what that 2465B C/T option is all about to tighten up the counter accuracy. My 2247A was effortless counting the same signal as 10.000071MHz (yes the scope counter calibration is actually off by about 71Hz), and counter is good and stable to about 300-350MHz.

BTW the traces look much brighter on this picture than they actually where, was trying to avoid using a flash, so the camera opened way up. Nowhere near what looks like CRT melting levels.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on October 31, 2018, 12:43:35 am
Already have 2 probe pouches and while I'd really like to have a front cover for my 2465 I think $76 USD plus shipping is a little (no, a lot) too much.   :-- (And yes, I understand they are rare and sell at a premium which is why mine will remain naked)

Not too long ago a 2465B cover (new style with the indentation) sold on ebay for a cool 100 bucks plus shipping from the Philippines. But it took quite some time to sell. Supply and demand market, unfortunately. I was looking for these for some time anticipating my future scope would not have it, and not even one other ever came up. I'm glad I actually got lucky, makes me think the scope alone actually sold for a mere $110, plus the cover (and a pouch).
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on October 31, 2018, 02:27:18 am
Good deal on getting your DAC issues straightened out.  :-+ And yes, recapping the Regulator and Inverter boards should be next on the agenda. You can follow my post back in July on getting those boards out with minimal hassle.
Edit, starts at reply 1091.

Thanks for the heads up Med, will certainly take a look at it! The traces seem a bit fuzzy under certain conditions, specially while using the 10x horizontal magnification, and most probably recapping the PS might help cleaning up the traces. On the other hand, it really helps using the 20MHz BW limit, it makes the traces much sharper. That tells me there must be HF noise probably creeping in through the power supply.

Here is a pic of the scope still triggering on a 800.000MHz signal, even tough at this point the trace looks quite fuzzy due to the vertical input amp gain running way out of bandwidth (the input signal was 400mV). The automatic counter would only read up to 650MHz. But in general the counter doesn't seem to be very accurate, always seems to be off by 10% or so. Even with an accurate 10MHz signal the 2465B was showing a counter best reading at something like 10.173 MHz. I guess that is what that 2465B C/T option is all about to tighten up the counter accuracy. My 2247A was effortless counting the same signal as 10.000071MHz (yes the scope counter calibration is actually off by about 71Hz), and counter is good and stable to about 300-350MHz.

BTW the traces look much brighter on this picture than they actually where, was trying to avoid using a flash, so the camera opened way up. Nowhere near what looks like CRT melting levels.

Does your 2465B have the Counter/Trigger option? If yes and you don't have the equipment as per the manual to calibrate it I have an alternate procedure that came from an old gray bread on the Yahoo Tek group that is simple and will get it dead nuts.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on October 31, 2018, 02:30:56 am
Already have 2 probe pouches and while I'd really like to have a front cover for my 2465 I think $76 USD plus shipping is a little (no, a lot) too much.   :-- (And yes, I understand they are rare and sell at a premium which is why mine will remain naked)

Not too long ago a 2465B cover (new style with the indentation) sold on ebay for a cool 100 bucks plus shipping from the Philippines. But it took quite some time to sell. Supply and demand market, unfortunately. I was looking for these for some time anticipating my future scope would not have it, and not even one other ever came up. I'm glad I actually got lucky, makes me think the scope alone actually sold for a mere $110, plus the cover (and a pouch).

Considering that I paid a grand total of $60 for my 2465 paying more for a piece of plastic makes absolutely no sense to me.  :palm:
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on October 31, 2018, 07:50:08 am
Was going back to page one and looking at your pictures of the scope, very nice indeed. Which reminds me, at some point I will probably have to check on the power supply caps, and wrestle with those two boards to get them out.

Yep, especially the film caps as others experienced in this thread.


BTW looking at you options sticker in the back, mine is a bit different, and the only option marked on this one is numbered 46, which I still have not been able to figure out what it is. Do you (or anyone ) know what option 46 is for? Asked before but no answers, so give it another try.

Sorry, I have no idea at all.


So from the origin of your scope I assume you are located on the other side of the "pond". Bet you never thought about this thread lasting so many years.

Yeah, I started this just to share the teardown photos as I didn't find any at this forum, it is now growing into a big thread with so many valuable information by many contributors, you included.  :clap:
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: grbk on October 31, 2018, 04:58:41 pm
Does your 2465B have the Counter/Trigger option? If yes and you don't have the equipment as per the manual to calibrate it I have an alternate procedure that came from an old gray bread on the Yahoo Tek group that is simple and will get it dead nuts.

I would be interested to see it if you don't mind sharing.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on October 31, 2018, 05:51:54 pm
Does your 2465B have the Counter/Trigger option? If yes and you don't have the equipment as per the manual to calibrate it I have an alternate procedure that came from an old gray bread on the Yahoo Tek group that is simple and will get it dead nuts.

I would be interested to see it if you don't mind sharing.

No problem. In few days after I return home. Don't have it with me at the moment.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on October 31, 2018, 07:35:44 pm
That will be great to have. Seemed a difficult/impossible task until all the proper items are in hand to complete that cal...
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 01, 2018, 05:02:52 am
Could someone please explain how one does put the values gathered with the EXER 02 routine into a BIN file?

I downloaded a file that is from a B055xxx serial number scope that is very close to mine. I wanted to replace the cal constant values to match the ones gathered from my own scope into this file at the corresponding locations. For one just to learn how to do it, and possibly to also have a backup file ready if the reading of my NVRAM should go wrong for some reason. There was a brief explanation of the value writing procedure into the file that I read somewhere else some time ago, but I didn't really understand the procedure as the explanation sounded overly simplistic, probably meant for someone that had a much better general understanding. My new replacement DS1225-AD-150 from Mouser is already in the mail, but I still need to order a programmer, and of course pull the NVRAM from the scope and install a socket.

Basically each value read with the Ex02 goes as "00 00C7", "01 26B7", and so on all the way up to "FF  0000 X". Some values also have this "X" appended, and I understand the X is just to indicate even parity. I have a Hex editor program installed and have done some very basic editing in the past (edit maybe 1 or 2 values at a very specific and clearly spelled out location), but I'm lost with the cal data. How do I write the individual values into the BIN file that has a line format like shown bellow, and what part of the data corresponds to what position in this layout?

Offset (h)  00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F
00000000 18 3E 60 B1 60 B1 60 B2 60 B2 7D 16 7D 17 7D 17
00000010 7D 17 13 .... and so on.

BTW found this at the TekIO group, but again the technical information is a bit too advanced for me.
https://groups.io/g/TekScopes/topic/7656133#120148

Any explanations, pointers, or even links to other already existing clear explanations for a newbie in this procedure will be much appreciated.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on November 01, 2018, 05:31:27 pm
Could someone please explain how one does put the values gathered with the EXER 02 routine into a BIN file?
...
Any explanations, pointers, or even links to other already existing clear explanations for a newbie in this procedure will be much appreciated.
Here, try this explanation...

Each of the 256 values shown in EXER 02 is placed into two consecutive bytes in the DS1225, and in the order shown in EXER 02 since the 6800 processor in these scopes is big-endian (most significant byte first).  Assume the EXER 02 data is all cal data and important, since there is no map of the locations and what they actually do.

The EXER 02 data is stored at the end of the DS1225 starting at location 0x1E00 and ending at 0x1FFF (that's a total of 512 bytes for all 256 values).

The remainder of the DS1225 (0x0000 - 0x1DFF) does not need to be initialized to any particular value that I'm aware, but you could put all 0x00 or all 0xFF in there for good measure.

For for example, suppose your EXER 02 data looks like this:

  00  1122
  01  3344
  02  5566
  03  7788
  04  99AA

  ...etc...

  FE  BBCC
  FF  0000

You would use your hex editor to enter these values into the DS1225:

  1E00  11 22 33 44 55 66 77 88 99 AA

  ...etc...

  1FFC  BB CC 00 00

The parity, "X", doesn't matter in this procedure.

If you're starting with someone else's contents, it should be 8192 bytes long.  You can replace the values at 0x1E00 to 0x1FFF with your EXER 02 values.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 02, 2018, 01:11:32 am
MarkL

Hi thanks for the explanation so far. So the address you indicate as "1E00" (only 4 digits) which I understand would be the first line to start entering the values, would be equivalent to what I see in my Hex editor as "00001E00" ? (8 digits).

Also on my editor I see 16 offset columns for each address row (00, 01, 02, 03 ... to 0F - see my attached image), whereas your example does only show 10 offset columns for each address row. Is there maybe a setting I need to modify in my editor so things will look like the example you are presenting? I am using HxD Editor v1.7.7.0.

Thanks again, much appreciated  for taking the time to explain this.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 02, 2018, 04:03:37 am
MarkL:

OK I started trying some things on the Hex Editor program and found that by changing the bytes per row from 16 to 10 (DOH) it will give me the correct row length that matches your example. I still get the four zeros in front of the 4 digit address, I assume this the usual way to look at the addresses and just ignore the leading zeros?

Could you please check the updated attached image and let me know if this would be correct in accordance to your example from your post above?

Thanks again.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on November 02, 2018, 03:24:32 pm
MarkL:

OK I started trying some things on the Hex Editor program and found that by changing the bytes per row from 16 to 10 (DOH) it will give me the correct row length that matches your example. I still get the four zeros in front of the 4 digit address, I assume this the usual way to look at the addresses and just ignore the leading zeros?

Could you please check the updated attached image and let me know if this would be correct in accordance to your example from your post above?

Thanks again.
Yes, you are right that the leading zeros don't matter.

The selection of 10 or 16 also doesn't matter in that field.  Although I don't have that hex editor, it looks like it's just controlling the number of bytes displayed on each line.  I only provided 10 values in the example starting at 0x1E00, but it could have been 16.  There's no significance in the data to the number of bytes displayed on each line.  Sorry if that led to confusion.

So, what you've typed in so far is consistent with the example data I gave.  Just keep going until you've entered all 256 of your EXER 02 values (not the example data I showed).  The last byte you enter should be at 0x1FFF.

If this is still not clear, I've attached a 8192 byte template that might help.  Starting at location 0x1E00, the bytes in the template appear like this (and everything else is 0x00):

0001e00: 00 00 00 01 00 02 00 03 00 04 00 05 00 06 00 07  ................
0001e10: 00 08 00 09 00 0a 00 0b 00 0c 00 0d 00 0e 00 0f  ................
0001e20: 00 10 00 11 00 12 00 13 00 14 00 15 00 16 00 17  ................
0001e30: 00 18 00 19 00 1a 00 1b 00 1c 00 1d 00 1e 00 1f  ................
...
0001fe0: 00 f0 00 f1 00 f2 00 f3 00 f4 00 f5 00 f6 00 f7  ................
0001ff0: 00 f8 00 f9 00 fa 00 fb 00 fc 00 fd 00 fe 00 ff  ................

Replace each pair of bytes with the corresponding data from your EXER 02.  In other words, "00 00" gets replaced with the data from EXER 02 location 00.  "00 01" gets replaced with the data from EXER 02 location 01.  "00 02" with the data from EXER 02 location 02.  And so on, all the way to EXER 02 location FF which replaces the pair "00 FF".

EDIT: Fixed typo.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 03, 2018, 12:16:53 pm
MarK, thanks very much for the template and additional clarification. I will work on rewriting my own Exer02 data into it. That was very helpful. Maybe I could even post my finished BIN file and if someone out here in the US with a programmer would be willing to write the data for me into a fresh DS1225AD-150 and mail it to me to FL zip 33152, I would be more than willing to pay for the efforts and cost of shipping. That way once I pull my original NVRAM and install a socket I could compare them and verify that it actually works to copy the exer02 values into a chip and put to rest that this might not be feasible as some members of the TekIO group stated in older messages I found. Or maybe in the end they will be proven right, but at least we will know.

One last question if you don't mind, when you refer to a line by labeling it as "0x1E00", what is the meaning of the "x" in it? Is this a common convention just to save not having to write it with all the leading zeros as in 00001E00, or does it have another meaning?

Thanks again.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on November 03, 2018, 12:38:51 pm
One last question if you don't mind, when you refer to a line by labeling it as "0x1E00", what is the meaning of the "x" in it? Is this a common convention just to save not having to write it with all the leading zeros as in 00001E00, or does it have another meaning?

In C and similar computer languages, 0x indicates a number specified in hexadecimal notation. Frequently, but not strictly, the number of digits implies the number of bits, e.g. 0x0001 is stored in 16-bits whereas 0x01 is stored in 8-bits. Hence if you had a 32-bit address space the lowest address would be 0x00000000 and the highest 0xffffffff.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 03, 2018, 01:07:04 pm
Mark: I typed in all the Exer02 values into your template and it fit exactly within the expected address range, so i guess all is well. The changed fields are in red. Took about 25 minutes, not too bad, just don't distract me while I'm typing.

What i will do next is save the file and reopen it so it will all be shown again in black, and make a second data input pass, so if I made any mistakes earlier, they would be shown in red and easy to see.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on November 03, 2018, 05:24:49 pm
As requested here is an alternate procedure for calibrating the Counter/Trigger option. First, here is the copy of the cal procedure from the 2465 Options Service Manual. I assume the procedure is the same or similar for the 2465A/B.

(https://imagizer.imageshack.com/v2/xq90/924/KPrSnZ.jpg) (https://imageshack.com/i/poKPrSnZj)
(https://imagizer.imageshack.com/v2/xq90/922/YOeXJM.jpg) (https://imageshack.com/i/pmYOeXJMj)

The alternate procedure was from a gray beard on the Yahoo Tek Group who's name I forget and I take no credit for developing this procedure. But I can tell you from experience that it does work. You can use a function generator, oscilloscope calibrator, or home made pulser with the following requirements:

Square wave must be exactly 1 MHz.
Rise time of 1ns or less.
0.8 to 1 volt peak to peak.
Preferably as close to 50% duty cycle as possible but not absolutely necessary.
Must not have an either positive or negative offset. In other words, must be equally above and below 0 (GND) centerline. See first trace example. I have a Heath IG-4244 Oscilloscope Calibrator which meets all the requirements except it has a fixed negative offset as shown. If your signal source has an adjustable offset set it for approx .4V to .5V p-p above and below centerline (.8V to 1 V p-p total). Then set up your scope as per the cal instructions and proceed right to step F and do the cal. As long as your source is exactly 1 MHz it should work. If you have an offset issue see next step.

Negative offset:
(https://imagizer.imageshack.com/v2/xq90/923/iQzh3E.jpg) (https://imageshack.com/i/pniQzh3Ej)

What you'll need:

BNC  “T” connector.
6dB inline attenuator.
DC supply that goes down to 0 volts.
50 ohm coax.

Connect the signal source to the left. Connect the power supply to the attenuator. If your source is a negative offset connect positive to center pin. If the source is a positive offset connect negative to the center pin. Slowly increase the voltage until you obtain a waveform similar to the 2nd pix. .8 volt - 1 volt p-p equal to centerline. Then proceed to step F and do the cal. It should take. If not go back and check your setup.   

(https://imagizer.imageshack.com/v2/xq90/922/2WMwLb.jpg) (https://imageshack.com/i/pm2WMwLbj)
(https://imagizer.imageshack.com/v2/xq90/924/a8FQZU.jpg) (https://imageshack.com/i/poa8FQZUj)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on November 03, 2018, 05:37:24 pm
MarK, thanks very much for the template and additional clarification. I will work on rewriting my own Exer02 data into it. That was very helpful. Maybe I could even post my finished BIN file and if someone out here in the US with a programmer would be willing to write the data for me into a fresh DS1225AD-150 and mail it to me to FL zip 33152, I would be more than willing to pay for the efforts and cost of shipping. That way once I pull my original NVRAM and install a socket I could compare them and verify that it actually works to copy the exer02 values into a chip and put to rest that this might not be feasible as some members of the TekIO group stated in older messages I found. Or maybe in the end they will be proven right, but at least we will know.
...
Glad it worked out for you!

If your goal is to prove that writing the EXER 02 values into the NVRAM works, that's already been verified.

There have been multiple conversations about it on TekScopes groups.io.  Which one are you referring to?  The last one I recall was the thread "tektronics 2465b 400mhz nvram battery info" where someone verified it with a 2467B in April.

Although I didn't mention it in a post a couple of weeks ago (reply #1182), I also verified that both the EXER 02 and the GPIB dump of the cal data was an exact copy of what's in the NVRAM on a 2445A.  But I didn't bother mentioning it because it had been done before.

It's also been verified on a 2465, although that scope is a little different since it doesn't use a Dallas NVRAM.

So, we have all the versions covered for this series (A, B, and plain).

More verification is always nice, but it may not be worth the extra hassle if you don't already have a programmer or other equipment to do it.

That being said and you still want to experiment, I'm willing to drop your BIN data in a fresh DS1225AD-150 for you for free, if you want to send me the chip and a self-addressed, pre-paid return envelope.  PM me if you want to set this up.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on November 03, 2018, 11:41:25 pm
My Tek 2445B developed an interesting belly dance at first power up when cold. I think it is the capacitors on the main board. What do you masters think? It stabilises after 2 - 3 minutes and it is stable after that.

https://www.youtube.com/watch?v=VZyulSz85W4 (https://www.youtube.com/watch?v=VZyulSz85W4)

I tried to remove two of the knobs from the front panel and both broke, that's how brittle they are. Without removing those knobs there's no way to get to the main board. Anyone has a set of brightness, focus, etc knobs?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on November 04, 2018, 12:40:50 am
Dirty H Position pot ?
An analog meter would probably be the best thing to clearly show it with tests.

You also might be able to confirm it in X-T mode.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on November 04, 2018, 02:31:27 am
My Tek 2445B developed an interesting belly dance at first power up when cold. I think it is the capacitors on the main board. What do you masters think? It stabilises after 2 - 3 minutes and it is stable after that.


I tried to remove two of the knobs from the front panel and both broke, that's how brittle they are. Without removing those knobs there's no way to get to the main board. Anyone has a set of brightness, focus, etc knobs?

Agree with tautech. Try cleaning the horizontal position pot.

Knobs....mnementh had a spare focus knob for my 2465. He may have some additional. PM him and make sure you tell him I sent you.
If he doesn't, Google is your friend. There are multiple sites selling Tek parts. I'm sure you can find them. 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: grbk on November 04, 2018, 03:07:58 am
As requested here is an alternate procedure for calibrating the Counter/Trigger option. First, here is the copy of the cal procedure from the 2465 Options Service Manual. I assume the procedure is the same or similar for the 2465A/B.

(https://imagizer.imageshack.com/v2/xq90/924/KPrSnZ.jpg) (https://imageshack.com/i/poKPrSnZj)
(https://imagizer.imageshack.com/v2/xq90/922/YOeXJM.jpg) (https://imageshack.com/i/pmYOeXJMj)

The alternate procedure was from a gray beard on the Yahoo Tek Group who's name I forget and I take no credit for developing this procedure. But I can tell you from experience that it does work. You can use a function generator, oscilloscope calibrator, or home made pulser with the following requirements:

Square wave must be exactly 1 MHz.
Rise time of 1ns or less.
0.8 to 1 volt peak to peak.
Preferably as close to 50% duty cycle as possible but not absolutely necessary.
Must not have an either positive or negative offset. In other words, must be equally above and below 0 (GND) centerline. See first trace example. I have a Heath IG-4244 Oscilloscope Calibrator which meets all the requirements except it has a fixed negative offset as shown. If your signal source has an adjustable offset set it for approx .4V to .5V p-p above and below centerline (.8V to 1 V p-p total). Then set up your scope as per the cal instructions and proceed right to step F and do the cal. As long as your source is exactly 1 MHz it should work. If you have an offset issue see next step.

Negative offset:
(https://imagizer.imageshack.com/v2/xq90/923/iQzh3E.jpg) (https://imageshack.com/i/pniQzh3Ej)

What you'll need:

BNC  “T” connector.
6dB inline attenuator.
DC supply that goes down to 0 volts.
50 ohm coax.

Connect the signal source to the left. Connect the power supply to the attenuator. If your source is a negative offset connect positive to center pin. If the source is a positive offset connect negative to the center pin. Slowly increase the voltage until you obtain a waveform similar to the 2nd pix. .8 volt - 1 volt p-p equal to centerline. Then proceed to step F and do the cal. It should take. If not go back and check your setup.   

(https://imagizer.imageshack.com/v2/xq90/922/2WMwLb.jpg) (https://imageshack.com/i/pm2WMwLbj)
(https://imagizer.imageshack.com/v2/xq90/924/a8FQZU.jpg) (https://imageshack.com/i/poa8FQZUj)

Thanks for posting this; it may come in very handy  :-+
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on November 04, 2018, 12:38:20 pm
My Tek 2445B developed an interesting belly dance at first power up when cold. I think it is the capacitors on the main board. What do you masters think? It stabilises after 2 - 3 minutes and it is stable after that.


I tried to remove two of the knobs from the front panel and both broke, that's how brittle they are. Without removing those knobs there's no way to get to the main board. Anyone has a set of brightness, focus, etc knobs?

Agree with tautech. Try cleaning the horizontal position pot.

Knobs....mnementh had a spare focus knob for my 2465. He may have some additional. PM him and make sure you tell him I sent you.
If he doesn't, Google is your friend. There are multiple sites selling Tek parts. I'm sure you can find them.

In X-Y mode shown in the video, CH1 vertical position acts as horizontal. In Y-T though, the readout is affected as well and readout is independent of any pots. Maybe the picture below will clarify some things...   ;D
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on November 04, 2018, 01:05:40 pm
Next step then is to monitor the supply voltages at J119 on the main board and see if one of them is bouncing around. And with that many hours have the Inverter and Regulator boards ever been recapped? If not I highly recommend it be done.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on November 04, 2018, 01:09:58 pm
Next step then is to monitor the supply voltages at J119 on the main board and see if one of them is bouncing around. And with that many hours have the Inverter and Regulator boards ever been recapped? If not I highly recommend it be done.

I recapped the power supply few years ago with good Nichicon PW series caps.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 04, 2018, 01:34:39 pm
Maybe the picture below will clarify some things...   ;D

Wow, 41K plus hours of operation? Have you owned the scope since new or for a long time? Looks like during its life it might not have been officially recalibrated either, at least not at an accredited lab. The tech that performs the cal is supposed to also reset this counter after each calibration, so the next tech guy that has to deal with the instrument will know the elapsed time. But if just left to run it also can give a ballpark idea of the usage, but then again, it may have more than 41K hours on the clock, with one or more resets along the way.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on November 04, 2018, 01:45:08 pm
Next step then is to monitor the supply voltages at J119 on the main board and see if one of them is bouncing around. And with that many hours have the Inverter and Regulator boards ever been recapped? If not I highly recommend it be done.

I recapped the power supply few years ago with good Nichicon PW series caps.

OK, but I would still monitor the PSU voltages at initial power up and see if something is amiss. Rule that out first before digging into it further.
 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 04, 2018, 02:06:10 pm

Glad it worked out for you!

If your goal is to prove that writing the EXER 02 values into the NVRAM works, that's already been verified.

There have been multiple conversations about it on TekScopes groups.io.  Which one are you referring to?  The last one I recall was the thread "tektronics 2465b 400mhz nvram battery info" where someone verified it with a 2467B in April.

Although I didn't mention it in a post a couple of weeks ago (reply #1182), I also verified that both the EXER 02 and the GPIB dump of the cal data was an exact copy of what's in the NVRAM on a 2445A.  But I didn't bother mentioning it because it had been done before.

It's also been verified on a 2465, although that scope is a little different since it doesn't use a Dallas NVRAM.

So, we have all the versions covered for this series (A, B, and plain).

More verification is always nice, but it may not be worth the extra hassle if you don't already have a programmer or other equipment to do it.

That being said and you still want to experiment, I'm willing to drop your BIN data in a fresh DS1225AD-150 for you for free, if you want to send me the chip and a self-addressed, pre-paid return envelope.  PM me if you want to set this up.

I was not sure yet that it had been verified. It seems to be a touchy subject for some members over at TekIO when asked, as can be seen on some past messages. In a situation where a scope lost the calibration constants, some of them will tell you to rather invest the time in getting the scope properly calibrated than to thinker trying to rebuild the cal data with exer02 values, as it might not work, or at best be no longer accurate and on the dot anyhow. I get their point, but then again, my scope is intended for hobby use only, not on a bench at NASA. Also, I can understand the interest in using Exer02 data in a situation where someone lost the cal data, and has no intentions to send the scope out for calibration, or does not have the means to calibrate it himself. 10x better, maybe even 100x better to have your own Exer02 data to play with than having to use a third party bin file from another scope just to bring yours back to life.

I did not see the message thread over there that you mentioned. Will look it up later.

In my case I am just trying to do it mostly as an academic exercise, and of course to possibly avoid having to read my aging NVRAM to replicated the data as a first choice. As it has happened before to some people, the programmer itself might kill the data while trying to access it if the backup battery is on its very last legs. Yes, I've also seen the PDF about repowering the internal battery, and its of course yet another option to go.

Thanks for the offer to program a DS1225 for me and mail it back, I will keep it in mind. Thing is I don't have a programmer, and this would probably the only instance I would ever use it, so trying to decide if I should order one. I have read the GQ-4X4 programmer is probably the one to get, as it will handle both the DS1225, and also the FRAMs in case I decide to thinker with them in the future and get rid of the battery backup issue for good. Or if anyone can suggest a better alternative programmer I'll be happy to listen to recommendations.

Yesterday went again over my handwritten list of the Exer02 values and checked them against the video which I also made. Turns out that in one data pair I transposed two numbers (I had written 2647 and should have been 2674). Other than that I'm good to go, and I updated your BIN template file as well.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 04, 2018, 02:22:25 pm
I tried to remove two of the knobs from the front panel and both broke, that's how brittle they are. Without removing those knobs there's no way to get to the main board. Anyone has a set of brightness, focus, etc knobs?

I read somewhere that carefully warming up the knobs with a heat gun really helps to remove the stuck ones (after so long most of them will be) without breaking them. I have not tried this yet, and hope for now I will not need to. Knock-knock...
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on November 04, 2018, 03:16:36 pm
Maybe the picture below will clarify some things...   ;D

Wow, 41K plus hours of operation? Have you owned the scope since new or for a long time? Looks like during its life it might not have been officially recalibrated either, at least not at an accredited lab. The tech that performs the cal is supposed to also reset this counter after each calibration, so the next tech guy that has to deal with the instrument will know the elapsed time. But if just left to run it also can give a ballpark idea of the usage, but then again, it may have more than 41K hours on the clock, with one or more resets along the way.

No, I only have it since about 2012 when was decommissioned at work due to the trace waving like a flag in the wind. It was not worth fixing it and I got it for free. I recapped the power supply right away and the waving went away but considering it had bone dry capacitors in the PS, I don't think those on the main board are in much better shape.
The instrument was calibrated yearly by an accredited lab up until, I would guess, 2008 - 2009. It was probably left running 24/7/365 as I know the place.  ;D
Are you sure that counter is resettable? It is the ON counter and probably it is stored in the same infamous NVRAM that I replaced this summer.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 04, 2018, 04:08:31 pm
Are you sure that counter is resettable? It is the ON counter and probably it is stored in the same infamous NVRAM that I replaced this summer.

The explanation about the counter was given to me to a very knowledgeable TekIO group member that I understand keeps himself busy by providing calibration services for all variants of the 2465 scope and selling them as well. He routinely zeroes those counters. I don't know myself how to do this, but I'm sure its described somewhere in the calibration instructions of the service manual.

As he put it: "The power cycle counter, and on time counter are meant to be reset after every calibration. They are there to let the technician know how long it has really been since the last calibration... as opposed to whatever the customer says.. They don't mean much to a customer. If you see really low numbers, it simply means the scope saw little use since its last calibration."
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on November 04, 2018, 04:30:56 pm
Next step then is to monitor the supply voltages at J119 on the main board and see if one of them is bouncing around. And with that many hours have the Inverter and Regulator boards ever been recapped? If not I highly recommend it be done.

I recapped the power supply few years ago with good Nichicon PW series caps.

OK, but I would still monitor the PSU voltages at initial power up and see if something is amiss. Rule that out first before digging into it further.

I remember doing that some time ago, I will try that again before ordering the caps...  which probably is necessary.
Thanks!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on November 04, 2018, 04:34:37 pm
I tried to remove two of the knobs from the front panel and both broke, that's how brittle they are. Without removing those knobs there's no way to get to the main board. Anyone has a set of brightness, focus, etc knobs?

I read somewhere that carefully warming up the knobs with a heat gun really helps to remove the stuck ones (after so long most of them will be) without breaking them. I have not tried this yet, and hope for now I will not need to. Knock-knock...

That worked, thanks! :phew:
Now I have work to do.  ;D
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on November 05, 2018, 03:51:43 pm
I was not sure yet that it had been verified. It seems to be a touchy subject for some members over at TekIO when asked, as can be seen on some past messages. In a situation where a scope lost the calibration constants, some of them will tell you to rather invest the time in getting the scope properly calibrated than to thinker trying to rebuild the cal data with exer02 values, as it might not work, or at best be no longer accurate and on the dot anyhow. I get their point, but then again, my scope is intended for hobby use only, not on a bench at NASA. Also, I can understand the interest in using Exer02 data in a situation where someone lost the cal data, and has no intentions to send the scope out for calibration, or does not have the means to calibrate it himself. 10x better, maybe even 100x better to have your own Exer02 data to play with than having to use a third party bin file from another scope just to bring yours back to life.
I agree with you.

I'm willing to bet the vast majority of these scopes (that are still working) are now in the hands of hobbyists who don't care or need up-to-date calibration.  Having a way to backup and restore the existing cal data is all that's needed.  And the backup part is easy by just taking a video of flipping through EXER 02.

Why calibration backup and restore is not implemented and openly documented for every piece of test equipment, both old and new, continues to mystify me.

On these scopes, I find it strange that Tek would provide a way to display the cal data, but not have some easier way to put it back.  The data itself is meaningless to even a service tech, so why bother displaying it in the first place?.  I continue to be suspicious that there's a hidden way to do it from the screen, but I haven't had time to dig through the code to look for it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on November 05, 2018, 04:22:16 pm
My Tek 2445B developed an interesting belly dance at first power up when cold. I think it is the capacitors on the main board. What do you masters think? It stabilises after 2 - 3 minutes and it is stable after that.
...
After the already mentioned power supply checks, maybe try reseating the horizontal output hybrid U800 (no don't do this - see followup post).  You could also try some freeze spray on components in that area to try to find something sensitive to warm-up.

If it's affecting the whole screen, including the readout as you say, I would highly suspect something around U800 since it's in common to the readout and the traces.  At least it's the place to start.

EDIT - Strike out bad brain advice.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on November 05, 2018, 05:24:55 pm
My Tek 2445B developed an interesting belly dance at first power up when cold. I think it is the capacitors on the main board. What do you masters think? It stabilises after 2 - 3 minutes and it is stable after that.
...
After the already mentioned power supply checks, maybe try reseating the horizontal output hybrid U800.  You could also try some freeze spray on components in that area to try to find something sensitive to warm-up.

If it's affecting the whole screen, including the readout as you say, I would highly suspect something around U800 since it's in common to the readout and the traces.  At least it's the place to start.

Be very cautious with U800. There are credible accounts that its mounting bracket can easily be overtightened, destroying that excessively expensive ic.

Personally I'd rule out all other options and positively identify U800 as being the problem before fiddling with it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on November 05, 2018, 05:46:29 pm
My Tek 2445B developed an interesting belly dance at first power up when cold. I think it is the capacitors on the main board. What do you masters think? It stabilises after 2 - 3 minutes and it is stable after that.
...
After the already mentioned power supply checks, maybe try reseating the horizontal output hybrid U800.  You could also try some freeze spray on components in that area to try to find something sensitive to warm-up.

If it's affecting the whole screen, including the readout as you say, I would highly suspect something around U800 since it's in common to the readout and the traces.  At least it's the place to start.

Be very cautious with U800. There are credible accounts that its mounting bracket can easily be overtightened, destroying that excessively expensive ic.

Personally I'd rule out all other options and positively identify U800 as being the problem before fiddling with it.
Oops - tggzzz is absolutely right.  I was thinking of one of the plug-in hybrids.  Don't mess with U800 but you can certainly start your probing in that area.

Previous post updated.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on November 05, 2018, 06:10:25 pm
My Tek 2445B developed an interesting belly dance at first power up when cold. I think it is the capacitors on the main board. What do you masters think? It stabilises after 2 - 3 minutes and it is stable after that.
...
After the already mentioned power supply checks, maybe try reseating the horizontal output hybrid U800.  You could also try some freeze spray on components in that area to try to find something sensitive to warm-up.

If it's affecting the whole screen, including the readout as you say, I would highly suspect something around U800 since it's in common to the readout and the traces.  At least it's the place to start.

Be very cautious with U800. There are credible accounts that its mounting bracket can easily be overtightened, destroying that excessively expensive ic.

Personally I'd rule out all other options and positively identify U800 as being the problem before fiddling with it.
Oops - tggzzz is absolutely right.  I was thinking of one of the plug-in hybrids.  Don't mess with U800 but you can certainly start your probing in that area.

Previous post updated.

In other areas it is worth being careful not to slip and short out IC pins.

I absolutely refuse to discuss why I mention that :(
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on November 05, 2018, 06:56:16 pm
...
In other areas it is worth being careful not to slip and short out IC pins.

I absolutely refuse to discuss why I mention that :(
And U800 is especially fun since it has +87V coming into it (pin 7), which is not shown on the A1 schematic.  It's worth looking at the power distribution schematic to know where this and other power pins lie in wait.

It's also good place to use one of those plastic probe tip covers so it can only contact one pin at a time.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 05, 2018, 09:51:52 pm
And U800 is especially fun since it has +87V coming into it (pin 7), which is not shown on the A1 schematic.  It's worth looking at the power distribution schematic to know where this and other power pins lie in wait.

Uggghhh, yes why did Tek, in such a detailed service manual, not include any meaningful voltage readings in the schematics of at at least some of the more important nodes or power to IC pins??!!

I imagine any of the former Tek guys will always have a good answer/excuse for this. For me a service manual should have absolutely  -everything- I might need to troubleshoot the equipment, and it should rather have too much than too little information. Then again, by looking at some of the horrible mistakes (mixed up power supply caps in wrong positions and polarity, etc) and wonder if these manuals where just rushed out to rather concentrate on equipment sales, and not that much on after sales service literature. Maybe nobody was assigned  to proof read them.

Then again, I've seen some pretty obvious mistakes in the Motorola radio equipment service manuals. You would think that a huge company like them that makes absolutely top quality equipment would not make any/much mistakes of this sort, but I've seen it happen quite often. Makes you wonder how these mistakes still managed to slip through. Then again, those manuals where/are usually at least an inch (or more) thick.

Absolutely best service manuals I have ever come across, and so detailed and brimming with information to the level that virtually nothing was left out, where the service manuals for all the Kenwood ham radio equipment from the 80s I used to work on back then. You really got spoiled with those manuals. But I digress....
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 05, 2018, 10:18:41 pm
I agree with you.

I'm willing to bet the vast majority of these scopes (that are still working) are now in the hands of hobbyists who don't care or need up-to-date calibration.  Having a way to backup and restore the existing cal data is all that's needed.  And the backup part is easy by just taking a video of flipping through EXER 02.

Why calibration backup and restore is not implemented and openly documented for every piece of test equipment, both old and new, continues to mystify me.

On these scopes, I find it strange that Tek would provide a way to display the cal data, but not have some easier way to put it back.  The data itself is meaningless to even a service tech, so why bother displaying it in the first place?.  I continue to be suspicious that there's a hidden way to do it from the screen, but I haven't had time to dig through the code to look for it.

Could not agree more, that would really be something if you would discover some hidden code to do this. I mean, how is it that Tek did not anticipate that a good portion of these scopes would still be in use after the supposedly 10 year NVRAM backup battery expiration, specially at the price level they where sold back then. Build in corporate obsolescence? -Bad NVRam? -> buy a newer model scope! And I don't mean they did not use something better because back then it probably did not exist (EEPROM, FRAM, etc). But at least make it easy to replace the damn chip and reload the data.

Can't blame them for 30-40 years later, people like us still pushing the envelope, though.  ;D :-BROKE

Although I think that someone verified  (maybe it was you) that one can get the NVRam data dump via the GPIB? And even restore it (not so sure about this last part) the same way? But obviously this is not so easy and straight forward unless you know how to set it up and the proper commands, and not all scopes have this bus build in. My scope has GPIB but I would not even know where to start. (Read the book!, read the book!).  :-X
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on November 06, 2018, 02:12:20 am
...
Although I think that someone verified  (maybe it was you) that one can get the NVRam data dump via the GPIB? And even restore it (not so sure about this last part) the same way? But obviously this is not so easy and straight forward unless you know how to set it up and the proper commands, and not all scopes have this bus build in. My scope has GPIB but I would not even know where to start. (Read the book!, read the book!).  :-X
Yes, it's possible to do the dump and restore via GPIB.  The commands are here (but there's no GUI or wrapper program for it that I'm aware), and it works on all of them in the series:

  https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1167050/#msg1167050 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1167050/#msg1167050)

It's not a popular method because most scopes in this series are not equipped with GPIB.  And for good reason; there's not much you can do with the GPIB option.  The one thing most people would want is to capture the waveform, but being an analog scope it's just not possible.  The option was targeted at computer assisted setup and manual measurement sequences, and in the "B" case (I'm pretty sure) you can also control the scope's built-in automated waveform measurements.

GPIB control is worth setting up if you have other equipment that supports it.  Lot's of info on this forum on hardware, drivers, and application SW.  Good search terms also include IEEE-488 and HPIB.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on November 06, 2018, 02:30:20 am

In other areas it is worth being careful not to slip and short out IC pins.

I absolutely refuse to discuss why I mention that :(

Ouch...  :-BROKE
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 06, 2018, 02:37:08 am
Just out of curiosity I searched on ebay for a "USB-to-GPIB converter", and only two results came up, both from the UK. One priced at around $1200, and the other for a little over $1000. Both units look exactly the same. Is this really what an interface of this type costs, or did I miss something?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on November 06, 2018, 02:37:45 am
...
In other areas it is worth being careful not to slip and short out IC pins.

I absolutely refuse to discuss why I mention that :(
And U800 is especially fun since it has +87V coming into it (pin 7), which is not shown on the A1 schematic.  It's worth looking at the power distribution schematic to know where this and other power pins lie in wait.

It's also good place to use one of those plastic probe tip covers so it can only contact one pin at a time.


I measured the voltage on pin 7, it is 86.18V sharp on DMM and scope on AC 500mV, straight line, no move whatsoever. I'll do more tests in the weekend when I can find some time. It looks like U800 has been replaced or at least resoldered judging by the amount of solder and flux around the pins. It is a Tek chip, not Maxim and after 5 - 6 minutes it is barely warm, I don't think it needs a heatsink.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 06, 2018, 02:42:41 am
I measured the voltage on pin 7, it is 86.18V sharp on DMM and scope on AC 500mV, straight line, no move whatsoever. I'll do more tests in the weekend when I can find some time. It looks like U800 has been replaced or at least resoldered judging by the amount of solder and flux around the pins. It is a Tek chip, not Maxim and after 5 - 6 minutes it is barely warm, I don't think it needs a heatsink.

I might be wrong, and please do correct me if I am, but I think I read somewhere that the temperature of U800 will vary depending on the "load" it is put through. On an idle scope it might remain cool to the touch, but might get hotter while trying to handle more complex or fast signals. Correct?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on November 06, 2018, 05:45:09 am
I measured the voltage on pin 7, it is 86.18V sharp on DMM and scope on AC 500mV, straight line, no move whatsoever. I'll do more tests in the weekend when I can find some time. It looks like U800 has been replaced or at least resoldered judging by the amount of solder and flux around the pins. It is a Tek chip, not Maxim and after 5 - 6 minutes it is barely warm, I don't think it needs a heatsink.

I might be wrong, and please do correct me if I am, but I think I read somewhere that the temperature of U800 will vary depending on the "load" it is put through. On an idle scope it might remain cool to the touch, but might get hotter while trying to handle more complex or fast signals. Correct?

I believe that is a true statement.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 07, 2018, 03:07:19 am
Are you sure that counter is resettable? It is the ON counter and probably it is stored in the same infamous NVRAM that I replaced this summer.

I got a confirmation today that yes, those 2465 total hours and power on/off counters are not only resettable to zero, but they can also be set to anything you want. CAL05 is the routine that can read/set/reset the counters. Default is to reset. Requires to select the increment using the X10 button, and to rotate the Delta Ref, and the Delta controls to make the appropriate counter change.

Third party information. I have not played with these counters as of yet on my own 2465B.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: james_s on November 07, 2018, 07:56:53 am
Just out of curiosity I searched on ebay for a "USB-to-GPIB converter", and only two results came up, both from the UK. One priced at around $1200, and the other for a little over $1000. Both units look exactly the same. Is this really what an interface of this type costs, or did I miss something?

Maybe if you buy a commercial one? I don't know. I think I spent about $10 building mine, most of that was a GPIB cable which I chopped in half and wired to a Arduino nano clone. I found the firmware online somewhere, it's not something I need often but I've used it to clear the error log and enable options on my scope.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Gixy on November 07, 2018, 08:34:35 am
The procedure is official and perfectly described in the service manual.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 07, 2018, 12:21:32 pm
Looking at a 28 pin SOIC to DIP converter board to mount the FRAM chip and be able to plug it into the 28 DIP machine tooled socket I plan to install at some point once I desolder the original DS1225. Recommended converter board seems to be Aries 28-650000-10 (Mouser PN 535-28-650000-10 $18.55) but the part is currently out of stock until mid December, and then they only ordered 13 pieces. Digikey has the part, but its usually not my favorite go-to supplier, besides I already have all the other parts I wanted to order in the cart at Mouser. I don't know of other main stream suppliers that might have this adapter in stock.

Anyway, at this point mainly just wanted to know if I am on the right track, can anyone confirm that the Aries 535-28-650000-10 is the correct part to mount a FM16W08? Or if Mouser might have a viable alternative in stock? I searched at Mouser for other similar options but found none where available. The machined socket I'm planning on installing is Mouser PN 571-2-1571552-9  $3.43.

On ebay there are plenty of these chinese 28 pin SOIC-DIP adapters but its only the plain board, they don't have any pins soldered onto them, so not the ideal part, as I would prefer a ready-made solution like the Aries converter above anyhow.  And it usually takes around a month or more for the chinese stuff to arrive.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: macboy on November 08, 2018, 02:54:09 pm
Just out of curiosity I searched on ebay for a "USB-to-GPIB converter", and only two results came up, both from the UK. One priced at around $1200, and the other for a little over $1000. Both units look exactly the same. Is this really what an interface of this type costs, or did I miss something?
On ebay, you can easily find Agilent 82357b USB/GPIB adapters for well under $100. Beware that most are clones/counterfeit, not Agilent-made, especially those sold as New. Fortunately, the clones are straight copies with the same 75161 and 75160 proper GPIB bus driver ICs, the same CPLD and USB interface ICs, and copied PCB layout. They use the Agilent I/O suite drivers.  The inside of the clones' plastic case is usually not plated for RFI shielding, probably not a big deal. Mine is a clone but works perfectly for me. Some people complain about issues especially with many instruments on the bus... GPIB can be finicky and not all instruments play nice, e.g. I have one older instrument which always "listens" so the drivers think there are 30 devices connected, since something always handshakes for any listen address.  Since GPIB-to-GPIB cables (for daisy-chaining devices) cost nearly as much as these adapters, don't bother, just get one per instrument that you must have connected at the same time, and/or swap the adapter(s) between instruments as needed.  Having one device per bus also greatly simplifies scripts you write since you can hog the bus instead of trying to write fully asynchronous scripts.


FS: Tek 2465-2467 front cover and probe pouch (https://www.eevblog.com/forum/buysellwanted/fs-(canada)-tek-2465-2467-front-cover-and-probe-pouch/)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on November 10, 2018, 06:27:12 pm
Next step then is to monitor the supply voltages at J119 on the main board and see if one of them is bouncing around. And with that many hours have the Inverter and Regulator boards ever been recapped? If not I highly recommend it be done.

I recapped the power supply few years ago with good Nichicon PW series caps.

OK, but I would still monitor the PSU voltages at initial power up and see if something is amiss. Rule that out first before digging into it further.

Ok, I think I found the reason for the jitter. It is +15V that bounces around for a minute or so and then stabilizes. The question now is if the LM317 - U1260 is defective or the problem comes from the input. The difficulty with this defect is that it goes away after about 1 minute and I need to wait for hours before it shows up again for a minute or less.
One thing that I've noticed is that the unregulated voltages are a bit low. For example +15V Unreg should be 19.2V according to the schematic but I measure only +18.4V, +5VD should be +5.1V but in my case it is +5.00V.
Maybe  I'm on the edge of the minimum VIO for LM317.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on November 10, 2018, 10:02:24 pm
Next step then is to monitor the supply voltages at J119 on the main board and see if one of them is bouncing around. And with that many hours have the Inverter and Regulator boards ever been recapped? If not I highly recommend it be done.

I recapped the power supply few years ago with good Nichicon PW series caps.

OK, but I would still monitor the PSU voltages at initial power up and see if something is amiss. Rule that out first before digging into it further.

Ok, I think I found the reason for the jitter. It is +15V that bounces around for a minute or so and then stabilizes. The question now is if the LM317 - U1260 is defective or the problem comes from the input. The difficulty with this defect is that it goes away after about 1 minute and I need to wait for hours before it shows up again for a minute or less.
One thing that I've noticed is that the unregulated voltages are a bit low. For example +15V Unreg should be 19.2V according to the schematic but I measure only +18.4V, +5VD should be +5.1V but in my case it is +5.00V.
Maybe  I'm on the edge of the minimum VIO for LM317.

I had a vaguely similar problem on my Tek 485. It would take 60s to startup, and then work. If I switched it off for a few seconds, it started immediately. If I switched it off for a 30 mins, it would restart after 15s. It would only tale 60 to startup if it had been off for >6hours. That made fault location slow!

I eventually traced the problem to an old electrolytic in the startup circuit. It felt as if it took 60s for the dielectric to reform, and several hours for the dielectric to decay. So, if there is an old electrolytic "near" that LM317, it might be worth replacing it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on November 11, 2018, 01:35:07 am
Unfortunately there are no electrolytic caps around the LM317 so it's either the input or U1371. I'll keep you posted.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on November 11, 2018, 02:45:28 am
Could anyone measure the unregulated voltages in a working 2465B? My scope is 2445B but I think the PS is identical to 2465B. Not sure about 2467.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 11, 2018, 03:14:51 pm
Ok, I think I found the reason for the jitter. It is +15V that bounces around for a minute or so and then stabilizes. The question now is if the LM317 - U1260 is defective or the problem comes from the input. The difficulty with this defect is that it goes away after about 1 minute and I need to wait for hours before it shows up again for a minute or less.
One thing that I've noticed is that the unregulated voltages are a bit low. For example +15V Unreg should be 19.2V according to the schematic but I measure only +18.4V, +5VD should be +5.1V but in my case it is +5.00V.
Maybe  I'm on the edge of the minimum VIO for LM317.

I am assuming that any of the unregulated voltages may vary 10% from what is stated in the manual, in accordance to the mains voltage variation at your location. Also in general, maybe not directly related to your problem but good to keep in mind is that all regulated voltages of the power supply are referenced to the +10 supply, and any deviation there will reflect on all others. This power supply should measure between +9.99 and +10.01V. Anything outside is considered out of spec. Problem is, if you attempt to readjust it, you might affect a whole bunch of other internal scope calibrations as well, so best to leave as is, unless its seriously out of spec, or you intend to perform a full scope calibration.

I would try to measure the input voltage to the LM317, if you also see variations there you know the problem is originating before the regulator. Also check the reference input of the regulator. I would think that an input of +18.4v as opposed to the expected +19.2v should make no difference whatsoever to get a stable 15V output as it is more than 3v above which I would think is still very much ok.

Maybe solder a couple of temporary flying wires at the points of interest that you can easily access to quickly make the measurement as soon as you turn on the scope without having to move things around too much.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: james_s on November 11, 2018, 06:19:57 pm
On ebay, you can easily find Agilent 82357b USB/GPIB adapters for well under $100. Beware that most are clones/counterfeit, not Agilent-made, especially those sold as New. Fortunately, the clones are straight copies with the same 75161 and 75160 proper GPIB bus driver ICs, the same CPLD and USB interface ICs, and copied PCB layout. They use the Agilent I/O suite drivers. 


I really wish they would market them as "Agilent compatible" instead of trying to pass counterfeit products off as genuine, then it wouldn't bother me a bit to buy one. I suppose the counterfeit aspect is a way you could get one for free though. Just order it and then file a refund claim due to it being counterfeit goods. If enough people did that places might stop trying to sell counterfeit ones.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on November 11, 2018, 06:37:07 pm
Ok, I think I found the reason for the jitter. It is +15V that bounces around for a minute or so and then stabilizes. The question now is if the LM317 - U1260 is defective or the problem comes from the input. The difficulty with this defect is that it goes away after about 1 minute and I need to wait for hours before it shows up again for a minute or less.
One thing that I've noticed is that the unregulated voltages are a bit low. For example +15V Unreg should be 19.2V according to the schematic but I measure only +18.4V, +5VD should be +5.1V but in my case it is +5.00V.
Maybe  I'm on the edge of the minimum VIO for LM317.

I am assuming that any of the unregulated voltages may vary 10% from what is stated in the manual, in accordance to the mains voltage variation at your location. Also in general, maybe not directly related to your problem but good to keep in mind is that all regulated voltages of the power supply are referenced to the +10 supply, and any deviation there will reflect on all others. This power supply should measure between +9.99 and +10.01V. Anything outside is considered out of spec. Problem is, if you attempt to readjust it, you might affect a whole bunch of other internal scope calibrations as well, so best to leave as is, unless its seriously out of spec, or you intend to perform a full scope calibration.

I would try to measure the input voltage to the LM317, if you also see variations there you know the problem is originating before the regulator. Also check the reference input of the regulator. I would think that an input of +18.4v as opposed to the expected +19.2v should make no difference whatsoever to get a stable 15V output as it is more than 3v above which I would think is still very much ok.

Maybe solder a couple of temporary flying wires at the points of interest that you can easily access to quickly make the measurement as soon as you turn on the scope without having to move things around too much.

The minimum voltage differential for a LM317 to properly regulate is +3.0V. You have a +3.4V differential which is mighty close to minimum. As mentioned verify the reference voltage. And monitoring the input and output of the LM317 is also a good idea.

LM317's are cheap and a dime a dozen. If you see a variation between input and output and it never exceeds less than +3.0V I would try another LM317.   
 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on November 11, 2018, 10:10:48 pm
The reference voltage is stable at 10.004V right after power up and goes down slowly to 10.0005V few minutes after that. Flat line on the scope and rock stable on the multimeter so it is out of the suspects list. The input voltage doesn't drop much below 8.4V so I think the min 3V I/O requirement for LM317 is met.
What's left is LM317 itself, U1371 that drives it, or a fluctuating load (a dying capacitor or hybrid IC) on the +15V line. This drives me nuts...
At one point I wanted to sell the bastard as is and be done with it but now I really want to fix it even if it is only to humiliate it...... It can't win    :rant:
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on November 11, 2018, 10:33:35 pm
The reference voltage is stable at 10.004V right after power up and goes down slowly to 10.0005V few minutes after that. Flat line on the scope and rock stable on the multimeter so it is out of the suspects list. The input voltage doesn't drop much below 8.4V so I think the min 3V I/O requirement for LM317 is met.
What's left is LM317 itself, U1371 that drives it, or a fluctuating load (a dying capacitor or hybrid IC) on the +15V line. This drives me nuts...
At one point I wanted to sell the bastard as is and be done with it but now I really want to fix it even if it is only to humiliate it...... It can't win    :rant:

Here's a thought to help narrow it down. Isolate the +15V from the LM317 and connect power supply to the load and watch the current as it powers up. If it never exceeds 1.5 amps I'd say the LM317 is weak and the source of the variation. If it does exceed 1.5 amps then your problem is on the load side.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on November 12, 2018, 01:01:41 am
The reference voltage is stable at 10.004V right after power up and goes down slowly to 10.0005V few minutes after that. Flat line on the scope and rock stable on the multimeter so it is out of the suspects list. The input voltage doesn't drop much below 8.4V so I think the min 3V I/O requirement for LM317 is met.
What's left is LM317 itself, U1371 that drives it, or a fluctuating load (a dying capacitor or hybrid IC) on the +15V line. This drives me nuts...
At one point I wanted to sell the bastard as is and be done with it but now I really want to fix it even if it is only to humiliate it...... It can't win    :rant:

Here's a thought to help narrow it down. Isolate the +15V from the LM317 and connect power supply to the load and watch the current as it powers up. If it never exceeds 1.5 amps I'd say the LM317 is weak and the source of the variation. If it does exceed 1.5 amps then your problem is on the load side.

If you look at the schematic, there's a power up sequence that goes +87V > +42V > +15V .... It would be pretty hard to do that with an external power on +15V and the result may be less than happy. I think is better to replace the LM317 and see the result. It costs only a buck or two, the hard part is to get to it.  :palm:
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on November 12, 2018, 01:09:41 am
The reference voltage is stable at 10.004V right after power up and goes down slowly to 10.0005V few minutes after that. Flat line on the scope and rock stable on the multimeter so it is out of the suspects list. The input voltage doesn't drop much below 8.4V so I think the min 3V I/O requirement for LM317 is met.
What's left is LM317 itself, U1371 that drives it, or a fluctuating load (a dying capacitor or hybrid IC) on the +15V line. This drives me nuts...
At one point I wanted to sell the bastard as is and be done with it but now I really want to fix it even if it is only to humiliate it...... It can't win    :rant:

Here's a thought to help narrow it down. Isolate the +15V from the LM317 and connect power supply to the load and watch the current as it powers up. If it never exceeds 1.5 amps I'd say the LM317 is weak and the source of the variation. If it does exceed 1.5 amps then your problem is on the load side.

If you look at the schematic, there's a power up sequence that goes +87V > +42V > +15V .... It would be pretty hard to do that with an external power on +15V and the result may be less than happy. I think is better to replace the LM317 and see the result. It costs only a buck or two, the hard part is to get to it.  :palm:

Yup, you're right. I forgot about the power up sequence. Agree, change the LM317 and see what happens. And yes, it's not the easiest to get to but you've done it before and you can use my procedure documented in this thread to help you along.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on November 13, 2018, 02:59:24 am
Here's a series of scope shots right after the power up. CH1 is pin 2 of LM317 and CH2 is pin 1. It looks like the inverting amplifier is not doing it's job but rather is the source of the jitter. I think the issue is with U1371B, CR1263, C1261 (unlikely) or R1261/R1262.

Edit: Bingo! U1361 doesn't like the freezing spray. Who does?  :--
Edit1: I meant U1371...
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 13, 2018, 04:17:38 am
Has anyone noticed the ripple frequency of CH1? (yellow trace). Its all over the place, first its 1.77KHz, then 1.6KHz, then 25Hz when it finally starts to be stable, then on the three last pictures its shown at around 15Hz. Maybe that power supply is oscillating somehow at startup, and the associated instability is what is causing the jitter.

Or am I looking at the wrong area of the screen shot? Never used one of those Rigol digital scopes but the CH1 label inside the rectangle on the top right side with the square wave seems to be indicating the measured frequency of the (AC) input signal.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on November 13, 2018, 04:57:11 am
...
Or am I looking at the wrong area of the screen shot? Never used one of those Rigol digital scopes but the CH1 label inside the rectangle on the top right side with the square wave seems to be indicating the measured frequency of the (AC) input signal.
It would be indicating frequency if it was a normal, repeating signal.  But the signal is essentially random noise, and in addition it's low amplitude, so who knows what points it's picking to compute the frequency.

Garbage in, garbage out.


Miti: Sounds like you found your culprit!  Did you freeze the other suspect components with little to no effect?  The problem seems to be so sensitive and subtle that the cold could have wicked along the board and traces to affect more than just U1371.

It might also be good to put a little pressure on U1371 and the other suspects to make sure it's not something mechanical like a bad solder joint or cracked trace.

In general I would agree that C1261, a ceramic, would be an unlikely candidate, but I've been surprised on a several occasions.  Suspect *everything* in these old scopes!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 13, 2018, 05:23:58 am
Hey Mark,

Last week ordered a GQ-4x4 programmer, and already have the new D1225 waiting in the drawer. Only need to get the low profile machined socket, which I thought I had ordered the correct one, but received a narrow 28 pin DIP instead, its like two 14-pin sockets end to end. Never trust pictures, they are for "reference only", although the description seemed right. Oh well. But this time I've got the right one in the cart.

Also have my eye on a FM16W08, but can't seem to get the SOIC to DIP adapter board until they are back in stock at Mouser early December. Rather buy one that has the pins installed and ready to go then those plain chinese boards on ebay.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on November 13, 2018, 05:44:17 am
Hey Mark,

Last week ordered a GQ-4x4 programmer, and already have the new D1225 waiting in the drawer. Only need to get the low profile machined socket, which I thought I had ordered the correct one, but received a narrow 28 pin DIP instead, its like two 14-pin sockets end to end. Never trust pictures, they are for "reference only", although the description seemed right. Oh well. But this time I've got the right one in the cart.

Also have my eye on a FM16W08, but can't seem to get the SOIC to DIP adapter board until they are back in stock at Mouser early December. Rather buy one that has the pins installed and ready to go then those plain chinese boards on ebay.
Great - let us all know how it goes!  The Aries adapters are good quality.

It may be a little ugly, but you could always cut the socket in half lengthwise if it's just ribs holding the two rows together.  Who's going to see it under the chip?  Or file down the cuts to make it look like two nice SIP headers.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 13, 2018, 06:02:43 am
Great - let us all know how it goes!  The Aries adapters are good quality.

It may be a little ugly, but you could always cut the socket in half lengthwise if it's just ribs holding the two rows together.  Who's going to see it under the chip?  Or file down the cuts to make it look like two nice SIP headers.

Yes I could do that if no other option, but the contacts on this socket are not machined, but rather of the one leaf swipe type, not the ideal socket for the DS1225 round pins. But it could work.

BTW, one thing I want to definitely try first is to write the template file with all the values I added from the exer 02 data. I presume it would be safe to just write the DS1225 with this data, then test the scope, and if all works out, erase the chip, and then write it again but this time with the data I hopefully was able to read to a file from the original NVRAM. Doable?

EDIT: I was thinking a good way to check the data integrity of the first programming with the exer02 values, would be to run the exer02 again with the new chip in the scope, and if all the data matches it should be good to go. Or am I missing something?

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on November 13, 2018, 06:37:03 am
Yes I could do that if no other option, but the contacts on this socket are not machined, but rather of the one leaf swipe type, not the ideal socket for the DS1225 round pins. But it could work.
Ah, I was imagining it was a machined socket.

Quote
BTW, one thing I want to definitely try first is to write the template file with all the values I added from the exer 02 data. I presume it would be safe to just write the DS1225 with this data, then test the scope, and if all works out, erase the chip, and then write it again but this time with the data I hopefully was able to read to a file from the original NVRAM. Doable?
Yes, to both.  When you bring up the scope with just the template EXER 02 data, however, the settings will be random since the settings are not stored in the EXER 02 data.  When you boot with the original NVRAM data it should be indistinguishable from when you powered it off.

Quote
EDIT: I was thinking a good way to check the data integrity of the first programming with the exer02 values, would be to run the exer02 again with the new chip in the scope, and if all the data matches it should be good to go. Or am I missing something?
That would be a good check, but the scope will do it for you.  Stored in the EXER 02 data is a checksum at location 00, so if you got something wrong it's is going to complain about it at boot time with a FAIL 04.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on November 13, 2018, 01:33:47 pm

Miti: Sounds like you found your culprit!  Did you freeze the other suspect components with little to no effect?  The problem seems to be so sensitive and subtle that the cold could have wicked along the board and traces to affect more than just U1371.

It might also be good to put a little pressure on U1371 and the other suspects to make sure it's not something mechanical like a bad solder joint or cracked trace.

In general I would agree that C1261, a ceramic, would be an unlikely candidate, but I've been surprised on a several occasions.  Suspect *everything* in these old scopes!

I froze the area first then only U1371 using a frozen Q tip. It is the culprit apparently but I will do more experiments tonight.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 13, 2018, 01:37:44 pm
Sounds good Mark, thanks for the confirmation. I read somewhere that all the front panel settings are stored in the NVRAM during the shutdown sequence. Then again, they don't necessarily have to be something random, but rather the scope will just boot up with the settings you had when you read your data into the template file you sent me. We'll see as I report back. Hoping programmer will be here sometime this week. Ooops still need to reorder that socket....
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on November 13, 2018, 03:50:19 pm
I froze the area first then only U1371 using a frozen Q tip. It is the culprit apparently but I will do more experiments tonight.
Great idea on the Q tip... sounds like you've really got it pin-pointed.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 13, 2018, 11:00:03 pm
CHASING THE ILLUSIVE MILLIVOLT & NANOSECOND – PART II

....
Letting the scope automatically measure the 462 MHz frequency via. the red HELP button, indicated 474.7 MHz, which is 2.3% high.
...

Hey Old-E, was rereading some older posts of this thread and came across your post. I wonder if you are still around and ever where able to draw any causes/solutions/improvements or conclusions in reference to the inaccuracy of the parametric measurements in comparison to using cursors on the waveform. I also found that in particular the frequency measurements where way off for my taste and expectation, specially for a top of the line scope as the 2465B. But to be fair and realistic, of course it deserves many merits, but frequency counting is definitively not one of the fortes of this model.

Just for kicks recently I tried to measure the frequency of a 10MHz output from my recently calibrated Rubidium oscillator, and after a few seconds after pushing the Measure and then selecting CH1 for Frequency, the scope just presented a scant measurement result of "10.16MHz" :--. If I use the cursors to measure frequency, they seem dead on. If I measure that same signal on any of my counters or with the 2247A scope, it shows of course 10-dot plus a whole lot of zero decimal places all the way into the  lower Hz region.

I also did some testing with my R2008HS service monitor that can generate up to 1GHz and has the High-Stability time base option and is calibrated within a few hertz of the expected frequency output, and got similar disappointing results while trying to measure frequency on the 2465B. The error seems to get larger as frequency goes up. At 400MHz it was showing an error of several MHz high (I seem to remember it was showing 416MHz). The frequency measurement stopped responding around 650MHz, but the scope would still trigger without any issues even at 800MHz, although the waveform was mighty fuzzy due to using the lower 10mV input range, but rock solid stable.

The semi conclusion that I have reached is that at least frequency parametric measurements on the 2465B are not very accurate, maybe unless you have the CT options things might get better (?), so don't expect much in that sense. Also, as it was explained to me recently, the way the scope actually tries to measure the frequency of a signal is not at all like a traditional frequency counter would, but it rather uses a very convoluted procedure to get to the results. Only to start with, it involves a Miller integrator, and the CPU and DAC interacting to get a result. In case anyone is interested, still do have the detailed explanation of the measuring procedure by someone that knows these scopes very well in and out, and has been working on them and calibrating/selling them for many years.

BTW: I just recently got this 2465B, and so far have not done any calibration to it. But after some testing it seems still to be quite well calibrated in both time/div and volts/div. At least with the equipment I have available which does not allow me to do a full verification/calibration.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 16, 2018, 03:09:25 pm
Great - let us all know how it goes!  The Aries adapters are good quality.

In case anyone was also waiting for the Aries 28-pin SOIC-DIP adapter boards to arrive at Mouser, they actually came in early (ETA was early Dec-18), so I finally placed my order, plus the correct machined socket for the NVRAM and one FRAM to play with on my GQ-4X4 programmer that should arrive this weekend. BTW only 13 Aries boards came in, 12 left now. This is the board you will need to mount the FM16W08 FRAM and convert it to 28-pin DIP.

Also ordered all the recommended PS stuff needed for a full LVPS recap, which I will tackle later on (or sooner), and replace one cap at a time to avoid any mistakes due to the well documented error in the service manual pcb layout, and make sure all the new caps go into the correct location and orientation.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on November 18, 2018, 12:21:18 am
I froze the area first then only U1371 using a frozen Q tip. It is the culprit apparently but I will do more experiments tonight.
Great idea on the Q tip... sounds like you've really got it pin-pointed.

Son of a gun, I replaced U1371, now it doesn't react to the cold anymore but it stays at 14.78V instead of 15V. Before, it would drop to about 14.8 when cold but would stabilise to 14.98V after awhile. Now it is worse. The IC is from Digikey so I don't expect it to be defective. The interesting thing is that the inverting and non inverting inputs are at different levels. The positive input (pin5) is at 10.00V sharp and the negative one (pin 6) is at 9.84V. Shouldn't they be at the same level?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on November 18, 2018, 12:37:44 am
I froze the area first then only U1371 using a frozen Q tip. It is the culprit apparently but I will do more experiments tonight.
Great idea on the Q tip... sounds like you've really got it pin-pointed.

Son of a gun, I replaced U1371, now it doesn't react to the cold anymore but it stays at 14.78V instead of 15V. Before, it would drop to about 14.8 when cold but would stabilise to 14.98V after awhile. Now it is worse. The IC is from Digikey so I don't expect it to be defective. The interesting thing is that the inverting and non inverting inputs are at different levels. The positive input (pin5) is at 10.00V sharp and the negative one (pin 6) is at 9.84V. Shouldn't they be at the same level?

I would think they should be the same. But the big question is.....did it fix your start up jitter?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on November 18, 2018, 02:54:19 am

I would think they should be the same. But the big question is.....did it fix your start up jitter?

Yes it did, but now it stays at the jittery level without jitter. Monday I will install a socket and I'll try few more 324 that I have in my junk box. It cannot have 150mV input voltage offset, something is not right.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 18, 2018, 04:55:30 am
Son of a gun, I replaced U1371, now it doesn't react to the cold anymore but it stays at 14.78V instead of 15V. Before, it would drop to about 14.8 when cold but would stabilise to 14.98V after awhile. Now it is worse. The IC is from Digikey so I don't expect it to be defective. The interesting thing is that the inverting and non inverting inputs are at different levels. The positive input (pin5) is at 10.00V sharp and the negative one (pin 6) is at 9.84V. Shouldn't they be at the same level?

If your +15V PS buss is now at 14.78V it is a tiny bit out of spec, it should be between 14.775 and 15.225V with no more than 15mV ripple (check at J119 pin 6). Strange for a 317 not to output something closer to the expected 15V, with the associated circuitry unless something is still amiss. What is the voltage at the 317 reference input?

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on November 18, 2018, 03:00:06 pm
Son of a gun, I replaced U1371, now it doesn't react to the cold anymore but it stays at 14.78V instead of 15V. Before, it would drop to about 14.8 when cold but would stabilise to 14.98V after awhile. Now it is worse. The IC is from Digikey so I don't expect it to be defective. The interesting thing is that the inverting and non inverting inputs are at different levels. The positive input (pin5) is at 10.00V sharp and the negative one (pin 6) is at 9.84V. Shouldn't they be at the same level?

If your +15V PS buss is now at 14.78V it is a tiny bit out of spec, it should be between 14.775 and 15.225V with no more than 15mV ripple (check at J119 pin 6). Strange for a 317 not to output something closer to the expected 15V, with the associated circuitry unless something is still amiss. What is the voltage at the 317 reference input?

It is 1.23V below the output and it is where it should be. I don't suspect 317.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on November 23, 2018, 12:14:20 am
Done:
- Full refurbishment of A5 board. I replaced the DS1225Y NVRAM with FM18W08 FRAM. No problems whatsoever. I was able to read the contents of my original NVRAM and put them in the FRAM without any problem. The scope boots and works normally.


This is very interesting. Some time ago I bought a Ramtrom FM16W08 from Ebay and it didn't work in my 2445B. Now I bought a Cypress FM16W08 thinking that the one from Ebay was defective but this one doesn't work either. First time after it is programmed in the programmer, it starts normally but after the first power cycle, I get Test 04 Error 10.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 23, 2018, 03:46:36 am
Done:
- Full refurbishment of A5 board. I replaced the DS1225Y NVRAM with FM18W08 FRAM. No problems whatsoever. I was able to read the contents of my original NVRAM and put them in the FRAM without any problem. The scope boots and works normally.


This is very interesting. Some time ago I bought a Ramtrom FM16W08 from Ebay and it didn't work in my 2445B. Now I bought a Cypress FM16W08 thinking that the one from Ebay was defective but this one doesn't work either. First time after it is programmed in the programmer, it starts normally but after the first power cycle, I get Test 04 Error 10.

I'm curious what programmer where you using? I am new to all this, never done it before, and will be receiving a FM16W08 from Mouser soon. Already have the new DS1225AD-150 chip but somehow messed up the socket PN so had to reorder it. Already received a new version GQ-4X4 programmer which is already installed with latest SW v10. So after desoldering and hopefully reading my original NVRAM without any issues, and writing the new DS1225, was also planning to try out the FRAM CHIP. Just need to wait for the Aries SOIC to DIP converter board, along with the correct 28-DIP machined socket to arrive. The FRAM and those two last missing bits where supposed to arrive by the end of this week, but thanks to Turkey day in the US the last leg of the shipment was delayed. So looks like the big date where everything will happen is now been postponed for another week.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on November 23, 2018, 10:40:36 am
I have a Xeltek 5000 at work.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 23, 2018, 12:02:44 pm
I have a Xeltek 5000 at work.

Maybe its not fully compatible with the FRAM. Is the FM16W08 specifically mentioned in the list of compatible devices? From what I learned so far, there is one crucial difference between programming a D1225 and the FRAM, in that one of the control lines needs to be toggled during each individual write instead of staying in a specific state all the way throughout the whole write process of the chip. Not sure that makes sense as it is only what I remember reading, and again I am new to programmers and will use one for the first time once I have all the remaining bits here to save my 2465B cal data.

I ordered the GQ-4X4 because its the newest version hardware, and the FM16W08 is specifically listed as being supported with the current v10 software, as well as the D1225. I also went by the comments of other people that say the FRAM writing worked for them on this programmer. I will report back my own results next week.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on November 23, 2018, 03:37:01 pm
From what I learned so far, there is one crucial difference between programming a D1225 and the FRAM, in that one of the control lines needs to be toggled during each individual write instead of staying in a specific state all the way throughout the whole write process of the chip. Not sure that makes sense as it is only what I remember reading, and again I am new to programmers and will use one for the first time once I have all the remaining bits here to save my 2465B cal data.

FRAM uses sense amplifiers for reading which much be precharged before each read.  Precharge occurs while -CS is high so -CS must be toggled for every memory read unlike SRAM.  Usually this is not a problem because in most applications, -CS is toggled between every access anyway but a programmer might rely on holding -CS low and operating asynchronously which will not work.

Writes should not matter as either -CS or -WE may be toggled like with a standard SRAM.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on November 23, 2018, 04:55:59 pm
The programmer is not the problem, Ramtron FRAM is in the list of devices and it verifies after programming. Even the scope works well very first time after programming. Once I power cycle, some locations in the calibration constants area get corrupted. That doesn't happen with the DS1225. I'm surprised that it works well for some people but not for others. Well, at least for one...
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on November 24, 2018, 11:02:14 pm
Son of a gun, I replaced U1371, now it doesn't react to the cold anymore but it stays at 14.78V instead of 15V. Before, it would drop to about 14.8 when cold but would stabilise to 14.98V after awhile. Now it is worse. The IC is from Digikey so I don't expect it to be defective. The interesting thing is that the inverting and non inverting inputs are at different levels. The positive input (pin5) is at 10.00V sharp and the negative one (pin 6) is at 9.84V. Shouldn't they be at the same level?

If your +15V PS buss is now at 14.78V it is a tiny bit out of spec, it should be between 14.775 and 15.225V with no more than 15mV ripple (check at J119 pin 6). Strange for a 317 not to output something closer to the expected 15V, with the associated circuitry unless something is still amiss. What is the voltage at the 317 reference input?

It is 1.23V below the output and it is where it should be. I don't suspect 317.

I installed a socket in place of U1371 and I tried all my collection of 324 that I bought and found in my junk box. That is one brand new TI LM324AN bought from Digikey, two National Semiconductor LM324N bought from a local store, one TI LM324N from my junk box and one TSL ??? LM324N from my junk box. Only the last one works, all the other give me between 14.6V and 14.75V at the output. I also tried a TL064 from my junk box and a new TL084 that I bought today, no problem with them. The parts are OK, I tested them all in a buffer circuit with 20V supply, 10V at the non inverting input and 10K resistor in the feedback loop.
The original IC is a NEC C324C that either has some special performances (I can't imagine what can be so special about a 324) or  there's something wrong with that part of the circuit. I know it's Tektronix and suspecting a design screwup is almost insane but....who can come up with a reasonable explanation?
Anyway, I installed the TL084 in the end and the output is a stable 14.98V.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Satbeginner on November 25, 2018, 12:25:52 am
I think I had something similar, it turned out that a specific version OpAmp had a +and- 15V range power supply, and others had a +and- 18V power supply range, so only the version with the higher specs on power supply voltage would work.

It had something todo with the version letters after the 324...

I have to look into my notes for more details.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on November 25, 2018, 01:29:35 am
I think I had something similar, it turned out that a specific version OpAmp had a +and- 15V range power supply, and others had a +and- 18V power supply range, so only the version with the higher specs on power supply voltage would work.

It had something todo with the version letters after the 324...

I have to look into my notes for more details.

That crops up for a lot of old bipolar process operational amplifiers but you need to check the specific part numbers for each manufacturer because they are not always consistent about which ones are 36 volts and which are 40 or 44 volts.

TL series JFETs - All 36 volts
LF series JFETs - Some are 36 and some are 44 volts
101A and 201A (military and industrial) - 44 volts
301A (commercial) - 36 volts
108 and 208 (military and industrial) - 40 volts
308 (commercial) - 36 volts
741 (commercial) - 36 volts
741 (other) - 44 volts

Tektronix used to grade 36 volt 741s for operation at 44 volts.  I assume they were using plenty of them at lower voltages so did this as a cost saving measure in the few applications where a higher voltage part was needed.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on November 25, 2018, 03:31:46 am
But this is only supplied at 26V or less. On the other hand, only U1371B seems to be bad, or at least U1371C seems to work in all of them. It must have something to do with the way it is used in this schematic.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on November 25, 2018, 10:06:42 pm
It all makes sense now   8). The positive supply voltage to U1371 is 15V. Its output swing has reach the limit about 300mV too low, it simply cannot go higher on majority 324s, but TL084 can, enough to maintain regulation. One thing that made me think of that was that, using the ICs that don't regulate properly, during the boot time, the +15V drops a bit further. Probably there's an increased current during the self test and that would need higher voltage at the reference pin of LM317, while with TL084, it is rock solid 14.98V.

There are few factors contributing to this. First is the unregulated voltages being a bit lower than expected, I don't know why. If the unregulated +15V was 19.2V as shown in the schematic and not 18.4V that I measure, I wouldn't have this issue.
Second is that R1400 seems to have increased its value, I measure 108Ohm in circuit instead of 100Ohm. Being in circuit I should measure lower that nominal and not higher, that means it may be even higher than 108Ohm. That contributes with another about 270mV voltage drop. If I restore R1400 to 100Ohm I expect an increase in the supply voltage to U1371 of about 270mV.

One interesting thing is why do they expect to get 5.1V on +5VD. First I thought there's something wrong with my inverter feedback as I'm getting +5.00V on +5VD, but if you look in the schematic, there's no way to get +5.1V if that loop works well.

Can anybody measure the unregulated voltages in a working Tek 2465B or 2445B please? A marginal design in that area, thumbs down for Tektronix.

The repair adventure continues....

Edit: Actually can anyone measure all the voltages at the output of the inverter, including +5VD?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on November 26, 2018, 07:10:59 pm
I'm calculating a decent operating margin for the LM324.

The LM324 is driving the LM317 through a diode drop, so the LM324 output should be around: LM317out - LM317drop - diode --> 15.0V - 1.25V - 0.7V = 13.05V.

The LM317 adjust terminal current max is 100uA, so under normal conditions that will also be the max current for the LM324 output.

The LM324 datasheet does not show a spec for V+ = 18V, so using the V+ = 30 spec, Vo to a 10k load has a drop of 30V - 27Voh = 3V, and with that there's a current of 27V/10k = 2.7mA.  That's well under the 100uA max in the Tek circuit.  According to the typical characteristics, the Voh drop is independent of V+, so the drop should not be any worse at V+ = 18V.  The typical  characteristics plot puts the drop at around 1.2V for 100uA.

But still if we use the absolute worst case, in order to drive 13.05V on the LM324 output towards the LM317, we need a V+ supply of 13.05V + 3V = 16.05V minimum.

I think you're saying you're measuring 18.4V for the unregulated supply, but what is it on the other side of R1400 (which is also the LM324 V+)?

The LM317 dropout voltage is 3V, so that is a little tight if the unregulated supply is 18.4V and the output is 15V, but is still within 400mV.  The typical dropout is 2.5V at 1.5A.

Can you measure *all* the pins on the the LM317 and LM324 and post?  Even though it works with the TL084, I still think there's something wrong.  I don't think it's a bad design and there should be enough margin.  (And the answer to a previous question is yes, Vin+ and Vin- should be equal in this circuit since LM324 section B is normally amplifying.)


Also, on the FRAM corruption, I think it's odd that it happens and then the scope continues to run.  The FRAM is also acting as the scope's operating RAM, so if there's a problem with read/write I would expect it to crash or become unstable almost immediately.

I'm wondering if there's still some kind of start-up power supply issue that the FRAM is more sensitive to that's causing corruption.  At boot, one of the first things the scope does is a write/readback check of every RAM location, *including* the cal locations.  Starting with address 0x9FFF and going to 0x8000, the scope reads the value, does a write/readback check with 0x55, then with 0xAA, and then writes back the original value.

The previous power supply issue and FRAM corruption could be completely unrelated, but I'm throwing it out there as a possibility.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on November 27, 2018, 03:01:06 am
Hey MarkL,

The LM324 V+ on the other side of R1400 is 15V. Not enough for safe operation.

Regarding the FRAM, if it does that...crazy thing...at boot, that explains a lot. For some reason my TL866II Plus can "almost" program this FRAM even though it is not in the device list. I select DS1225 as the device and it can program successfully 0x00 and 0xFF but when I try to program the real content of my scope's NVRAM, it fails to program few locations.....the same locations that get altered after the first power cycle.

What I mean is, if I program properly the FRAM using the Xeltek programmer (that fully supports it), the first power up is ok, it runs well or at least I didn't see any issues in the short time that I ran it. But once I power cycle, two locations in the calibration constants area, the same locations that can't be programmed with TL866II Plus, are modified. Probably once it does the 0x55 then 0xAA, it cannot put back the original content. But why does it work for some people, that beats me.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 27, 2018, 03:29:50 pm
In preparation for the arrival of the socket and FRAM hopefully by tomorrow afternoon, the NVRAM is now off the A5 board. Not too bad, a few of the pins needed a little bit of extra care to fully free them and make them "swing", but even pin 14 fully cleared on the first try. All in all, process went rather smoothly and the chip actually fell off the board all by itself when I unsoldered the last pin.

Now on to read the chip. Will report results once that part is done as well.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 27, 2018, 03:59:00 pm
Read the NVRAM chip, apparently all went well, took 0.24 secs according to programmer and no errors. Actually just in case read it twice and saved separate BIN files. My first chip reading.

So first thing I did was to compare the values between 1E00 and 1FF0 of the file that was just read and the data I had from the Exer02 procedure. After a simple overview it is clear that the first one and a half lines have some differences (up to 1E1005 - I think that would be the right reference), but all the rest of the data seems to be equal. I've attached pictures of both the template I filled some time ago with the EXER02 data into an empty bin file template kindly provided by MarkL, and also the resulting file of the actual scope NVRAM reading just done.

Maybe I should have gone through another EXER02 routine just to double check for any changes before removing the NVRAM chip, but it just slipped my mind. In any case I will be able to verify it once the machined socket is in place. The only things I could think of that would have caused the changes are that I performed a vertical channel DC balance (by pushing both input selectors up). Other than, I don't think that the total hours and power ups are part of the data contained between 1E00 and 1FF0, so that would not had any effect. Unless of course the last resistor change of the DAC divider chain has something to do with it, and the scope just adjusted itself to the slightly higher reference voltages after I replaced the temporary 5% resistors used just to bring back the DAC to life, with the correct 10K 0.1% ones.

I do already have the new DS1225AD on hand, and wanted to write it with a copy of the template file that I filled out by hand from the Exer02 data and see what the scope says. Then I would have erased it, and put in an exact copy of the data I just read from my own NVRAM. But now in light of the differences in the data, I will wait until I can run another NVRAM data verification and compare it with my existing Exer02 data gathered some weeks ago and see if there are actual changes that match. I suspect they will.

And as it seems to be customary here on this thread, I have also attached a zipped up BIN file of the NVRAM content, along with the serial number added to the file name, to maybe provide something helpful for others to use, and at the same time have just another BU of the file as well.

EDIT: Replaced the image of the EXER02 data, as I found a mistake I made filling it in at 1F3000 which was written as FF while it had to be FD.
EDIT2: Added another picture that shows the differences in data between Exer02 and the NVRAM read.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on November 28, 2018, 10:25:01 pm
The LM324 V+ on the other side of R1400 is 15V. Not enough for safe operation.

Quite so.  Just out of curiosity, I measured the voltages on a 2445A on the LM324 (U1371).  The power supply design is the same as the 2465B, at least in this section.

  +15.06 --- 1  14 --- -6.30
  +15.00 --- 2  13 --- +2.651
  +15.57 --- 3  12 --- +2.501

  +16.24 --- 4  11 --- -6.95

  +10.00 --- 5  10 --- +5.00
  +10.00 --- 6   9 --- +5.01
  +13.33 --- 7   8 --- +2.916

And the LM317 (U1260):

  +13.77 --- 1
  +15.01 --- 2
  +18.73 --- 3

So, the unregulated +15 supply (+18.73) is also low on this scope.  I'm not digging into it any further since it's working, but I think I do need to modify what I said and instead say this is not such a great design.  There's too much loss through R1400 and even the typical margins become quite small when the unregulated supply is even a little low (we're only talking 0.5V here since it should be 19.2V).

My R1400 reads 106.3 ohms, so it's also a little high like yours.  But my loss through R1400 is only 2.49V, and not 3.4V like yours.  I think you have something drawing excessive current on that side of R1400, maybe from +10V REF.

Quote
Regarding the FRAM, if it does that...crazy thing...at boot, that explains a lot. For some reason my TL866II Plus can "almost" program this FRAM even though it is not in the device list. I select DS1225 as the device and it can program successfully 0x00 and 0xFF but when I try to program the real content of my scope's NVRAM, it fails to program few locations.....the same locations that get altered after the first power cycle.

What I mean is, if I program properly the FRAM using the Xeltek programmer (that fully supports it), the first power up is ok, it runs well or at least I didn't see any issues in the short time that I ran it. But once I power cycle, two locations in the calibration constants area, the same locations that can't be programmed with TL866II Plus, are modified. Probably once it does the 0x55 then 0xAA, it cannot put back the original content. But why does it work for some people, that beats me.
If it's consistently the same locations, maybe it's a bad FRAM?  Are there counterfeit FRAMs floating around?

I'm surprised it gets through the 0x55/0xAA test in the first place.  I can't explain that.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on November 29, 2018, 12:23:11 am
Thanks MarkL,

This is great info!
One more voltage that I was interested in was the 5VD that I don't think can measure 5.1V no matter what.
I'm not too worried about the extra ~7mA in my R1400 as long as everything else works as it should, I wonder if it isn't exactly this pushing to the maximum of the U1371B that draws it.
What I will do is to replace R1400 with a selected 100R that measures a bit below nominal and replace the diodes CR1103 - CR1106 in the preregulator with Schottky, so I gain few hundred mV there too, and continue to be disappointed in Tek's design. I think even the best can screw up sometimes, eh? I'm sure it's a known issue among the Tek gurus and probably there's a solution too but it's not worth the time looking.
The FRAM is not a knock off, it is a Cypress bought from Digikey but that doesn't mean it cannot be defective. The first one bought from Ebay gives me garbage in the readout.
However, Xeltek can program it, no problem, it's only the TL866 (which is excused as it doesn't officially support it) and the scope that messes up the content. Anyway, it passes 0x00, 0xFF, 0x55 and 0xAA in my TL866 II Plus but I can't test it "at speed".
I see that AMR Labs is waiting for his FRAM these days so I'm curious how it works out for him.

Edit: Actually I think I have the answer regarding 5VD in the level at Pin 9 U1371. Not sure what meter you used but if it has a 10M input, 5VD should be around 5.03-5.04V.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 29, 2018, 04:10:32 pm
Parts arrived, pictures attached.

Surprisingly FRAM came in a humidity controlled anti-static bag. Anybody ordering a FRAM from Mouser (or elsewhere) got this as well? Dodn't know this part was so humidity sensitive. For the fun of documenting it took pics.

Will report back once new NVRAM is written, and scope powers up, and verify Exer02 data. Then will erase new NVRAM and write it with the Exer02 data template file.

Last will write the FRAM, and see how it goes.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: emece67 on November 29, 2018, 07:27:40 pm
.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 29, 2018, 08:15:35 pm
Everything worked out well. Just to make sure the old NVRAM was still OK after all the desolder and reading procedures, inserted it into the newly installed socket and the scope booted up normally into the exact same configuration before last powering it off. I also went to Exer02 and confirmed all the changes I saw when I first read the original NVRAM data, and it matched the ones reflected on the chip data. So maybe the vertical balance adjust I did, or something else changed those first and a half lines of the data between 1E00 and 1E10, as I pointed out a few posts back.

Did one last read of the original NVRAM of the scope and programmed the new NVRAM. Scope came up like nothing happened, exactly the same configuration, as seen in one of the attached pictures. Then programmed all FFFF"s into the new NVRAM (not sure that is the correct way to erase all data, as the Erase function on the programmer itself seemed not to work and was giving me an error). Anyway, verified that the new chip was all FFs by reading it, and the proceeded to open the template BIN file with all the data from the EXER02 procedure (updated to reflect those later changes). The scope booted almost normally without any errors but as expected showed a somewhat strange configuration as seen on another picture (I also made a movie of the boot-up process, but its in 1080P so its a 70MB MOV file), and at the end of the boot process there was no trace or readout on the screen. After some fiddling I noticed the trigger was set to Single SEQ, and after changing it back to Auto a really slow and extremely bright sweep came up. Uuups quickly turned down the intensity knob. Also the trace was no where near being centered, neither horizontally or vertically. But after turning all the related knobs either way a bit things started to settle, and the readout also came back on screen. I did not do any extensive tests for accuracy, but from what I saw all seemed to be OK, and since the scope did not complain I'm guessing the cal data checksum was good. Pulled the NVRAM to read it and saved the contents to file so any changes done by the scope to the template data are recorded for future analysis if needed.

Then again wrote all FFs into the fresh 1740 datecode NVRAM and wrote the data from the last read of the original NVRAM and put it into the scope. Upon boot up all seemed fine other that one relay made a bit of a short buzzing sound instead of the usual single click, and the scope came up normally. Then pulled out the NVRAM and read the contents to file as well, again just to document and archive everything, since I noticed that quite a bit of data from 1E00 down had been changed, not sure this would be because the scope was still expecting to see the earlier Exer02 data from the last test after it settled all the front panel settings. So once again pulled out the new NVRAM and wrote FFs, then proceeded to write once again the data from the last read of the original NVRAM, and this time the scope came up normally, no buzzing of the relay (that might have been a fluke?), and it came up to the same configuration that the scope was into when the old NVRAM was still installed. But this time upon reading again the new NVRAM, there where no changes in the cal data from 1E00 and on.

Last but not least, the FRAM. Soldered it onto the converter board, read it and it was all 0000 (zeros), so proceeded to write again the same data from the last read of the original NVRAM, and pushed it into the socket. Result: scope came up normally, no errors, and in the exact same configuration as expected. Powered down the scope and on again a few times over the course of several minutes, same thing no errors, all seems OK. Waited about 15 minutes, power up and again, everything came up the same and without any errors. Now just checked again, must have been like 30 minutes since I last powered the scope, and it is still booting up perfectly.

So not sure which one of the memory modules I will leave in. Maybe leave the old original NVRAM and see how long it will take for it to fail, but then I might loose some data along the way if any operations are performed (other than a full calibration) that might alter the end result, as it happened between the period of about a month where I first took the Exer02 data down, and the last read of the NVRAM once it was desoldered. Again, I only recall doing a vertical balance by pushing up both channel 1 and 2 input selectors, and it would make sense that this change would get written into the NVRAM, although seems obviously non-critical, as I have not done any serious calibration at all.

Or I could just put away the old NVRAM, and start using the new one, and just forget about it (for a while). But the old one would then probably die silently at some point, which at this point is inevitable anyway. So I think the old NVRAM will definitively stay out.

The other option, and which is probably what I will do for now, is to leave the FRAM in order to see how it behaves over a more prolonged period of time, and put away both the old and the new DS1225's. After all the initial idea was that if the FRAM is confirmed to be stable and working fine, it would allow me to dispense with backup battery blues altogether. Maybe at some point I could swap it out with the new NVRAM if I feel like doing some more tests, and of course always keep up with any minor changes that appear in the cal data.

What do you guys think?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on November 29, 2018, 08:47:46 pm
...
What do you guys think?
Wow - thanks for the detailed write up!  It's nice when things work as expected.

I think I would leave the FRAM in there.  You went to a lot of trouble to create it and you'll never have to worry about the NVRAM again (knock wood).

As for the changed values after the channel balance, you could repeat the balance procedure and see if those locations change again.  EXER02 location 00 (RAM: 1E00/1E01) is the checksum, so it's expected to change if any of the other constants change (EXER02 locations 0B thru E3, if I'm reading the code right).
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on November 29, 2018, 11:35:15 pm
...
Edit: Actually I think I have the answer regarding 5VD in the level at Pin 9 U1371. Not sure what meter you used but if it has a 10M input, 5VD should be around 5.03-5.04V.
It's a Fluke 79 III.  The range for measuring the 5V is 10Mohm (40V range) with 10mV resolution.  So we're talking about the least significant digit here.

I dragged the scope over to a different bench with a 3456A (6 1/2 digits).  The impedance on the 3456A on the 10V range is >10^10 ohms.  Here's a re-read:

5VD measured on J232: 5.01501V

U1371: pin 10: 5.01095V
       pin  9: 5.01193V

There's a little bit of offset, but within spec, and some of it is probably because the input impedances are not matched in this circuit.

Is your concern that the 5VD is noted as 5.1V in the schematic?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on November 30, 2018, 12:04:38 am
Thanks AMR Labs!

Now I'm really pissed off.... Is it possible that both my FRAMS are defective? I can understand the one from Ebay for $6 but from Digikey?
How can I test it? What can be wrong with my scope considering that it works perfect with the old and two new DS1225?

Edit: I just had a live chat with Digikey's customer service. They will send a replacement, no questions asked. Impressed!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on November 30, 2018, 12:36:53 am

Is your concern that the 5VD is noted as 5.1V in the schematic?

Thanks MarkL!
I'm not concerned, I just wondered what intern was tasked with marking the voltages on that schematic and if he used a dice or a multimeter.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 30, 2018, 05:09:47 am
Thanks AMR Labs!

Now I'm really pissed off.... Is it possible that both my FRAMS are defective? I can understand the one from Ebay for $6 but from Digikey?
How can I test it? What can be wrong with my scope considering that it works perfect with the old and two new DS1225?

Edit: I just had a live chat with Digikey's customer service. They will send a replacement, no questions asked. Impressed!

Did your FRAM from Digikey arrive in a controlled humidity package like mine did? Maybe yours got a bit wet along the way!  ;)  ;D

Well, I never really liked Digikey too much, back in 2011 or 12 when I was still located in PR, they managed to piss me off when I tried to order from them for the first time a couple of common parts (a couple of 74xx and/or 40xx chips, and some other passive parts and ship them directly to PR. They where giving me some crap that they where not able to "export" these parts (PR being an associated US State!) and asking for some other BS documentation. >:( So ever since I passed on them and really get anything I need from Mouser, which I consider a high quality and very efficient supplier. At least in my experience, Digikey was back then no longer worth the hassle, so I never looked back. And not that it would matter much, but their prices are almost always a bit higher in direct comparison to Mouser.

Just in case you decide as a backup plan to order the FRAM from Mouser as well:

FM16W08-SGTR, Mouser PN 877-FM16W08-SGTR, in stock 357, $10.85
https://www.mouser.com/ProductDetail/Cypress-Semiconductor/FM16W08-SGTR?qs=sGAEpiMZZMtsPi73Z94q0OKOSVYv1Kg2z52nkh0S%252bvo%3d (https://www.mouser.com/ProductDetail/Cypress-Semiconductor/FM16W08-SGTR?qs=sGAEpiMZZMtsPi73Z94q0OKOSVYv1Kg2z52nkh0S%252bvo%3d)

28-650000-10 Aries 28P SOIC/DIP SOCKET, Mouser PN 535-28-650000-10, in stock 12, $18.55
https://www.mouser.com/ProductDetail/Aries-Electronics/28-650000-10?qs=sGAEpiMZZMs%2fSh%2fkjph1tjJZclYmfaNPlov7zqaFl0I%3d (https://www.mouser.com/ProductDetail/Aries-Electronics/28-650000-10?qs=sGAEpiMZZMs%2fSh%2fkjph1tjJZclYmfaNPlov7zqaFl0I%3d)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 30, 2018, 05:38:34 am
Some time ago I built this Avalanche Picosecond Pulse Generator:

https://entangledwaves.wordpress.com/2013/07/15/avalanche-pulse-generator/ (https://entangledwaves.wordpress.com/2013/07/15/avalanche-pulse-generator/)

BTW the specified now obsolete 2N2369 transistor is still available at Mouser in TO-18 metal case for about $2, although a usable alternative seems to be a common 2N3904, but the former has a more desirable breakdown characteristic. I did not need to build the DC-DC converter part for the 90V avalanche bias supply, but instead used my Heathkit IG-4505 Scope Calibrator as a power source with the DC output set to the 100V position.

There is also another very well known website on the same subject:
http://www.kerrywong.com/2013/05/18/avalanche-pulse-generator-build-using-2n3904/ (http://www.kerrywong.com/2013/05/18/avalanche-pulse-generator-build-using-2n3904/)

Wanted to share pictures of the pulse as shown on both my 2465B and the 2247A, and possibly hear opinions. Cursor time measurement are located between the 10% and 90% points of the rising edge. Thanks.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on November 30, 2018, 04:54:59 pm
...
What I mean is, if I program properly the FRAM using the Xeltek programmer (that fully supports it), the first power up is ok, it runs well or at least I didn't see any issues in the short time that I ran it. But once I power cycle, two locations in the calibration constants area, the same locations that can't be programmed with TL866II Plus, are modified. Probably once it does the 0x55 then 0xAA, it cannot put back the original content. But why does it work for some people, that beats me.
So, you're saying the corruption shows up on the second boot.  It's possible the FRAM is getting corrupted during the scope's power-down sequence.  That would also explain why it passes the 0x55/0xAA test; the corruption has already happened.

You could use the PWR DN signal as a trigger and start looking at the behavior of the control signals into the FRAM, including the +5V power, during power down.  Maybe there's something marginal that the DS1225 tolerates.

If you have an MSO or a logic analyzer with enough inputs, you might also try setting up a trigger to capture when the corrupted address in the FRAM is accessed or written.  But keep in mind this could be an analog signal issue and a logic analyzer might not catch it.

EDIT:  One more thought before starting down this path... With good data in the FRAM, you could do one power cycle, remove the FRAM, and read it to see if corruption occurred.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 30, 2018, 07:41:55 pm
EDIT:  One more thought before starting down this path... With good data in the FRAM, you could do one power cycle, remove the FRAM, and read it to see if corruption occurred.

If it is of any help, yesterday I went manually through the Exer 02 procedure with the FRAM in place, and all cal data values where still spot on to what I programmed into it, nothing changed. As of today scope still booting up fine.

Is it possible there might be some kind of a Firmware difference in the 2445B that might be causing his corruption problem? I wonder if there are any documented 2445B scopes running FRAMs. As far as I can remember, all the writeups out there seem to refer to '65B scopes.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on November 30, 2018, 09:10:17 pm
EDIT:  One more thought before starting down this path... With good data in the FRAM, you could do one power cycle, remove the FRAM, and read it to see if corruption occurred.

If it is of any help, yesterday I went manually through the Exer 02 procedure with the FRAM in place, and all cal data values where still spot on to what I programmed into it, nothing changed. As of today scope still booting up fine.

Is it possible there might be some kind of a Firmware difference in the 2445B that might be causing his corruption problem? I wonder if there are any documented 2445B scopes running FRAMs. As far as I can remember, all the writeups out there seem to refer to '65B scopes.
That's a good question.  According to the two service manuals I have, the 2445B and 2465B have the same EPROM part numbers 160-5370 and 160-5371 for U2160 and U2260.  The 2445B lists versions -04, -08, and -09, and the 2465B lists versions -04, -05, -08, -09.

So, with the exception of -05 available for the 2465B, they run the same firmware.  The firmware of course discovers which scope it's running on, so it *could* do something different for power-down or other memory handling.  But I'm guessing probably not.

I also don't have the 2445B schematics to look for any hardware differences that would affect the FRAM.  All the on-line 2445B copies that I could find are missing the schematic section.

(If anyone has a copy or could point me to one that would be great.  And, no, I'm not buying one.  I don't have this scope.  Thx.)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on December 01, 2018, 12:19:38 am

Did your FRAM from Digikey arrive in a controlled humidity package like mine did? Maybe yours got a bit wet along the way!  ;)  ;D


Yes, it did come in moisture barrier package but that is not important unless you do a reflow in an oven or you use the hot air station to solder it. Soldering one pin at a time cannot damage a part due to moisture and MSL does not affect operation, only reflow.
I just received a new replacement part from Digikey. If it doesn't work, I intend to write a short code on a PIC or Atmel board to test them all.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on December 01, 2018, 12:43:31 am
...
What I mean is, if I program properly the FRAM using the Xeltek programmer (that fully supports it), the first power up is ok, it runs well or at least I didn't see any issues in the short time that I ran it. But once I power cycle, two locations in the calibration constants area, the same locations that can't be programmed with TL866II Plus, are modified. Probably once it does the 0x55 then 0xAA, it cannot put back the original content. But why does it work for some people, that beats me.
So, you're saying the corruption shows up on the second boot.  It's possible the FRAM is getting corrupted during the scope's power-down sequence.  That would also explain why it passes the 0x55/0xAA test; the corruption has already happened.

You could use the PWR DN signal as a trigger and start looking at the behavior of the control signals into the FRAM, including the +5V power, during power down.  Maybe there's something marginal that the DS1225 tolerates.

If you have an MSO or a logic analyzer with enough inputs, you might also try setting up a trigger to capture when the corrupted address in the FRAM is accessed or written.  But keep in mind this could be an analog signal issue and a logic analyzer might not catch it.

EDIT:  One more thought before starting down this path... With good data in the FRAM, you could do one power cycle, remove the FRAM, and read it to see if corruption occurred.

The question is how does it test the integrity of the calibration constants? If it does a CRC, that mean the constants are correct at the first power up. What I will do first is an Exerciser 02 right after the first power up so if the self test corrupts the data, I will catch it.
I don't have a logic analyzer but I do have a Rigol DSO with 4 channels.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on December 01, 2018, 01:37:23 am
I'm trying to raise the unregulated +15V by few hundred mV. For that I want to replace the four diodes in the bridge CR1103 - CR1106 with Schottky diodes. The original diodes are 400V 1A but I don't see the need for 400V. I bought two type of diodes from Digikey and I would like to ask your opinion.
1. STPS1L60RL            60V 1A
2. SB1H100-E3/73       100V 1A

The first one has the lowest forward voltage drop of about 500mV at about 800mA.
I think 60V VRRM should be good enough, what do you think?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on December 01, 2018, 03:57:52 pm
...
The question is how does it test the integrity of the calibration constants? If it does a CRC, that mean the constants are correct at the first power up. What I will do first is an Exerciser 02 right after the first power up so if the self test corrupts the data, I will catch it.
I don't have a logic analyzer but I do have a Rigol DSO with 4 channels.
After the 0x55/0xAA test, which is considered part of the TEST 00 kernel test, it gets to TEST 04, which is a checksum procedure across all the constants (but not the entire 0x1E00 - 0x1FFF block).  It's a read-only test.

If you want to watch this area of the FRAM being accessed, you can run TEST 04 from the service menu, and you can also set the test to loop repeatedly until you stop it.  This is all detailed in the service manual, section 6.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on December 01, 2018, 04:36:45 pm
In the end, I've chickened out and I installed the 100V diodes, just to be on the safe side. I still gained 360mV, +15V unregulated is now at 18.76V and U1371 +Vcc Pin 4 is now at 16.3V. The regulated +15V at Pin 2 U1260 is at 15.02V, 14.98V on Pin 6 J119 so is back to "normal", with the normal being too close to the edge for my taste due to crappy design. Interesting, the voltage drop over the R1400 is around 2.46V now, more in line with MarkL's measurements so the fact that the output has some more head room may help.
The FRAM now.
The only location that gets corrupted is 0x1F00, location 80 in EXER 02, validated through EXER 02 and with the programmer.
I ran TEST 04 multiple times after the first power up and passed with flying colours. Once it even passed the second power up but usually, after the second power up, location 80 changes from 0x11 to 0x20.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on December 01, 2018, 04:40:36 pm
I'm trying to raise the unregulated +15V by few hundred mV. For that I want to replace the four diodes in the bridge CR1103 - CR1106 with Schottky diodes. The original diodes are 400V 1A but I don't see the need for 400V. I bought two type of diodes from Digikey and I would like to ask your opinion.
1. STPS1L60RL            60V 1A
2. SB1H100-E3/73       100V 1A

The first one has the lowest forward voltage drop of about 500mV at about 800mA.
I think 60V VRRM should be good enough, what do you think?
I think either would be ok for substitution.  If it were me I'd probably use the 100V one.  The difference in the Vf @ 1A is only 0.06V.

But rather than substituting parts, I would recommend trying to figure out why the unregulated outputs are low in the first place and/or why the other side of R1400 is so low.  The feedback loop only keeps +5VD regulated (U1371C) so there could be excessive current on the unregulated rails and/or something wrong with anything connected to the other side of R1400.  I'm saying "and/or" because it could be two separate problems.  My $0.02.

EDIT: Posted this anyway since I just typed it up.  Glad the new diodes got you the extra margin but I think there's still a problem, albeit masked now.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on December 01, 2018, 05:00:24 pm
...
The only location that gets corrupted is 0x1F00, location 80 in EXER 02, validated through EXER 02 and with the programmer.
I ran TEST 04 multiple times after the first power up and passed with flying colours. Once it even passed the second power up but usually, after the second power up, location 80 changes from 0x11 to 0x20.
My primary suspicion is still that it's happening during power down.  I think something is happening with the FRAM control inputs while the +5 is fading.  They're not being controlled carefully enough for the FRAM while it's transitioning to power off, and it's trashing that location most of the time.

Something similar could be happening on power up, but you said it always works perfectly on the first power up after externally reprogramming the FRAM.


EDIT: The DS1225AB cuts off writes when Vcc reaches 4.62V (typ).  The FM16W08 remains active down to 2.7V, by the time the rest of the chips on that board have already lost their marbles.  The datasheet recommends a pullup from nCE to Vdd, but it's not clear to me that would work here.  FYI.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on December 01, 2018, 05:36:23 pm

My primary suspicion is still that it's happening during power down.  I think something is happening with the FRAM control inputs while the +5 is fading.  They're not being controlled carefully enough for the FRAM while it's transitioning to power off, and it's trashing that location most of the time.

Something similar could be happening on power up, but you said it always works perfectly on the first power up after externally reprogramming the FRAM.

That was my suspicion as well but take a look at the power down sequence. The power down sequence happens between PWR_UP going down and RESET going down. +5V Digital is still stable at least 7ms after that. With the scope probes attached, it passed 3 power ups. What a .....
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on December 01, 2018, 05:48:39 pm

My primary suspicion is still that it's happening during power down.  I think something is happening with the FRAM control inputs while the +5 is fading.  They're not being controlled carefully enough for the FRAM while it's transitioning to power off, and it's trashing that location most of the time.

Something similar could be happening on power up, but you said it always works perfectly on the first power up after externally reprogramming the FRAM.

That was my suspicion as well but take a look at the power down sequence. The power down sequence happens between PWR_UP going down and RESET going down. +5V Digital is still stable at least 7ms after that. With the scope probes attached, it passed 3 power ups. What a .....
What matters is what's happening on the nCE and nWE pins to the FRAM.  Follow the +5 all the way down to 2.7V while watching those pins.

Once the CPU and other chips get below their specified operating voltages, all bets are off and you best assume their outputs are random unless the power down characteristics are specified, which are for some chips.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on December 01, 2018, 06:15:55 pm
Here you go. There are some glitches on nCE but nothing on nWE.

Edit: I guess the question is why does it works for everybody but me?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on December 01, 2018, 07:14:42 pm
Here you go. There are some glitches on nCE but nothing on nWE.
Interesting.  Did this cause a corruption event?  And tried it several times since it doesn't happen consistently?

Does your scope have a PEAK acquisition mode (just to make sure there's not a short pulse lurking in nWE)?

I'm not happy with the glitch on nCE, especially right when chip is transitioning to power down, but as long as nWE remains high I think it should be ok according to the datasheet.

Maybe it's also worth looking at the power-up cycle to make sure there's nothing odd with nWE or nCE there.

Quote
Edit: I guess the question is why does it works for everybody but me?
I don't why it would be inconsistent.  Maybe everyone else is getting away with it.  Or there's something wierd about the FRAM.

Have you tried your new FRAM from Digikey yet?  Your likely to get one from the same batch - check the date code.

You said your TL866II had an issue with a location.  Was it also 0x1F00?  Maybe don't let the new FRAM near the TL866II; just use the Xeltek.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on December 01, 2018, 08:45:34 pm
Interesting.  Did this cause a corruption event?  And tried it several times since it doesn't happen consistently?

Does your scope have a PEAK acquisition mode (just to make sure there's not a short pulse lurking in nWE)?

I'm not happy with the glitch on nCE, especially right when chip is transitioning to power down, but as long as nWE remains high I think it should be ok according to the datasheet.

It is not the event that caused corruption, I tried multiple times to trigger exactly where I wanted, but it is very consistent. There's nothing on the WE, I acquired 12M points and then I zoomed in. I also tried to trigger on WE, there's nothing.

Maybe it's also worth looking at the power-up cycle to make sure there's nothing odd with nWE or nCE there.

In all my experiments, not once the first power up failed Test 04. I don't think power up is at fault.

I don't why it would be inconsistent.  Maybe everyone else is getting away with it.  Or there's something wierd about the FRAM.
Have you tried your new FRAM from Digikey yet?  Your likely to get one from the same batch - check the date code.
You said your TL866II had an issue with a location.  Was it also 0x1F00?  Maybe don't let the new FRAM near the TL866II; just use the Xeltek.

No, TL 866 can write 0x1F00. I tried both FRAMs, same date code, both fail the same. Xeltek is at work, it is a bit harder to experiment.
Interesting is that the first power up will work well forever....well for 15 min at least with no issues, with the FRAMs from Digikey, but will fail immediately with garbage in the readout with the FRAM from Ebay. That means the FRAMs from Digikey are OK. It is some external event that corrupts the data, most likely power down.

I also have a crazy theory that this is content dependent. My 0x1F00 always changes from 0x11, which is the correct value for that location in my case, to 0x20. Should the correct value be 0x20, probably I wouldn't see this issue until next calibration. I can't see how my scope can be different than others except for the content of the NVRAM

There is a solution though, a NAND gate on FRAM CE with inputs from CPU RESET and CE from the CPU inverted.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on December 01, 2018, 11:01:48 pm
I found two easy ways to make it work. It is indeed that glitch that corrupts it.

1. Eliminate the glitch. Solder a 1K resistor series between the nCE pin of the FRAM and the driver U2250. Then connect the nCE pin to pin 6 of U2240. In this way, while the CPU is in reset, nCE cannot be pulled low anymore. Works like a charm even though it doesn't completely eliminate the glitch, it reduces it significantly, see the pictures.

2. Connect a 1K resistor between nWE and +VCC (pins 27, 28) :palm: Why didn't I try this from the beginning? After 10+ power cycles still going strong. We'll see for how long.

MarkL,

Apparently there is a glitch on nWE that I cannot catch (I doubt) or it is level that just needs a little pull up.

Edit: The FRAM from Ebay doesn't work with the pull up resistor, so it is a piece of .... Luckily I got a refund.. :phew:
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on December 01, 2018, 11:28:06 pm
Great - glad you came up with a couple of solutions!  The datasheet likes pullups on both nCE and nWE.

I was reading more about FRAM technology.  From the datasheet:
Quote
Internally, a F-RAM operates with a read and restore mechanism. Therefore, each read and write cycle involves a change of state. The memory architecture is based on an array of rows and columns. Each read or write access causes an endurance cycle for an entire row. In the FM16W08, a row is 64 bits wide. Every 8-byte boundary marks the beginning of a new row. Endurance can be optimized by ensuring frequently accessed data is located in different rows. Regardless, F-RAM offers substantially higher write endurance than other nonvolatile memories. The rated endurance limit of 10^14 cycles will allow 150,000 accesses per second to the same row for over 20 years.

So, the falling edge of nCE, even without a low nWE, initiates a read/restore cycle.  If it doesn't get a chance to complete the cycle because of power loss, I think it could lose the data.  The datasheet doesn't specify nCE low to power down minimum time, but it does specify a minimum nCE low of 70ns and a minimum cycle time of 130ns.  It's also pretty consistent about keeping nCE held to Vdd during the power down ramp.

This seems somewhat less likely to happen, but still possible.  Maybe it's that short spike on nCE.  But I think the newly found nWE glitch is more likely since the correuption is so consistent.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on December 03, 2018, 01:30:35 am
Thanks MarkL and everyone else who helped me!

After figuring out the FRAM, I recapped the A1 main board, did a CRT adjustment and I checked the horizontal calibration using my Feeltech FY6600. The Feeltech original oscillator has been replaced with a stable TCXO and tuned using the GPSDO so it is pretty accurate, short term.
What I want to say is ....WOOW.
After probably more than 10 years since the last calibration, the horizontal sweep is spot on.
The only issue that I found during the CRT adjustment was that the High Drive Focus was way off, that causing the readout to go out of focus at high intensity.
I could not believe my eyes how sharp this scope is now, at par with Hitachi V-1585, and that is one razor sharp tube.
The trade-off is that the readout best focus is not where the trace best focus is, or it may need some more fiddling with the adjustments.
Oh well, maybe one day when he weather is hot and the sky is blue....For now I'm done.....no, really.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on December 03, 2018, 08:08:38 pm
So the take away from all this is that the FM16W08 FRAM is NOT a reliable drop-in solution for the DS1225 NVRAM.

The Tek designers made sure that the memory control signals were stable up until they knew the DS1225 would be powered down and immune to changes when Vdd reached 4.62V (typ).  Below that, they didn't have to care what the signals did.

But with the FM16W08, it matters.  It's active down to at least 2.7V (there's no Vdd value in the spec for guaranteed off).  A proper solution would be to gate the nCE signal and turn off the gate below 4.62V.  There's plenty of circuit possibilities to do that, but it's more components than a simple drop-in.

It may work for the majority of other people because of differences in the +5 off ramp and how various gates handle under-voltage (non-operating) conditions.  It's possible they're also experiencing writes during power down, but by chance the writes aren't to any of the addresses in the cal data.  The majority of the FRAM is used as system RAM which is set before it's used by the firmware, so they would never know.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: cheeseit on December 03, 2018, 08:23:44 pm
Maybe, or not a reliable drop-in in a 2445B, right? Are the 2445B/2465B similar in the relevant hardware and code (paths) that this goes for both? Perhaps one or more 2465B owners should take some measurements to determine the behavior upon power down and compare. I have a working 2465B with FRAM but no time for it at the moment. I haven't seen this problem mentioned before so it's worth investigating.

Edit: congrats on the fix and nice work Miti!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on December 03, 2018, 08:25:29 pm
You're spot on MarkL. I also think that it depends on the content of that address, in my particular case 0x1F00. If that location happened to be 0x20 in my scope, I wouldn't have seen this issue until, eventually, I recalibrate the scope and if that location's content changes.

The voltage sense has the advantage of not needing any external connection to the FRAM module but I would prefer the reset line to block access to CE and WE when it is active.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on December 04, 2018, 03:48:03 pm
Maybe, or not a reliable drop-in in a 2445B, right?
I don't think so.  The basic problem is putting a FM16W08 in a circuit where the control inputs (nCE, nWE) are undefined during a power down because, in both scopes, the chips driving those inputs are way out of their operating range while the FM16W08 is still listening.

The chips driving on the 2445B are 74LS74 and PLDC20xx, and on the 2465B it's 74HCT74 and PLS153A.  So, that's different chips which could account for the different power down behavior.  There's also probably more revisions of the A5 cards floating around that may use other logic families and PLDs, adding to more behaviors.

But no matter if it works 99% of the time, it's still bad design to leave the power down behavior to chance when it's critical to data integrity.  Put another way, the FM16W08 datasheet is very specific about how to safely do power down, and the 2445B and 2465B circuits which were designed for the DS1225, do not adhere to that.

Quote
Are the 2445B/2465B similar in the relevant hardware and code (paths) that this goes for both?
I haven't looked at the NMI power down code.  But by the traces Miti obtained, the problem happens while nRESET is being asserted, so there's no code running at that time anyway.

Quote
Perhaps one or more 2465B owners should take some measurements to determine the behavior upon power down and compare. I have a working 2465B with FRAM but no time for it at the moment. I haven't seen this problem mentioned before so it's worth investigating.
I agree, it may be interesting to know exactly how bad it is.  I nominate AMR Labs if the lid is still off the 2465B.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: macboy on December 04, 2018, 05:52:22 pm
Some time ago I built this Avalanche Picosecond Pulse Generator:

https://entangledwaves.wordpress.com/2013/07/15/avalanche-pulse-generator/ (https://entangledwaves.wordpress.com/2013/07/15/avalanche-pulse-generator/)

BTW the specified now obsolete 2N2369 transistor is still available at Mouser in TO-18 metal case for about $2, although a usable alternative seems to be a common 2N3904, but the former has a more desirable breakdown characteristic. I did not need to build the DC-DC converter part for the 90V avalanche bias supply, but instead used my Heathkit IG-4505 Scope Calibrator as a power source with the DC output set to the 100V position.

There is also another very well known website on the same subject:
http://www.kerrywong.com/2013/05/18/avalanche-pulse-generator-build-using-2n3904/ (http://www.kerrywong.com/2013/05/18/avalanche-pulse-generator-build-using-2n3904/)

Wanted to share pictures of the pulse as shown on both my 2465B and the 2247A, and possibly hear opinions. Cursor time measurement are located between the 10% and 90% points of the rising edge. Thanks.

You can not measure rise time with an impulse. It can only be done with a step. The impulse can only show you the slew rate. The reason is simple: you never see the true "top" of the impulse before it begins decreasing in amplitude causing the scope response to follow. Therefore you can't set the 90% to anything meaningful. This is where the step is used; the top of the step eventually becomes clearly visible, so you can set the 90% mark against this 100% reference. Put another way, knowing that the trace is increasing is meaningless unless you know what point it is increasing toward.

My 2465A (350MHz) had a rise time to a very fast step (<50 ps rise time) of dead on 1.0 ns, and I had also measured the actual -3 dB point at about 375 MHz (using a leveled sine generator). It follows that a 400 MHz 2465B should be about 8.7 ns or so. The apparently significantly shorter response to your impulse generator is misleading and not accurate.

With that said, you can fairly easily convert an avalanche impulse generator to a step generator by substituting the capacitor for a short piece of 50 ohm coax, acting as a charge line. It needs only store a few ns of charge, so with 1 ns per 20 cm, you don't need much at all. (don't go too long, nor pulse too frequently as it stresses the transistor). A follow up Jim Williams app note builds upon his avalanche pulse (impulse) generator to make a step generator using coax as a charge line (AN94).
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: g4wyz6 on December 05, 2018, 04:35:31 pm
Hello

What is the model for your earom burner?

As an EBay search came up blank.

73's

Mike G4WYZ
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: guido on December 05, 2018, 09:53:29 pm

The only thing i ever found was here (diy): http://ic-prog.com/index1.htm (http://ic-prog.com/index1.htm). ER1400.
Never used it myself yet (have a 2465 with earom).
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on December 06, 2018, 01:16:22 am
Hello

What is the model for your earom burner?

As an EBay search came up blank.

73's

Mike G4WYZ

If this question is for me, the programmer that I have at work, and fully supports FM16W08 and many other FRAMs, is a Xeltek Superpro 5000.
The one that I have at home is TL866II Plus. This doesn't support parallel FRAM but if I select DS1225, it can program the majority of the FM16W08 except for few locations, one location being the first in the calibration constants area, 0x1E00. However, that location doesn't seem to trigger a TEST04 error, and the scope works well. There are few other locations that fail to program, but they are in the RAM area so it doesn't matter.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: DC1MC on December 09, 2018, 12:02:13 pm
So I've got this sad 2465 S/N B020171, in a relatively advanced state of decomposition  >:D, with the following issues:

What does look a bit OK:
 - Inside is very clean, I was surprised.
 - The tube si bright with no burn marks, the HV part (focus and stuff) seem to ork perfectly.
 - The channel 1 and 4 react to inputs.
 - The A1 board with U800 was definitely never unscrewed, just someone tried to put extra solder on U800 pins or it even be originally so. It does have a strange bodge wire (pictures at request ) but this seem to be an original intervention.
 - Having a brain fart I didn't measure the PS values before producing a bunch of parts and boards  |O, but the caps looks very good.
 - The ventilator is OK and not very noisy

Now after I look on the official Tektronix list of differences:
There were a multitude of changes between the original 2465 and the 2465B.
Changes between the 2465 to 2465A:
Auto Setup.
Save and Recall Setups.
Write Protection for Saved and Sequenced Setups.
Cursor Measurements on Delayed-sweep displays.
Elapsed-time record embedded in firmware.
Increase in bandwidth from 300 MHz to 400 MHz (350 MHz in 2465A).
2 mV/div Vertical sensitivity to probe tip at full bandwidth.
Rise time improvement from 1.17 ns to 1 ns.
Two independent B triggers for single- or Dual-channel dual-delay measurements (with CTT Option).
Changes between the 2465A to 2465B:
Standard probes changed from P6136 to P6137.
Rise time improvement from 1 ns to .875 ns.
Parametric Measurements: An additional button labeled "MEASUREMENT" was added to the front panel. By pushing "MEASUREMENT" and one additional button mapped with numbers around the vertical mode buttons, you can automatically measure several commonly used parameters:
1. Frequency
2. Pulse Width
3. Rise Time
4. Fall Time
5. Time Interval A to B
6. Voltage


 My big question is:

Is it worth trying to repair or should I split it for parts, anyone considers something of it worthy ?

And if I'm going on the repair paths, where should I start, the logic board seem to not be OK, besides the PS voltages what could go wrong to paralyze it completely, I've heard about different blinking codes, but this one stays with all leds on, in some kind of faint brightness ?

 Any words of wisdom and advice are welcome, also encouragements, or the poor old mummified 2465 will have a horrible fate  ;) !!!

 Cheers,
 DC1MC
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on December 09, 2018, 12:19:10 pm
Start with the basics. Go back and measure the supply voltages at J119 on the main board. You may get lucky and find one or two not in spec.

You can't compare the basics of a 2465 vs a 2465A. They are almost like 2 different animals especially with respect to the A5 board. So it's imperative that you have service manuals for the 2465. I have a copy if you need it. My e-mail is in my profile.

If it appears that U800 as been monkey'ed around with chances are it's probably bad. Finding one can be a challenge and expensive unless you buy a parts unit.

I have 2 - 2465's. I've never seen the need to replace the caps on the A5 board. But I DID recap both the Inverter and Regulator boards. If you get past your boot and horizontal issues I recommend performing the recap.

Check the supply voltages at J119 then report back.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Satbeginner on December 09, 2018, 01:31:05 pm
I own several, a 2465, 2465A ,2* 2465B and a 2465ADM , in my book they are always worthwhile repairing!

I agree, start at the PS voltages.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: DC1MC on December 09, 2018, 02:41:24 pm
OK then, I'll do the following:
- Finish recapping the A5/PS and put it to spec (the PS, I have no idea how to debug the A5 if it's not a power problem).
- Remove the A1 mainboard (looks a bit like a pain), recap it and remove U800 and replace it with a nice Augat socket.

Hopefully put all back together and come back here for ideas on how to revitalize the U800, I'll go medieval on it :)) and press it nicely in between 2 plates of metal and cook it at 240C for half an hour or something.
Probably the rebonding technique used but that famous Japanese company was using some specific wavelength IR where the package it's transparent but it's absorbed by the chip and bounding wires, who knows.
If the logic board is gone, then I'm out of ideas, but please confirm it for me: if the U800 it's dead this should not deactivate the panel controls ?

 Cheers,
 DC1MC

P.S: If someone could share a recap BOM with suitable capacitor IDs for Mouser or DIgikey I'll be grateful.

@med6753 PM sent with my e-mail address for the Service Manual
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on December 09, 2018, 02:54:56 pm
I would not do anything with U800 until you get a complete boot. I have a suspicion (unconfirmed) that you won't get any horizontal until it finishes booting, regardless if any trouble codes show up or not.

I got your PM and I'll send you the 2465 Service Manual. In Section 9 are the schematics and it also has a special section outlining the power distribution. I would check and make sure you have correct voltages on the A5 board and the display board. Since there is apparent evidence of someone being in there it's possible that a ribbon cable might be misplugged.

I have attached a file outlining the replacement PSU capacitor part numbers for Mouser and Newark.

Edit...also, if you go back in this thread I have a full pictorial and procedure for recapping the PSU.
 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: DC1MC on December 09, 2018, 04:10:33 pm
They raped the Display Reading board  |O :scared:, look at the pictures, they tried to change the EEPROM and the other chip (SRAM ?!?!)  or just, I really don't know WTF they did there, maybe replaced some socket or such, I'm looking at the EEPROM and on one of the legs it's the metalization of the hole, the little copper cylinder was peeled off and raised on the pin :rant: and they put the device back and flood it with solder.
This I really don't understand, the people working with this scopes should have been educated or at least trained, not blabering cretins and flipping morons :'(
Look at the pictures, this board, I really have no idea on what to do with it, it is available for ca. 50EUR from the Greek ebay seller, but this how the whole device costed and there's no guarantee that will help.
I guess there's no content of those memories somewhere, the rest of the surrounding chips seem to be obtainable at a first look ?

 Depressed,
 DC1MC
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on December 09, 2018, 04:11:26 pm
OK then, I'll do the following:
- Finish recapping the A5/PS and put it to spec (the PS, I have no idea how to debug the A5 if it's not a power problem).
- Remove the A1 mainboard (looks a bit like a pain), recap it and remove U800 and replace it with a nice Augat socket.
I would recommend not doing anything with the A1 board until you have the PS in spec.

And I know there are differing opinions on this, but if the PS is in spec I wouldn't do a re-cap or finish the re-capping on it either.  Because the scope doesn't work in the first place, re-capping only adds another variable to the troubleshooting mix.  Get it working first and then if you want to re-cap, go for it.

med6753 is right that you have to get it booting first.  By the look of the front panel, it doesn't look like it makes it through the boot.  Do any of the knobs, besides focus, do anything?  Those functions are controlled by the processor.

For the knob internal clip breakage, I've heard some people use a small dab of silicone adhesive to glue them back on.  The adhesion is weak and you can pull them back off again.  I like to use a small square of 3M #4926 VHB (very high bond) foam tape pushed into the knob.  It's very thin so it doesn't make the knob stick out, and you can pull it off again.  It's usually good for a few cycles of on/off and it's not as messy as the silicone

One trick to get the knobs off without breaking them is to heat them gently before pulling on them.

And I would put in another vote of encouragement to fix it!  There's always something to be learned in the process.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on December 09, 2018, 04:20:24 pm
That's a terrible repair job on the readout board, but at this point there's no information that says it's not working.  I wouldn't jump to buying a replacement.

Hold your nose and put it back in, and finish the power supply checks.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on December 09, 2018, 05:01:35 pm
MC,

As everyone said, take a deep breath, put everything back together as it was, power it on, and check the supply voltages in J119 using multimeter and scope.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on December 09, 2018, 11:18:44 pm
I've tested the -3dB bandwidth of my Tek 2445B... and all the others that I have... using a Marconi 2025 signal generator that goes from 9KHz to 2.51GHz and is pretty leveled and here are the results.

Scope                                      -3dB BW        Max reasonably visible freq.
Tek 2445B                               215 MHz         400 MHz
Tek TDS210                             85 MHz           250 MHz (1 or 2 channels)
Rigol DS1054 (not hacked)        98 MHz          400 MHz 1 channel, 200 MHz 2 channels
Hitachi V-1585                         100 MHz         150 MHz

I used a 50 Ohm cable that I thought is pretty good quality, the best I have anyway, with T adapter and 50 Ohm terminator at the scope side, except for the 2445B that has 50 Ohm input. I should have tested the cable's gain before the experiment. Anyway, I tested it after the fact and it dips about 1dB towards 400MHz so the real bandwidth is even better than what I've got.
I started with 1MHz/1Vpp and I increased the frequency until the Vpp dropped to about 0.708Vpp.
The big surprise is Hitachi, I expected a bit more overhead.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: DC1MC on December 11, 2018, 09:31:13 pm
Just an update on my sad little 2465, I have clenched my teeth and, as recommended, I've installed the PS back (provisorisch, there are some RIFA 2,2nF and 0,1uF HV caps with this transparent case that'll HAVE to go, they show fine cracks already) and I've measured the voltages on J119, of course, no luck, the voltages are perfect, both in value and in noise ;D.
Than I've changed focus to the A5 board, and the CPU seem to be dead as piece of wood, it is EXACTLY the same type and with the same symptoms like this thread, that I've strongly recommend for anyone interested in repairing an A5 board to read:

https://www.eevblog.com/forum/repair/tektronix-2445-bad-microprocessor-s68a08/ (https://www.eevblog.com/forum/repair/tektronix-2445-bad-microprocessor-s68a08/)


The same crappy S68A08P CPU with creeping corrosion on the pins, this time fully dead (the clock it's perfect, reset, halt and int signals are in 1), without any significant bus activity.
I've ordered some 68B02 originals form evilbay seller tv-sat, from Poland, it really pissed me off that nobody offers them in Germany, with this whole Christmas kerfuffle it will take AGES to reach me  >:(.
If somebody has one to sell or lend in Germany and can put it quickly in an envelope I'll be very grateful, also if someone wants one quick, I've got 3, to have a reserve, but I can offer 2 of them at cost to recover my shipping costs from Poland, I know what it means to need a part and not have it, now I have to stay with the table occupied for another 10 days or something.

So I'll let you know what will happen when I'll change the CPU, maybe Santa will give me a nice present if the U800 it's not gone  ;D.

Also thanks for encouragement and the BOM for PS rejuvenation.

 Cheers,
 DC1MC


Title: Re: Tektronix 2465B oscilloscope teardown
Post by: woodchips on December 14, 2018, 12:49:51 pm
Just read through this whole thread, taken over a week. My thanks to all that have spent hours of time working on their scopes, posting, swearing and celebrating.

Why? Just bought a couple of 2465 scopes from an auction.

A 2465B s/n 134xxx for about £140.
A 2465 s/n 104xxx for about £220.

These join a 2445 (s/n 107xxx) and 2445A (s/n 112xxx) I already have.

Both the 2445's have problems, one has smoking mains caps, the other a failed Y amplifier, only get deflection downwards.

Both the 2465's worked, one still does, the other started smoking, mains caps again.

From previous battles with a 2440 when I replaced the CRT, I am not overly keen on taking these to pieces. I did take the cover off the smoking 2465 and unscrewed the top screen, then it got caught up in the option 5 PCB and lots of leads from the character generator PCB. Put it all back together.

I have a number of parts mule mainboards etc, missing some chips, got others, but no useful label saying why it was turned into a parts mule. Is the only sensible way of checking the Y amplifier by substitution?

After the two 2445's died I went back to my 7000 series scopes, but they don't really fit on the shelf over the workbench so neatly. Got a 2245 there at the moment, works fine, fast enough, perhaps the 24x5's will go back on the one day pile.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on December 17, 2018, 04:58:23 pm
Adding this link here for reference in case some one else has same/similar issues...

https://www.eevblog.com/forum/repair/tektronix-2465a-troubleshooting/ (https://www.eevblog.com/forum/repair/tektronix-2465a-troubleshooting/)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: DC1MC on December 22, 2018, 08:35:19 pm
^-^ ^-^ ^-^ IT'S ALIVE !!! 8) 8) 8)

Hello everybody, finally my replacement MC6802 arrived from Poland (3 more available at cost in DE if anybody interested !!!) along with two 100ohm Isabellenhütte Manganin resistors, for no others reason that they were looking cool and will become  part of my calibration set of resistors (also dirt cheap).

The seller is: https://www.ebay.de/usr/tvsat_electronic (https://www.ebay.de/usr/tvsat_electronic) and I can only highly recommend him, as a customer I was always satisfied.

The replacement CPUs are original, but that means the pins were having this strange whitish oxidation/patina, nothing even remotely like the abject corrosion of the previous dead CPU, and the package was looks nicely closed and tight. A bit of ultra-fine sandpaper took care of it, just in case.
I plugged it in the A5 board socket and somehow victory, the board booted, the relays clacked, but there was no horizontal sweep   :palm:, oh well, I thought, here goes U800 and starts the hassle to remove it...
But then an old man dressed in red with a white beard stopped to my window and said "Ho, ho, ho, check again the voltages !!!", considering that he always brought me some nice gifts I've mumbled "But I did this already..." but did checked the voltages on J119, and then phuck, the high voltages were gone !!!  :scared:, what in the hell had happened now, check the PS, OK, check the J119, nothing, what the frak  :-BROKE, all other voltages were OK  :-// ?!?!?

So I got a look at the two cables that transport the power to the mainboard, and one of the plugs that goes to the mainboard was a bit crooked, pulled them out and cleaned the connectors with this occasion (planned to do it anyway at the final assembly) put them back and power on !!!
And amazing, everything worked OK from the start, I've put the buttons back for level and time base and even did run the auto-testing (I think I did managed to press and hold the right buttons ?!?), it showed the results like in the first picture, and there also some other pictures for you to observe if I have something else to do on it that must be done.
Now I have to put the A5 capacitors back (all the tests in the picture were run without the 3 elcos of the A5 board), eventually change the RIFA almost cracked caps on the PS, and then what, should I fully recap the PS and mainboard, should I just be happy that it works like a charm so far (there seem to not be too much noise on the highest sensitivity setting and the triggering seem to be stable), also should I attempt a calibration, barely I should have what is necessary for it ?
Also the U800 DO gets hot, should I put for peace of mind some radiator on it ? Please advise, or the lucky X-mas scope will be closed and it will take a place on the bench together with the AGILENT and Rigol.

Many thanks one more time for your encouragement and advice  :-+ :-+ :-+  :clap: :clap: :clap:

 Cheers,
 DC1MC

P.S> I faintly hear in dark "Ho, ho, ho, told you so..."

 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on December 22, 2018, 09:17:42 pm
Always good to see a successful repair. Congrats!  :-+ :-+

U800: Leave it alone. It WILL get warm when you have the scope outside the case and you have an active sweep. Once back in the case as long as the fan is in good shape the airflow will keep it within acceptable temperatures. 

The Regulator/Inverter boards: save the recap for another day as long as you are confident there are no leaking caps.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: DC1MC on December 22, 2018, 09:20:06 pm
Always good to see a successful repair. Congrats!  :-+ :-+

U800: Leave it alone. It WILL get warm when you have the scope outside the case and you have an active sweep. Once back in the case as long as the fan is in good shape the airflow will keep it within acceptable temperatures.

What about the recapping and calibration ?!?!?

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on December 22, 2018, 09:23:51 pm
Always good to see a successful repair. Congrats!  :-+ :-+

U800: Leave it alone. It WILL get warm when you have the scope outside the case and you have an active sweep. Once back in the case as long as the fan is in good shape the airflow will keep it within acceptable temperatures.

What about the recapping and calibration ?!?!?

I modified my answer for the recap. Calibration? Check some of the important parameters such as timebase accuracy, vertical height, etc. If they are in spec I wouldn't bother doing a recal.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on December 23, 2018, 01:46:53 am
I recaped my 2445B ... power supply, A5, A1, HV, everything. But it's just me, I'm a perfectionist.  :blah:
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on December 30, 2018, 03:31:57 pm

Also the U800 DO gets hot, should I put for peace of mind some radiator on it ? Please advise, or the lucky X-mas scope will be closed and it will take a place on the bench together with the AGILENT and Rigol.


I concur with med6753 on this: leave it alone. The consensus is Tektronix knew what they where doing, so no need for any meddling with U800. So far the U800 in your scope has been doing its thing for a very long time, and has survived fine.

Also, notice that while the scope is idle, U800 may only get mildly warm to the touch, which some people take as a relief but it really doesn't mean anything. Under normal operating condition the IC mostly only gets hot under heavy load while displaying high repetition, or high frequency waveforms, etc, but proper airflow as-is with the cover on the scope, and a properly functioning fan, should provide ample cooling to keep the IC temperature within spec.

On the ever popular issue of trying to make improvements on the U800 heat dissipation department, I wanted to share this TekIO group message bellow from a very experienced member I think is the best explanation that so far I have found:

===============================================
START https://groups.io/g/TekScopes/message/152372
===============================================

Everybody please listen!

U800 is not heat sensitive, and I have found that many of
the "tricks" folks have gotten from the internet on how
to "protect" their U800 chip actually harm the chip due
to over-tightening the nuts on the studs that support the
chip. I have also found that glued/taped on heat sinks
have raised the temperature of the chip by impeding the air
circulation around the chip.

I have also found glued/taped heat sinks floating freely
inside of scopes that have been sent to me for service!

Tektronix botched the mounting of U800. That, in my
experience, is why they fail.

U800 was designed to have its pins pass through a 2-3mm
thick aluminum heat sink mounted underneath the chip.
The belly of the chip is metal to engage this heat sink.

DIP style IC's have pins that are made with a wide part to
prevent the belly of the IC from bottoming onto the PCB.
This allows air circulation under the chip. U800 is no
exception.

The engineer that designed U800 was excessively cautious,
and overestimated the heat that would be generated by his
new IC. When it came back from fab, he found that it did
*NOT* need any heat sinking to meet the full +50C design
temperature rating of the brand new 2465 scopes. So, the
heat sink was left off of the board.

(Thought experiment: when was the last time you operated
your 2465 at 50C?)

The problem is the designer needed -5V to bias U800's
substrate, and he used the metal heat sink frame and tab
to make that connection.

He found that U800's stud could not clamp tightly to
the PCB (REMEMBER: shoulders on pins...) without putting
excessive pressure on U800's pins, so he put a pair of star
lock washers onto the mounting studs before mounting U800.

The washers served to make the electrical connection, and
to provide the needed spacing to protect the chip....

He hoped.

Everything is fine if nobody ever, ever, over-tightens the
nuts that hold the U800 to the board. If they do, the
extra pressure will collapse the star lock washers and
embed them into the PCB and the bottom of one end of the
epoxy body. When this happens, the lead frame of U800 will
crack at some of the pins

If you come along later, having listened to all the bloviation
about U800 fixes, and happen to tighten up the nuts a little
bit more: crack! You will have damaged the chip while trying
to protect the chip.
===============================================
END https://groups.io/g/TekScopes/message/152372
===============================================

So if at this point you still want to put some form of additional heat dissipation on U800, make sure to verify that heat is actually being conducted away from the IC body into the added heatsink and you have not inadvertently created a heat barrier instead. And in the case of clipped-on or epoxied-on heatsinks, make sure that it can definitively not at some point fall off, and land right into a live circuit and possibly destroy other "unobtainium" stuff. And above all, do not to over tighten the mounting nuts. Or even better, try to avoid having to mess with the U800 mounting nuts altogether.

Happy New Year to all!

EDIT: small typo corrections.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on December 30, 2018, 05:49:56 pm
Yep, the design is clearly flawed, badly.

Took a close up photos on the board without the chip and the chip's bottom view -> Post #933 HERE (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1214848/#msg1214848)

A quick sketch on the situation ... a picture speaks thousand words.

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=608827;image)

The ideal path for dissipating the IC's heat still thru a metal plate placed at the chip bottom though.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: PaulAm on December 30, 2018, 07:43:11 pm
Just a headsup for those thinking about a recap.

The 330uf/250V replacements for C1021 and C1022 are pretty scarce at the moment and I couldn't find anyone with current stock for Nichicon UPW caps.  Mouser has them on order with 2 delivery dates and, as of today, there were 10 uncommitted for the mid-January delivery.  Once those are gone the next scheduled delivery is in May.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on December 30, 2018, 09:58:30 pm
Just a headsup for those thinking about a recap.

The 330uf/250V replacements for C1021 and C1022 are pretty scarce at the moment and I couldn't find anyone with current stock for Nichicon UPW caps.  Mouser has them on order with 2 delivery dates and, as of today, there were 10 uncommitted for the mid-January delivery.  Once those are gone the next scheduled delivery is in May.

And I have also found that C1021 and C1022 to be in excellent condition on my 2nd 2465 and I did NOT replace them. So check them for ESR and value and you may find them to be OK.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on December 30, 2018, 10:36:37 pm
Yep, the design is clearly flawed, badly.

Yes, undoubtedly not ideal design, could have been somewhat better -mechanically- speaking, but given limitation at the time and clearly according to Tek engineers that hands on designed the chip, still perfectly OK to leave it alone and it will (has for many years) done just fine. So with all due respect the idea of any thermal concerns are clearly a non-issue in real world terms. Something that keeps on going and going for 30+ years will probably be perfectly alright to be left exactly the way it is and will keep on going and going. Just my 2 cents.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on December 31, 2018, 01:30:38 am
And to support the "leave U800 alone" idea, in the adjustment section of the service manual, they mention that you have to remove the cabinet in order to do the adjustments, you have to warm it up for 20 min, but it doesn't say anywhere to do it quick or you will blow up the U800.
The way I read this is, you can operate it without cabinet for quite long periods of time.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: LapTop006 on December 31, 2018, 02:03:18 pm
(Thought experiment: when was the last time you operated
your 2465 at 50C?)

Other than us Australian's without aircon.  :P
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on December 31, 2018, 04:08:13 pm
What I do not understand is why they did not put a thermally conductive spacer under U800 before soldering it down.  Was it too much trouble on an otherwise automated manufacturing processed?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on December 31, 2018, 04:13:26 pm
What I do not understand is why they did not put a thermally conductive spacer under U800 before soldering it down.  Was it too much trouble on an otherwise automated manufacturing processed?

Back at those era, did non metallic thermal pad was still not very good ?  :-//

Also the gap is quite large.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on December 31, 2018, 05:46:10 pm
What I do not understand is why they did not put a thermally conductive spacer under U800 before soldering it down.  Was it too much trouble on an otherwise automated manufacturing processed?

From the TekIO group message I posted a few posts ago should clarify your question:

===========================================================
START PARTIAL QUOTE FROM https://groups.io/g/TekScopes/message/152372
===========================================================

...

"The engineer that designed U800 was excessively cautious,
and overestimated the heat that would be generated by his
new IC. When it came back from fab, he found that it did
*NOT* need any heat sinking to meet the full +50C design
temperature rating of the brand new 2465 scopes. So, the
heat sink was left off of the board."

...

===========================================================
END PARTIAL QUOTE FROM https://groups.io/g/TekScopes/message/152372
===========================================================
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on December 31, 2018, 05:50:29 pm
But he underestimated the strain placed on the package by the mounting solution he ended up using.

What I do not understand is why they did not put a thermally conductive spacer under U800 before soldering it down.  Was it too much trouble on an otherwise automated manufacturing processed?

Back at those era, did non metallic thermal pad was still not very good ?  :-//

Also the gap is quite large.

Alumina and Kapton were readily available.  I have alumina spacers which are older than the 2465 series.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on December 31, 2018, 05:55:21 pm
Related to the U800 discussion. I conducted some experiments with the 24XX cooling system with these results and observations...

https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1215559/#msg1215559 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1215559/#msg1215559)

And....ALL 24XX scopes should have the black heatsink bonded to the front bottom of the case. If it's missing you could have issues.   
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on December 31, 2018, 05:57:21 pm
(Thought experiment: when was the last time you operated
your 2465 at 50C?)

Other than us Australian's without aircon.  :P

It is NOT very fun working on electronics (or electrical) stuff with sweat dripping down your arms and everywhere else into your tools and whatever you are working on. I know very well from working on boat electronics in the Caribbean when in the summer sometimes the inside temp in the cheapo customer sailing boats temps rise to the 35-40 deg C range with +90% humidity, specially if in a yard and out of the water. If I don't happen to have AC power to run my work fan the sweat taps really open big time!

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on December 31, 2018, 05:58:30 pm
But he underestimated the strain placed on the package by the mounting solution he ended up using.

+1 , thats the main problem that I see.

Even the two nuts were mildly fastened enough, there is no guarantee those two star washers will be the exact height to fill the gap underneath the chip, without stressing the embedded metal tab inside the chip, which is also will create the another strain vs the soldered pins.

Wonder if the stressed metal tab will affect the attached silicon die inside the chip, as the whole chip body + washers + nuts + soldered pins went thru so many thermal cycles and thermal expansion and contraction physically.  :-//
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on December 31, 2018, 06:05:51 pm
Related to the U800 discussion. I conducted some experiments with the 24XX cooling system with these results and observations...

https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1215559/#msg1215559 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1215559/#msg1215559)

And....ALL 24XX scopes should have the black heatsink bonded to the front bottom of the case. If it's missing you could have issues.

Hi med,

Do you by any chance have pics of that heatsink you mention? Did not see any pics of it on your post, not 100% sure where to exactly look for so as usual always would be nice to have one or two pics if you happen to have them. Thanks!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on December 31, 2018, 06:17:35 pm
But he underestimated the strain placed on the package by the mounting solution he ended up using.

+1 , thats the main problem that I see.

Even the two nuts were mildly fastened enough, there is no guarantee those two star washers will be the exact height to fill the gap underneath the chip, without stressing the embedded metal tab inside the chip, which is also will create the another strain vs the soldered pins.

Wonder if the stressed metal tab will affect the attached silicon die inside the chip, as the whole chip body + washers + nuts + soldered pins went thru so many thermal cycles and thermal expansion and contraction physically.  :-//

Also definitively a valid but again with all due respect <secondary> point unless one plans to mess with the mounting studs/nuts of U800. I thought we where mainly discussing the temperature issue of a <undisturbed> U800, which is what user DC1MC was initially inquiring about.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on December 31, 2018, 06:22:46 pm
Wonder if the stressed metal tab will affect the attached silicon die inside the chip, as the whole chip body + washers + nuts + soldered pins went thru so many thermal cycles and thermal expansion and contraction physically.  :-//

Strain in the lead frame absolutely affects reliability of the die attachment and it gets worse at higher temperatures and with more temperature cycles.  This is why the correct mounting of power packages is so important.  Motorola has a great application note (https://www.nxp.com/files/rf_if/doc/app_note/AN1040.pdf) discussing the issue.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on December 31, 2018, 06:26:49 pm
Also definitively a valid but again with all due respect <secondary> point unless one plans to mess with the mounting studs/nuts of U800. I thought we where mainly discussing the temperature issue of a <undisturbed> U800, which is what user DC1MC was initially inquiring about.

Ok, fair enough, thanks for reminding, its just this issue pop out again in my head when every time this U800 discussion surfaced.

Also the two nuts of mine are gone, not used anymore when I realized while ago, the U800's of course.  :P
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on December 31, 2018, 06:29:38 pm
Wonder if the stressed metal tab will affect the attached silicon die inside the chip, as the whole chip body + washers + nuts + soldered pins went thru so many thermal cycles and thermal expansion and contraction physically.  :-//

Strain in the lead frame absolutely affects reliability of the die attachment and it gets worse at higher temperatures and with more temperature cycles.  This is why the correct mounting of power packages is so important.  Motorola has a great application note (https://www.nxp.com/files/rf_if/doc/app_note/AN1040.pdf) discussing the issue.

Hi David, but just to be clear do you imply that there might be some mechanical strain already in place from the initial install/mounting of the U800 chip at the factory?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on December 31, 2018, 06:30:36 pm
Wonder if the stressed metal tab will affect the attached silicon die inside the chip, as the whole chip body + washers + nuts + soldered pins went thru so many thermal cycles and thermal expansion and contraction physically.  :-//

Strain in the metal tab absolutely affects reliability of the die attachment and it gets worse at higher temperatures and with more temperature cycles.  This is why the correct mounting of power packages is so important.

Wonder this is related with the service of fixing the U800 chip provided years ago by 3rd party, which they sent the chip to a special shop in Japan to be re-heated if I'm not mistaken, and they claimed this fixed the common problem that was affecting this particular chip.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on December 31, 2018, 06:39:57 pm
Also definitively a valid but again with all due respect <secondary> point unless one plans to mess with the mounting studs/nuts of U800. I thought we where mainly discussing the temperature issue of a <undisturbed> U800, which is what user DC1MC was initially inquiring about.

Ok, fair enough, thanks for reminding, its just this issue pop out again in my head when every time this U800 discussion surfaced.

Also the two nuts of mine are gone, not used anymore when I realized while ago, the U800's of course.  :P

All useful input in my view should always be more than welcomed, and definitively coming from this thread's originator. But I was just thinking in terms of keeping a proper sequence of QA's. Again, all relevant information to our 2465 scopes should always be posted specially taken into account the highly regarded reference status that this thread has achieved in the 2465 realm.

HAPPY -ALMOST- NEW YEAR!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on December 31, 2018, 08:24:02 pm
Related to the U800 discussion. I conducted some experiments with the 24XX cooling system with these results and observations...

https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1215559/#msg1215559 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1215559/#msg1215559)

And....ALL 24XX scopes should have the black heatsink bonded to the front bottom of the case. If it's missing you could have issues.

Hi med,

Do you by any chance have pics of that heatsink you mention? Did not see any pics of it on your post, not 100% sure where to exactly look for so as usual always would be nice to have one or two pics if you happen to have them. Thanks!

Here it is. But upon closer examination it's made of plastic. So now I'm not sure what it's intended function is.  :-// Both my 2465's have one.
(https://imagizer.imageshack.com/v2/xq90/923/0O0KLB.jpg) (https://imageshack.com/i/pn0O0KLBj)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on December 31, 2018, 08:53:12 pm
Never seen this on another 2465/x, and definitively not on my "B". Anyone else have input on this? Looks a bit weird being on the outside of the case, my two cents.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on December 31, 2018, 09:41:26 pm
Both my 2465s have it, my 2445B does not.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Satbeginner on December 31, 2018, 09:48:26 pm
I have an 2465, a 2465A, a 2465ADM and two 2465B's.
None of them have such a thing....
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on December 31, 2018, 09:55:10 pm
If this "heatsink" is made out of plastic, can help but feel this is not something that came from the factory, specially being on the outside of the case seems outrageous for tek ------------------------------ ????

EDIT: I am really enjoying this fast pace posting back and forth!!


Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on December 31, 2018, 10:21:08 pm
I propose that the piece is there to insure airflow to the vents just behind it when the scope is down on it's feet. That's where U800 is located. That's the only thing that makes sense to me.

It's definitely a factory piece and I also suspect it's easily damaged and knocked off.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on January 01, 2019, 03:32:33 am
Hi David, but just to be clear do you imply that there might be some mechanical strain already in place from the initial install/mounting of the U800 chip at the factory?

I am sure of it and that it was made worse by the high operating temperature and thermal cycling.  Those ICs (aren't they actually hybrids?) had poor reliability even before people started messing with them.  Maybe things could have been improved with a different die attachment material.

DIP package lead frames are pretty bad about this because all of the short pin connections leave very little mechanical compliance.  Some power DIPs had wide lead spacing or were used with a socket but more commonly the heat sink tabs were attached to the heat sink and not the board.

Wonder this is related with the service of fixing the U800 chip provided years ago by 3rd party, which they sent the chip to a special shop in Japan to be re-heated if I'm not mistaken, and they claimed this fixed the common problem that was affecting this particular chip.

Reheating melted the die attachment material reattaching the chip to the lead frame.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on January 01, 2019, 10:14:53 am
I propose that the piece is there to insure airflow to the vents just behind it when the scope is down on it's feet. That's where U800 is located. That's the only thing that makes sense to me.

I've wondered that, and am partially convinced.

It isn't beneficial on a flat surface, but if there is paper underneath, it may ensure that the paper is not sucked upwards to block the vent. Another failure mode might be perching the scope on top of something that is narrower than the distance between the feet.

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=610102)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on January 02, 2019, 07:13:30 am
Wonder this is related with the service of fixing the U800 chip provided years ago by 3rd party, which they sent the chip to a special shop in Japan to be re-heated if I'm not mistaken, and they claimed this fixed the common problem that was affecting this particular chip.

Reheating melted the die attachment material reattaching the chip to the lead frame.

If that is the case, looking at the way U800 mounted here below at the IC front metal tab that is secured by a nut + two washers.

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=16705;image)(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=317598;image)

If thermal expansions or contractions happened at the two star washers and the fastened nut, and/or also the embedded bolt at the pcb. I guess this will stress out the whole IC's bottom metal tab, against the whole chip black plastic body, that is being held so firmly by the 24 soldered pins.

Not sure if this is the right terms, its like the metal tab is being peel off downward from the body.

Again, I'm just guessing and imagining this, as it may not be a problem at all.  :-//

Btw, the two nuts that are holding the U800 basically have minimal purpose as heat dissipation is not optimal thru the bolt, its not like the chip is going to fall down and detached from the PCB as its firmly held by 24 pins soldered at the PCB.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mnementh on January 06, 2019, 02:25:11 am
(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=42868)    (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=317592;image)

Latest from Tek on this issue (still ages ago, of course) is that U800 is not supposed to have two nuts on it; there was a TSB on it I remember from when I first started messing with them decades ago. After a certain Ser# they shipped with only one nut on the metal tab, and earlier models sent in for service would have the one not on the metal tab removed. They were also supposed to have the one nut on the tab retorqued to a lower tension in an effort to reduce this failure mode.

The above image is of a preventive maintenance mod based on that TSB (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/25/), in which the IC is desoldered, socketed, and then reinstalled with a small heat sink/load spreader on the tab. IIRC, that is one of a number of mods performed by well-known eBay vendor 2465b (https://www.ebay.com/usr/2465b?_trksid=p2047675.l2559) on all his "Refurbished/Guaranteed" 24xx scopes.

I'm not exactly certain I believe that is a better approach than simply ensuring good thermal contact with the large copper fill directly under the IC, though all evidence I've seen on the subject indicates Tek deliberately placed these two star washers under the chip which clearly defeats any such heat sinking to that fill, and never reversed that design. My own gut reaction is that if I ever have reason to attempt such a service, I'll put some silicone thermal pads underneath the IC and shim the tab to eliminate any preload stress.

FWIW, none of the 3 2465s I own have that ribbed plastic/rubber/vinyl what-the-fuggever-it-is on the bottom front, though the suggestion that it serves to prevent occlusion of that most important vent over the U800 certainly sounds plausible. Possibly some vendor-added spacer for a 2465 that was assembled into/made part of a larger, special-purpose test gear?

mnem
*tzzt*
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on January 06, 2019, 08:02:56 am
If there was a TSB for U800 and it's mounting it apparently wasn't known outside Tektronix. And as a side light how come no one, other than that one individual, produced one with that mod?

One of my 2465's was owned by IBM. IBM was very diligent about insuring their test equipment was up to snuff and had it's own instrument labs who's sole responsibility was repair/calibration. Only "tuff nuts" or unable to fix equipment was sent back to Tek which didn't happen very often. The U800 in this 2465 is untouched and the scope would have been back to the instrument lab on a yearly basis for a minimum a calibration. So I'm questioning the validity of this "TSB". IBM has bought literally thousands of instruments from Tek over the past 60 years so my thought in the interest of customer support this "TSB" would have been published and available.

And as another side light the last IBM internal instrument lab was disbanded about 2006 or so and all instrument repairs/calibrations are now contracted to outside cal labs.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on January 06, 2019, 09:56:59 am


FWIW, none of the 3 2465s I own have that ribbed plastic/rubber/vinyl what-the-fuggever-it-is on the bottom front, though the suggestion that it serves to prevent occlusion of that most important vent over the U800 certainly sounds plausible. Possibly some vendor-added spacer for a 2465 that was assembled into/made part of a larger, special-purpose test gear?

mnem
*tzzt*

I disagree. I think it's a factory piece for all of them. My 2465 DMS came from a small electronics device placement facility in Colorado. As mentioned before my other 2465 came from IBM in New York. Tggzz said he has at least 2 with the piece and he's in the UK. I suspect it's easily damaged or the adhesive gives way and it falls off and is not reinstalled.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mnementh on January 06, 2019, 04:17:53 pm
Hmmm... possibly a poorly documented/undocumented late-production revision then?

You'd think with a sample of 3, one of mine would have SOME evidence of that belonging there; at least some adhesive residue. In all honesty... an afterthought peel-n-stick bumper really doesn't feel like Tektronix to me.

mnem
 :popcorn:
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mnementh on January 06, 2019, 05:45:38 pm
If there was a TSB for U800 and it's mounting it apparently wasn't known outside Tektronix. And as a side light how come no one, other than that one individual, produced one with that mod?

One of my 2465's was owned by IBM. IBM was very diligent about insuring their test equipment was up to snuff and had it's own instrument labs who's sole responsibility was repair/calibration. Only "tuff nuts" or unable to fix equipment was sent back to Tek which didn't happen very often. The U800 in this 2465 is untouched and the scope would have been back to the instrument lab on a yearly basis for a minimum a calibration. So I'm questioning the validity of this "TSB". IBM has bought literally thousands of instruments from Tek over the past 60 years so my thought in the interest of customer support this "TSB" would have been published and available.

And as another side light the last IBM internal instrument lab was disbanded about 2006 or so and all instrument repairs/calibrations are now contracted to outside cal labs.

Sorry... "TSB" was the wrong term. I'll blame multiple-discipline terminology cross-contamination. ;)  I guess Tek would have called it a "Service procedure" or "Service revision" or something similar.

As I can confirm after just now leafing through EVERY PAGE of my March '85 Version 2465 Service Manual, while Tek provided mind-numbingly detailed documentation regarding the electronic engineering and theory of operation on their 'scopes, mechanical service procedures are glaringly short on detail if not completely absent, particularly where specific unique components are concerned. I would not be surprised that if these procedures were not released outside of their own shop; once upon a time service was as much or more of what Tek offered as the product itself, so such knowledge would be their stock-in-trade.

Short version: I recall a discussion in one of the 2465 threads; I thought it was here somewhere, but more likely on Anatek or alt.sci.repair:

A user posted complaint that he had sent his 'scope in to Tek for repair after a U800 failure, and when they returned it, it had only one nut on the IC. He was furious that Tek service had been so careless. Some discussion ensued, consensus was that Tek knew what they were doing and it was probably supposed to be that way. A week or so later, he posts a followup including quotes from an eMail from his tech at Tek, with reference to a Tek document number outlining the change to only one nut on the IC flange with reduced torque specification as a revision to the service procedure to prevent recurrence of the U800 failure.  In retrospect, it is possible this reference was ONLY for cases where U800 had failed, and they replaced it at Tek.

Of course at this point I can only offer my recollection; so this is all 3rd-party hearsay. I assumed this was common knowledge by now; not a point of contention.  :-//

My ex-NASA 2465 has only that one nut on U800, and I have no intention of replacing the other. My personal opinion is that handling the chip in any way is likelier to cause failure at this point than any reliability gain that might be come from re-mounting.

Cheers,

mnem
*De-Christmas-ifying*
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on January 06, 2019, 08:47:47 pm
I knew what you meant by "TSB". TSB = Service Bulletin.
 
Does your nut less U800 also have that heat sink and warning label?

I think the best advice we can give anyone concerning U800 is two fold....

1. Make sure the fan and cooling system is in good shape (Dust free, etc)

2. Leave U800 the hell alone unless you have an issue. It's been in there +30 years and worked fine, despite the funky engineering.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mnementh on January 06, 2019, 11:19:21 pm
"TSB" indicates it was something they would actively broadcast. I'm not sure I believe that was the case. So, still wrong term in this context.  :-[

No, as I said, that pic is of a mod done based on that "Service revision"; not of any 'scope I know was handled by Tek. I just didn't feel like digging mine out of storage, taking it apart, then putting it back together again for a pic.

And add another point; this was also part of the discussion I recalled that service revision from:

3. Don't run your 24xx for too long without the cover on. Without it in place, the fan doesn't pull any air across U800.

mnem
 :-BROKE
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: N3SWR on January 13, 2019, 11:27:54 pm
Gentlemen,

There's too many of you to list that have helped me get my 2465B back up and running again.   So a big thanks to the community and all other involved.

In summary, I went through the supply re-cap which actually was fun.  The A5 board - well not so fun, but a learning experience somewhat.  I've been around good commercial equipment
for most of my career and each manufacturer is different the way they explain things in their service manuals.  Keep that in mind for a moment.

So, having removed the old Dallas RAM and swapped in a new RAMTRON, all seemed fine for the most part.  I went through the DAC ref voltage saga where the 10K resistor was open
only to be left with a screen full of dots and crazy aberrations haunting me through the cal procedure.  I had to stop - nothing made sense on screen.
Swapping out the Z-axis hybrid was no help - I had a bunch to play with just to be sure it wasn't that hybrid, and it wasn't.  It ended up being the grid bias turned way up by some one before me.

So with the scope back up and running and looking good for a change I did a cal.  So here's my question...

When you're done with the cal and scope is powered on still, is THAT THE TIME to return the jumper back to the no cal state?  Or, do you turn the scope off after completely done, THEN return the jumper to the no cal position?

I did while the scope was on - only to be greeted with a Fail 04 test 10 failure after re-powering the scope.  In essence, there was a checksum error. 

After that, I reloaded another set of cal data onto the RAM (for testing) and didn't touch the jumper (it was in the no cal position).  The scope works fine now.

My problem is in understanding just what they mean in the manual - when to move that jumper specifically.

So can anyone spell it out in no uncertain terms so I don't have to revisit the checksum error once again.  That's a long procedure. only to loose the data in the end....

Thanks guys and keep up the great work you all are doing!!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on January 13, 2019, 11:54:01 pm
Power off, then move the jumper back to the "No Cal" position. Power up and you should be OK.  :-+
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: N3SWR on January 14, 2019, 12:45:13 am
I thought that was my error.  Sucks getting old...   :palm:    But at least we have cool equipment to keep our minds busy!

Thanks  :-+
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on January 19, 2019, 05:12:39 pm
I have a question about the coding rings on the Tek 24xx series. If you don't use probes with coding pin, your scale factor is wrong. How do you mitigate that? Do you just ignore it? I use a small interposer ring with a 10K 0402 resistor on the edge and a springy ring on top, but it is not always reliable.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on January 19, 2019, 06:02:38 pm
I have a question about the coding rings on the Tek 24xx series. If you don't use probes with coding pin, your scale factor is wrong. How do you mitigate that?

Mental arithmetic and knowing what I'm probing :)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on January 19, 2019, 08:35:38 pm
Mental arithmetic and knowing what I'm probing :)

Are you saying that you are an engineer and you're not lazy enough not to do mental arithmetic? Come on, you're bragging... ;)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mnementh on January 19, 2019, 09:46:42 pm
That's actually pretty clever.  :-+ If you substitute some GP spring contacts scavenged from an old PC motherboard or card edge connector, and solder them to the copper rings, you might be able to improve reliability.

mnem
There are 10 kinds of people in the world; those who don't understand binary, and those who get their heads bashed in with a chair for being insufferable about it.
Title: Tektronix 2465B CTT OPT 06 CT TEST 81 Fail 03 OUT OF LIMITS?
Post by: jonpaul on February 08, 2019, 03:02:46 pm
Hello all:  I am struggling with both models to do a CAL.

Result form normal 2465/7B A5 board problem:

Failed NVRAM Dallas Semi battery, replace with new part, program with default parameters, place new NVRAM on low profile socket.

And removed and replaced all SMD lytics that leaked on the boards, repaired damages.

NEW Issue on 2465B CTT :  CT TEST 81 Fail 03

Using  TEK cal procedure with  1V pk sw wave at 1.00 MHz, to CH 1,

I consistently get  FREQ OUT OF LIMITS message.

I verified the input signal is fine.

Is there an internal clock CAL step? I am just doing this part of the CAL not the entire procedure.

I have the CAL/NO CAL jumper  on A5 board in CAL position.


Any assistance is appreciated!

Many thanks

Jon PAUL

Title: Re: Tektronix 2465B CTT OPT 06 CT TEST 81 Fail 03 OUT OF LIMITS?
Post by: med6753 on February 08, 2019, 03:27:32 pm
Hello all:  I am struggling with both models to do a CAL.

Result form normal 2465/7B A5 board problem:

Failed NVRAM Dallas Semi battery, replace with new part, program with default parameters, place new NVRAM on low profile socket.

And removed and replaced all SMD lytics that leaked on the boards, repaired damages.

NEW Issue on 2465B CTT :  CT TEST 81 Fail 03

Using  TEK cal procedure with  1V pk sw wave at 1.00 MHz, to CH 1,

I consistently get  FREQ OUT OF LIMITS message.

I verified the input signal is fine.

Is there an internal clock CAL step? I am just doing this part of the CAL not the entire procedure.

I have the CAL/NO CAL jumper  on A5 board in CAL position.


Any assistance is appreciated!

Many thanks

Jon PAUL

I can help. I have calibrated the Counter successfully. First, the square wave MUST be 1MHz within 10Hz or so. Verify it with a frequency counter. 2nd, the signal source must have a rise time of at least 1 ns or less. If it's more it may not take. And 3rd...and really important....the square wave must be more or less equal crossing the center line or 0. If it's all negative going or all positive going it will not take the cal.

Hopefully this helps...it should. But if you still have issues post back. 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: jonpaul on February 08, 2019, 05:16:50 pm
Hello there:

WOW PERFECT, the instructions seem to just specify a 1 uS period and 500 nS 1V pk sq wave, used TM501 time mark gen >>trig pulse gen.

Forgot to center the crossing on middle div!

Also: I can not locate the SERV manual or Adjustment for 2465B CTT opt 06, only for 2465B, and 2465 CTT.

Does it exist? Any differences in the adj procedure? May have to do a full CAL anyway, but hope a partial on just CTT will get it running without the failure errors.

MANY THANKS AGAIN!

Jon Paul
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on February 08, 2019, 05:56:23 pm
I have a question about the coding rings on the Tek 24xx series. If you don't use probes with coding pin, your scale factor is wrong. How do you mitigate that? Do you just ignore it? I use a small interposer ring with a 10K 0402 resistor on the edge and a springy ring on top, but it is not always reliable.

Not ideal, but when in need to use a non-readout pin 10x probe just making a mental note to multiply the readout by a factor of 10 works for me. So basically 100mV/DIV really is 1V/DIV, and so on. After all its not like this is going to affect the calibration of the scope or anything similar. Just the On-screen V/DIV -scale readout- will be wrong. Problem is in the middle of a procedure while my brain is concentrating on something more important, or I get distracted, sometimes I do forget.

Not suggesting you did not know this already, but your question seems to point a bit in the direction that the scope always needs to be told when using a 10x probe in order to stay accurate, or perhaps I just misunderstood your question.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on February 08, 2019, 11:03:40 pm

Also: I can not locate the SERV manual or Adjustment for 2465B CTT opt 06, only for 2465B, and 2465 CTT.

Does it exist? Any differences in the adj procedure? May have to do a full CAL anyway, but hope a partial on just CTT will get it running without the failure errors.

MANY THANKS AGAIN!

Jon Paul

Couldn't tell you about the service manual for the 2565B. I have a 2465 and the procedure is covered under the 2465 Option 06 and 09 Service Manual. Now I would ASSUME that the Counter cal procedure is the same across the 2465, 2465A, and 2465B but you know what happens when you assume.   :palm:
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on February 08, 2019, 11:12:54 pm
Also, see this post within this thread.......

https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1937605/#msg1937605 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1937605/#msg1937605)

I had forgotten that I posted this.  :-DD
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on February 09, 2019, 02:19:21 am
I have a question about the coding rings on the Tek 24xx series. If you don't use probes with coding pin, your scale factor is wrong. How do you mitigate that? Do you just ignore it? I use a small interposer ring with a 10K 0402 resistor on the edge and a springy ring on top, but it is not always reliable.

Not ideal, but when in need to use a non-readout pin 10x probe just making a mental note to multiply the readout by a factor of 10 works for me. So basically 100mV/DIV really is 1V/DIV, and so on. After all its not like this is going to affect the calibration of the scope or anything similar. Just the On-screen V/DIV -scale readout- will be wrong. Problem is in the middle of a procedure while my brain is concentrating on something more important, or I get distracted, sometimes I do forget.

Not suggesting you did not know this already, but your question seems to point a bit in the direction that the scope always needs to be told when using a 10x probe in order to stay accurate, or perhaps I just misunderstood your question.

No, I'm not saying that the scope is not accurate, is just that the readout is wrong and is about not using a feature that is there just because they didn't add a simple feature to manually select the scale factor.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on February 09, 2019, 02:47:39 am
Agree, a manual override for the readout pin sensor would have been useful. Strange Tektronix never though one would use a conventional probe without that pin, even tough quite a bit of the Tek probes don't have them.
Title: Tektronix 2465B oscilloscope teardown
Post by: jonpaul on February 11, 2019, 01:09:47 pm
Hello  med6753, many thanks for your help!

Big Progress here:  :)

a/ CAL: Your tips re the CTT CAL procedure signal were perfect, I used the TM501 to generate the 1.000000 MHz and  trusty PG502 250 MHz pulse gen to make a +0.5 ..-0.5V 5 uS fast rise squarewave. Freq exact ~ 1 HZ with DC508.

After centering transition and DC, cal CTT proceedure FINALLY worked, no "out of range". 
(note, with good NVRAM data and just CTT needing CAL, failing CAL CTT returns scope to the NVRAM error test 04 fail 10)

The HOR CAL seems OK but CH1 and CH 2 vertical are off 3..5% so VERT CAL is next.
Any tips in that procedure, (have PG506)? Even if other functions CAL seem OK, should I still do a full CAL?

b/  old issue:  This 2465B CTT op 06 (SN 066xxx) is  losing the panel settings at next turn on and default to 50 mv/DIV AC coupling etc regardless of previous settings.  :( I believe that this symptom existed before the old NV RAM failed and was replaced. Besides CAL data does the NVRAM also get FP settings written at shutdown?  Since NV RAM is new and works and the scope seems to initialize and shutdown normally, what can cause this symptom?

c/ Misc cleanup:

A5 board options connector J4241 mates to the option ribbon cable with 2 connectors on the A5 end and 2 more with greater separation on options end. That links A5 to CTT options board. At A5,  The second connector and thick cable loop interferes with the NVRAM as the machine pin socket raises it a bit. Any reason not to just cutoff the unused connectors?

The Fan is a bit noisy, replacement is the NIDEC Beta SL?  Many models exist, as fan is critical to cooling, have 12V 0.12 and 12V 0.16 A models. Any tips on best replacement part?

Usual dead graticule lamps, any pitfalls in replacing? Suggest the original incandescent lamps or try LEDs?

d/ Finally if anyone has a 2465B Options manual for sale or swap or the PDF I will appreciate, as I am missing that from my huge TEK manual library.

Enjoy,

Jon


PS: Going thru this repair and rejuvenation, I can only marvel at the electronic, mechanical and software design of the most marvelous and last CRT scope from TEK!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Satbeginner on February 11, 2019, 01:20:49 pm
Hi,

I have the option manual in pdf, will see if I can upload it.
Don't know how to upload 25Mb, so I put it in a DropBox, here is the link to it:

https://www.dropbox.com/s/7dgbqmnusf0ki5e/2465A_2467_070-5857-00_Options_Manual_Jun87.pdf?dl=0 (https://www.dropbox.com/s/7dgbqmnusf0ki5e/2465A_2467_070-5857-00_Options_Manual_Jun87.pdf?dl=0)

Stay tuned,

Leo

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on February 11, 2019, 01:40:07 pm
JonPaul....good deal, glad I could help!  :-+

As far as your other issues are concerned.....I have a 2465 (no suffix) and my experience is limited to that model. I have no experience with the 2465B. There's quite a few differences between the 2 models. But I'm sure MarkL will see this thread and I'm quite positive he'll be able to help.  :-+ 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: jonpaul on February 11, 2019, 01:57:12 pm
Satbeginner Leo: Many thanks but that manual seems to cover only 2445A, 2465A and 2467 but not 2465B or 2467B!

Perhaps you have those?

Jon
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Satbeginner on February 11, 2019, 02:30:21 pm
As far as I know, the options are the same, and no, don't have anything else...

I used it on my 2465B's and 2465 ADM without problems.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on February 11, 2019, 03:38:24 pm
Manuals should be useful on all versions but one thing to keep in mind is the 2465B differences from SN 50001 and up which are important to consider. There are also some individual components that where changed at some specific serial number range. This info would be only available mostly in the later 2465B/2467B manual.

Have you tried this download link?

http://w140.com/tek_2465B_2467B.pdf (http://w140.com/tek_2465B_2467B.pdf)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Satbeginner on February 11, 2019, 03:42:07 pm
Hi,

you are right where it comes to the scopes, there are differences with respect to the S/N, but I believe the Options Service manual is generic for all scopes.
I never found another Options manual, but if it exist, I for sure want a copy :-)

Un saludo,

Leo
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: jonpaul on February 11, 2019, 04:24:29 pm
Hello all: Yes used the 2465 opt proceedue to cal 2465B CTT, AOK! Perhaps the 2465B OPT man is vapro.

Can anyone please address my non-manual issues b/ c/  posted a few messages/hours back?

____________________

b/  old issue:  This 2465B CTT op 06 (SN 066xxx) is  losing the panel settings at next turn on and default to 50 mv/DIV AC coupling etc regardless of previous settings.   I believe that this symptom existed before the old NV RAM failed and was replaced. Besides CAL data does the NVRAM also get FP settings written at shutdown?  Since NV RAM is new and works and the scope seems to initialize and shutdown normally, what can cause this symptom?

c/ Misc cleanup:

A5 board options connector J4241 mates to the option ribbon cable with 2 connectors on the A5 end and 2 more with greater separation on options end. That links A5 to CTT options board. At A5,  The second connector and thick cable loop interferes with the NVRAM as the machine pin socket raises it a bit. Any reason not to just cutoff the unused connectors?

The Fan is a bit noisy, replacement is the NIDEC Beta SL?  Many models exist, as fan is critical to cooling, have 12V 0.12 and 12V 0.16 A models. Any tips on best replacement part?

Usual dead graticule lamps, any pitfalls in replacing? Suggest the original incandescent lamps or try LEDs?

MANY THANKS AGAIN!

Jon
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on February 11, 2019, 06:02:19 pm
b/  old issue:  This 2465B CTT op 06 (SN 066xxx) is  losing the panel settings at next turn on and default to 50 mv/DIV AC coupling etc regardless of previous settings.   I believe that this symptom existed before the old NV RAM failed and was replaced. Besides CAL data does the NVRAM also get FP settings written at shutdown?  Since NV RAM is new and works and the scope seems to initialize and shutdown normally, what can cause this symptom?
Take a look at EXER 06 in the diagnostic menu.  This allows you to select either SETUP 1 or the power-down configuration when powering on.  COUPLING UP selects between the two.  Sounds like it's set to SETUP 1.

Quote
c/ Misc cleanup:

A5 board options connector J4241 mates to the option ribbon cable with 2 connectors on the A5 end and 2 more with greater separation on options end. That links A5 to CTT options board. At A5,  The second connector and thick cable loop interferes with the NVRAM as the machine pin socket raises it a bit. Any reason not to just cutoff the unused connectors?
Offhand I wouldn't go cutting off any connectors.

Perhaps a photo of the issue?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: jonpaul on February 11, 2019, 07:04:39 pm
Dear MarkL!

WOW perfect, indeed  EXER 06 was on SETUP 1. Changed to  initialize to last settings. MANY THANKS!

Last issues (I hope).......

1/  Fan is noisy, replacement is the NIDEC Beta SL? 
Many such NIDEC models exist, I have 12V 0.12 and 12V 0.16 A spares. Any tips on best replacement part?

2/ Usual dead graticule lamps, any pitfalls in replacing? Suggest the original incandescent lamps or LEDs?

With Kind Regards,

Jon
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on February 11, 2019, 07:49:21 pm
I would suspect that either fan is probably OK. At least the fan is easy to service on the 2465B. Not so the case on the 2465. If you want to get real anal about it and determine which fan is best you can perform an experiment similar to what I did here:

https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1215559/#msg1215559 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1215559/#msg1215559)

I attached a thermocouple to the rear plate near the power supply and then ran the sweep at high speed to get U800 good and hot then monitored the temp. Never rose above 97 F (36 C) in ambient 72 F (22 C). And you can "smoke test" the airflow from the bottom vents which are directly below U800. That's really the most important is to maintain that airflow. If you can "see" the airflow with the smoke it's probably OK.

Hope this helps. As far as the graticule lamps I've never had to change one. 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on February 11, 2019, 08:34:21 pm
Dear MarkL!

WOW perfect, indeed  EXER 06 was on SETUP 1. Changed to  initialize to last settings. MANY THANKS!

Last issues (I hope).......

1/  Fan is noisy, replacement is the NIDEC Beta SL? 
Many such NIDEC models exist, I have 12V 0.12 and 12V 0.16 A spares. Any tips on best replacement part?

2/ Usual dead graticule lamps, any pitfalls in replacing? Suggest the original incandescent lamps or LEDs?

With Kind Regards,

Jon
You're welcome!

I have a Nidec Beta SL in my 2465, D08G-12TH, 12VDC 0.16A.  But it doesn't look like it's a factory installation to me.  If your Nidec spares work and aren't noisy (yet), go for it.  I slipped a little bit of thin neoprene sheet underneath the areas where it contacts the chassis to reduce noise even further.

I've never replaced a graticule light.  Perhaps someone who has can answer that one.  Personally, I like the look of the old incandescent lamps.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: LADmachining on February 13, 2019, 11:04:56 am
Thanks to all of the contributors so far, this has been a good read of the previous 58 pages of the journeys people have had to take to restore their scopes.

I have now joined the party and acquired a 2445B.  Due to serial number confusion I was expecting a model with the SMD A5 board and DS1225, but instead got an earlier model with through-hole A5 and Keeper battery.  Last calibration of the scope was performed by Tek in 1999, and the tamper seals were still intact, so it hasn't been apart in the intervening period.  The unit 10K hours and approx 3K power-up cycles.

Firstly, before knowing this didn't have a NVRAM, I captured and recorded the cal data using EXER02.  The Keeper battery reads 3.5V still (date code 0689), but I think it is still prudent to replace it.  Will follow the guides available to change it out, but the question is what to, as the LTC-7P is not easily available in the UK.  Other LiSOCl2 cells are available, it is just choosing which type to use.

Has anybody looked into how the 6264 RAM could be reprogrammed with cal data if the worst happened and it was corrupted or cleared accidentally?  I guess you could solder wires directly to the chip with a CR2032 and diode, and transfer it between a programmer and the A5 board after reloading the cal data.  Does the cal data sit at the same address in RAM (0x1E00 to 0x1FFF) as on the DS1225?

Could the 6264 RAM be replaced with a DS1225 - pinout is the same apart from pin 26 which is CE2 on the RAM and NC on the DS1225?

Enough questions, here are pictures of the machine question...

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: jonpaul on February 13, 2019, 12:29:45 pm
Hello MarkL and med6753!

progress update,  Have total 4, the working units are a 2467 IEEE  and  another 2467B
Both 2465B CTT/2467B needed A5 board cap damage and NVRAM fixes and  restoration.
All low hours (2K, 3K, 8K) physical/cosmetic excellent.

0/ Analog calibration:  set 10.000 V REF and DAC REF (+/- 1.25V) procedure. Notice the initial settings if you do this!

1/ FAN: original Nidec 12V 0.16A still useable. Substitutes had wrong current or low airflow.
Peel paper label, drop of oil on  ball-bearing. Added 0.035" thk 1.5" dia neoprene between the fan hub and sheetmetal rear bracket.
Fine for noise.  PS: Old fans (soldiers) never die, they just fade away (apologies to Gnl Douglas McArthur).

1A/ Heat/U800: Seems a lot of notes and some disagreement re the original U800 thermal desing and lifetime.
2467B original U800, no heatsink, 2465B  original TEK U800,  resoldered or replaced in the dim past, with a small heatsink.
Temps seem cool. QUESTIONS: a. setup to check worst case U800 temp, fastest sweep rate?
b. With no HS and TEK U800, what typical temp are recorded with cabinet closed? Cabinet open?

2/ CAL: After A5 rework and load new NVRAM with default image, 2465B was CTT FAIL, after CTT CAL, ALL PASS!
Check: Vert ampl ~ 2-5% all ranges,  HOR ~ 1%. Useable but need CAL. Fast rise edge response OK (PG506) but need TD pulser for HF/Edge CAL. Trise ~ 900 nS.

After CAL, unplugged both NVRAMs,  to read and save NVROM images. (used XGecu "MiniPro" TL866CS programmer $40)

3/ LAMP: Graticule lamps: 5.0V 0.115A T-3/4 40,000 hrs 7153AS15 at  DK 7153AS15-10PK-ND pack of 10!

4/ PSU: All units seem fine, PSU voltages and ripple OK. Visual of RIFA caps and lytics seem OK. To the 2465/7X PSU veterans and rebuliders:

a/ Leave it alone or recap? b/ Time/tools/pitfalls to pull and rework PSU? c/ BOM: Source for caps, special resistors, rectifiers, etc?


For some years, and last few months,  I worked on these scopes, with fine components, gold PCBs, complex but easy to service mechanical and well written documentation.

As I reread the manuals and did some CAl, I realized what a fantastic quality design the TEK engineers did.
Amazing that these machines (1980s..early 1990s)  still work perfectly, there is no modern replacement!
What a contrast to the minimum cost/life/performance digital Chinese junk marketed today with deceptive specs and compliance.

Again many thanks to all for the great feedback and support info.


Jon

PS: Please see my SIGSALY first ADC recreation in February IEEE Spectrum:

https://spectrum.ieee.org/geek-life/hands-on/rebuilding-a-piece-of-the-first-digital-voice-scrambler
https://spectrum.ieee.org/geek-life/hands-on/sigsaly-analogtodigital-converter-construction-and-debugging

Your comments and feedback appreciated.





Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on February 13, 2019, 12:59:56 pm
I can answer 2 of your questions.

U800: LEAVE IT ALONE. If you read back through this thread there's lots of opinions. But the consensus seems to be that adding heatsinks DON'T help. In fact, they may inhibit cooling. U800 depends upon AIRFLOW to keep it within it's operating temp. That's achieved by keeping the cooling system in good shape. Things such as dust free and a running fan. And don't run the scope outside the case any longer than necessary because there's inadequate airflow with the case off.

I highly recommend recapping the PSU. Here's the link. I also attached the parts list.

https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1658102/#msg1658102 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1658102/#msg1658102) 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: jonpaul on February 13, 2019, 03:00:27 pm
med6753, wow, fast and perfect answer!

1/ U800: Rodger that, cannot understand the overheating posts.

2/ PSU: Wonderful rebuild, you are the expert. I have some NOS Sprague radial caps, but they might be dried out. BOPM XLS is a great aid. Approx time you needed to PSU  rebuild?

3/ EDGE:  response with TEK TD pulser (drive:  PG506), about perfect. Very wary of HF response tweaks (LEAVE IT ALONE?)

4/ FAN: On the 2467, with Siemens hall effect fan, (a bit noisy), any way to lube bearings besides complete disassembly and rewind?

Cheers,

Jon


Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on February 13, 2019, 04:42:38 pm
If you hustle you can do the PSU recap in one day. But I don't recommend that because you can easily introduce errors. Plan on 2 days.

If you are satisfied that you can't get the wave form looking any better then I would leave it as is....unless it's grossly out of spec.

The Seimens fan motor: Yes, it is possible to restore operation of this motor without tearing it down. You can get lucky like I did here:

https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1861713/#msg1861713 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1861713/#msg1861713)

But if that fix doesn't work you can follow mnem's excellent pictorial of tearing down the motor starting here:

https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1863798/#msg1863798 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1863798/#msg1863798)





 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: jonpaul on February 14, 2019, 03:10:13 pm
Hello All:  This was posted on eevblog elsewhere, thought you may enjoy:

----Please see my SIGSALY 1942  ADC recreation with tubes, in February IEEE Spectrum:

Printed magazine has the first link article.

https://spectrum.ieee.org/geek-life/hands-on/rebuilding-a-piece-of-the-first-digital-voice-scrambler
https://spectrum.ieee.org/geek-life/hands-on/sigsaly-analogtodigital-converter-construction-and-debugging

Your comments and feedback appreciated.

Jon -----
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on February 14, 2019, 08:22:36 pm
...
Has anybody looked into how the 6264 RAM could be reprogrammed with cal data if the worst happened and it was corrupted or cleared accidentally?  I guess you could solder wires directly to the chip with a CR2032 and diode, and transfer it between a programmer and the A5 board after reloading the cal data.  Does the cal data sit at the same address in RAM (0x1E00 to 0x1FFF) as on the DS1225?
The cal data still sits at those locations.

If you have a EPROM programmer, it should be possible to write a very simple 6802 assembly program to set up the ROM SELECT and PAGE SELECT latches, and then write the 512 bytes directly into 0x1E00 to 0x1FFF.  I made a couple of attempts at writing the program, but someone else was trying it on their scope because I didn't have an A or B scope to test it.  I do now.  It's on my list.  But if you can do 6802 assembler, it should be a no-brainer.

Quote
Could the 6264 RAM be replaced with a DS1225 - pinout is the same apart from pin 26 which is CE2 on the RAM and NC on the DS1225?
I don't have the 2445B schematics to know for sure, but after looking at the 2445A schematics which use a keeper battery, and the 2465B schematics which use the DS1225, it looks like it would work.  CE2 is only used as an enable once the +5V is stable and nRESET is high.  The DS1225 has an internal enable controlled by the Vcc voltage so it doesn't really need the protection function that CE2 provides.
Title: Tektronix 2465
Post by: BravoV on February 15, 2019, 07:45:14 am
New upcoming "home-work"  ::), a dead fail to power on, 2465 with Option 10 & 11, missing 2 front feet, 4 front knobs and also top cover thin plastic that covers the opening for accessing the filter screen, looks like previous owner replaced the blue with clear acrylic, and forgot to install it back.

Anyone got spare knobs ?  :P
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: jonpaul on February 15, 2019, 10:38:13 am
Hello all: End of the long A5/NVRAM/recalibration/restoration of my 2465B/2467B rebuild:

HOR and other CAL seem OK.  But Vert Cal. CH 1/2 cal  ~ 2-5% error consistent error per scope/channel on all deflection factors.

Test Equipment: TM510, PG506, TD pulser, 50 ohm atten, precision cable, etc.

Asking you veteran TEK gurus for tips or pitfalls in CAL 02, I have seen posts with errors in various CAL procedures, but lost track the exact sections and errors. 

Many thanks!

Jon
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on February 15, 2019, 12:40:18 pm
I stumbled across this video 2 days ago and all I can say is "Wow!" |O  It took him 3X as long to service those RIFA caps than it should have. He didn't realize that the entire Regulator/Inverter board assembly would pull out as one unit just by removing 2 screws on the back plate and 3 screws down by the heat sink.   :palm:

https://www.youtube.com/watch?v=IaRkgtPxPyw (https://www.youtube.com/watch?v=IaRkgtPxPyw)
Title: Re: Tektronix 2465
Post by: med6753 on February 15, 2019, 12:58:09 pm
New upcoming "home-work"  ::), a dead fail to power on, 2465 with Option 10 & 11, missing 2 front feet, 4 front knobs and also top cover thin plastic that covers the opening for accessing the filter screen, looks like previous owner replaced the blue with clear acrylic, and forgot to install it back.

Anyone got spare knobs ?  :P

I've used these guys in the past for some Tek parts and they seem to have a good selection of knobs for the 24XX series.

https://www.qservice.tv/ (https://www.qservice.tv/)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: jonpaul on February 16, 2019, 10:05:22 am
Dear med6753 and others: Many thanks for the notes. Before CAL 02, doing CAL 01, HOR, the timing off  ~ 3%.

Reading the CAL 01 procedure, some steps have confusing instructions, I  found the forum note re CAL 01  3 undocumented steps "..manual shows 31 steps for CAL 01, but the 2465B actually has 34 steps. After  completing the 31 steps, advance through 32, 33,  and 34...

Am using TM501, any other pitfalls or tips for a novice in CAL 01?

Many thanks again!

Jon
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: jonpaul on February 18, 2019, 10:17:06 am
Hello all:  RE U800, temps

Scared to overheat U800 during full CAL.

From Chuck Harris at https://groups.io/g/TekScopes/

...At 25C ambient, U800 runs 49C with the scope... 46C with case installed.... U800 would..handle 30C + 46C = 76C  max specified ambient.

1/ working on 2465/7B, with  original TEK U800s. U800 runs cool.
Continuous op at highest H sweep would be a worst case temp  of U800? Any temp measurements running on the 5ns/div sweep?

2/ Doing a full (or even partial) CAL requires cover off and preliminary 20 min warmup. Procedures can take hours and U800 and other hybrids on A1 could overheat.

3/ Placing an external fan on A1 mainboard could cool the A1 board below normal op temp in the case.

So there seems to be contradictions in cooling when doing long CAL.

I appreciate any recommendations and observations from the 2465B veterans  re cover/external fan/cooling  during a CAL 01/02 or full cal for cover, warmup and external fan.

Many thanks again!

Jon
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on February 18, 2019, 02:50:45 pm
Hello all:  RE U800, temps

Scared to overheat U800 during full CAL.

From Chuck Harris at https://groups.io/g/TekScopes/

...At 25C ambient, U800 runs 49C with the scope... 46C with case installed.... U800 would..handle 30C + 46C = 76C  max specified ambient.

1/ working on 2465/7B, with  original TEK U800s. U800 runs cool.
Continuous op at highest H sweep would be a worst case temp  of U800? Any temp measurements running on the 5ns/div sweep?

2/ Doing a full (or even partial) CAL requires cover off and preliminary 20 min warmup. Procedures can take hours and U800 and other hybrids on A1 could overheat.

3/ Placing an external fan on A1 mainboard could cool the A1 board below normal op temp in the case.

So there seems to be contradictions in cooling when doing long CAL.

I appreciate any recommendations and observations from the 2465B veterans  re cover/external fan/cooling  during a CAL 01/02 or full cal for cover, warmup and external fan.

Many thanks again!

Jon
See replies #6 and 12. Read carefully. All you need to know is there.  ;)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: jonpaul on February 18, 2019, 03:09:49 pm
"See replies #6 and 12. Read carefully. All you need to know is there.  ;)"

Unsure you mean PAGE 6, 12 of the 58 pages or how to locate, by date?

Links to those replies appreciated!

MANY THANKS

Jon
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on February 18, 2019, 03:12:00 pm
"See replies #6 and 12. Read carefully. All you need to know is there.  ;)"

Unsure you mean PAGE 6, 12 of the 58 pages or how to locate, by date?

Links to those replies appreciated!

MANY THANKS

Jon
On page 1.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on February 18, 2019, 04:20:36 pm
"See replies #6 and 12. Read carefully. All you need to know is there.  ;)"

Unsure you mean PAGE 6, 12 of the 58 pages or how to locate, by date?

Links to those replies appreciated!

MANY THANKS

Jon
On page 1.

As tautech just pointed out (Page 1 of this thread) and as I have said. Airflow is the most important element in keeping U800 cool.

Now, having said that. Yes, a full calibration can take a long time and the case is off. I personally have not had to do a full cal on either of my 2465's. But if I were I would rig a fan pointed at the A1 board. Now it may not be absolutely necessary but it certainly couldn't hurt.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: jonpaul on February 21, 2019, 11:50:29 pm
Hello there: Just an update: On 2465B, CAL procedure, HOR CAL was off ~ 1-4%.

1/  CAL 01: Good instructions, just a few that I puzzled over the routine.

Equip:  TM501, and 2467 as bench scope. 3 steps hit limits, fixed by the repeat of those steps.

About 1 hr for CAL 01. Checked HOR timing afterwards, perfect!


2/Cover off CAL cooling: During HOR CAL 01, about 2 hrs total, all IC, Hybrid HS and U800 temps just slightly warm, did not need an external fan.

Next for the easier CAL 02.

Many thanks to all for their fine CAL notes!

Enjoy!

Jon
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: jonpaul on March 01, 2019, 11:03:50 am
Hello all: Working on another 2467B, SN B050xxx, ~ 8K hrs 1K cycles. Works fine, good CAL, perfect CRT and transient response.



1/ A5 NO SMD lytics, no corrosion, all Tant or TH bypass caps

2/ NVRAM original date 8852 = 31 years!
Passes all self test, No NVRAM errors

3/ A1 main orig TEK U800, no HS

4/ Fan replaced, works fine

a/Understand some  PROM readers misread or destroy data, also possible damage can occur to NVRAM in removal from PCB.

How to manually read out NV RAM contents before removal?

b/ Recommended DK and Mouse PN for NVRAM and low profile 28 pin machined pin socket?

c/ Precautions to desolder/remove  NVRAM and to read data on programmer (using XGecu TL866CS programmer) ?

MANY THANKS

Jon

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on March 01, 2019, 12:17:20 pm
Suggestion, just unscrew the two nuts that are holding the U800 chip, it is not going to fall down or separated from the board anyway, as the chip's pins all are soldered firmly on the pcb.

Thermal expansions and contractions actually stress out the whole U800 chip body with that 2 nuts attached, imo.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on March 01, 2019, 12:19:00 pm
Hi Jon,

These are the parts I used from Mouser on my 2465B and they worked very well.

828-AG11D-ESL-LF IC Socket DIP .6CL 28P
MOUSER PN 571-2-1571552-9

DS1225AD-150+ NVRAM 64k Nonvolatile SRAM
MOUSER PN 700-DS1225AD-150

But I ended up using a FRAM instead of the SDRAM to do away with any future battery issues:

FM16W08-SGTR F-RAM F-RAM 64Kb 70ns 8K x 8 Parallel FRAM
MOUSER PN 877-FM16W08-SGTR

Fram is SMD type so it requires an adapter board:
IC & Component Sockets IC & Component Sockets 28P SOIC/DIP SOCKET
MOUSER PN 535-28-650000-10

I used the GQ-4X4 programmer which supports both the 1225 and the FM16W8.

Desoldering the 1225 was no big deal, just be extra careful as the A5 board is a multi-layer board. I used a regular 40W Weller pencil soldering iron dialed down to about 25W, and a soldapult. Make absolutely sure all pins are free by jiggling them a bit before trying to pull the chip. For me it was just straight forward, even pin 14 which is ground and usually requires a bit more heat came out just fine without any issues.

To back up the cal constants from the NVRAM before pulling it use EXER02 routine (check service manual section 10) and write the values down with paper and pencil, or take a video while you scroll trough all the individual values. Once you have the chip out read it and save it to file, then program the new chip.

Good luck with the procedures
Alex
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: jonpaul on March 01, 2019, 02:21:53 pm
Hello again: RE the 2467B, I just checked H and V CAL, CRT and transient response, incredibly, its perfect.
For a machine built in KUDOS to the TEK engineers!

To BravO re A1/U800:

I wonder if the screws provide any heatsinking or better thermal contact to PCB?
Perhaps replacement of the lockwasher with a constant tension spring or Belleville washer?


To AMR Lab/Alex: re A5 NVRAM: Understand re the FRAM, will use the Dallas parts avail from DK.
For removal of the NVRAM, the internal ground and power planes make certain pins very difficult to remove.
For EXER 02, I used it but had only a few values. Which buttons to scroll up><down?


Irons for removal NVRAM: I found the best iron for such work:  Metcal SP-200 "smartheat"
http://www.testequipmentdepot.com/metcal/pdfs/sp200_manual.pdf (http://www.testequipmentdepot.com/metcal/pdfs/sp200_manual.pdf)

Just a few deg. tip temp regulation instead of the 50-100 deg overshoot and hunt of normal irons.




Enjoy!

Jon

PS: Full disclosure: in 1992,  I  designed the SP-200, resonant mode SMPS that drives 30W constant current sinewave to iron  the curie point tip (500 kHz),

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Satbeginner on March 01, 2019, 02:25:06 pm
Same here, I could clean all pins but pin 14 using a vacuum soldersucker, I used a soldering iron for pin 14 when I removed the Dallas.

Using a small nose tip pliers to wiggle the pins first to make sure they are all loose is the trick.

I choose to replace the Dallas with a new Dallas I got from Mouser, using a TL866 MiniPro programmer.

Good luck,

Leo
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on March 01, 2019, 03:17:19 pm
Suggestion, just unscrew the two nuts that are holding the U800 chip, it is not going to fall down or separated from the board anyway, as the chip's pins all are soldered firmly on the pcb.

Thermal expansions and contractions actually stress out the whole U800 chip body with that 2 nuts attached, imo.

Please tell me you're not serious.  :o Just kidding, right?  :-// It's been in there 30 years and worked fine and now you want to monkey with it? Do so at your own risk.

Anecdotal evidence: This thread is 8 years old. Has ANYONE come in here and said that U800 took a dump? Not that I recall.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: jonpaul on March 01, 2019, 04:13:11 pm
Hello Med6753, old but great thread.   Please see my previous posts today for full story.

This is preventive maintaince especially for the 1989 battery backup NVRAM.
Eventual battery failure was my motivation to open the scope up!

Agree to leave U800 asis.
If it ain't broke don't fix it!

With  2 other 2465/7B with the failed NVRAM and complete reCAL, I have learned the hard way.

Enjoy,


Jon

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on March 01, 2019, 04:39:12 pm
Hello Med6753, old but great thread.   Please see my previous posts today for full story.

This is preventive maintaince especially for the 1989 battery backup NVRAM.
Eventual battery failure was my motivation to open the scope up!

Agree to leave U800 asis.
If it ain't broke don't fix it!

With  2 other 2465/7B with the failed NVRAM and complete reCAL, I have learned the hard way.

Enjoy,


Jon

Understood. I was only referring to U800. I agree with the need to open it up and deal with the NVRAM issues.   
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on March 01, 2019, 04:41:02 pm
To BravO re A1/U800:

I wonder if the screws provide any heatsinking or better thermal contact to PCB?
Perhaps replacement of the lockwasher with a constant tension spring or Belleville washer?

Jon,

As I said, its just my "suggestion". As I've concluded this thru lots of studying and also through close up photos of the U800, I do have few spare U800s (just in case you missed it, I did post them here too in this thread with close ups), and my conclusion is the two nuts basically are useless, and "PROBABLY" may do harm than good, again, this is just my own conclusion.

As I never summarize this up, so here we go. Again, this my own conclusion, and if you don't agree then don't touch them, as simple as that.

Ok, 1st, this photo below, is the standard untouched U800 chip with the locking nuts at the two embedded bolts, and watch closely there are serrated washers that are sandwiching the ic metal tab.

(click photo to enlarge)
(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=16705;image)


Now, this is the close up of the PCB where I de-soldered my spare U800 chip off the board, and the two bottom serrated washers location, which are sort of lift the whole ic body not touching the big exposed pcb pad below it. So no effective direct contact for heat dissipation path on it.

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=317596;image)


Intuitively we will think that the generated heat dissipation path is from the chip through the ic metal tab, and then pass through the washers that are compressed by the nuts, and then to the two embedded metal bolts/screws.

This is how the U800 chip looks like at bottom side. If you watch closely, you can see there are dented "dots" in circle at the tab, that are made by the serrated washer tips, meaning, the metal to metal contact is really poor for heat transfer as its just "touched" by the washer's sharp tips.
(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=317598;image)

Again, intuitively, we will think, why not we just fasten the two nuts that will squeeze the washers to the chip's metal tab to make it better thermal path. The answer is NO , as this below illustration, as you just CAN NOT tighten the nuts, as it will sort of peel off or push down the metal tab downward from the chip's body, once the bottom serrated washer are squeezed down, as the whole ic body is already secured firmly by 24 ic's pins that are soldered at the board.

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=608827;image)


Just simple question, say your U800 is toasted as this is the common problem, you replace it with a working one, then solder at it's 24 pins as usual, and then you put the two nuts. When you starting to fasten them, how much torque do you need ? Ever think about that ?

Ever imagine that once you starting to even slight put a force on the nut, it will starting to bend the ic metal tab downward or peel off from the chip black body as there is a gap there.

Also we all know, that this part and region experienced thermal cycles, what happened to the tightened nuts and washers as it expand or contract, basically its like micro bending the ic metal tab up and down on every cycle.

This is my conclusion, I could be wrong, but this what I believe, the two nuts basically serve no purpose, and if over tightened, will actually do more harm than good.

So, its up to you.  :-//
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on March 01, 2019, 04:43:41 pm
Suggestion, just unscrew the two nuts that are holding the U800 chip, it is not going to fall down or separated from the board anyway, as the chip's pins all are soldered firmly on the pcb.

Thermal expansions and contractions actually stress out the whole U800 chip body with that 2 nuts attached, imo.

Please tell me you're not serious.  :o Just kidding, right?  :-// It's been in there 30 years and worked fine and now you want to monkey with it? Do so at your own risk.

Anecdotal evidence: This thread is 8 years old. Has ANYONE come in here and said that U800 took a dump? Not that I recall.

I'm serious med, and don't want to argue and I've posted my argument above.

Its my believe and my own reasoning, as I just "suggest" it to Jon, he is free to reject it if he doesn't buy it, as simple as that.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on March 01, 2019, 05:01:14 pm

This is my conclusion, I could be wrong, but this what I believe, the two nuts basically serve no purpose, and if over tightened, will actually do more harm than good.

So, its up to you.  :-//

Absolutely agree with that. As far as I can tell Tek never published the torque spec for those nuts. It would be all too easy to overtighten the nuts. And I while I have no direct evidence or experience otherwise let me give a counter theory. Isn't the most common failure mechanism of the U800 a delamination of the internals, especially on Maxim sourced chips? If that's the case I could argue that the nuts may help to PREVENT a delamination by keeping the IC together. Perhaps a dumb theory but who knows.  :-//     

Edit...I don't wish to argue it either. Peace.  :-+

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: jonpaul on March 01, 2019, 05:43:30 pm
Hello Med and Bravo

ACK on all!

Any thoughts on the other questions I pose in my posts earlier today?

RE U800, In the 4 pcs 2465/7/B I have worked on, all have original TEK U800, and none overheat, just warm to the touch. 

Is there a worse case test condition for U800 heat, eg run at 5 ns/ div or use 10X mag?

Has anyone done temp test with thermocouple or IR probe?

Or calculated the worst case Pdiss?

Cheers,

Jon

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on March 01, 2019, 09:08:34 pm
The U800 write up bellow is one of  the best ever explanation I came across, and it is from someone that has tons of experience repairing and calibrating 2465x/67x scopes on a very frequent schedule. He is THE authority on these scopes, or at least definitively one of "THE"...

Original message at:
https://groups.io/g/TekScopes/message/152372

==== Start Quote ====>

Everybody please listen!

U800 is not heat sensitive, and I have found that many of
the "tricks" folks have gotten from the internet on how
to "protect" their U800 chip actually harm the chip due
to over-tightening the nuts on the studs that support the
chip. I have also found that glued/taped on heat sinks
have raised the temperature of the chip by impeding the air
circulation around the chip.

I have also found glued/taped heat sinks floating freely
inside of scopes that have been sent to me for service!

Tektronix botched the mounting of U800. That, in my
experience, is why they fail.

U800 was designed to have its pins pass through a 2-3mm
thick aluminum heat sink mounted underneath the chip.
The belly of the chip is metal to engage this heat sink.

DIP style IC's have pins that are made with a wide part to
prevent the belly of the IC from bottoming onto the PCB.
This allows air circulation under the chip. U800 is no
exception.

The engineer that designed U800 was excessively cautious,
and overestimated the heat that would be generated by his
new IC. When it came back from fab, he found that it did
*NOT* need any heat sinking to meet the full +50C design
temperature rating of the brand new 2465 scopes. So, the
heat sink was left off of the board.

(Thought experiment: when was the last time you operated
your 2465 at 50C?)

The problem is the designer needed -5V to bias U800's
substrate, and he used the metal heat sink frame and tab
to make that connection.

He found that U800's stud could not clamp tightly to
the PCB (REMEMBER: shoulders on pins...) without putting
excessive pressure on U800's pins, so he put a pair of star
lock washers onto the mounting studs before mounting U800.

The washers served to make the electrical connection, and
to provide the needed spacing to protect the chip....

He hoped.

Everything is fine if nobody ever, ever, over-tightens the
nuts that hold the U800 to the board. If they do, the
extra pressure will collapse the star lock washers and
embed them into the PCB and the bottom of one end of the
epoxy body. When this happens, the lead frame of U800 will
crack at some of the pins

If you come along later, having listened to all the bloviation
about U800 fixes, and happen to tighten up the nuts a little
bit more: crack! You will have damaged the chip while trying
to protect the chip.

-Chuck Harris

<==== End Quote ====
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: ezalys on March 17, 2019, 01:44:26 am
Hey folks, I'm really struggling with a 2467B with a "CT TEST 86 FAIL 02."

The options manual indicates this failure corresponds to "In Trigger After Delay mode with the delay time set longer than the delay, there was no sweep. Check B AUX TRG and HO at U6190 and output O1 at U6140." Is this a failure that others have seen? Could I have left a cable loose somewhere? U6190 appears to be some sort of gate array, and I'm not sure where I'd find a replacement. I'm also not sure how to get at the B AUX TRG/HO/O1 signals on the specified ICs, as the board needs to be installed face down to be powered by the power supply.

To me is really seems like I must've left a cable undone, but I've verified that I've connected, in the appropriate positions, ribbon cables C and E, and the pair of coaxes D, and on the opposite side of the instrument, a rather wide ribbon cable that passes through the side of the chassis. Seems like everything is connected OK. What's the next thing to check?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 18, 2019, 09:55:30 pm
Hey folks, I'm really struggling with a 2467B with a "CT TEST 86 FAIL 02."
...
I don't have the 2467B options service manual, but the options from model to model in the 24xx family are very similar.

The 24x5A options service manual, which I do have, has a troubleshooting flowchart in the back that says (and I'll summarize the relevant thing here) if CT test 86 failed and any of the bits 0, 1, or 2 of the error code is a 1, it may indicate that the sweep speeds are uncalibrated.  If you have the actual 2467B options service manual, you could see if it says the same thing.

In reading the chart that you point out for "CT TEST 86 FAIL 02", I'm honestly having trouble deciphering exactly what behavior it's complaining about.  Can you determine what's not working with delay-by-events (besides the self-test)?

Is this a new problem or did it come like this?

Can you point to a copy of the 2467B options service manual on-line somewhere?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: EEVblog on April 22, 2019, 02:30:24 am
About a week ago I started on recapping the low voltage regulator and inverter boards in my 2467B after a few anomalies started showing up.

I would like to draw people's attention to an error on the board layout sheet fig 10-13 in the Service Manual 070-6863-01 that has C1115 and C1132 transposed on the inverter board (250uF/20V vs 10uF/160V). This took several hours to figure out, and a few burnt out parts too.

Necro posting time!
I just discovered the exact same fault. Measured C1115 ESR in circuit and it looked sussed, so sucked out only to find a 10uF 160V cap. Traced and the circuit a bit and figured it was swapped on the overlay diagram  |O
Sucky thing is, changing that cap (which was failed) made no difference to the 5V rail ripple (output cap C1280 seems fine), so  :-//
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: EEVblog on April 22, 2019, 04:25:05 am
Oops

https://www.youtube.com/watch?v=1zKNQNiHeJc (https://www.youtube.com/watch?v=1zKNQNiHeJc)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on April 22, 2019, 04:28:15 am
Geez... what happened Dave ?  :o
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: kj7e on April 22, 2019, 04:49:29 am
At least the problem will be easy to find now.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on April 22, 2019, 05:22:02 am
Yep, known problem and Tek never fixed the manuals. I've done complete re-caps of the Inverter/Regulator boards on both my 2465's and I do one capacitor at a time (remove/replace) and I follow what's physically installed on the boards.

I haven't had the excitement of magic smoke.  :-DD   
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: 0culus on April 22, 2019, 05:41:25 am
Ooof, that was a good bang!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: EEVblog on April 22, 2019, 08:58:59 am
Geez... what happened Dave ?  :o

You'll find out in the next video, about 30min in or something..
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on April 22, 2019, 08:56:54 pm
I would like to draw people's attention to an error on the board layout sheet fig 10-13 in the Service Manual 070-6863-01 that has C1115 and C1132 transposed on the inverter board (250uF/20V vs 10uF/160V). This took several hours to figure out, and a few burnt out parts too.

I just discovered the exact same fault. Measured C1115 ESR in circuit and it looked sussed, so sucked out only to find a 10uF 160V cap. Traced and the circuit a bit and figured it was swapped on the overlay diagram  |O

That specific mistake has come up a couple times on the Tekscopes mailing lists.  Also, sometimes the board or layout will have polarity marked wrong.

I have tried to make it a habit to record part locations and orientation as I remove them to avoid those sorts of problems.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on April 23, 2019, 12:27:05 am
New Dave's video relating to 2465B, post here again as reference, originated from this thread -> EEVblog #1203 - REPAIR: Tektronix 2465B Oscilloscope (https://www.eevblog.com/forum/blog/eevblog-1203-repair-tektronix-2465b-oscilloscope/)

https://www.youtube.com/watch?v=Rp-0FqxQkBw (https://www.youtube.com/watch?v=Rp-0FqxQkBw)
Title: Fake Tektronix 2465B ?
Post by: BravoV on April 24, 2019, 09:18:02 am
Fake 2465B ? As Dave's 2465B's badge is different from mine.  :-//

Pointed out by Scopetechniques -> Fake 2465B in EEVblog #1203 (https://www.eevblog.com/forum/blog/fake-2465b-in-eevblog-1203/)

Repost here as reference.

(https://www.eevblog.com/forum/blog/eevblog-1203-repair-tektronix-2465b-oscilloscope/?action=dlattach;attach=714963;image)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on April 24, 2019, 09:58:55 am
Uh oh. Possible one of those fakes "built" by that EBay scammer?  :-// :scared:
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on April 24, 2019, 10:16:23 am
Uh oh. Possible one of those fakes "built" by that EBay scammer?  :-// :scared:

Very suspicious indeed, example the well known eBay seller called "2465b" , the shop is also selling the handle decal for 2465B, example ebay item -> 123714403213

They're printed in single color, as example mine it was printed with dual colours, check the very 1st post of this thread.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on April 24, 2019, 10:19:17 am
Uh oh. Possible one of those fakes "built" by that EBay scammer?  :-// :scared:

Very suspicious indeed, example the well known eBay seller called "2465b" , the shop is also selling the handle decal for 2465B, example ebay item -> 123714403213

They're printed in single color, as example mine it was printed with dual colours, check the very 1st post of this thread.

Are you going to inform Dave that he might possibly have a fake?

Edit.....the labels on both my 2465's are multi-color and raised lettering. Wasn't that same guy "converting" 2445's to 2465's too?  :palm:
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on April 24, 2019, 10:33:32 am
Dave already aware of this (HERE (https://www.eevblog.com/forum/blog/fake-2465b-in-eevblog-1203/msg2364522/#msg2364522)), also I did remind him to bring this out on his upcoming 2nd part of this 2465B fixing video -> HERE (https://www.eevblog.com/forum/blog/eevblog-1203-repair-tektronix-2465b-oscilloscope/msg2364909/#msg2364909)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mnementh on April 25, 2019, 03:44:54 am
Oh gawd... this schizz has infected ANOTHER thread.  :palm:

These are JUNKED OSCILLOSCOPES. You can't assume anything about them.

mnem
 :popcorn:
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: grbk on April 25, 2019, 05:44:50 pm
Oh gawd... this schizz has infected ANOTHER thread.  :palm:

These are JUNKED OSCILLOSCOPES. You can't assume anything about them.

mnem
 :popcorn:

What's your point? In Dave's case, the scope in question appears to be rebadged. As you say, that's a risk you run when you get a used scope of unknown provenance.

In the general case, however, Dave is in a position to make a video about it, which may educate others that this is something to look out for when trying to purchase a used 2465. In particular, it might lead people to avoid the unscrupulous ebay seller in question (other epithets may apply).
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mnementh on April 25, 2019, 06:12:54 pm
Show me anything that in any way ties this guy we all already know about to a busted, scrapped out scope on a trash heap halfway around the world.

THAT is what's wrong with this. It's effing mob mentality, pure & simple. Dave has been notified; that could have been done via PM. All the rest of this is needless sensationalism that makes this place smell more like an episode of COPS than anything resembling reasonable discourse.  ::)

There's a whole thread already DEDICATED TO STIRRING UP THE SENSATIONALISM... can we PLEASE just leave it there until we actually KNOW something?

mnem
 |O
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on April 26, 2019, 09:00:45 am
Show me anything that in any way ties this guy we all already know about to a busted, scrapped out scope on a trash heap halfway around the world.

THAT is what's wrong with this. It's effing mob mentality, pure & simple. Dave has been notified; that could have been done via PM. All the rest of this is needless sensationalism that makes this place smell more like an episode of COPS than anything resembling reasonable discourse.  ::)

There's a whole thread already DEDICATED TO STIRRING UP THE SENSATIONALISM... can we PLEASE just leave it there until we actually KNOW something?

mnem
 |O

There are two separate things going on here. Firstly Dave's scope, and secondly the (alleged) activities of a fleabay seller.

Each can, and arguably should, be discussed on its own merits - either for amusement or as a cautionary tale.

There may or may not be a linkage between the two - but that doesn't change the above.

As for SENSATIONALISM, my feeling is that is a somewhat overwrought characterisation.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Satbeginner on April 30, 2019, 01:06:32 pm
Hi all,

Here a solution I found for a horizontal problem I had on (one of) my 2465.

The problem was that all horizontal traces, readout, etc. were waaaay too wide, also the time cursors were not shown.
Also when put in X-Y mode I still had a horizontal line, instead of a dot.


But the good news is: I solved it!!  :popcorn: :popcorn:

My assumption was that the horizontal shaped line must have been some kind of deflection??
In a way it was, but not some hum or ripple, it turned out to be the control of the last set of convergence grids.

On the A9 High Voltage board there is the Edge Focus potmeter (R1864), that sets the voltage on the vertical convergence grid.
Amplifier U1890B and Q1890 are supposed to invert that voltage to be used on the horizontal convergence grid as an inverting voltage follower.

After some searching I found that the voltage on the Quad Pole #3 was always -285V, regardless of the setting of the R1864 potmeter that did change the voltage on quad pole #4.
It was the €0,03 1MOhm feedback resistor R1891 that went all open :-), so no feedback so the output went as negative as negative can be.

So, instead of extra focussing the beam it did exactly the opposite, it spread the beam out completely, hence the line and the way too wide traces!

After replacing that resistor I have about the sharpest trace of all my scopes, so I am a happy bunny!  :-+ :-+

Now I will put it all together again and start the calibration.

Un saludo,

Leo
Title: Tektronix 2465B vs 2465 case comparison
Post by: BravoV on May 01, 2019, 07:59:11 am
Repost here as reference.

A fellow forum member, mnementh was requesting for a confirmation (HERE (https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/msg2380248/#msg2380248)), whether 2465B vs 2465 blue outer cases are identical, as he has part mules that planning to donate it related to Dave's at his EEVblog #1203 - 2465B repair video.

While for the back cover, the B version has thicker part at the internal axial fan location, compared to non B that uses a squirrel cage fan instead, I guess its not suitable for replacement, not very sure though.  :-//

Click to enlarge.
(https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=722181;image)

(https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=722259;image)
Title: Re: Tektronix 2465B vs 2465 case comparison
Post by: MarkL on May 01, 2019, 03:11:24 pm
Repost here as reference.

A fellow forum member, mnementh was requesting for a confirmation (HERE (https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/msg2380248/#msg2380248)), whether 2465B vs 2465 blue outer cases are identical, as he has part mules that planning to donate it related to Dave's at his EEVblog #1203 - 2465B repair video.

While for the back cover, the B version has thicker part at the internal axial fan location, compared to non B that uses a squirrel cage fan instead, I guess its not suitable for replacement, not very sure though.  :-//
...
Looking at the part numbers in the service manual, the case is part 437-0286-03 for 2465 serial B021870 and up, and also for 2465B serial B050000 to B050740.  So, for some period of time it was the same case for both scopes.  Looking back at the video, it's a little hard to read, but it looks like Dave's 2465B is B050574.

The rear cover for the 2465 has two part numbers, 200-2685-00 for the squirrel cage fan and 200-2685-01 for the updated axial fan.  The 2465B is 200-3200-01.  So, Dave will presumably need the rear cover specifically for the 2465B.

(I'll just post here since mnementh reads this thread too.)

Title: Re: Tektronix 2465B vs 2465 case comparison
Post by: BravoV on May 01, 2019, 06:34:29 pm
Repost here as reference.

A fellow forum member, mnementh was requesting for a confirmation (HERE (https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/msg2380248/#msg2380248)), whether 2465B vs 2465 blue outer cases are identical, as he has part mules that planning to donate it related to Dave's at his EEVblog #1203 - 2465B repair video.

While for the back cover, the B version has thicker part at the internal axial fan location, compared to non B that uses a squirrel cage fan instead, I guess its not suitable for replacement, not very sure though.  :-//
...
Looking at the part numbers in the service manual, the case is part 437-0286-03 for 2465 serial B021870 and up, and also for 2465B serial B050000 to B050740.  So, for some period of time it was the same case for both scopes.  Looking back at the video, it's a little hard to read, but it looks like Dave's 2465B is B050574.

The rear cover for the 2465 has two part numbers, 200-2685-00 for the squirrel cage fan and 200-2685-01 for the updated axial fan.  The 2465B is 200-3200-01.  So, Dave will presumably need the rear cover specifically for the 2465B.

(I'll just post here since mnementh reads this thread too.)

Thanks for bringing this out.  :-+

I didn't have any idea at all, that 2465 has two versions, and even both use axial fans, the 2465B vs 2565 back covers probably are different too, good to know.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mnementh on May 02, 2019, 01:25:01 pm
Yup, I'm aware of the differences between the rear covers; I'm actually working up an article that revolves around modern replacements for the 1st-gen 2465's Seimens motor & blower. Whether or not the motor on yours has actually died ( I posted a DIY on refurbishing that (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1863828/#msg1863828) about a year ago here), the stupid plastic collet on the blower wheel ALWAYS breaks sooner or later, so the stock cooling solution is always suspect.  :palm:

Right now I'm waiting on a HVAC anemometer to arrive so I can actually do some qualitative assessment of the various candidate solutions I've collected; going to do a shootout of "closest to OEM functionality" to "easiest to implement but still cools adequately".

Here's what I consider to be my top candidate solution that A) fits under the stock 2465 rear cover and 2) works similarly to OEM. It's a lot of hand fabrication, though.

https://youtu.be/Gn_-z-noVGs (https://youtu.be/Gn_-z-noVGs)

mnem
(https://i1183.photobucket.com/albums/x462/mnemennth/TinkerDwagonRevised.jpg)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: bdunham7 on May 08, 2019, 09:15:35 pm
I've been reading this thread, but I haven't yet found the info relevant to my problem.  Apologies if I'm being repetitive.

I recently acquired an older 2465B, s/n B016294.  It displays a Test 04 Failure 02 on startup. I've run it on my bench and tested a number of functions and everything works OK as far as I can test it--there's a couple of snapped off knobs and a few more bent ones--and the unit is in otherwise good condition.  I also don't really know the ins and outs of operating this thing, so I can't say "everything works".  The Exer 05 test reveals 49 power on hours and 8 power cycles.  It must be new!

It has the battery and board as pictured below.  The battery is not low and has 3.6+ volts, and cycling the power increased the power cycle count to 9. 

This unit came from a recycler that works with DOD and similar industries, some of which have requirements to "clear everything" before anything can be scrapped.  Is it possible--and likely--that the calibrations were deliberately cleared somehow?  Is there some other likely cause?  What should I do next with this beast?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: jonpaul on May 09, 2019, 04:34:34 am
Hello test 04 fail means cal data lost

Serial number indicates early production

Hours and starts are stored in the cal data, can be reset on cal and not a reliable indicator of treu hours!

The odd readout confirms need for complete recalibrattion

The 3.6 v lithium should be replaced as its probably from 1987.

See earlier posts on calibration or search 2465b calibration

Power supply caps may also need recapping.

Good  luck

Jon
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: bdunham7 on May 09, 2019, 08:35:10 pm
Thanks!

The question for me is *HOW* the cal data was lost!  Is there a front-panel way to erase it?  My approach to old equipment like this is first repair, then restore--simply because I don't want to put a lot of time and money into something that may ultimately be unfixable.  If I have a parts scope, then I'd like to know sooner than later.  I don't know the age of the battery, but the fact that it is 3.6+ volts seems to me to indicate that it is not the cause of my cal data loss.

Other than the power supply, is there anything else (especially unobtanium parts) I should check out before digging in?  And is early production a problem at all?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on May 09, 2019, 10:01:04 pm
2 basic ways your calibration data could have been lost. If the battery was improperly replaced it will lose cal data. An outside power source must be provided while changing the battery or else the data goes bye-bye. The other method is you have bad ROM and the cal data is corrupt. Either way a full calibration will be necessary and it requires a lot of equipment that typically most of us don't have. 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mnementh on May 13, 2019, 02:42:38 pm
I've seen folks get one up & running by using a copy of the cal data posted in this thread; obviously your scope won't be calibrated properly, but you can at least get past that point in the POST to see if there are other terminal failures that would be cost-prohibitive to repair. No, I can't give a more detailed outline on the process with your machine; I've never actually done it myself. ;)

Can you inspect the other side of the board? Since your battery is showing as-new voltage, I suspect somebody may have replaced the Keeper pack either after the cal data was already lost, or without providing proper backup power while doing the swap.

[EDIT]

Woops... I'm not sure, but that was probably on a newer machine with the Dallas NVRAM, which can be programmed with a burner. On yours it would probably need to be programmed in situ, so not sure how one could do that without doing the actual cal procedure. I don't know if you can manually edit the cal data from the front panel; even if possible would be very tedious with low probability of success.

[/EDIT]

mnem
*Back into the abyss*
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: WastelandTek on May 14, 2019, 03:18:45 am
This thread is huge, and my search attempts are being frustrating.

Can someone point me at a writeup on reading out the Dallas NVRAM?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Cooler Than I Look on May 16, 2019, 01:00:13 am
From my notes, very likely from this thread somewhere...

The calibration constants from EXER 02 are located at addresses 1E00 - 1FFF in the NVRAM.

This means that if you see "00 12BC" this means the word at address 00 is "12BC" hex. This is stored on chip at address 1E00. So on address 1E00 on the chip you will have 12 hex, than on address 1E01 you will have BC hex. Than, if you got "01 3456" on the screen, this is stored as 34 hex on address 1E02 and 56 hex on address 1E03. And so on...

This routine allows the operator to examine the contents of 256
decimal locations, 00 (Hex) through FF (Hex), in RAM.
When entered, the Exerciser displays the contents of RAM
location 00 (Hex) on the top line of the CRT display. One
hundred and seventy calibration constants reside between
addresses 01 (Hex) and AA (Hex). Calibration constants
residing between 01 (Hex) and 6E (Hex) should have odd
parity as explained below. The remaining locations may be
of either parity. The readout display line has the following
format:
AA DDDD P
The format is defined as follows:
"AA" is the eight-bit address in hexadecimal notation.
"DDDD" is the 14-bit word stored at that location (13
bits of data and one parity bit).
"P" is a parity indicator for the data word: X indicates
even parity; blank is odd parity.


I recorded the screen as a movie while stepping through the locations as a safe backup in case things went wrong removing the chip from the board.  But it all went well.

Murray
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: bdunham7 on May 16, 2019, 03:36:27 pm

Can you inspect the other side of the board? Since your battery is showing as-new voltage, I suspect somebody may have replaced the Keeper pack either after the cal data was already lost, or without providing proper backup power while doing the swap.
mnem
*Back into the abyss*

That appears to be the answer (see photo) as the battery solder connections look different and less precise than the rest of the board.  I went into this project thinking I had and old, dusty, damaged (it has been dropped on its nose with some minor damage) but unmolested scope.  Now I see that it someone has attempted to fix it at some point and done some hopefully minor damage.  The impact damage is worse than I thought as well, so I'll be asking for even more help here.  I hope I don't have a parts mule, but if I do, somebody tell me now!

Somebody has put three screws that are too long into the back cover, two of them have contacted internal parts, although I see no serious uncorrectable damage...

The impact damage looked to be mainly the cal/var knobs on the two volt/div controls--the small knobs are missing and the plastic shafts are sheared flush.  I located replacements from QService in Greece.  There are a few of the smaller pots (intensity and readout intensity) that wobble, but work.  However, I now see that the time/B-sweep controls are wrecked---I can't get B-sweep as the controls don't respond to either pushing or pulling, but the regular time/div and var controls work more or less normally.  As you can see in the photo below, the backside of the var pot is busted out--I haven't disassembled this far enough to see what has happened to the A6A1 board or switch S3019. 

The scope mostly works OK, bandwidth appears OK (900 ps rise time) and so forth.  Tube is bright and even, no anomalies so far.  I'm assuming this is still worth fixing, unless some control part I need is unobtanium.  Advice please, and if it isn't too basic, what is the best way to remove the front panel circuit board?  I just repaired a 2235 that needed a thumb switch, which was actually a lot of work and I realized later I'd really taken the long way around in removing the panel.  This one looks different, so I thought I'd just ask.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on May 16, 2019, 04:02:56 pm
Yep, some gorilla has been in there. Now I can't help you with the availability of parts but I can tell you how to get that front panel assembly out.

Remove the Intensity, Focus, Readout, and Scale knobs. Be careful and use heat or else they will crack.

Running along the top edge of the scope is a plastic strip. Carefully pry it up.

There will be screws in there. Remove them. There will also be screws on the bottom. Remove them too. Edit....and on both sides too.

The front bezel will pull off. Once off you can pull the front panel assembly.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: bdunham7 on May 16, 2019, 08:00:27 pm
Yep, some gorilla has been in there. Now I can't help you with the availability of parts but I can tell you how to get that front panel assembly out.

Remove the Intensity, Focus, Readout, and Scale knobs. Be careful and use heat or else they will crack.

Running along the top edge of the scope is a plastic strip. Carefully pry it up.

There will be screws in there. Remove them. There will also be screws on the bottom. Remove them too. Edit....and on both sides too.

The front bezel will pull off. Once off you can pull the front panel assembly.

Thanks--that was actually easier than I expected!  And I was able to leave those 4 knobs stuck in the front bezel just like the other knobs stay in the front panel.  I've got a broken B-sweep actuator collar, two snapped shafts and a busted-out pot.  Lucky me, QService has them all, now I just wait for a package from Greece.

Whoever was in there really tried to fix it--they stuffed the guts back in the busted pot and tried to put a little screw in one of the empty holes.  In this case, I am going to decline the usual practice of giving credit for trying. 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: bdunham7 on May 16, 2019, 08:23:23 pm

Can you inspect the other side of the board? Since your battery is showing as-new voltage, I suspect somebody may have replaced the Keeper pack either after the cal data was already lost, or without providing proper backup power while doing the swap.
mnem
*Back into the abyss*

That appears to be the answer (see photo) as the battery solder connections look different and less precise than the rest of the board.

Well, maybe not!  I just now noticed that the battery has a printed code (in white) on the side that says "1589".   If that's a date code, the battery is 30 years old.  I suppose Mr. Gorilla B. Hacker still could have unsoldered and resoldered it for some reason.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: WastelandTek on May 19, 2019, 03:37:56 pm
From my notes, very likely from this thread somewhere...

/e-pirate quote snipped/

Thank you, yes a search for that text points to a post on page 12 of this thread  https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg510586/#msg510586 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg510586/#msg510586) , and that is some good information.

I am hoping for a more general writeup outlining the equipment I will need and any pitfalls for new players, I don't have any experience working with chips like this.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Cooler Than I Look on May 19, 2019, 10:21:42 pm
Quote
I am hoping for a more general writeup outlining the equipment I will need and any pitfalls for new players, I don't have any experience working with chips like this.

Neither have I so it was with some trepidation that I took this on.   I unsoldered the Dallas chip with a S-993A vacuum pump (cheap Hakko copy) after practising on some old PC boards.  I just took it slow and released one pin at a time, letting the board cool in between.  From memory there is at least one earth pin that takes some heat to get right through and I left this to last and used my normal iron to release it.     In its place I installed a low profile socket.

I read the NVRAM in a TL866 minipro (made serveral copies!) and burnt that to a 'new' Dallas chip from Ebay dated 2009 but thats much younger than the 1992 chip it replaced!  And now that the NVRAM is socketed its an easy job to replace in the future.

Reassembled the scope, held my breath and turned it on.  Worked and has done since I did this about 18 months ago.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: WastelandTek on May 21, 2019, 05:11:24 am
Thank you Cooler, I will get one of those programmers and see what I can do.

Is there any "permanent" solution for this?  or is plugging in "less old" parts the best we can do?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Cooler Than I Look on May 21, 2019, 10:01:36 pm
Quote
Is there any "permanent" solution for this?  or is plugging in "less old" parts the best we can do?

Probably but its good enough for me.  Now I have a copy of the data I can burn a new NVRAM as needed but they seem to last for decades.  In that time will the calibration data still be valid anyway?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on May 22, 2019, 02:39:13 am
Thank you Cooler, I will get one of those programmers and see what I can do.

Is there any "permanent" solution for this?  or is plugging in "less old" parts the best we can do?

I replaced the Dallas NVSRAMs in my 2440 with EEPROM backed up SRAMs so there are alternatives.  FRAMs have some special precharge requirements but apparently work.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: WastelandTek on May 22, 2019, 02:43:19 pm
What part did you use David?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Cooler Than I Look on May 22, 2019, 11:12:49 pm
Have a look at http://worldphaco.com/ (http://worldphaco.com/)  about half way down "...2465B...  ...repowering the DS1225..." (title too long to type).  Hugo talks about alternatives to the Dallas NVRAM in that pdf article.

Don't get distracted by his amazing restoration work, especially on early televisions. 

OK, do get distracted.  Well worth it.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on May 23, 2019, 03:05:32 am
What part did you use David?

Well, let's see.  I bought a couple extras and have them right here.

The 2440 used a pair of DS1230AB-120s and I replaced them with Simtek (https://en.wikipedia.org/wiki/Simtek_Corporation) STK16C88-WF45s which being in DIP packages were direct drop-in replacements.  Simtek was bought by Cypress in 2008 which was years before I bought the chips but they were still marked Simtek.

For those who are not aware of this technology, it uses a SRAM which is backed up by floating gate memory.  The entire array is backed up in parallel when power is removed and restored in parallel when power is applied.  Some variations require an external capacitor connected to a dedicated pin to provide backup power but many like the STK16C88-WF45 I used do not.

Last time I checked, the DIP parts were discontinued but surface mount parts were still available and could be adapted with an interposer.  Third parties may have the DIP packaged parts as NOS (new old stock) for sale.

I have also heard reports of parallel FRAM memories working as direct replacements as I mentioned in an earlier post.  This have special timing requirements for their -CS pin because they require a precharge operation before every read but these Tektronix oscilloscopes apparently meet this requirement which is not unusual.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on May 23, 2019, 11:43:55 am
...
I have also heard reports of parallel FRAM memories working as direct replacements as I mentioned in an earlier post.  This have special timing requirements for their -CS pin because they require a precharge operation before every read but these Tektronix oscilloscopes apparently meet this requirement which is not unusual.
I would not opt for the FRAM solution.  There was a discussion from user Miti having corruption problems starting here-ish:

  https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg2003207/?topicseen#msg2003207 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg2003207/?topicseen#msg2003207)

The short version of the related posts is that the power-down behavior of the 24xx does not meet the FRAM (in Miti's case, FM16W08) datasheet requirements for safe power down.  It seems to work for most people, but from a design perspective it's still risking the data without additional support circuitry to safely control the chip select.

The Simtek/Cypress part, now CY14E256LA, looks like a great suggestion.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on May 23, 2019, 03:28:53 pm
My scope works well with FRAM after I installed the pull-up resistor. If you have a copy of the calibration constants, I think it's worth a try. Even though, replacing DS1225 with a new DS1225 would push scope's life beyond its reasonable life expectancy. I don't expect many Tek 2445, 2465 in use in another 20 years.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: WastelandTek on May 23, 2019, 04:25:26 pm
I want to express my thanks for you guys veering into this discussion for me.  I'm sure it is all in the thread back there somewhere...but 60 pages...

My 2445 still boots fine, for now, but this is clearly something I need to get up to speed on and address sooner than later.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Hamid_tehran62 on May 28, 2019, 05:54:23 pm
What is it?
DMI 500-2044
It is in the tek tronix power supply
How i can check it?
Anu data sheet?
(http://)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: bdunham7 on May 28, 2019, 06:32:11 pm
What is it?
DMI 500-2044
It is in the tek tronix power supply
How i can check it?
Anu data sheet?
(http://)

Is this in a 2465B?  I think it is a common-mode RF choke, but I remember seeing one like it in my 2235, but not my 2465B.  I'll be digging around in the 2465B later on and I'll look.  You can check it for continuity--it has four pins and two isolated coils.  What problem are you trying to solve?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on May 29, 2019, 05:30:55 am
...
I have also heard reports of parallel FRAM memories working as direct replacements as I mentioned in an earlier post.  This have special timing requirements for their -CS pin because they require a precharge operation before every read but these Tektronix oscilloscopes apparently meet this requirement which is not unusual.
I would not opt for the FRAM solution.  There was a discussion from user Miti having corruption problems starting here-ish:

  https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg2003207/?topicseen#msg2003207 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg2003207/?topicseen#msg2003207)

The short version of the related posts is that the power-down behavior of the 24xx does not meet the FRAM (in Miti's case, FM16W08) datasheet requirements for safe power down.  It seems to work for most people, but from a design perspective it's still risking the data without additional support circuitry to safely control the chip select.

The Simtek/Cypress part, now CY14E256LA, looks like a great suggestion.

I am arriving late to this discussion, but wanted to confirm that the FRAM that I put into my 2465B has been working flawlessly for months now and has so far yet to show any data corruption problems as mentioned since it replaced last year the original NVRAM. And I would think there are for sure other documented examples out there successfully using a FRAM and that had no problems either. So just wanted to constructively bring this to the discussion, and point out that maybe there is still some unidentified "X-factor" out there that makes some scopes corrupt the data. But for sure mine is booting up perfectly every time, and with the same configuration before power down which is also being saved. So just saying that maybe don't blame yet the problem squarely only on the FRAM itself being incompatible with the scope.

EDIT: ok so after re-reading the above, as stated by MarkL the X-factor might be that the FRAM requirements for safe power down are not being fully met. But if it works for the majority of the cases it sounds it must be very close. Does anybody know if there is anything that can be done (that is not too complicated) in order to come closer to those power down requirements?

So if the preceding is right, sounds like I'm just one more that got lucky? Back then besides the FM16W08 I also had programmed the fresh NVRAM with the original data, and put it aside in case it is ever needed.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MavMitchell on July 30, 2019, 03:53:52 am
Hi all, I was able to wrangle down a clean high sn#  2465B on our favorite auction site for a reasonable price. Sold as not working(out of calibration) it had minor damage on the A5 from the pesky SMD caps.

It also had a 1990 Dallas chip.

Thanks to all those who have contributed on this forum, I have been able to do a full re-cap and copy and replace the Dallas.
I got caught by the reversed C1132/C1115 issue, which was mentioned in this forum.

Thanks to all...

 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on July 30, 2019, 05:35:24 am
HiMavMitchell,

Welcome to hotel 2465, where you can check in at any time, but you can never -quite- check out.

Seems like this thread must be getting really good as a reference if you managed to successfully get through all the rebuilding process and did not need to ask a single question. By any chance got any pictures of your recap/A5 rebuild? Its always nice and interesting to see other persons work, and it further adds to the knowledge base of this long running thread.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MavMitchell on July 31, 2019, 12:21:00 am
Hi,

Pics as requested, C2113 caused the most damage. I had to remove and replace C2520,C2222 and R2016 for the cleanup.

The track repair was no issue except for the via between C2113 and C2520(completely gone). I was able to wire through the via to the pad on the other side. Its only a pad as its connected to an inner layer. I could have gone to the connector if needed as this net connects to the first pins on J251(-5 or 15v if I remember).

De-soldering the Dallas was no problem, and was able to read it fine. I had also done the Exer 02 screen capture just in case.



 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on July 31, 2019, 01:08:09 am
Good job, indeed much less damage than other cases. BTW on the same A5 board remember to check the capacitor on the exact opposite top corner, which also causes the same kind of corrosion problems.

EDIT: did you take any pictures of the power supply recap?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MavMitchell on July 31, 2019, 01:28:26 am
Yep, C2965 was also replaced. It had minor leakage that just needed cleaning of the board and C2890.

Also found leaking caps on the A3. One had completely lost one leg.

Rifas  were ok but replaced.


Very happy with my result.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on July 31, 2019, 02:02:55 am
Wow that cap missing one leg was definitively not doing any good anymore. Did you notice any sharpness improvement in the traces after the recap? Frequently that is the case. How long did it take you to get everything done, including pulling out the two power supply boards?

That reminds me I still have to do my own power supply recap and replace Rifa caps, luckily I'm on 120VAC so they have not exploded yet, but already show lots of little surface cracks. Since scope is working fine have been procrastinating, but at least already have everything here that is needed for a full PS rebuild. Soon...
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on July 31, 2019, 02:19:54 am
My scope works well with FRAM after I installed the pull-up resistor. If you have a copy of the calibration constants, I think it's worth a try. Even though, replacing DS1225 with a new DS1225 would push scope's life beyond its reasonable life expectancy. I don't expect many Tek 2445, 2465 in use in another 20 years.

Miti, if you don't mind, what value pull-up resistor did you use, and at what pin did you connect it to?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MavMitchell on July 31, 2019, 02:32:54 am
Actually I didn't run the scope for long when I received it. Just turned it on to make sure it worked, then shut it down. I didn't want to risk any explosions.

Removing the PSU boards is very easy, just need to remove the screws from the mains connector and move it out of the way to get access to the Voltage Selector wires. Also de-solder the fan power wire(make sure to re-connect during install - just saying).

After separating the boards, the recap took about an hour. I removed all the caps and cleaned the board then replaced with the new using the board overlay from the manual as a guide. This is where I hadn't done enough research about the error on the overlay.

After re-assembly and replacing the PSU, I discovered it was ticking on what I assumed to be over current. While checking the unregulated rails on the A3, I discovered the overlay error which I quickly fixed. Replaced the PSU and all was well.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on July 31, 2019, 05:35:43 am
Actually I didn't run the scope for long when I received it. Just turned it on to make sure it worked, then shut it down. I didn't want to risk any explosions.

That was a good call given you are on 240VAC mains, those old Rifa caps can go anytime at that voltage level. Worst part is that they smell like fish after they burst!  :(

Removing the PSU boards is very easy, just need to remove the screws from the mains connector and move it out of the way to get access to the Voltage Selector wires. Also de-solder the fan power wire(make sure to re-connect during install - just saying).

After separating the boards, the recap took about an hour. I removed all the caps and cleaned the board then replaced with the new using the board overlay from the manual as a guide. This is where I hadn't done enough research about the error on the overlay.

After re-assembly and replacing the PSU, I discovered it was ticking on what I assumed to be over current. While checking the unregulated rails on the A3, I discovered the overlay error which I quickly fixed. Replaced the PSU and all was well.

Best way to avoid that board overlay error is to pull one cap at a time and replace before moving on to the next one, and noting the polarity of the cap itself before pulling it off the board. That is what I intend to do.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on July 31, 2019, 03:39:01 pm
Quote from: AMR Labs link=topic=5397.msg2582682#msg2582682 date
Miti, if you don't mind, what value pull-up resistor did you use, and at what pin did you connect it to?

1K nWE to VCC, pins 27, 28.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on July 31, 2019, 04:02:34 pm
OK got it. WE to VCC.
Thanks.

My FRAM so far has never had any problems, but I guess adding this resistor won't hurt anything. Will do it once I get to the LVPS recap.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Alfons on September 05, 2019, 03:07:00 pm
Super Thread, has always really helped. :-+

I purchased a defective Tektronix 2457B with Option 9 and 10. Error was, that the device turned on and off again and again. Even the smell showed that electrolyte must have leaked out. The device stank like a trash can.

After I opened the device, I discovered the leaked SMD electrolytic capacitors on the A5 controller board. The traces were not attacked and also neighboring components were still OK. After I had cleaned everything and used new Elkos, the device worked again. The error did not occur anymore.

Then my mishap: I soldered out the NVRAM chip to read it out. From now on I made all the mistakes you can only make.  :palm: When I put the chip in Programmer, which I only had a few hours, I just wanted to test the chip and erase all the data.  :phew: All data gone.
OK, I had the video of Exerciser 02 for safety's sake. The video quality was so bad that it's a miracle that I was still able to write all the data to the hex editor. But the device did not start now, Trigger'D flickered happily, the device complained about corrupt calibration values. Ok, I stayed calm, did not smash the device, I knew I could find the mistake. |O

I read everything there was to read, read the service manual, nothing. Then I came up with the idea of ​​looking at the solder joints of the NVRAM under the microscope and discovered that I had severed a trace directly at the solder pad while soldering out.  |O That's never happened to me. I am getting old.  :(

After I fixed that, everything work again. A great device, I've never seen such a good Oscillscop before.

A problem that was already there before: The display, but only the beam, flickers slightly and slow, not always and only in conjunction with my digital function generator. Not for example with my old analog pulse generator. However, the signal of the function generator does not flicker with the DSO and also not with the old Tek 475. The readout I had switched off, even with Cal 08 set the display. All voltage values ​​on the board are OK and look clean, ref values ​​of the DAC are -1.248 and 1.363.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on September 05, 2019, 05:30:44 pm
OK, I had the video of Exerciser 02 for safety's sake. The video quality was so bad that it's a miracle that I was still able to write all the data to the hex editor ... <snip>

But the device did not start now, Trigger'D flickered happily, the device complained about corrupt calibration values.....<snip>

... looking at the solder joints of the NVRAM under the microscope and discovered that I had severed a trace directly at the solder pad while soldering out ...<snip>

<snip>... everything work again.

Bravo  :clap: ... reading your "adventure" above, that you are saved by the Exer 02 video really excites me.

Thanks for sharing, this will be handy for others, or at least motivate them.  :-+
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Alfons on September 05, 2019, 06:06:33 pm
Thanks for the feedback.

Well, I wanted to be sure. That's why the video. And in my first tests with the device, I had the impression, that the calibration values are still OK. It had only 1200 hours behind and it has a high serial number, probably one of the last devices?.

Of course, I downloaded some bin-images here because I thought I had not transferred my data correctly. But the mistake remained. The chip was OK, could be described and read clean. Actually, it was logical, that I had caused a demange. Under the magnifying glass was nothing to see, only under the Microscope it was visible. And of course I could have measured all the traces and find it ...
I can only advise anyone to watch the video synonymous, if it is OK. I had extra download a video-cut-program to improve the image quality and then it went. My God, two days went for it, just because I did not work properly. Well, I learned something else for that.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Alfons on September 06, 2019, 12:27:18 pm
Still looking for the cause of the flicker. And came across other things ...

I programmed the NVRAM with a bin file from another 2467B to see, if it changed a bit because of the flickering, so it might be affected by the cal values. The device started normally, but reported errors because of the installed option 9. Also in the lower readout points appeared between displayed values. Nothing changed on the flickering. So again programmed the original firmware, that I had previously saved as a video and copied.

The device started normally, but at the end it showed Fail 4 10. After I pressed A / B-trig everything went normal. What happened now? Another NVRAM programmed, the same. Something was wrong with the Cal values. But why did it work without errors, before I played the other bin file.

It occurred to me then, that in the meantime I was running Cal 08 and that, after I played the original bin file. So I ran through CAL 08 again, without setting anything and then the error disappeared. As it stands, the software actually stores CAL 08 values, even though they are not set by software, but by trimmers.

You always learn something new about the device. It is only important that the error message Fail 4 does not necessarily indicate a defective NVRAM or incorrect (Cal 1) calibration values.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Alfons on September 07, 2019, 01:53:13 pm
Ok, even if I give the solo entertainer here: :)

The flicker occurs only in connection with the Owon AG1012 and only in the range between 5-10Mhz. If I press the x10Mag button, the flicker disappears too. The signal representation is otherwise first class. The CRT is extremely bright, so I almost completely reduce the intensity for normal signals. Only with critical signals do I turn up a little more. There is a screen panel installed, which increases the contrast. It is not this blue that you usually see on the other devices in the series.
Actually I wanted to sell the device again, but I will keep it. You should not give that up. A fantastic device.  :-+

Maybe I'll change the Elkos in the power supply. I have all lying here (Panasonic FR).
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on September 07, 2019, 02:08:11 pm
Are you aware that the CRT beam is used for both the readout and the trace. If it it drawing the readout, it isn't drawing the trace. This timesharing leads to flicker.

Test. Get a display with flicker. Rotate the readout knob to the centre, so that there is no readout. Does the flicker disappear?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Alfons on September 07, 2019, 02:29:04 pm
The flicker is independent of the position of the readout knob. But others also wrote that, who have this flicker too. It has nothing to do with the readout, it also occurs when the readout is turned off. It has a very slow frequency, anything around the 2-3 Hz, it looks like waves of a modulation.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Koreth on September 12, 2019, 06:06:38 pm
Hello all,

I have recently come into possession of 4 Tek 2465Bs. I purchased them on the cheap as they were all listed as "for parts", "not working", "untested", etc. I'm well aware of the fact that all of them will need repair work to be functional, and some parts may be hard to come by. I'm okay with that; the whole point of the purchase was to begin a restoration on a complex device, which, after completing, I would have a useful and capable tool,  and understand it's function, capabilities and limitations better than the average bear. I'm pretty sure that between the 4 scopes, there's enough parts to get at least one of them operational, if not two. If I can get 3 or all 4 fully functional, freaking awesome :D, but I'll be happy with two.

I wasn't sure if I should post here in this thread, start my own thread here in the Test Gear section of the forums, or perhaps one in the Repair section. But, this thread seems to have become the de facto thread for pictures of 2465B teardowns, so I figured the photos I took during the teardown I did of the first scope would be appropriate here, at least.

So here they are. The first two arrived earlier in the week, the 2nd two arrived later in the week.

B0152xx - 2465B CT
B0120xx - 2465B
B0123xx - 2465B CT
B0595xx - 2465B CT
[attach=1]
[attach=2]

I'll be honest, I purchased B120xx to serve as a parts mule for the others. As I go through these scopes, I'll be moving all the broken bits and problems to that one. Then, if it is still in salvageable shape at that point, I may work on restoring it. Or I may part it out to have spares on hand to keep the others alive, or sell off the parts to recoup my costs. We'll see. It seems a shame to treat what was once a nice instrument as scrap, but if its still good or easily-restoreable parts can serve to keep its brothers functional and useful, that strikes me as less of a shameful waste than it ending up in a landfill or dissolved in hazardous chemicals to extract the precious metal content.

I was hoping to put this all in a single post to this thread, as it's been my experience on other forums that such is considered better etiquette. However, it looks like there are limitations on total attachment size, and I didn't want to shrink my photos down too small, lest details be lost. So, I'll be following this post with a number of other posts, each containing a logical group of photos, shrunk to keep it under the attachment limit.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Koreth on September 12, 2019, 06:11:49 pm
B0152xx  I opened up first; I have not even attempted to power it up. When I received it, I heard something rattling around inside, and I did not want to take the chance that whatever the something was, that it was something conductive, or that it might land across a couple points that should not be conducted across.

First up is pictures of the casing. The case was a right mofo to get off. I don't know how clear it is in the photos, but the case has taken a few good, hard smacks, including one to the right handle mount, collapsing that inward causing it to rub against the chassis. I ended up bending a bit of the rear panel trying to pry the collapsed parts past where they were hanging up. I'll have to bend that back later to the case will mount properly. You can see in one of the pictures that one of the screws for the bag on the top had been lost and replaced with another screw that's way too long. I had to screw that out to avoid it hanging up on the chassis or damaging the components as I pulled the case off.
[attach=1][attach=2][attach=3][attach=4][attach=5]
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Koreth on September 12, 2019, 06:26:16 pm
After disassembling the scope enough to get at the power supply and seeing its condition, I knew that this project was going to take a while. With that in mind, I focused on getting the case back into shape that it could slide on the chassis easier without scraping on the chassis or being a risk to the components therein. Some work with a 45oz deadblow hammer and some flat boards did the job. Turns out, a piece of scrap 1x6 board from the local big box home improvement store fits inside the case just perfectly.

There is definitely a visceral satisfaction that comes from bending things to your will by pounding them with a hammer.

It's not perfect, but it will do. Hopefully the pictures show the reduced degree of protrusion on the inside of the case. In the future, I'd like to get another board and cut a 3 inch hole it it so as to give some room for the mounting boss to be hammerd out, while properly flattening the rest of the case, but this will do for now. It lets the case slide back onto the chassis, keeping dust and debris out of the unit while I'm not working on it, hopefully reducing the amount of self-inflicted work I will have to do in order to get B0152xx operational again.
[attach=1][attach=2][attach=3][attach=4]
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on September 12, 2019, 06:26:42 pm
Yes, this thread has become a "catch all" for the entire 2465 series. So go ahead and post your adventures of repair or questions here. You'll get the quickest response because a lot of folks monitor this thread.  :-+
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Koreth on September 12, 2019, 07:19:49 pm
med6753: noted (and exemplified by your reply not a minute after my own, while I was preparing the next batch of pictures!)

With the case off, let's examine the A1 board,  in all of it's fully-optioned glory (note the extra cables draped across it going to various headers on the board). One of the cables routes right by the much-discussed unobtanium U800. I'm slightly worried that they might impede airflow, but if the scope still works after I get the power supply repaired and U800 doesn't show any signs of thermal stress, then I intend to leave it the hell alone. I suspect more U800s have been destroyed by monkeying with them when it wasn't necessary.

When I posted this picture elsewhere, I was told that this board was a thing of beauty. I kinda agree. When I was a child, all those through-hole doodads were inscrutable deep magic. Now that I've grown and understand that the actual magic is the smoke hidden inside each doodad, I can really appreciate this board. This board was not trivial to lay out and took some serious engineering to get right. And with the invariable parasitic impedance that comes with through-hole components, the fact that it sucessfully operates at 400Mhz is quite impressive. Mad props to the Tektronix engineers for making it it all work without wholly sacrificing the ability to effect adjustments or repairs in the field.

There will be close-ups in the next post.
[attach=1]
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Koreth on September 12, 2019, 07:33:37 pm
[attach=1][attach=2][attach=3][attach=4]

Not much to say here other than remark on the date codes. The date codes on the various 3rd party ICs look to be from late '88, and the Tek-made heat-sinked opamps have date codes from the last week of February, and the 1st week of March, of '89. The latter is the latest datecode I've seen so far. So I'm going to guess that this scope was  built in early to early-mid March of '89.

I don't see any damage to any of the parts of the board, or broken components, thank-god. Some of the parts on that board are definitely unobtanium.

There's only a few electrolytic capacitors on the board, but given their age, I intend to at least check them and verify they are still within spec. But that can come later.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Koreth on September 12, 2019, 07:53:18 pm
Next up, we have pictures of the CRT-side of the chassis. If you look you can see scrapes on the chassis where the case refused to come easily. But, looking closely, I an see that none of the parts going down into the tube's drive mechanism itself are damaged.
[attach=1][attach=2][attach=3]

After that, we can see the top plate, which protects the power supply, and the various option boards. In these pictures you can see scrape marks from that way-too-long screw in the second post in this series. I'm glad I noticed that before it did some serious damage.
[attach=4]

In the next photo, I have a confession to make. You can see from the disconnected leads going to the word-recognizer trigger board that I had in fact begun taking this scope apart before taking pics. I put it back together again so I could properly document the teardown with pictures, but I couldn't remember which order the leads went on, because stupid me hadn't taken pictures before disassembly, and there were no helpful markings stamped into the metal plate. Oh well, I'll look it up in the service manual later.
[attach=5]
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Koreth on September 12, 2019, 08:03:15 pm
Nothing terribly exciting here except some more pics of the the top plate.

I do note a couple things.  There's various marking stamped on the plate denoting connections, A-E for example on the CRT side of the plate. I have headers C, D, and E, populated. For comparison, those were not present when I opened up the plain 2465B, B0120xx. I wonder, are those cables supposed to carry signals from the option boards down to the main board?

Another stamped marking to note is Pin 1, in various places, where a ribbon cable connects either to the option board, or the A5 board down just the side of the chassis from the marking. Another bit of attention to detail that tells you that Tek build this thing intending for it to last and be servicable, not be some hermetically sealed throwaway device. Such design came with a pricetag of more than my parents' combined monthly salary in the 80s, but, hey, you get what you pay for.
[attach=1][attach=2][attach=3][attach=4]
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Koreth on September 12, 2019, 08:24:08 pm
Onto the A5 board.

One thing I note here, is that unlike most of the teardown pictures I've seen of 2465Bs, is that the A5 board is 1) all through-hole in design, and 2) the infamous leaky SMD capacitors, with their board-and-component-destroying corrosive electrolytic aren't present. In their place are a few regular through-hole axial electrolytics. So, I think I dodged a bullet there. However, due to the scope's age, I do intend to test those electrolytics to ensure they have not drifted out-of-spec over the past 30 years.

[attach=1][attach=2]

Another thing I note is that I don't have the famous Dallas battery-backed SRAM, as seen on the later, SMD-style A5 boards. This thing looks like a plain battery, not a RAM-chip or ROM chip of any kind, especially given it's only 4 pins on the board. Apologies for the blurry photo there, but it looks like there's some dried flux residue on those solder joints. I don't know if that's normally there, or if that means that this board has been worked on before, and the battery has already been replaced once. It's hard to tell, given the lack of date codes on the label. I'll have to compare the A5 boards in my other pre-B5xxxx scopes.
[attach=3][attach=4]

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on September 12, 2019, 08:25:24 pm
Some of your scopes have the Counter/Trigger option which accounts for the additional ribbon cables you see.

You are wise to leave U800 alone. The additional ribbon cables over it from the options will NOT affect it. I have a 2465 DMS which is fully optioned with the C/T as well as the DMM option and I've never had any issues with U800. The key to U800 longevity is adequate airflow which means keeping the fan operational. Playing around with U800's mounting screws and attempting to add additional heatsinking is just asking for trouble....although they are some who will disagree with me. 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Koreth on September 12, 2019, 08:42:14 pm
The more astute of you might have thought that maybe something was missing in those pictures of the A5 board. You would be correct. As I mentioned before, when I first received the scope, I heard something rattling around inside the case. When I stated to remove the case, I found what it was: the 10.000Mhz crystal from the A5 board. Apparently, when the side of the case took the hard smack that collapsed the handle-mounting boss inward, that impact also knocked the A5's crystal free from the board. Well, damn. That's gonna be an important thing to fix if I want the scope to work at all. Microprocessors have a hard time working without a clock to drive them, after all. I forgot to take pictures of this, or of the crystal itself. Sorry. :(

Fortunately, I dodged another bullet here in a way. Take a careful look at the solder joints on the back of the board where the crystal was. The joints are still there, less two tiny holes in the middle where the crystal's leads were. I do believe I somehow managed to escape damage to the board, pads and traces. I'll probably want to replace the crystal with a new one, but damn! That could have been much, much worse, with potentially the A5 board damaged beyond repair.
[attach=1]

A well laid out board is a thing of beauty. Anyone else here getting memories of Tron? :D
[attach=2][attach=3][attach=4]
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Koreth on September 12, 2019, 08:58:07 pm
Onto the front of the scope. Probably should have done that first, before disassembly. Live and Learn. Before you ask, no I don't have pictures of the rear of the scope. I'll take some later.

While all the main controls are intact, I'm especially thankful that the volts/div and time/div knobs were undamaged by prior owners or during shipping. Unfortuantely, there is some damage to the front panel. Note the punctured hole on the trigger indicator lights. Additionally, the knobs under the display are missing their outer part.

I can borrow the smaller knobs from B0120xx. I also have a couple face plates that I ordered, without damage to their clear portions for the indicator LEDs. That will go back on during reassembly. I will tear apart the front panel further at a later date to make sure that there isn't any other damage that needs addressing. As a bonus, the face plates ordered also have the markings for the TV trigger option board controls, and I managed to snag a couple of those. So, when this scope is brought back online, it will be damn near fully optioned. What person wouldn't want a fully-optioned Tek scope for their home lab or hackerspace? :D
[attach=1][attach=2][attach=3][attach=4][attach=5]
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Koreth on September 12, 2019, 09:18:18 pm
With the top plate off, now we can take a look at the options boards. One of these controls the GPIB interface, the other controls the Counter/Trigger/Timer option. I apologize for the light levels in these photos, the flash on my phone is fairly powerful and can do a pretty good job of overwhelming the sensor.

In the 1st pic, you'll see a blank label on one of the chips. When I opened this up originally, the window of that PROM was exposed, and a no-longer-sticky label came fluttering out of the chassis. I cut a piece of plain label and stuck it atop the chip to protect it. The label is tucked in a baggie with the screws and the crystal from the A5 board, so it doesn't get lost.
[attach=1][attach=2][attach=3][attach=4]

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Koreth on September 12, 2019, 09:24:20 pm
I'm not sure what this board is, or what it does. I do believe it is a standard board, as when I opened up B0120xx for comparison, it also had this board in it. Whatever it is/does, it fits in the central cavity of the scope, between the option boards and metal wall, and has a ribbon cable that goes through the floor of the central cavity and connects to the A1 board. I was going to leave it in place, initially, but I found it easier to get at the power supply assembly with both hands with it out of the cavity.
[attach=1][attach=2]
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Koreth on September 12, 2019, 10:07:01 pm
And finally! Onto the power supply! :D

I was especially interested in this, given that there are known failure modes with the power supply, especially the capacitors hanging off the rectifier cracking their cases from heat and age, and eventually blowing.

Of course, as soon as I got the assembly free and out into the light, I had to wince. Yeah, something caught fire and went boom there. I knew the box caps in the rectifier were problematic, but damn. They took out at least one resistor and possibly other components with them, as well. But fortunately nothing else in the rectifier section *looks* immediately damaged. Looks be damned, I'll be verifying the spec of every other component in this section and immediately downstream of the rectifier section. If only a minimum of components in the rest of the power supply assembly are damaged, then I'm tempted to turn that fried resistor into memorial, honoring its self-sacrifice to protect the rest of the PSU.
[attach=1][attach=2]

It may amuse y'all to know that the fried resistor actually has not released *all* of its magic smoke. I measured it after taking these photos. Per the schematic, it's supposed to be 30 Ohm. Well, now it's a very crispy 2.68 kOmh resistor (or 26.8 kOhm, I'll check again when I get home).

Moving onto the rest of the CPU, we can see the usual components of a switching power supply. Fortunately, none of the regular electrolytic capacitors look swollen or otherwise damaged, but they're going to be checked anyway, given their age, and especially given the current surge the PSU was subject to. I do see more of those problematic box caps. Those are getting replaced, period, given their history. I'm not waiting for them to fail.
[attach=3][attach=4][attach=5]
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Koreth on September 12, 2019, 10:15:06 pm
That's all I got for now. I'll post more pictures as I do more work.

I know there's a parts list (or a few of them) for the various capacitors in the PSU floating around both in this thread and the Tek Scopes group on group.io. However, I want to do a bit more research first, test and verify the components on the A2 and A3 boards, and understand what it is I am replacing and why. For that was one of the points of buying a pile of broken scopes to repair; get a better understanding of my tools by learning how to fix my tools.

A member of my local hackerspace found the service manual for these scopes. Additionally, I have found reprints for sale, and I'm tempted to pick up one of those as well. digital copies can be convenient, but paper can be pretty convenient as well, especially when you need the whole diagram in front of you in a readable size.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on September 13, 2019, 06:04:09 am
Of course, as soon as I got the assembly free and out into the light, I had to wince. Yeah, something caught fire and went boom there. I knew the box caps in the rectifier were problematic, but damn. They took out at least one resistor and possibly other components with them, as well. But fortunately nothing else in the rectifier section *looks* immediately damaged. Looks be damned, I'll be verifying the spec of every other component in this section and immediately downstream of the rectifier section. If only a minimum of components in the rest of the power supply assembly are damaged, then I'm tempted to turn that fried resistor into memorial, honoring its self-sacrifice to protect the rest of the PSU.

I've had that Rifa take out that resistor and some of the prepreg :( It was fine after cleaning and replacement.

I presume you've seen http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf (http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf)

Don't forget two of the PSU electrolytic caps are swapped in the documentation. Remove and replace one at a time.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Koreth on September 13, 2019, 04:50:58 pm
I presume you've seen http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf (http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf)

I have. That was going to be part of the basis of putting together my own list of parts to order from Mouser or Digikey. However, I wanted to take the time to understand the circuit at little better, and get a feel for what the components in that list (or elsewhere on the board, if needed) are supposed to do in that circuit. I figure if I can understand a component's role, then why Tek selected the parts they did during the original design should become apparent, and therefore inform what currently-available parts would best serve as replacements in that role. For all I know, that list is still current. But, I'd like to understand why, as opposed to just blindly throwing a bunch of parts on a board.

I've had that Rifa take out that resistor and some of the prepreg :( It was fine after cleaning and replacement.

In your experience, what other parts tend to be damaged when that RIFA and resistor blow?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on September 13, 2019, 06:29:26 pm
From memory, there is a series resistor, and if the capacitor is a short circuit then the resistor has too much voltage across it.

Just follow the smoke and clean it up!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on September 13, 2019, 08:24:00 pm
However, I wanted to take the time to understand the circuit at little better, and get a feel for what the components in that list (or elsewhere on the board, if needed) are supposed to do in that circuit. I figure if I can understand a component's role, then why Tek selected the parts they did during the original design should become apparent, and therefore inform what currently-available parts would best serve as replacements in that role. For all I know, that list is still current. But, I'd like to understand why, as opposed to just blindly throwing a bunch of parts on a board.
Wise approach.  :-+

Today there are better components available than the designers had available however as always the cost of the BOM always guided component choice.
But there are some traps where existing component characteristics must be carefully considered before any substitution can be made.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Koreth on September 14, 2019, 07:25:13 am
Today there are better components available than the designers had available however as always the cost of the BOM always guided component choice.
But there are some traps where existing component characteristics must be carefully considered before any substitution can be made.

I had suspected that was the case. I recall reading about how some linear power supplies in older audio gear were susceptible to becoming unstable if new caps with too low an ESR were substituted, as the design and layout considerations of the time, coupled with the characteristics available at the time, caused the power supplies to somewhat dependent on the not-so-great-today ESR specs of the the then-acceptable capacitors for stability.

In the case of these Tek 24xx series power supplies, are you aware of gotchas in component substitution? Anything that if substituted with a part with supposedly better specs would actually work against the goal of a stable, clean, supply voltage with sufficient amp capacity?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on September 14, 2019, 07:50:52 am
In the case of these Tek 24xx series power supplies, are you aware of gotchas in component substitution? Anything that if substituted with a part with supposedly better specs would actually work against the goal of a stable, clean, supply voltage with sufficient amp capacity?
Not 24xx in particular but study these posts where a member battled with FET Millar capacitance after selecting a replacement.
Start here:
https://www.eevblog.com/forum/repair/tektronix-2215-scope-repair/msg1647551/#msg1647551 (https://www.eevblog.com/forum/repair/tektronix-2215-scope-repair/msg1647551/#msg1647551)
Then jump to here:
https://www.eevblog.com/forum/repair/tektronix-2215-scope-repair/msg1824401/#msg1824401 (https://www.eevblog.com/forum/repair/tektronix-2215-scope-repair/msg1824401/#msg1824401)
Then read a few more posts.

I found it quite interesting and it just proves there are hidden traps for the unwary especially when just dropping a substituted component in and not understanding or modifying the design to account for it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on September 14, 2019, 08:21:33 am
If you follow the procedure as posted here and use the parts listed you will have no issues when re-capping the PSU:

https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1658102/#msg1658102 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1658102/#msg1658102)

And also here is an alternative procedure for calibrating the Counter option if required:

https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1937605/#msg1937605 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1937605/#msg1937605)

Edit, forgot to include parts list. See attached.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on September 14, 2019, 02:57:30 pm
...
Another thing I note is that I don't have the famous Dallas battery-backed SRAM, as seen on the later, SMD-style A5 boards. This thing looks like a plain battery, not a RAM-chip or ROM chip of any kind, especially given it's only 4 pins on the board. Apologies for the blurry photo there, but it looks like there's some dried flux residue on those solder joints. I don't know if that's normally there, or if that means that this board has been worked on before, and the battery has already been replaced once. It's hard to tell, given the lack of date codes on the label. I'll have to compare the A5 boards in my other pre-B5xxxx scopes.

Others have reported flux residue on their batteries.  Although these batteries are rated for wave soldering (temporary short and elevated temperature), maybe Tek decided to be ultra-conservative and mount them afterwards anyway.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on September 14, 2019, 03:16:28 pm
I'm not sure what this board is, or what it does. I do believe it is a standard board, as when I opened up B0120xx for comparison, it also had this board in it. Whatever it is/does, it fits in the central cavity of the scope, between the option boards and metal wall, and has a ribbon cable that goes through the floor of the central cavity and connects to the A1 board. I was going to leave it in place, initially, but I found it easier to get at the power supply assembly with both hands with it out of the cavity.
(Attachment Link) (Attachment Link)
That's the A4 readout board, responsible for the on-screen text and cursor display generation.  The labeled chip in the middle is the character ROM (actually an EPROM).  There's a giant section (10 pages) in the theory part of the service manual on how this board works, if you're curious.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Koreth on September 15, 2019, 05:20:29 am
That's the A4 readout board, responsible for the on-screen text and cursor display generation.  The labeled chip in the middle is the character ROM (actually an EPROM).  There's a giant section (10 pages) in the theory part of the service manual on how this board works, if you're curious.

Interesting. I remember seeing an easter egg of Tetris, or maybe it was Centipede hidden on an HP scope, so perhaps I shall have to dump the ROM and see what secrets lurk therein. At a later date, though.

If you follow the procedure as posted here and use the parts listed you will have no issues when re-capping the PSU:

https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1658102/#msg1658102 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1658102/#msg1658102)

Thank you. I took a look at that and will remember that as a reference. A thing I recall from this thread was a caveat about one of the capacitors on one of the power supply boards being wrong on the schematic or the board, or the schematic swapped them, or something like that. However, I notice the power supply from your 2465 in that link looks different from mine; the capacitors are laid out slightly differently. Nonetheless, I agree with your admonition in that link; it makes sense to replace the capacitors one at a time.

In the case of these Tek 24xx series power supplies, are you aware of gotchas in component substitution? Anything that if substituted with a part with supposedly better specs would actually work against the goal of a stable, clean, supply voltage with sufficient amp capacity?
Not 24xx in particular but study these posts where a member battled with FET Millar capacitance after selecting a replacement.
Start here:
https://www.eevblog.com/forum/repair/tektronix-2215-scope-repair/msg1647551/#msg1647551 (https://www.eevblog.com/forum/repair/tektronix-2215-scope-repair/msg1647551/#msg1647551)
Then jump to here:
https://www.eevblog.com/forum/repair/tektronix-2215-scope-repair/msg1824401/#msg1824401 (https://www.eevblog.com/forum/repair/tektronix-2215-scope-repair/msg1824401/#msg1824401)
Then read a few more posts.

I found it quite interesting and it just proves there are hidden traps for the unwary especially when just dropping a substituted component in and not understanding or modifying the design to account for it.

Quite interesting indeed. I hadn't thought about miller capacitance in a while; last time I read about it was how it applied to audio amplifiers. But seeing how it can mess with the inverter gate drive in an SPMS is a good thing to realize. Hopefully none of the components in the gate drive section have been damaged, because it seems like drive mosfets with sufficiently low miller capacitance can be kind of hard to find.

On the topic of replacement components, I want to talk about going high and low from the original spec.

There is a pair of 15Ohm, 1/2W carbon film resistors parallel with the NTCs (R1010 & R1019) as part of the inrush protection mechanism. In the work I've read on this so far, I've seen people up-rating them and replacing them with 3W resistors or the like. Clearly, these are subject to some degree of thermal stress, being inline with with the mains before it enters the first rectifier. Is this necessary, or is it a bit of an insurance policy to make sure they don't fail and thus cause a cascade of failure in more expensive parts? Or is upgrading these resistors risking the failure of more expensive parts by causing what was intended as a sacrificial component to not fail when it should?

Additionally, I note that in both of the Pre-B05xxxx supplies I've seen so far, one or both of resistors R1016 and R1018, have been burnt by failures of C1015 and C1018. I find myself wondering if perhaps it wouldn't be a good idea to increase those from 1/2 watt thermal ratings to something higher. My understanding from reading about X and Y ratings for caps is that an X-rated capacitor is supposed to fail shorted, with the idea being that in doing so it would cause a breaker to trip or a fuse to short. By my reading, resistors typically fail open. So of C1015 or C1018 fails, and draws the full mains current across R1016 or R1018, forcing them to release their magic smoke and become open in short order. Do we want to preserve that short so fuses start blowing? Or are these resistors intended as sacrificial components, and thus supposed to self destruct in the presence C1015 or C1018 shorting? In which case, would it be a good idea to go for a lower thermal rating so the resistor blows even sooner? Or is 1/2W the smallest thermal rating that could fit in that role?

Or am I over thinking this and the job of these resistors is simply to be part of the RLC filters across the mains before the rectifier, 1/2W was the cheapest size appropriate for the role, and it should be left alone or  replaced with like?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on September 15, 2019, 06:24:28 am
@ Koreth
Much depends on the engineer of that time and the % rating he/she was permitted to use when determining the W rating of components selected plus the always overarching concern of the BOM cost.
When we are reworking old instruments the time spent and the cost of replacements in no way can be related to the original BOM so were possible it does no harm to uprate componentry especially resistors in the power sections unless they are low % tolerance where it is wise to match the BOM.

Back to % ratings, a designer these days may choose to subject components to close to their full rating whereas in years gone by they were more conservative with lower stresses placed on components namely for better long term reliability particularly for silicon however manufacturing processes today have in general made most components more reliable.
A retired Dr EE buddy told me for Telco designs he wasn't to subject ANY componentry beyond 63% of ANY of its ratings. Today much has changed and for us all we need consider what % rating we need limit ourselves to for long term reliability of designs.
To use an old saying; we are each masters of our own destiny.

Quote
There is a pair of 15Ohm, 1/2W carbon film resistors parallel with the NTCs (R1010 & R1019) as part of the inrush protection mechanism. In the work I've read on this so far, I've seen people up-rating them and replacing them with 3W resistors or the like. Clearly, these are subject to some degree of thermal stress, being inline with with the mains before it enters the first rectifier. Is this necessary, or is it a bit of an insurance policy to make sure they don't fail and thus cause a cascade of failure in more expensive parts? Or is upgrading these resistors risking the failure of more expensive parts by causing what was intended as a sacrificial component to not fail when it should?
Yes, preventive replacement.
With SMPS the startup behaviour is crucial and it must be predictable so to not let the silicon magic smoke escape.
Quote
Additionally, I note that in both of the Pre-B05xxxx supplies I've seen so far, one or both of resistors R1016 and R1018, have been burnt by failures of C1015 and C1018. I find myself wondering if perhaps it wouldn't be a good idea to increase those from 1/2 watt thermal ratings to something higher. My understanding from reading about X and Y ratings for caps is that an X-rated capacitor is supposed to fail shorted, with the idea being that in doing so it would cause a breaker to trip for a fuse to short. By my reading, resistors typically fail open. So of C1015 or C1018 fails, and draws the full mains current across R1016 or R1018, forcing them to release their magic smoke and become open in short order. Do we want to preserve that short so fuses start blowing? Or are these resistors intended as sacrificial components, and thus supposed to self destruct in the presence C1015 or C1018 shorting? In which case, would it be a good idea to go for a lower thermal rating so the resistor blows even sooner? Or is 1/2W the smallest thermal rating that could fit in that role?
Sacrificial resistors IMHO.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Koreth on September 15, 2019, 06:38:25 am
Looking at this parts list, I find myself questioning the the changes in voltage or capacitance.

For example let's take the filtering capacitors hanging off the output of the inverter transformer, C1110, C1111, C1113, C1114, C1115, and C1116. The originals are a blend of 180 and 250 uF. 330 seems like a bit of a jump, moving the poles of the LC filters the form from 2.2 kHz and 1.9kHz to 1.6kHz. That, I'm less worried about, since I don't see knocking an extra few dB off the ~41Khz switching noise as a particularly bad thing, and I don't think the increase in charging current from the increase in capacitance would load down the inverter too much more.  However, is there not a consideration on undercharging electrolytic capacitors shortening their life? Per the voltages in the diagram, the stock 180uF caps on the +/- 15V lines, at 19.2V at this point in the circuit are being charge up to about 48% of their max voltage, and the 250uF caps on the unregulated +/- 5V lines (at 7.1V) are being charged up to about 35%. However, with the 50V rating on the proposed parts list, those unregulated lines are only being charged up to 14% of their rating. Is this too low of a charge for a healthy cap life?

I'm not saying these are unreasonable choices, given the choice of the Panasonic EB series. Looking on the datasheet, 330uF was the smallest value that wasn't lower than the original value 250uF caps. However, 220 uF is available to replace the 180 uF 40V, and a 220uF 50V is cheaper than 330uf 50V. Was this part selection driven somewhat by a desire to keep the parts list small and simple?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on September 15, 2019, 08:42:25 am
Looking at this parts list, I find myself questioning the the changes in voltage or capacitance.

For example let's take the filtering capacitors hanging off the output of the inverter transformer, C1110, C1111, C1113, C1114, C1115, and C1116. The originals are a blend of 180 and 250 uF. 330 seems like a bit of a jump, moving the poles of the LC filters the form from 2.2 kHz and 1.9kHz to 1.6kHz. That, I'm less worried about, since I don't see knocking an extra few dB off the ~41Khz switching noise as a particularly bad thing, and I don't think the increase in charging current from the increase in capacitance would load down the inverter too much more.  However, is there not a consideration on undercharging electrolytic capacitors shortening their life? Per the voltages in the diagram, the stock 180uF caps on the +/- 15V lines, at 19.2V at this point in the circuit are being charge up to about 48% of their max voltage, and the 250uF caps on the unregulated +/- 5V lines (at 7.1V) are being charged up to about 35%. However, with the 50V rating on the proposed parts list, those unregulated lines are only being charged up to 14% of their rating. Is this too low of a charge for a healthy cap life?

I'm not saying these are unreasonable choices, given the choice of the Panasonic EB series. Looking on the datasheet, 330uF was the smallest value that wasn't lower than the original value 250uF caps. However, 220 uF is available to replace the 180 uF 40V, and a 220uF 50V is cheaper than 330uf 50V. Was this part selection driven somewhat by a desire to keep the parts list small and simple?
While I've not analyzed the design there are more important consideration for SMPS cap selection than primarily capacitance or for that matter even voltage headroom.
The principle spec is the caps ripple current capability and just another parameter we wouldn't want to run too close to 100% so to minimize internal self heating. Without examining the cap specs of the original BOM one expects the designers to have taken account of the ripple current each cap is subjected to and selected capacitance values with ripple current specs that would easily meet actual current ripple and still give low ripple on each rails output.
If we look at the datasheet for the original caps used and modern replacements of equal capacitance we'll notice modern low ESR caps are superior to what was available back then.
41 KHz is typical for that time while many SMPS run faster than that these days and a ripple current spec is commonly for 100 KHz today.
Good substitutions are never straightforward.  :)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on September 15, 2019, 10:03:54 am
While it's smart to question the validity of the capacitor substitutions I can tell you from a practical perspective that I have done two 2465's with the upgraded recommendations and there have been absolutely no issues. Both powered up clean and the voltages are in spec. And from a reliability perspective again, no issues. One was done over 3 years ago and another last year.   
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: jonpaul on September 15, 2019, 03:21:43 pm
Hello all, fine notes. But the recent posts refer only  to 2465 and 2465A power supply recap. The 2465B PSU must be different.

At the moment, I have a very late SN 2465B opt 06,09 that needs recapping.

Is there a recent BOM for the 2565/7B PSU recap, the old boms have many broken links/ stock numbers from DK, Mouser.

Many thanks

Bon Soirée

Jon

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on September 15, 2019, 04:49:04 pm
That's the A4 readout board, responsible for the on-screen text and cursor display generation.  The labeled chip in the middle is the character ROM (actually an EPROM).  There's a giant section (10 pages) in the theory part of the service manual on how this board works, if you're curious.

Interesting. I remember seeing an easter egg of Tetris, or maybe it was Centipede hidden on an HP scope, so perhaps I shall have to dump the ROM and see what secrets lurk therein. At a later date, though.
...
The A4 EPROM is just character data.  If you're after the actual 6800 code, you'll want to look at the EPROMs on the A5 board on the side, or just grab one of the many images that others have already read out.

The operating code for options is contained on an EPROM on each option board, so just looking at the A5 EPROMs is not everything.

I've disassembled some of the code.  You'll find a rather complex tangle of jump tables because all the code is bank switched.  Good luck, and if you find anything interesting please post.  I'm sure everyone on this thread would be interested in any secrets you uncover.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on September 15, 2019, 05:20:20 pm
Hello all, fine notes. But the recent posts refer only  to 2465 and 2465A power supply recap. The 2465B PSU must be different.

At the moment, I have a very late SN 2465B opt 06,09 that needs recapping.

Is there a recent BOM for the 2565/7B PSU recap, the old boms have many broken links/ stock numbers from DK, Mouser.

Many thanks

Bon Soirée

Jon

Not true. They are almost identical with some minor changes. Proof.

2465 A2 Board.
(https://imagizer.imageshack.com/v2/xq90/922/eNgi4A.jpg) (https://imageshack.com/i/pmeNgi4Aj)

2465B A2 Board
(https://imagizer.imageshack.com/v2/xq90/922/r9thR8.png) (https://imageshack.com/i/pmr9thR8p)

2465 A3 Board
(https://imagizer.imageshack.com/v2/xq90/921/Fs7jgn.jpg) (https://imageshack.com/i/plFs7jgnj)

2465B A3 Board
(https://imagizer.imageshack.com/v2/xq90/921/ewAhvf.png) (https://imageshack.com/i/plewAhvfp)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: neo on September 16, 2019, 03:30:33 am
I have a 2465B that I've come to (lovingly?) address as a red headed child. All voltages present at the test point and in spec, ripple is in spec, Nothing wrong with it except that it has no cal data (new chip) and won't boot. Anybody have any ideas here?

Thanks in advance.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on September 16, 2019, 02:01:12 pm
I have a 2465B that I've come to (lovingly?) address as a red headed child. All voltages present at the test point and in spec, ripple is in spec, Nothing wrong with it except that it has no cal data (new chip) and won't boot. Anybody have any ideas here?
What's the history with this unit?  Did it work and now it doesn't or did you receive it broken?

Are there any LEDs lit on the front panel?  Does it go through part of the boot sequence and get stuck?  Are any relays clicking as it boots?  Any flashes of anything on the CRT?  Or does it just sit there like a lump?  Need more info.

One thing you could do is try working through the troubleshooting flowcharts in the back of the service manual (immediately after the schematics).  They don't cover every possibility, but can at least lead you to the right area to start digging.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: neo on September 16, 2019, 11:43:52 pm
I have a 2465B that I've come to (lovingly?) address as a red headed child. All voltages present at the test point and in spec, ripple is in spec, Nothing wrong with it except that it has no cal data (new chip) and won't boot. Anybody have any ideas here?
What's the history with this unit?  Did it work and now it doesn't or did you receive it broken?

Are there any LEDs lit on the front panel?  Does it go through part of the boot sequence and get stuck?  Are any relays clicking as it boots?  Any flashes of anything on the CRT?  Or does it just sit there like a lump?  Need more info.

One thing you could do is try working through the troubleshooting flowcharts in the back of the service manual (immediately after the schematics).  They don't cover every possibility, but can at least lead you to the right area to start digging.

Worked when I got it, then i tried restoring it.

Right now, what it does when powered on is exactly this;
Brief flash on the CRT, fan comes on, seemingly all front panel LEDS light, then it just sits there like a lump. Doing nothing except running the fan and staring at me with a brightly lit front panel.
Completely unresponsive beyond this and it will sit there for half an hour at least without change, does this every single time I try turning it on.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on September 17, 2019, 07:29:23 pm
...
Worked when I got it, then i tried restoring it.

Right now, what it does when powered on is exactly this;
Brief flash on the CRT, fan comes on, seemingly all front panel LEDS light, then it just sits there like a lump. Doing nothing except running the fan and staring at me with a brightly lit front panel.
Completely unresponsive beyond this and it will sit there for half an hour at least without change, does this every single time I try turning it on.
What "restoring" things did you do?  Maybe posting decent resolution photos of those areas you worked on would allow someone to spot something.

One of the first things the CPU does is take control of the front panel LEDs.  So, it's not even getting off the ground.  Very few components need to be working for this initial phase.  Not even the SRAM is needed.

I would focus on the CPU and EPROM functions.  Make sure nRESET is going high and that the CPU has a working clock and supply.  Make sure J503 NORM/DIAG jumper is in the NORM position.

Have you tried the troubleshooting flowchart?  It will take you through all these checks, plus if the NOP diagnostic loop on the CPU should be run.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: neo on September 18, 2019, 04:32:12 pm
What "restoring" things did you do?  Maybe posting decent resolution photos of those areas you worked on would allow someone to spot something.

One of the first things the CPU does is take control of the front panel LEDs.  So, it's not even getting off the ground.  Very few components need to be working for this initial phase.  Not even the SRAM is needed.

I would focus on the CPU and EPROM functions.  Make sure nRESET is going high and that the CPU has a working clock and supply.  Make sure J503 NORM/DIAG jumper is in the NORM position.

Have you tried the troubleshooting flowchart?  It will take you through all these checks, plus if the NOP diagnostic loop on the CPU should be run.
New capacitors, a new fan and a new chip. I tried to transfer the cal data to the new chip but, like an idiot, botched it. 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: jonpaul on September 19, 2019, 08:18:56 pm
Check all connectors properly mated, recapping.....note error on schematic or layout on PSU 2 lytics interchanged.


Jon
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: USMC_Spike on October 08, 2019, 10:59:46 pm
I bought this programmer:

http://www.ebay.com/itm/321085130796 (http://www.ebay.com/itm/321085130796)

it arrived safely and quickly.

for the chip, this is the one I ordered but it seems to be out of stock right now:

DS1225AD-200IND+-ND

AD is a wider temperate range (I think) but nothing critical to the scope.  the 200 is the speed of the device and I used the same speed as the original chip.  not sure if going faster or slower would matter but I just matched the same chip speed.

mouser has one that is not AD but very close and that's probably also ok:

DS1225AB-200+

Maybe some one can answer this for me and others, maybe it has already been done.
Can we use the:

DS1225AD-70+ chip here?  is 70ns vs 200ns.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on October 09, 2019, 01:38:12 am
...
Maybe some one can answer this for me and others, maybe it has already been done.
Can we use the:

DS1225AD-70+ chip here?  is 70ns vs 200ns.

The 70ns version should be fine.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: 4thDoctorWhoFan on October 09, 2019, 10:26:46 am
Looking at this parts list, I find myself questioning the the changes in voltage or capacitance.

For example let's take the filtering capacitors hanging off the output of the inverter transformer, C1110, C1111, C1113, C1114, C1115, and C1116. The originals are a blend of 180 and 250 uF. 330 seems like a bit of a jump, moving the poles of the LC filters the form from 2.2 kHz and 1.9kHz to 1.6kHz. That, I'm less worried about, since I don't see knocking an extra few dB off the ~41Khz switching noise as a particularly bad thing, and I don't think the increase in charging current from the increase in capacitance would load down the inverter too much more.  However, is there not a consideration on undercharging electrolytic capacitors shortening their life? Per the voltages in the diagram, the stock 180uF caps on the +/- 15V lines, at 19.2V at this point in the circuit are being charge up to about 48% of their max voltage, and the 250uF caps on the unregulated +/- 5V lines (at 7.1V) are being charged up to about 35%. However, with the 50V rating on the proposed parts list, those unregulated lines are only being charged up to 14% of their rating. Is this too low of a charge for a healthy cap life?

I'm not saying these are unreasonable choices, given the choice of the Panasonic EB series. Looking on the datasheet, 330uF was the smallest value that wasn't lower than the original value 250uF caps. However, 220 uF is available to replace the 180 uF 40V, and a 220uF 50V is cheaper than 330uf 50V. Was this part selection driven somewhat by a desire to keep the parts list small and simple?

A 330uf will work fine in place of the 250uf cap.
If you look at the BOM in the service manual, the 250uf cap have a tolerance of +100% and -10%.  Clearly, it's better to go up in value.  Since 100% would be 500uf, a 330uf will be no problem.
Other caps listed have +50% and similar rating.  Check out the parts list.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on October 09, 2019, 03:10:49 pm
all this makes me glad I have held off for so long with (3) 2465/7B units PSU recaps...
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Retro_Collector on October 09, 2019, 04:35:27 pm
This is my first post and am a newbie.

I am waiting for my 2465B to show up. Everything is like new, the only thing is the scale illumination is not working. Is it worth replacing? I looked in the service manual and there are not pics to help me replace it.

Should I replace the board or just leave it?

If I should replace it and pics or video that show how to do it? I searched YouTube and everywhere and can't find anything

Thanks in advance for the help!

Bill
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on October 09, 2019, 04:42:28 pm
This is my first post and am a newbie.

I am waiting for my 2465B to show up. Everything is like new, the only thing is the scale illumination is not working. Is it worth replacing? I looked in the service manual and there are not pics to help me replace it.

Should I replace the board or just leave it?

If I should replace it and pics or video that show how to do it? I searched YouTube and everywhere and can't find anything

Thanks in advance for the help!

Bill

What do you mean the board ?

Try read post #19 -> HERE (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg74104/#msg74104), is that what are you looking for ?

The illuminator is just an incandescent lamp, which I think, can be modded to use red LED.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on October 09, 2019, 05:35:01 pm
This is my first post and am a newbie.

I am waiting for my 2465B to show up. Everything is like new, the only thing is the scale illumination is not working. Is it worth replacing? I looked in the service manual and there are not pics to help me replace it.

Should I replace the board or just leave it?

If I should replace it and pics or video that show how to do it? I searched YouTube and everywhere and can't find anything

Thanks in advance for the help!

Bill

There's no pics, but there is a step-by-step description in the service manual in section 6 near the end, "A8 - Scale Illumination Circuit Board Removal".

The bulbs are in series and it's probably a burned out bulb.  The bulb type is 7153 (T-3/4).  Sources detailed here:

  https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg842072/#msg842072 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg842072/#msg842072)

Before you go through the trouble of removing the board to replace lamps (or substitute LEDs), measure the voltage going to the board to be sure it's nothing else.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: factory on October 11, 2019, 08:48:35 pm
Anyone else had problems trying to get the 1uF Bipolar capacitors (UEP1H010MDD RS part #5232678) from the list, the UK site says they are unavailable, yet other global RS sites say they are available?  :wtf:

[attachimg=1]

David
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on October 17, 2019, 07:04:00 am
There must be a RIFA flu going around, saw a recent post here a couple of pages back saying the same thing. Was using my 2465B (serial +50K) today and all of the sudden POP and a lot of smoke. RIFA cap exploded and burned up 30 ohm resistor in series, even tough this scope has been on 120V line all its life, as far as I know. Saw the RIFAs where pretty crazed when I did the NVRAM/A5 caps about a year ago but figured I'll get to it eventually. Well, it got to me instead.

No other evident damage was found anywhere inside. So decided it would be a good time to finally use all those caps that I ordered months ago to do the full recap. Pulled out the power supply board sandwich and installed new caps all around (one at a time to avoid mistakes) including the main filter caps, the 4.7uF Tantalum, and the 3x 1uF NP. The only film caps I forgot to order back when where the two 2200pf 250V, one 0.01uF 250V, and one 0.056uF 250V so I'll do those next time. Also replaced both 15 ohm resistors with bigger units, and the 270K resistor.

Upon first plugin test the fan runs and all front panel lights flash once in unison and then only the green Sweep/Trig led stays on and nothing else happens. The 3 GPIB indicator are also staying lit. Not sure the Sweep/Trig Led might mean something (error code) although I looked it up in the SM and all I found is the list of indicators the scope goes through in sequence on boot, and if it stops on one that can be looked up in this list. But mine is not even going through this sequence, so not even booting. Nothing visible on screen, no trace no nothing.

Measured voltages at J119 as follows:

-15 -> -11.7v
+5D -> +4.3V
+10 -> +7.3
-5 -> -3.5V
+15 -> +10.4V
+87 -> +59.6V
+42.4 -> +28.8V
-8 -> -5.3V
+5A -> +3.3V


Needless to say all rails are low and way out of spec. Also checked voltage on the (new) main caps and got about 150V on each and around 300V total, so the primary rectifier is working and juice is getting into the supply. No sounds, no clicking, nothing heard.

Just now after pulling out the power supply again double and tipple checked that all caps are in the correct position, correct value/voltage, and correct polarity before installing the boards. All are correct. And yes, I am aware of the cap layout error in the service manual. Actually I did one cap at a time, just to be extra sure not to mix anything up.

All connectors are positively in place. There is the one going to A5 which is impossible to screw up, one with the multicolor wires under the fuse, and the all-white wires next to it, and no misaligned/missed pins. Other than that, the only other plug is a 3-wire that sends power to the GPIB board. Oh, and also checked continuity of all the pins of the stab (long pin) connectors between the two boards, as they sometimes can go intermittent if pushed the wrong way.

Anybody have any ideas/suggestions? I was reading the troubleshooting charts in the SM but wanted to first ask here in case these symptoms ring a bell and have happened before to someone else after a recap. I know there are plenty of people here that have gone through this procedure, some even more then once. Besides in order to for those charts to make sense would first need to order a couple of 20/25-watt resistors to construct a load as shown in the manual in able to run the supply outside the scope to be able to poke into it without blowing it up after shorting out something. BTW has anybody build one of those test loads? The SM only shows Tek PN for a diode and a 3.3uF cap (v?) needed.

Oh man, I was so hoping this recap would go without a hitch. I found that all the 180uF and 250uF where just staring to leak a tiny bit, so that would probably mean that now with better filtering in place I would get those sharper traces etc that many people have reported. O well... And yes what little was leaking from those caps was cleaned up, no harm at all to any traces or the board. Just a funny smell when desoldering those blue caps. All other caps looked fine but where replaced anyhow. Why not have all the fun at one time. Right, I'm having fun now.

Thanks for any input.
Alex
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on October 17, 2019, 07:31:43 am
And finally! Onto the power supply! :D
....

Moving onto the rest of the CPU, we can see the usual components of a switching power supply. Fortunately, none of the regular electrolytic capacitors look swollen or otherwise damaged, but they're going to be checked anyway, given their age, and especially given the current surge the PSU was subject to. I do see more of those problematic box caps. Those are getting replaced, period, given their history. I'm not waiting for them to fail.

Besides the RIFAs, change all those blue electrolytics, they may still look ok (not swollen, etc) but they start leaking underneath and you won't notice it until they are removed. Just went through this on my 2465B on a long overdue full recap and found both 180uF and all 250uF caps where leaking a tiny bit and obviously no longer doing their job. These are the caps that are under the most stress as they are on the switcher output so they had/have a hard life. I caught mine just about in time. As a matter of fact the same thing happened to me today that a RIFA popped (on 120VAC) and burned up the 30 ohm resistor. Lots of smoke but the main fuse did not blow so I figures it should be an easy fix as these components are ahead of the actual power supply.  But now my only problem is that after the full recap I did, my power supply is no longer starting. If interested, I posted the whole story on a separate post here in this long time thread.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on October 17, 2019, 07:55:43 am
Ya gotta thank the designers for putting 30 ohm current limiting resistors in there.  :clap:
Resistors might be toast but at least you have the traces left.  :phew:
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on October 17, 2019, 12:54:47 pm
There must be a RIFA flu going around, saw a recent post here a couple of pages back saying the same thing. Was using my 2465B (serial +50K) today and all of the sudden POP and a lot of smoke. RIFA cap exploded and burned up 30 ohm resistor in series, even tough this scope has been on 120V line all its life, as far as I know. Saw the RIFAs where pretty crazed when I did the NVRAM/A5 caps about a year ago but figured I'll get to it eventually. Well, it got to me instead.

No other evident damage was found anywhere inside. So decided it would be a good time to finally use all those caps that I ordered months ago to do the full recap. Pulled out the power supply board sandwich and installed new caps all around (one at a time to avoid mistakes) including the main filter caps, the 4.7uF Tantalum, and the 3x 1uF NP. The only film caps I forgot to order back when where the two 2200pf 250V, one 0.01uF 250V, and one 0.056uF 250V so I'll do those next time. Also replaced both 15 ohm resistors with bigger units, and the 270K resistor.

Upon first plugin test the fan runs and all front panel lights flash once in unison and then only the green Sweep/Trig led stays on and nothing else happens. The 3 GPIB indicator are also staying lit. Not sure the Sweep/Trig Led might mean something (error code) although I looked it up in the SM and all I found is the list of indicators the scope goes through in sequence on boot, and if it stops on one that can be looked up in this list. But mine is not even going through this sequence, so not even booting. Nothing visible on screen, no trace no nothing.

Measured voltages at J119 as follows:

-15 -> -11.7v
+5D -> +4.3V
+10 -> +7.3
-5 -> -3.5V
+15 -> +10.4V
+87 -> +59.6V
+42.4 -> +28.8V
-8 -> -5.3V
+5A -> +3.3V


Needless to say all rails are low and way out of spec. Also checked voltage on the (new) main caps and got about 150V on each and around 300V total, so the primary rectifier is working and juice is getting into the supply. No sounds, no clicking, nothing heard.

Just now after pulling out the power supply again double and tipple checked that all caps are in the correct position, correct value/voltage, and correct polarity before installing the boards. All are correct. And yes, I am aware of the cap layout error in the service manual. Actually I did one cap at a time, just to be extra sure not to mix anything up.

All connectors are positively in place. There is the one going to A5 which is impossible to screw up, one with the multicolor wires under the fuse, and the all-white wires next to it, and no misaligned/missed pins. Other than that, the only other plug is a 3-wire that sends power to the GPIB board. Oh, and also checked continuity of all the pins of the stab (long pin) connectors between the two boards, as they sometimes can go intermittent if pushed the wrong way.

Anybody have any ideas/suggestions? I was reading the troubleshooting charts in the SM but wanted to first ask here in case these symptoms ring a bell and have happened before to someone else after a recap. I know there are plenty of people here that have gone through this procedure, some even more then once. Besides in order to for those charts to make sense would first need to order a couple of 20/25-watt resistors to construct a load as shown in the manual in able to run the supply outside the scope to be able to poke into it without blowing it up after shorting out something. BTW has anybody build one of those test loads? The SM only shows Tek PN for a diode and a 3.3uF cap (v?) needed.

Oh man, I was so hoping this recap would go without a hitch. I found that all the 180uF and 250uF where just staring to leak a tiny bit, so that would probably mean that now with better filtering in place I would get those sharper traces etc that many people have reported. O well... And yes what little was leaking from those caps was cleaned up, no harm at all to any traces or the board. Just a funny smell when desoldering those blue caps. All other caps looked fine but where replaced anyhow. Why not have all the fun at one time. Right, I'm having fun now.

Thanks for any input.
Alex


They key is your +10V reference. It's at +7.3V. It originates from the unregulated +15V on the A2 board.

Here's a thought....are you sure you connected the jumpers from the AC line filter to the A2 board correctly? If you scrambled them the A2 board may think it's connected for 120V which would explain the low voltage.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on October 17, 2019, 03:39:21 pm
They key is your +10V reference. It's at +7.3V. It originates from the unregulated +15V on the A2 board.

Here's a thought....are you sure you connected the jumpers from the AC line filter to the A2 board correctly? If you scrambled them the A2 board may think it's connected for 120V which would explain the low voltage.

Hi Med,

I am on 120VAC mains. And yes I would be quite sure that the AC input cables from the line filter and the fuse holder are securely connected to J204 and J205 which are located further towards the top of the board in comparison to the remaining two tabs where the voltage selector switch goes. I measured about 150V (at J231A/B) across each of the new 330uF 250V main input filter caps, total a bit more than 300V, so there must be a good input connection wouldn't you say? I was close to leaving in those original Sprage's as they look pristine (still have to test them), but since I had the two new Nichicons on hand, replaced them as well.

Another thought occurred to me about the voltage selector switch not being securely connected to the lower two tabs JU206 and JU207, or the switch being open for some reason. If any of those two connections where loose (causing an open circuit) then the power supply would assume to be on 240V but only getting 120V and a similar low-volt situation like now might arise. But I just checked continuity of the voltage selector switch from the tip of the two terminals on the wires that go onto the PS and there is good continuity all the way.

I now once again have the PS outside of the scope and on the bench.

BTW did you ever need to build that test load they describe in the service manual to troubleshoot any of your your power supplies? It allows to run the PS without T1060 the primary output transformer or the switching transistors being part of the circuit by just opening a jumper (W1060) next to the transformer. But first I need to have the proper load and I don't have the specified resistors on hand.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on October 17, 2019, 06:15:21 pm
Ya gotta thank the designers for putting 30 ohm current limiting resistors in there.  :clap:
Resistors might be toast but at least you have the traces left.  :phew:

The resistor along with the series cap is just a damper for any incoming spikes/surges. Is known as a "snubber" circuit. In this case the resistor just allows the cap failure to happen in relative slow motion and that is why not even the main AC fuse bothers to blow. With a short in the cap the resistor will slowly hara-kiri itself, but in the end its not a very useful sacrifice, other than preventing maybe a bit louder cap pop. In other circumstances I'm sure the fuse would quickly open before any damage is done to the board traces.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on October 17, 2019, 06:31:16 pm

I now once again have the PS outside of the scope and on the bench.

BTW did you ever need to build that test load they describe in the service manual to troubleshoot any of your your power supplies? It allows to run the PS without T1060 the primary output transformer or the switching transistors being part of the circuit by just opening a jumper (W1060) next to the transformer. But first I need to have the proper load and I don't have the specified resistors on hand.

No, I haven't had the need to build up an external load to run the PSU on the bench. I've re-capped two 2465's and I guess I've been lucky in that both of them powered up with no issues.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on October 18, 2019, 12:32:32 am
UPDATE: I found a problem and now the power supply is working again. But I am being greeted now by a 04 11 error message which indicates a faulty cal constant checksum. Maybe the FRAM did not like the lower power supply voltages or spikes etc. When I swapped out the old NVRAM I also programmed a fresh one and put it away just in case the FRAM would not work out, plus I also have the original 1990 NVRAM which should be still ok. Guess I could just swap in that new programmed NVRAM to confirm if the error goes away, and then try to reprogram the data back into the FRAM.

What happened with the power supply? Well as said I had double/triple checked all caps, but... only against my OWN NOTES which I had taken prior to start removing and replacing caps one by one. Turns out that in the case of C1220 and C1240 I read 10uF 100V but instead wrote down 100uF 10V!! Then when it came to replace those two I grabbed a bag with two extra and somewhat different looking 100uF 25V separate from the other same value/volt caps that I was correctly using for the other spots. So I figured I had ordered those two extra ones just to "upgrade" those pesky outdated "100uF 10V" units up to 25V. Surely enough found another bag with the remaining 10uF 100V ones. I ordered these parts many months ago and lost track of some details of what was destined for which cap replacement. Live and learn from your mistakes.

Found out about the mistake after I left the power on for a few minutes and heard another pop. Upon inspection C1220 had vented its top. That 25V cap was obliviously pulling down the 87V rail. Oooops...

UPDATE 2: Happy to report that I just swapped out the FRAM for the old original 1990 NVRAM, and the error code went away. Will try to erase and reprogram the FRAM a bit later see how that goes, otherwise will just order a new one.

UPDATE3: just reprogrammed the FRAM with backup data and put it back into the scope, its once again working fine.
Time to put the cover back on.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on October 18, 2019, 02:05:16 am
Good deal on getting it sorted out.  :-+ It is so easy to mix up or install capacitors backwards. Done it myself several times but on other projects.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on October 18, 2019, 03:15:10 am
Yeah I'm happy this episode is over. On the plus side I could now easily get that power supply in or out of the scope in a minute or two.
Still have to eventually replace those last 4 film caps: 2x 2200pf 250VAC, 1x 0.01uF 250V, and 1x 0.056uF 250V on the inverter board.
The 2200pf and 0.01 look like Rifas and are already showing a bit of craze.

BTW one of the 15 ohm resistors is completely open circuit, and has a small surface crack on the side.

While I was in the scope also replaced one 100uF 25V cap on the A9 HV Supply board which is said to be very important.

Some pictures included.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on October 18, 2019, 03:40:53 am
UPDATE: I found a problem and now the power supply is working again. But I am being greeted now by a 04 11 error message which indicates a faulty cal constant checksum. Maybe the FRAM did not like the lower power supply voltages or spikes etc. When I swapped out the old NVRAM I also programmed a fresh one and put it away just in case the FRAM would not work out, plus I also have the original 1990 NVRAM which should be still ok. Guess I could just swap in that new programmed NVRAM to confirm if the error goes away, and then try to reprogram the data back into the FRAM.

1st, congratulation !  :clap:

So the problematic one is the new FRAM which was normal before ?

If the voltage rails were the culprit, this is important reference.

Thanks for sharing your journey btw.  :-+
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on October 18, 2019, 03:47:35 am
So the problematic one is the new FRAM which was normal before ?

If the voltage rails were the culprit, this is important reference.

I did not replace the FRAM, just reloaded the data from the backup file with the GQ-4X4 programmer and it was again good to go.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: factory on October 21, 2019, 09:02:11 pm
Anyone else had problems trying to get the 1uF Bipolar capacitors (UEP1H010MDD RS part #5232678) from the list, the UK site says they are unavailable, yet other global RS sites say they are available?  :wtf:

(Attachment Link)

David

Well I asked RS and they claim the part number doesn't exist, even though you can add it to the quick order box here https://uk.rs-online.com/web/ which gives the error pictured (also provides the details they can't find).
Neither RS or Farnell in the UK can supply a 1uF non-polar capacitor (CPC only have no-name brand), so I'm left with the choice of trying to buy the Nichicon part from RS Germany or from reseller on ePay, or to use a film capacitor which I have some of.
[attach=1]

I've already found all the other parts or equivalents at RS or Farnell for the four 24x5 scopes I have, I've chosen not to use Kemet for any of the X2/Y2 capacitors and found Farnell have the LTC-7PN lithium battery for the A5 board in the 2465B.
Also I've already got a stock of 4.7uF 35V tantalum bead capacitors for replacing the original 10V part.

The only part I've not looked for yet is the mains IEC filter unit, some people have said these can smoke too, I'm curious as to which ones can fail as I'm sure they must have used a few different brands for this part.

David
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on October 21, 2019, 09:28:59 pm
Anyone else had problems trying to get the 1uF Bipolar capacitors (UEP1H010MDD RS part #5232678) from the list, the UK site says they are unavailable, yet other global RS sites say they are available?  :wtf:
David

Well I asked RS and they claim the part number doesn't exist, even though you can add it to the quick order box here https://uk.rs-online.com/web/ (https://uk.rs-online.com/web/) which gives the error pictured (also provides the details they can't find).
Neither RS or Farnell in the UK can supply a 1uF non-polar capacitor (CPC only have no-name brand), so I'm left with the choice of trying to buy the Nichicon part from RS Germany or from reseller on ePay, or to use a film capacitor which I have some of.
.....

If it is of any help I used Mouser PN 647-UMP1H010MDD1TP for the 1uF NP caps, currently it shows 2,968 in stock.

https://www.mouser.com/ProductDetail/Nichicon/UMP1H010MDD1TP?qs=%2Fha2pyFadugmOnc%252BigsU4z5Jp%252BINWyYVLC%252B8cvmeus63yOAeljh67w%3D%3D (https://www.mouser.com/ProductDetail/Nichicon/UMP1H010MDD1TP?qs=%2Fha2pyFadugmOnc%252BigsU4z5Jp%252BINWyYVLC%252B8cvmeus63yOAeljh67w%3D%3D)

I have never dealt with the sources you mention, and I know you are on "the other end of the pond" but I would suggest start dealing with top tier suppliers, and there will be no more headaches.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: factory on October 23, 2019, 09:55:47 pm
Thanks for the alternate part, but unfortunately RS & Farnell haven't got those either.
I've now ordered most of the parts from RS components (used to be able to buy from Allied in the US through them) and Farnell (aka Newark in the US, now both part of AVNET).
I'm going to see if I can order the 1uF NP from the German part of RS, but not tonight as it's late and looks like I need to register with them.

Also going to have a look at the IEC filter at the weekend, forgot to photo it.  :blah:

David
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on October 23, 2019, 10:12:08 pm
David this might be a silly question to ask, but being in the UK why don't you just place your order direct at Mouser USA? It should be straight forward unless there is some detail I am not aware of. Mouser even has an European branch at https://eu.mouser.com/
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: factory on October 24, 2019, 09:28:56 pm
Not a silly question at all, firstly they won't sell the battery for the A5 board (restricted) so I had to use Farnell as they were the only supplier I could find for the UK, secondly I had some other parts I wanted from RS so I chose them too.

We did use Mouser & Digi-key at work a lot, but they were paying the extra for the international shipping.
The shipping for a pack of ten 1uF NP caps is four times the cost of the parts, I don't want to pay that, so unless I can find something else I want from them to meet the minimum for free shipping I won't be buying from them.

David

P.S. Hopefully most of the packages will arrive tomorrow, I'm keen to get that back-up battery replaced ASAP.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on October 24, 2019, 09:54:47 pm
Ok David understood and thank you for the clarification. But if what you are saying is that to bring in about $5 worth of capacitors you have to pay around $20 shipping, I think it is still manageable. A as long as it is small amounts like these I for one in the same circumstances would still go for it just to solve the situation, specially as you say if you could add in some more parts to make it worth the cost. But if the shipping numbers get out of control then I'm definitively with you. Oh and then I assume that even if you place your order through Mouser EU the parts are still shipped from the US?

In any case I hope you get your parts in soon and good luck with the scope repair/restoration, most of us here have been through it in varying degrees and almost always end up with success and the satisfaction of having restored a very nice instrument, plus the added knowledge gained in the process.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: martinr33 on October 28, 2019, 12:27:35 am
A couple of notes on a 2467b repair - graticule bulbs and SRAM.

1) To replace the graticule bulbs:
      - remove the four knobs under the CRT. They just pull off. Be careful.
      - Pop the cover strip on the top edge and use a T10 to remove the screws there.
      - remove the four T10s on the bottom edge, including the two in the feet. The feet will come off, don't lose them.
      - The entire front cover now comes off, exposing the metal CRT surround.. There is a plastic shield that comes loose and is easy to lose.
      - Remove the 8 T10s holding the heavy steel CRT guard in place.
      - Lift off the plastic light bulb cover. This is a thick, shaped acrylic strip.
      - Now, you can lift up the bulb strip. It is wired into the scope, but you can work on it from here.
      - Replace the three bulbs and reassemble. Don't forget the plastic shield.

This job is pretty quick, and you don't have to pull the case.

2) Replacing the SRAM.
My experience with these parts is that they can sometimes get corrupted in handling. I like to pull all pins except ground (14) and ~CE (20). Then I pull CE, and then ground. I think this approach keeps the RAM locked off until the very last minute. Then you can dump it with your TL866 or whatever.
 
My scope has 25000 hours on it, but the display looks unblemished. I think this unit probably just sat powered on in a lab. The 267b times the display out after a few minutes, so there's no burnin. Capse are next.

These are very fine instruments. Obviously, modern digital scopes surpass them, but the 400MHz analog system is amazing.


Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on October 28, 2019, 01:15:10 am
A couple of notes on a 2467b repair - graticule bulbs and SRAM.

1) To replace the graticule bulbs:
      - remove the four knobs under the CRT. They just pull off. Be careful.
      ........

These knobs are a two part insert and cap and sometimes they are notoriously difficult to pry off after many years of being in place. I had so far no need to remove them but  if they feel stuck and hard to pull the recommended procedure to avoid damaging them seems to be to carefully warm them up with a hot air gun. If they still won't budge then gently pry from the back of the knob using needle-nose pliers set around the shaft and slightly open just enough so each side of the pliers will fall behind on opposite sides of the knob skirt, then pull off with careful leverage against the front panel.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: factory on November 04, 2019, 03:27:17 pm
Ok David understood and thank you for the clarification. But if what you are saying is that to bring in about $5 worth of capacitors you have to pay around $20 shipping, I think it is still manageable. A as long as it is small amounts like these I for one in the same circumstances would still go for it just to solve the situation, specially as you say if you could add in some more parts to make it worth the cost. But if the shipping numbers get out of control then I'm definitively with you. Oh and then I assume that even if you place your order through Mouser EU the parts are still shipped from the US?

Mouser do have a UK website too, but as far as I know there is no stock held in Europe, all the parts come from the US and I don't want to give FedEx FedAxe £12 to ship a few small low value parts, also I'd rather order parts locally (RS have free shipping on any UK order).

Anyway I solved the problem with the "findparts" advert that sometimes appears at the top of the forum, it found what I couldn't on the RS website  :-+, a bulk pack of the 1uF non-polar capacitors, the rest will go in my spares stock.  :)

David
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Satbeginner on November 04, 2019, 03:36:10 pm
Hi,

I have an 2467B that has that slight flickering of the intensity as well...
Recap already done, all voltages rock steady, but still.
Must be something with these MCP intensity amplifier CRT's.

None of my 2565, 2465A or 2465B's have this.

Good luck, un saludo,

Leo
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on November 04, 2019, 04:08:05 pm
So it may be a "feature" of 2467B's...  nice...   Come to think of it, I don't remember my 2465B exhibiting the flicker, but both 2467Bs certainly do it, and it IS annoying.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on November 04, 2019, 04:23:32 pm
I have an 2467B that has that slight flickering of the intensity as well...
Recap already done, all voltages rock steady, but still.
Must be something with these MCP intensity amplifier CRT's.

Haven't had access to a 2467 type scope yet, so no idea how the flickering looks like,  but if possible a short video would document that flicker nicely for future references. I wonder what the experts over at Tekgroup-io would have to say about it, normal or not?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: factory on November 04, 2019, 04:28:45 pm
Also going to have a look at the IEC filter at the weekend, forgot to photo it.  :blah:

Almost forgot about this, the mid 1980's 2465 I'm currently working on has a Japanese made TDK IEC filter module, has anyone had any problems with this type?

Two of the slightly newer scopes here, a 2445A & 2465B (later 1980's) have a Swiss made Schaffner IEC filter module, these are known to fail in the same way as the infamous RIFA paper filter capacitors do, we had one release the smoke at work (in a Cropico ohm meter), I don't ever want the smell of another one of those stink bombs failing again.  :--

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=866502)

David
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: WastelandTek on December 05, 2019, 01:21:58 am
I apologize again for messing up this thread with somewhat off topic questions.  I am always fearful when I actually post on this forum that I will demonstrate myself to be painfully ignorant. 

It is 6 months later and I am finally getting around to actually ordering parts for my vanilla 2445, in particular to address the RAM issue.
There is a fair bit of information around on various models.  David piped up a few pages ago with the parts used in his 2440, and I get Google hits on the 2445A and 2445B, both of which also seem to use the Dallas NVRAM parts.

However, it appears that the 2445 (no A or B) uses an ER1400 EAROM instead.  There is a thread from 2013 here (https://www.eevblog.com/forum/testgear/tektronix-2445-teardown-pictures/) that suggests a replacement part as M5G1400P, they can be had, but I don't know if it is even safe to desolder this thing?
Any ideas guys?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on December 05, 2019, 04:03:34 am
...

However, it appears that the 2445 (no A or B) use an ER1400 EAROM instead.  There is a thread from 2013 here (https://www.eevblog.com/forum/testgear/tektronix-2445-teardown-pictures/) that suggests a replacement part as M5G1400P, they can be had, but I don't know if it is even safe to desolder this thing?
Any ideas guys?

It is my understanding the the plain models (no A or B suffix) do not require a replacement of the RAM chip (unless defective), as these older models do not use a NVRAM chip but rather they rely on a completely separate on-board external battery as backup, instead of the battery being hidden inside the same RAM chip. So in this case the battery replacement is a much simpler procedure and the only thing to keep in mind is to provide a temporary 3V supply to the board while the old battery is being extracted and the new one is soldered in. Usually you can do that by joining two AA cells in series and connect this in parallel with the existing old battery with a couple of short wires to keep the memory contents alive during the surgery.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Satbeginner on December 05, 2019, 07:54:47 am
Hi, I have a 2465 with a through hole A5 pcb, that one has a ER1400 chip. I found a replacement, but in the end it was not broken. Just an incomplete calibration caused the dots to show.

My 2464A has a battery backed up memory on a through hole pcb, and my 2465B and 2467B ( both and A5 SMD PCBs) have a Dallas chip.

So, there are three versions of the A5, where the battery backuped versions exist in two versions again.

ER1400, 2* Battery backup, Dallas

Un saludo,

Leo
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on December 05, 2019, 09:47:04 am
However, it appears that the 2445 (no A or B) uses an ER1400 EAROM instead.  There is a thread from 2013 here (https://www.eevblog.com/forum/testgear/tektronix-2445-teardown-pictures/) that suggests a replacement part as M5G1400P, they can be had, but I don't know if it is even safe to desolder this thing?
Any ideas guys?

I have no comment about that specific IC.

Unless you have the equipment to be able to do a full calibration, the problem would be getting the calibration coefficients out of the existing ROM and inserting them into the new ROM. Getting them out can be done using the test sequence and writing down what you see on the screen.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on December 05, 2019, 12:39:18 pm
It's basically broken down as follows:

2445/2465 (No suffix): Pin thru hole A5 board. The EAROM does not have, nor does it require, a battery backup.

2445A/2465A: Pin thru hold A5 board. Don't recall chip type but it does have an external battery soldered to the A5 board.

2445B/2465B: SMT A5 board. Has the Dallas chip with internal battery.

Now supposedly some 2445A/2465A also have the SMT A5 board but not sure. 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: emece67 on December 05, 2019, 01:05:18 pm
.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: WastelandTek on December 05, 2019, 02:06:29 pm
It's basically broken down as follows:

2445/2465 (No suffix): Pin thru hole A5 board. The EAROM does not have, nor does it require, a battery backup.

snip

Thank you.  This seems to be the case as I can locate no battery on my A5 and a search for the word "battery" in the service manual reveals no hits.

I guess manually recording the cal data just in case and some caps and I am "safe" to keep using this thing.

One other wrinkle you folks are probably aware of but I will throw in for the benefit of anyone searching in the future; common EPROM programmers do not supply the -30V necessary to program EAROMs...so there's that...
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on December 05, 2019, 03:41:37 pm
It's basically broken down as follows:

2445/2465 (No suffix): Pin thru hole A5 board. The EAROM does not have, nor does it require, a battery backup.

2445A/2465A: Pin thru hold A5 board. Don't recall chip type but it does have an external battery soldered to the A5 board.

2445B/2465B: SMT A5 board. Has the Dallas chip with internal battery.

Now supposedly some 2445A/2465A also have the SMT A5 board but not sure.

I do have a 2465B with the THT A5 board and the Li/SOCl2 cell soldered on it.

OK, apparently I had at backwards. I guess some early 2445B/2465B's had a pin thru hole A5 board.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: LADmachining on December 05, 2019, 08:57:42 pm
It's basically broken down as follows:

2445/2465 (No suffix): Pin thru hole A5 board. The EAROM does not have, nor does it require, a battery backup.

2445A/2465A: Pin thru hold A5 board. Don't recall chip type but it does have an external battery soldered to the A5 board.

2445B/2465B: SMT A5 board. Has the Dallas chip with internal battery.

Now supposedly some 2445A/2465A also have the SMT A5 board but not sure.

My 2445B has a through-hole board.  The memory IC is an NEC D4364C-15LL

[attachimg=1]
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bud on December 05, 2019, 10:17:10 pm
Heck, that made me google for Guernsey channel islands  :)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on December 05, 2019, 10:45:12 pm
My 2445B has a through-hole board.  The memory IC is an NEC D4364C-15LL

Your "Keeper"  battery seems to have a 1990 date code, perhaps its time to replace it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: WastelandTek on December 06, 2019, 01:06:26 am
well this is stupid

I can't seem to find suitable axial caps anywhere to replace the 290uF 200V units in the fan motor plastic on A3.

You would think that 330uF 250V would be the modern one...Digikey lists 2, both non stock with minimums in the tens...

Mouser has none

RFParts is showing 470uF 200V axials in stock...but that seems like a lot of extra cap...do I just buy radials and fold the lead over and extend it??  seems...inelegant.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on December 06, 2019, 01:24:48 am
well this is stupid

I can't seem to find suitable axial caps anywhere to replace the 290uF 200V units in the fan motor plastic on A3.

You would think that 330uF 250V would be the modern one...Digikey lists 2, both non stock with minimums in the tens...

Mouser has none

RFParts is showing 470uF 200V axials in stock...but that seems like a lot of extra cap...do I just buy radials and fold the lead over and extend it??  seems...inelegant.

Had the same issue. Yep, bought the radials and folded the lead and extended it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on December 06, 2019, 01:30:42 am
well this is stupid

I can't seem to find suitable axial caps anywhere to replace the 290uF 200V units in the fan motor plastic on A3.
Plenty to choose from here:
https://www.tedss.com/Capacitors/Browse/aluminum-electrolytic-axial (https://www.tedss.com/Capacitors/Browse/aluminum-electrolytic-axial)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: WastelandTek on December 06, 2019, 01:39:23 am
Plenty to choose from here:
https://www.tedss.com/Capacitors/Browse/aluminum-electrolytic-axial (https://www.tedss.com/Capacitors/Browse/aluminum-electrolytic-axial)

That is a neat site that I was not aware of, but the only 330uF 250V axial I'm seeing is 3" long  :(

looks like long leads and elegance be dammed...
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on December 06, 2019, 01:40:33 am
well this is stupid

I can't seem to find suitable axial caps anywhere to replace the 290uF 200V units in the fan motor plastic on A3.
Plenty to choose from here:
https://www.tedss.com/Capacitors/Browse/aluminum-electrolytic-axial (https://www.tedss.com/Capacitors/Browse/aluminum-electrolytic-axial)

That is a neat site that I was not aware of, but the only 330uF 250V axial I'm seeing is 3" long  :(
Try this one:
https://www.tedss.com/2020058128 (https://www.tedss.com/2020058128)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: WastelandTek on December 06, 2019, 01:45:32 am
hmmmmmmmm

even better  https://www.tedss.com/2020058049 (https://www.tedss.com/2020058049)

like they were made for it, I wonder how old this stock is though


editing to add these useful links for easy finding

http://www.kerrywong.com/2013/04/25/tektronix-2445-teardown/ (http://www.kerrywong.com/2013/04/25/tektronix-2445-teardown/)

http://www.kerrywong.com/2016/02/22/teardown-of-a-tektronix-2465/ (http://www.kerrywong.com/2016/02/22/teardown-of-a-tektronix-2465/)

http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf (http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf)

https://antiqueradios.com/forums/viewtopic.php?f=8&t=235478 (https://antiqueradios.com/forums/viewtopic.php?f=8&t=235478)

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: LADmachining on December 15, 2019, 07:54:26 pm
My 2445B has a through-hole board.  The memory IC is an NEC D4364C-15LL

Your "Keeper"  battery seems to have a 1990 date code, perhaps its time to replace it.

Well spotted!  This photo was taken before I exchanged the battery - it was replaced shortly after. :)

Anthony
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on December 15, 2019, 08:13:38 pm
My 2445B has a through-hole board.  The memory IC is an NEC D4364C-15LL

Your "Keeper"  battery seems to have a 1990 date code, perhaps its time to replace it.

Well spotted!  This photo was taken before I exchanged the battery - it was replaced shortly after. :)

Anthony

 :-+
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: WastelandTek on January 04, 2020, 11:48:58 pm
so guys

I am just about to reassembly on my vanilla 2445 after a full recap and I wanted to show off my custom U800 heatsink solution.  I'm pretty proud of it.

It seems pretty clear to me that Tektronix, at some point in the design process, contemplated a heatsink here given the mounting screws they included.  So I tried to make something close to what I imagined they had in mind.

(https://i.imgur.com/RcKAwjZ.jpg)

(https://i.imgur.com/Bcwkhk1.jpg)

(https://i.imgur.com/Pb2VPqd.jpg)

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Electro Fan on January 05, 2020, 02:36:43 am
so guys

I am just about to reassembly on my vanilla 2445 after a full recap and I wanted to show off my custom U800 heatsink solution.  I'm pretty proud of it.

It seems pretty clear to me that Tektronix, at some point in the design process, contemplated a heatsink here given the mounting screws they included.  So I tried to make something close to what I imagined they had in mind.

(https://i.imgur.com/RcKAwjZ.jpg)

(https://i.imgur.com/Bcwkhk1.jpg)
was
(https://i.imgur.com/Pb2VPqd.jpg)

That looks pretty cool, and it’s very neat to think about and maybe actually extend/improve upon whatever Tektronix might have contemplated. (And gregarious is great too.) Thanks for sharing.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on January 05, 2020, 02:37:12 am
I don't want to fire up the debate concerning heatsinking U800 again...which has been discussed ad nauseum in this thread....but IMHO an additional heat sink, especially on a Tek die U800, is completely unnecessary if the cooling system in the scope is properly maintained.   
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on January 05, 2020, 02:11:45 pm
Correct me if I am wrong as I have never bothered with any additional U800 heat sinking solutions and probably never will as they are not really required unless your internal air flow should go south and the situation is not noticed for some time, then perhaps additional heat sinking might be useful and potentially save your chip under certain heavy duty complex high frequency waveform display usage situations, but....

As I understand one of the U800 threaded studs is at +5V potential and the other is at ground, so joining both with a piece of aluminum will in essence create a short circuit. Again, I am up for being corrected if this is not correct, but I think I am not wrong.

Edit: And in my general opinion messing at all with the U800 setup as it came from the factory might create serious problems were there where none, specially if undoing and reinstalling those two nuts onto the studs. Be very careful about the torque and evenness of both nuts or the delicate IC substrate will be damaged during the process, of possibly even further down the line due to thermal stresses added to improperly torqued down nuts.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: WastelandTek on January 05, 2020, 03:12:36 pm
Hmmmm,

First I have heard of this being in any way controversial.  I was under the impression that it was a standard modification.

Certainly going to look into the +5V stud and isolate if necessary, thank you.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on January 05, 2020, 08:39:11 pm
As I understand one of the U800 threaded studs is at +5V potential and the other is at ground, so joining both with a piece of aluminum will in essence create a short circuit. Again, I am up for being corrected if this is not correct, but I think I am not wrong.

Nope, those two studs are connected to -5 Volt (negative 5 volt). Or connected to U800 pin 19.

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=317592;image)


Edit: And in my general opinion messing at all with the U800 setup as it came from the factory might create serious problems were there where none, specially if undoing and reinstalling those two nuts onto the studs. Be very careful about the torque and evenness of both nuts or the delicate IC substrate will be damaged during the process, of possibly even further down the line due to thermal stresses added to improperly torqued down nuts.

Even they're installed with "right and perfect" torque, think again, these nuts serve no purpose at all. And may do more harm than good, its the thermal cycle that the chip endures, while its secured firmly, the expansion and contraction will stress out the die attached to the metal tab.

- Are they holding the U800 chip from falling out ? Nope, as the whole chip is soldered firmly on the board.

- Are they serve to improve the thermal conduction to the studs ? Nope, as both nuts use sandwiched 2 star washers, which is clearly not a good way to let the heat generated transferred from the tab to the studs. Beside the studs are not a good heat sink anyway.

Pic speaks thousands words.
(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=317596;image)

Pay attention or maybe zoom in really close, watch for the tiny2 circled indentations around the hole, made by the star washer at the metal tab, definitely not good for thermal transfer from the metal tab to the stud.
(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=317598;image)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on January 05, 2020, 11:12:10 pm
Yep, BravoV makes a lot of good points concerning the funky construction and mounting of U800. And we've had a lot of debate about whether to heat sink it or leave it alone.

I'm in the "leave it alone" camp. The funky construction and mounting of U800 is just asking for trouble. And to my knowledge Tek never published the torque specs. It would be all too easy to over torque it and damage the die.

Look at it this way....these 24XX scopes are over 30 years old and MOST of the U800's out there are functioning just fine. And no one to my knowledge has ever posted in this thread that they had one crap out. I have two 2465's and I have no intention of touching U800. But I DO insure the fan is working properly and there's adequate air flow at all times.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: GerryR on January 06, 2020, 12:14:47 am
It is my understanding that Tek subbed out the making of the U800 IC to anther vendor (I'd have to look up to whom) and they had production problems, where the die would come loose from the heat sink.  These overheated and failed.  That problem was addressed and corrected, but the "legend" of the overheating U800 lives on.

When I had my unit opened for calibration, I monitored the U800 temperature (mainly because of the legend) and found that even with no fan blowing air across the board, the temperature of the IC never went above 135 deg F.  With a little air running across it, it settled to about 120 deg F.  I didn't think there was any reason for concern and left everything as stock.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on January 06, 2020, 12:26:47 am
Tektronix sold their fab to Maxim.  I have some Tektronix parts marked with the Maxim logo.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: WastelandTek on January 06, 2020, 12:30:03 am
Well, it certainly was not my intention to stir up controversy.

I can verify that the 2 studs in mine are electrically connected.

Cautions about torque are well taken, but I believe I will go ahead with my heatsink with moderate torque applied.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on January 06, 2020, 12:30:25 am
And allegedly those U800 Maxim dies are more failure prone than the Tek dies. If you have a late 2465A and most 2465B's they have Maxim U800's.   
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: siggi on January 10, 2020, 11:43:03 pm
Cautions about torque are well taken, but I believe I will go ahead with my heatsink with moderate torque applied.

The problem with this plan - allegedly - is that when you torque down on the tab, you risk pulling the lead frame away from the die, which will kill your U800.
Good luck!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on January 11, 2020, 01:01:09 am
Subject to debate of course, my opinion only, the ideal case for U800 chip is de-solder the whole chip, then put a SIP socket (not DIP socket).

With dual SIP IC sockets, the chip body once installed will be lifted and has more space underneath it.

This opened up opportunity to have some custom heatsink with 2 pieces of metal + thermal pad for sticking underneath the chip, and using both studs + washers and nuts to sort of clamp the chip body from the top and bottom without stressing the chip body as its now socketed, this will make an effective thermal path thru the chip's die from the bottom.

Again, imo this is not worth it, unless the owner happened to have a case that the A1 board must be de-soldered and lifted from the scope for a serious repair, with this condition it will be a good opportunity to fix this funky U800 chip installation.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: LarryS on January 24, 2020, 10:52:15 pm
Hi,

I thank you for your post.

Black body radiation is how you begin your studies of radiation in Physics 10? ( I forget 1,2 or 3 - it was more than 50 years ago).  i.e. it is the simplest and best radiator.  I know not the black substrate on which you would be putting the heat sink, but I would think it adhearent to whatever lay below.
-------
It seams that my comment is posted as the last comment even though I was commenting about the 1st or 2nd page of this subject header. i.e. "Reply #5 on: November 04, 2011, 04:32:39 am".
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: syau on February 07, 2020, 06:15:57 am
Scored a 2465B, while try to replace the NVRAM with STK16C68-W45 found the board with 2 feed through capacitor from the factory instead of the SMD leaking one  :-+

[attach=1]

[attach=2]
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on February 07, 2020, 06:28:37 am
Scored a 2465B, while try to replace the NVRAM with STK16C68-W45 found the board with 2 feed through capacitor from the factory instead of the SMD leaking one  :-+

Congratulation  :clap: , yeah, your A5 board revision is exactly like mine (see 1st post), its using the thru hole caps, instead of those evil SMD electrolytic ones.

I've replaced mine, and just fyi, if my memory serves me well, that both thru hole electrolytic caps were basically still in spec & healthy when I de-soldered them, but I replaced them anyway as I already bought their replacements.

Is it made in Guernsey UK ?


Just curious, what are you planning on your U800 chip ? Leave it as is ?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: syau on February 07, 2020, 08:13:16 am
The unit S/N is B06xxxx and made in USA.

For the U800, I just whipped the dust off and leave it as is.

[attach=1]
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: syau on February 07, 2020, 08:17:01 am
For the power supply, I just replaced 2 68nF RIFA cap.

[attach=1]
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on February 07, 2020, 08:20:55 am
For the power supply, I just replaced 2 68nF RIFA cap.

Good call  :-+ , from the photo, those 2 RIFAs already cracked, aren't they ?

Any chance you could share the close up photo for those de-soldered cracked 2 RIFAs, another good example and will serve as a good reference.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: syau on February 07, 2020, 09:30:56 am

At least no visible crack on the casing

[attach=1]

[attach=2]

[attach=3]
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on February 07, 2020, 09:34:17 am
Thanks, still better safe than sorry.  ;D

(https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=772293;image)

According to TEA (https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?topicseen) dictionary ... RIFA Madness - May refer to the state of the equipment or its owner when old RIFA capacitors suddenly let out copious amounts of pungent magic smoke. With some devices, this can occur even when the power switch is turned off. Beware!  :-DD
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Satbeginner on February 07, 2020, 10:00:48 am

At least no visible crack on the casing

(Attachment Link)

(Attachment Link)

(Attachment Link)

Not yet you mean...  ;D

I have seen the other capacitors go dry as well, but never the two big ones.
Beware, there is a mix-up of a 30V and a 150V capacitor in the silkscreen printed partnumbers, C1132 and C1115 are swapped by mistake.
If you put them according to the silkscreen you will have magic smoke and more damage done.....

Good luck with your 2465, they are the best!!

Un saludo,

Leo
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on February 08, 2020, 07:36:51 pm

At least no visible crack on the casing


Did you ever power it when the RIFAs were installed ? Consider your self lucky.

I saw your photos for just a quick glance using my phone at the 1st time, and didn't catch the details, and when I visited this thread again and used desktop big monitor, was curious and tried to zoom in  :o , well, picture speaks thousand words, attached of the zoomed & tweaked photo of your RIFA below.  :scared:
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: WastelandTek on February 08, 2020, 07:57:17 pm
she's fixin' ta BLOW
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on February 08, 2020, 08:39:38 pm
Yep, big chance it will go kablooey once the ingressed water thru those cracks is accumulated enough.

Also those visible weird egg shaped, darken patterns, suspect those are actually the trapped water vapor ?  :-//
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: syau on February 08, 2020, 11:20:56 pm

At least no visible crack on the casing


Did you ever power it when the RIFAs were installed ? Consider your self lucky.

I saw your photos for just a quick glance using my phone at the 1st time, and didn't catch the details, and when I visited this thread again and used desktop big monitor, was curious and tried to zoom in  :o , well, picture speaks thousand words, attached of the zoomed & tweaked photo of your RIFA below.  :scared:

I did power it up for an hour or so to video record  the NVRAM using exec 02 :phew:
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: syau on February 22, 2020, 02:09:12 am
Scored a 2465B, while try to replace the NVRAM with STK16C68-W45 found the board with 2 feed through capacitor from the factory instead of the SMD leaking one  :-+

(Attachment Link)

(Attachment Link)

Just open it up again to replace the 5V light bulb.

Below showing STK16C68-W45 fitted in the place of NVRAM.

[attach=1]
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on February 24, 2020, 10:31:34 pm
If anyone with a plain 2465 or the A version is in need of the original Siemens fan motor, over at the Tekscopes-IO group someone found a seller on ebay that seems to have a big inventory of what seems to be brand new exact replacement motors. As far as I know the B series scopes never used this motor but rather a more common muffin fan type. But I might be wrong on that, and even some early B SN also use this fan. Since this motor is not easy to source, let alone in new condition, and a pain to repair, I thought I pass along this information. Even if yours is still working fine, perhaps a good idea to keep a spare on hand just in case for future needs.

Edit: this fan will also fit the plain 2445 scopes, and as pointed out by the seller, it will also fit some 46x and 47x series as well. Do your own homework, and probably a good idea to check the Tekscopes thread to be sure as I have no experience with those older scopes.

I am in no way connected to the sale.
https://www.ebay.com/itm/274013390896 (https://www.ebay.com/itm/274013390896)

Here is the original thread at Tekscopes group:
https://groups.io/g/TekScopes/topic/71491839 (https://groups.io/g/TekScopes/topic/71491839)

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on February 25, 2020, 02:06:38 pm
If anyone with a plain 2465 or the A version is in need of the original Siemens fan motor, over at the Tekscopes-IO group someone found a seller on ebay that seems to have a big inventory of what seems to be brand new exact replacement motors. As far as I know the B series scopes never used this motor but rather a more common muffin fan type. But I might be wrong on that, and even some early B SN also use this fan. Since this motor is not easy to source, let alone in new condition, and a pain to repair, I thought I pass along this information. Even if yours is still working fine, perhaps a good idea to keep a spare on hand just in case for future needs.

Edit: this fan will also fit the plain 2445 scopes, and as pointed out by the seller, it will also fit some 46x and 47x series as well. Do your own homework, and probably a good idea to check the Tekscopes thread to be sure as I have no experience with those older scopes.

I am in no way connected to the sale.
https://www.ebay.com/itm/274013390896 (https://www.ebay.com/itm/274013390896)

Here is the original thread at Tekscopes group:
https://groups.io/g/TekScopes/topic/71491839 (https://groups.io/g/TekScopes/topic/71491839)
The price is going up.  I bought one for a 2445A a few days ago at $9.99.  Yesterday they were $14.99.  Now $19.99.

The buying history says someone bought 20 of them, maybe to cash in when they're unobtanium again.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on February 25, 2020, 02:51:02 pm
The price is going up.  I bought one for a 2445A a few days ago at $9.99.  Yesterday they were $14.99.  Now $19.99.
The buying history says someone bought 20 of them, maybe to cash in when they're unobtanium again.

Yes indeed saw that too. The person that bough the 20 units might be someone servicing these scopes.
So get your spare motor while there is still a chance.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: syau on March 15, 2020, 10:57:30 am
Just do another 2465B recap, serial number 01xxxx. Fuse blow up after 10 minutes after re-cap, no magic smoke. Turn out that the input bridge rectifier shorted  |O.

This unit have only 3xxx hrs run time and very clean inside. Only issue (if any) is the beam not prefect circular when I operate in X-Y mode.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: factory on March 20, 2020, 08:47:38 pm
Finally completed the 2465B I started last year, all the radial electrolytic capacitors in the PSU were replaced along with the RIFA stink bombs.
It was then tested before replacing the lithium battery on the A5 board, I soldered on a temporary battery to keep the cal data, I had to write the date of manufacture on the top of the new battery as they decided it was better on the bottom |O, all was good after reassembly.  :-+

Just got a 2465, 2445 & 2445A left to repair, the 2465 & 2465B both have the TV option (05) fitted, no options fitted to the 2445/A.

David
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on March 20, 2020, 09:21:59 pm
They sold you a 2018 battery in 2020, or did you buy it some time ago?
Even tough we know now these batteries usually will last way past their 10-year life expectancy, academically speaking you basically have only about 80% life left in that one. Still ok but I would have hoped to receive a fresh one that was manufactured not more than 1 year ago or ideally less.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: factory on March 20, 2020, 10:13:48 pm
It was bought from Farnell in October last year, the only trustworthy supplier I could find that would sell this type of battery in the UK.

David
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on March 20, 2020, 10:57:49 pm
Should be ok as long as you did not buy it from a chinese seller on ebay!
Enjoy your scope.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: factory on March 26, 2020, 08:05:45 pm
Had to order another battery from Farnell for the 2445A, I had wrongly assumed it used the older A5 board, it should be here tomorrow.

https://uk.farnell.com/eve/ef651625/battery-lithium-3-6v-prismatic/dp/1973588

David
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Gixy on March 27, 2020, 08:15:32 am
I used this one on my 2445A. It has a bigger capacity (1200 mAh), so will last quite forever...
https://fr.farnell.com/saft/ls14250/batterie-1-2aa-lithium-standard/dp/1282760
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: syau on March 28, 2020, 01:36:31 am
I am not able to locate similar battery in Hong Kong and sending one from US through a qualified DG shipment forwarder is extremely expensive therefore I just solder a AA size 3.6V lithium battery  :-DD
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: factory on March 29, 2020, 01:41:50 pm
Can you not find the EVE LTC-7PN battery (made in China) in Hong Kong? I'm guessing the AA or half AA size lithium batteries probably cost less anyway.

David
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: syau on March 29, 2020, 02:04:50 pm
Unable to find it in Hong Kong except those Israel made AA lithium battery  :-DD
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: factory on March 29, 2020, 08:49:47 pm
Funny you should mention that, I used one of those Israel made half AA batteries as a temporary supply during replacement.

David
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on March 29, 2020, 11:40:37 pm
The reason the LTC-7P battery may be difficult to source is that lithium batteries cannot go air freight. So if your country has no local stock it may be difficult, if not impossible, to procure. The Tek 2430 DSO uses the same battery for NVRAM. I recently replaced the battery in mine and I purchased it from Mouser but it had to ship UPS ground. And when I received the package it had a label on it stating that it contained hazardous material that could not go air freight. 

Here's the change out procedure for the 2430. It's more complex than the 2465 as the board containing the battery is not readily accessible like the A5 board. I used an HP 6215A power supply set to 3.6V as backup while changing the battery.

(https://imagizer.imageshack.com/v2/640x480q90/921/3XRIJN.jpg) (https://imageshack.com/i/pl3XRIJNj)
(https://imagizer.imageshack.com/v2/640x480q90/922/Iw8r00.jpg) (https://imageshack.com/i/pmIw8r00j)
(https://imagizer.imageshack.com/v2/640x480q90/923/BZXtQ6.jpg) (https://imageshack.com/i/pnBZXtQ6j)
(https://imagizer.imageshack.com/v2/640x480q90/921/QnVHwn.jpg) (https://imageshack.com/i/plQnVHwnj)
(https://imagizer.imageshack.com/v2/640x480q90/922/2SPzsG.jpg) (https://imageshack.com/i/pm2SPzsGj)
(https://imagizer.imageshack.com/v2/640x480q90/923/PC71k9.jpg) (https://imageshack.com/i/pnPC71k9j)
(https://imagizer.imageshack.com/v2/640x480q90/922/R3uNjO.jpg) (https://imageshack.com/i/pmR3uNjOj) 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: emece67 on March 30, 2020, 01:16:46 pm
.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: syau on March 31, 2020, 03:52:13 pm
Unable to find it in Hong Kong except those Israel made AA lithium battery  :-DD

Found RS did sell cheaper than I get from local retail shop who sell various battery. RS said it will take them around 44 days to ship on ship from UK  :-DD
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: rigmo on August 15, 2020, 11:46:58 am
HI, can you help me to fix my new oscilloscope 
flickering  https://youtu.be/s0we1dCMUXw

I got a gift 2465B from my dear friend in Germany  who died from cancer a few months ago... 
I have a problem with an oscilloscope and for legacy and memory on him  I won't repair.. can you help

Thank You in Advance
Best Regards
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Satbeginner on August 15, 2020, 12:49:32 pm
Looks perfectly ok to me
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on August 15, 2020, 02:51:35 pm
If you are complaining that all LEDs are blinking "faintly altogether" whenever button is pressed, yes, that is normal for 2565B, no worry.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: rigmo on August 15, 2020, 06:35:06 pm
I believe problems bad caps... thank you..
one more question.. my curiosity is  hoe to see  power on hours and cycle counts on machine... how to know?
Today i find crazy link https://hackaday.io/project/163890-tektronix-2465-series-servicing#j-discussions-title
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Gregory on August 15, 2020, 11:45:13 pm
Hi guys!

I bought a 2465A with a bad channel 1 input module. The problem was a burned resistor in the 50ohm input path.

I soldered two thru hole resistors and the unit got back to normal operation! I got very impressed because with a fast pulse generator I'm not seeing any difference between this channel and the original channel 2. Pretty interesting !

(https://i.ibb.co/YbRzhMX/image.png) (https://imgbb.com/)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on August 15, 2020, 11:54:15 pm
Not very familiar with the input board, but just wondering what was the value of the original resistor that burned up? Two 68-ohm in parallel as you seem to have used will give you about 34 ohms.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Gregory on August 16, 2020, 12:09:34 am
Yep, It was very close to 34 ohms.. It makes a input attenuator with other Rs.
I was afraid to open the input module but it was my only option!

In this picture you can see the burned resistor complete split in half
(https://i.ibb.co/Gk88wK5/image.png) (https://imgbb.com/)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mawyatt on August 16, 2020, 01:36:57 pm
Hi guys!

I bought a 2465A with a bad channel 1 input module. The problem was a burned resistor in the 50ohm input path.

I soldered two thru hole resistors and the unit got back to normal operation! I got very impressed because with a fast pulse generator I'm not seeing any difference between this channel and the original channel 2. Pretty interesting !

(https://i.ibb.co/YbRzhMX/image.png) (https://imgbb.com/)

I'm surprised that the extra inductance of the leaded resistors didn't effect the BW or pulse response. Might want to consider a large chip resistor (lower inductance) instead of the leaded resistors.

I had a bad channel 1 (very erratic) and 2 had some issues also on a ebay purchased 2465. This was traced to the input hybrid modules and the relay contacts. I carefully cleaned the relay contacts and hybrid contact areas with a lightly abrasive pencil eraser, then cleaned with alcohol. This fixed the problem, I suspect that film had deposited on the contacts, maybe from cigarette smoke, which interfered with the contacts. While you have these hybrids open you might want to consider cleaning the relay contacts and contact area.

Anyway, nice work :-+

Best,
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on August 16, 2020, 05:01:20 pm
Since it is not mentioned, the question would of course be what was the highest frequency (or fastest pulse width) used as comparison between ch1 and ch2 performance. I bet it was not anywhere near to about 100MHz where you would  expect the leads of the resistors to start playing a part by adding inductance.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on August 16, 2020, 06:14:28 pm
Since it is not mentioned, the question would of course be what was the highest frequency (or fastest pulse width) used as comparison between ch1 and ch2 performance. I bet it was not anywhere near to about 100MHz where you would  expect the leads of the resistors to start playing a part by adding inductance.

The pulse width and pulse frequency are irrelevant. The only parameter that matters is the transition time (i.e. risetime/falltime). The only advantage of a higher pulse frequency on a non-digitising scope is that the higher the pulse frequency the brighter a trace will appear. For simple theory and illustrative measurements, see https://entertaininghacks.wordpress.com/2018/05/08/digital-signal-integrity-and-bandwidth-signals-risetime-is-important-period-is-irrelevant/

For a 2465B, the pulse risetime should be <1ns, and the pulse frequency can be anything above, say, 100kHz. Obviously the scope bandwidth shouldn't be 20MHz, and the internal 50ohm termination should be used :)

But we can make some wild guesses, from looking at the picture...

It appears that the 50ohm termination resistor (the one that fails if too high a voltage is applied in 50ohm mode) has been replaced by two 68ohm resistors in parallel, i.e. 34ohms. That would be a very poor termination; the VSWR would be very high.

That would be a very long SMD resistor, let's guess 10mm. The inductance of a 10*4*1mm wire is 4nH. https://chemandy.com/calculators/flat-wire-inductor-calculator.htm

The inductance of a 10mm long 0.5mm diameter wire is around 7.2nH (the rule of thumb is 0.8nH/mm) https://chemandy.com/calculators/round-wire-inductance-calculator.htm Since there are two in parallel, the inductance would be around 3.5nH. The inductance of the resistor body is dependent on the construction, especially if the resistance is defined by a helical cut into a metal film. Hence the inductance of the through-hole resistors vs SMD resistor might or might not be a problem.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Gregory on August 16, 2020, 06:47:46 pm
The original resistor was not 50 ohm. It was very close do 34 ohm. The amplitude response is right on the mV level and the rise time is near 800ps

(https://i.ibb.co/k2cn5Jk/image.png) (https://imgbb.com/)

 :)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on August 16, 2020, 08:30:32 pm
The original resistor was not 50 ohm. It was very close do 34 ohm. The amplitude response is right on the mV level and the rise time is near 800ps

(https://i.ibb.co/k2cn5Jk/image.png) (https://imgbb.com/)

 :)

Good news about the resistor value!

You cannot tell anything about the risetime from an avalanche pulse, since the trace is the conclusion of the input pulse and the scope's response. To find the scope's response it would be necessary to know input pulses shape and then mathematically perform the deconvolution.

Without that information and processing, the easiest technique is to have a step waveform with a rise time much shorter than the scope's rise time.

One technique for generating a step is to take an avalanche generator and add a parallel transmission line which is shorted at the other end. The line length determines the pulse width.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Gregory on August 16, 2020, 10:18:41 pm
I can't see why the avalanche pulse is not useful for bandwidth estimation.

Obviously that the trace will be the convoluted response of the pulse and the scope front-end, but the rise-time needs to be preserved in the perspective of a first-order bandwidth estimation. If the test avalanche impulse is fast enough, the dominant pole will be from the scope itself.

Unfortunately this is the fastest rising edge I can generate here in the lab and it's rise time is not far from the 2465B bandwidth :-\
I measured it with a 1Ghz scope and it still measures ~800ps
(https://i.ibb.co/wBscjKD/image.png) (https://ibb.co/wBscjKD)

But what I really think that matters is that the 2465B fixed channel 1 and original channel 2 still show exactly the same waveform, so it seems that the parasitics of the modification are not so important in for the bandwidth of this Tek...

Well..  I'm happy with the results and the purpose of my latest posts was to show that a burned Tek 24XX input module is not the end of the world hehehe
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on August 16, 2020, 11:23:29 pm
I can't see why the avalanche pulse is not useful for bandwidth estimation.

Obviously that the trace will be the convoluted response of the pulse and the scope front-end....

Here's a simple example from one of my scopes, illustrating why you need to accurately know the input waveform. My apologies for the poor picture.

The timebase is 1ns/div. What's the scope's bandwidth?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on August 16, 2020, 11:32:50 pm
I can't see why the avalanche pulse is not useful for bandwidth estimation.

Obviously that the trace will be the convoluted response of the pulse and the scope front-end, but the rise-time needs to be preserved in the perspective of a first-order bandwidth estimation. If the test avalanche impulse is fast enough, the dominant pole will be from the scope itself.

Unfortunately this is the fastest rising edge I can generate here in the lab and it's rise time is not far from the 2465B bandwidth :-\
I measured it with a 1Ghz scope and it still measures ~800ps
(https://i.ibb.co/wBscjKD/image.png) (https://ibb.co/wBscjKD)

But what I really think that matters is that the 2465B fixed channel 1 and original channel 2 still show exactly the same waveform, so it seems that the parasitics of the modification are not so important in for the bandwidth of this Tek...

Well..  I'm happy with the results and the purpose of my latest posts was to show that a burned Tek 24XX input module is not the end of the world hehehe

Sometime ago I also fell into the same misconception about measuring rise time that way with just a pulse, and was quickly put on the right track by another member. See bellow quote from his response message to me when I published my own "pulse" rise time results, very similar to yours. Since this exact explanation applies to your scenario as well I though it would be relevant to re-quote this response.

You can not measure rise time with an impulse. It can only be done with a step. The impulse can only show you the slew rate. The reason is simple: you never see the true "top" of the impulse before it begins decreasing in amplitude causing the scope response to follow. Therefore you can't set the 90% to anything meaningful. This is where the step is used; the top of the step eventually becomes clearly visible, so you can set the 90% mark against this 100% reference. Put another way, knowing that the trace is increasing is meaningless unless you know what point it is increasing toward.

My 2465A (350MHz) had a rise time to a very fast step (<50 ps rise time) of dead on 1.0 ns, and I had also measured the actual -3 dB point at about 375 MHz (using a leveled sine generator). It follows that a 400 MHz 2465B should be about 8.7 ns or so. The apparently significantly shorter response to your impulse generator is misleading and not accurate.

With that said, you can fairly easily convert an avalanche impulse generator to a step generator by substituting the capacitor for a short piece of 50 ohm coax, acting as a charge line. It needs only store a few ns of charge, so with 1 ns per 20 cm, you don't need much at all. (don't go too long, nor pulse too frequently as it stresses the transistor). A follow up Jim Williams app note builds upon his avalanche pulse (impulse) generator to make a step generator using coax as a charge line (AN94).
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Gregory on August 17, 2020, 12:31:02 am
Really nice !!

I'm back with pictures using the coax charge line

(https://i.ibb.co/2KSDpKY/image.png) (https://ibb.co/2KSDpKY) (https://i.ibb.co/bWNZ9sR/image.png) (https://ibb.co/bWNZ9sR) (https://i.ibb.co/jgPKw8Q/image.png) (https://ibb.co/jgPKw8Q) (https://i.ibb.co/x2m6yB1/image.png) (https://ibb.co/x2m6yB1)

channel 1 with the thruhole resistor on the input attenuator and original channel 2
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on August 17, 2020, 12:41:05 am
 :-+

Good job updating your impulse gen. So there seems to be after all no difference between ch1 and ch2 response.
Perhaps the function of the resistor you replaced is somehow not critical to the input response characteristics.
Interesting indeed.

Edit1: However, given BW = 0.35/T, your scope seems to only have a calculated bandwidth of about 236MHz, and since you have an "A" version 2465 you should rather be seeing a 350+ MHz bandwidth result.

Edit2: by looking again at your pictures, I am now seeing that for the ch1 measurement the top of the step is not properly aligned to the 100% mark, so that is causing a measurement error. You should try again while making sure both the 0% and 100% marks correspond to the bottom and top of the step.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Gregory on August 17, 2020, 01:22:39 am
Thanks !

Yep.. maybe the pulse gen is not fast enough. Also, the signal seems to have a slow ramp before the fast rise, it's difficult to align it precisely.

Sweeping with a RF synth shows me a 3db knee of 430Meg if I remember it correctly

I don't have an attenuator to measure the pulse with my 1gig scope, the max vertical scale is too low =/
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on August 17, 2020, 01:27:28 am
Check my previous post, I think you made a measurement error on the ch1 side, as the top of the step is not properly aligned to the 100% mark. It seems ok on the ch2 measurement, but there should definitively be a difference between both channels once you measure both by properly aligning the step between 0% and 100%.

Also make sure that you position as accurately as possible the two time markers between the 10% and 90% marks on the scale and then read off the time.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Gregory on August 17, 2020, 02:02:40 am
You are right, I messed this up!

I will try again but I think the results will still be very close.

Thanks !
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on August 17, 2020, 10:08:20 am
Good upgrade! It does look as if the two channels are pretty much identical.

What is the type of resistor you uses; at these frequencies the devil is in the details. I presume they aren't wirewound :)

Don't become too obsessed with the exact bandwidth. The only purpose of a scope is to show the waveform's shape, and that is a combination of frequency and phase response. The BW=0.35/tr is only an approximation, and 0.35 is sometimes replaced by 0.4.

Finally, there is a b*****d on fleabay that "upgrades" 2445B to 2465B. The results are "imperfect", but he takes precautions to avoid having to refund money. See the TekScopes groups.io group for further information.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: bdunham7 on August 17, 2020, 06:37:59 pm
Does anyone know offhand how many layers there are on the mainboard of these scopes?  I have an otherwise nice 2465 that was 'drilled' and I'm considering whether to attempt a bodge repair or part it out.  I actually have two of these boards that have been drilled in two slightly different spots.  Apparently some corporation out there decided to drill all of their test equipment before selling it to the surplus (scrap) market. 

[attachimg=1]
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on August 17, 2020, 07:12:40 pm
Quite a few layers for sure, not sure exactly how many. Long shot, but if you look at the board edgewise that might give you a general clue if you manage to visualize the actual layers. A good place to ask this question where you are most likely get a good accurate answer is at the Tekscopes group. My bet is that it will be very though to fix the damage done by the drilling, as there might be severed connections that do not even surface to any above board component. But if you feel adventurous by all means go for it, we will certainly root for your success.

TekScopes Group:
https://groups.io/g/TekScopes
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on August 17, 2020, 08:21:04 pm
Does anyone know offhand how many layers there are on the mainboard of these scopes?  I have an otherwise nice 2465 that was 'drilled' and I'm considering whether to attempt a bodge repair or part it out.  I actually have two of these boards that have been drilled in two slightly different spots.  Apparently some corporation out there decided to drill all of their test equipment before selling it to the surplus (scrap) market. 
Wow, that's a shame.

BravoV has photos showing it is a 4-layer board:

  https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1212961/#msg1212961 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1212961/#msg1212961)

Why not give it a try?  You can't make the board any worse.  You could carefully excavate more of the surface around the hole on the top and bottom and see if you can expose any additional layers.  You should find at least a ground plane, which might not need any repair.

Looking at a 2445A A1 board, I can see traces on a second layer from the top, and none from the bottom.  So it might be, top to bottom: signal/power, signal/power, ground, signal/power.

EDIT: Another idea is to use a shallow counter-sink bit on the hole from one or both sides.  This would cut the PCB at an angle and make the copper layers more obvious.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Kartika on August 30, 2020, 07:37:13 pm
so guys
I am just about to reassembly on my vanilla 2445 after a full recap and I wanted to show off my custom U800 heatsink solution.  I'm pretty proud of it.
It seems pretty clear to me that Tektronix, at some point in the design process, contemplated a heatsink here given the mounting screws they included.  So I tried to make something close to what I imagined they had in mind.


Hi people :)
I want to present you my first prototype heatsink cooler for U800 IC chip that you may have in the future?
made on a CNC machine and the material is aluminium EN AW 6061.
This is not the final look. it will be completed soon
if anyone is interested let me know
Thanks. greeting


Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on August 30, 2020, 09:05:44 pm
OK here we go again, guess I'll chip in for this one. Anyone is of course free to do whatever they feel is best for their scope but please read this first...

As said quite a few times before, both here on this thread and also repeated by some very knowledgeable people close to Tektronix on the TekScopes group: the heatsink on U800 is completely unnecessary, of course as long as the normal internal flow is unimpeded by anything blocking either the intake or exhaust, and of course that the inside of the scope is not covered in dust or any other stuff that could affect the heat dissipation of the critical components. BTW U800 is just one of several delicate chips temperature wise that fully depend of a healthy airflow which again is easily achieved as long as nothing is blocked and the scope has a good working fan.

Fact is that the U800 chip is totally fine as-is, and as a matter of fact Tektronix had initially designed the board in order to accommodate a heatsink thinking it would be necessary but then after initial testing was done they noticed that the chip temperature was keeping well within the limits without it, so the heatsink idea was abandoned. This is the reason that there are those two threaded studs which where already incorporated into the board production. And since the heatsink was going to go under the chip, they put washers between the IC and the PC board simply to make up for the correct spacing as the chip pins can only be inserted so far into the holes on the board before hitting the limits while the IC bottom is still not firmly seated against the board. This IC is also very sensitive to overtightening and can easily be damaged by delamination of the actual die from the substrate, something that will certainly ruin your day.

The odds are really not in anyone's favor when disturbing a perfectly working chip that has been operating for decades, and that will continue to do so, against the risk of causing damage if you accidentally over tighten those studs, or even if one side is slightly torqued down tighter than the other could cause enough unbalance to create internal stress to break something. It really does not take much to reach that breaking point, and there is also the expansion of the component that has to be accounted for once the die starts to heat up during normal operation. And yet another well known problem, but that specifically applies to the glue-on type heatsinks, is that they often will come loose and fall off. This might obviously short out something inside, perhaps some other "unobtanium" part. So absolutely not wort the risk. If I where you, just leave it alone and enjoy your scope. Hope that helps.

Nice looking design, though.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on August 30, 2020, 09:19:26 pm
Agree with AMR Labs 100%

1. Keep bottom vents clear at all times.

2. Don't stack the scope on top of another instrument that generates heat.

3. Insure the fan is operational.

4. Leave U800 alone. 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Kartika on August 31, 2020, 09:07:09 am
Quote
Tektronix had initially designed the board in order to accommodate a heatsink thinking it would be necessary but then after initial testing was done they noticed that the chip temperature was keeping well within the limits without it, so the heatsink idea was abandoned.
Quote
This IC is also very sensitive to over tightening and can easily be damaged by decontamination of the actual die from the substrate, something that will certainly ruin your day.
Quote
or even if one side is slightly torqued down tighter than the other could cause enough unbalance to create internal stress to break something.

Quote
4. Leave U800 alone.
  - unacceptable  8)

Hi nice observation but you do not take cost-effectiveness, investment, programmed obsolescence, etc. if the factory meant absolute quality, then it would not install or produce a maxim IC chip that is structural unstable, etc. very bad also RIFA madness :) @ all! and a complete minimum investment / performance calculation for maximum profit.
the goal is to stop the temperature oscillation in order to make us lucky. we should achieve absolutely better cooling, with higher air flow, I found a great replacement.
p.s.
why they do not tell us how to, or build, make new U800.... i believe on market we heave 1000 units still operate... because of this IC all unit become trash permanently......
I am indignant because of that .. and then I wonder what ecology and consciousness is ...

PMD1208PKB1-A 90m3/h
fan dimesion 80x80x20mm

https://www.tme.com/ca/en/katalog/dc12v-fans_112524/?visible_params=2%2C173%2C181%2C2699%2C174%2C98%2C179%2C183%2C259%2C120%2C117%2C184%2C68%2C74%2C176%2C536%2C77%2C32%2C175%2C23%2C177%2C1774%2C2546%2C178%2C2190%2C1605%2C82&mapped_params=2%3A391%3B174%3A1439649%3B (https://www.tme.com/ca/en/katalog/dc12v-fans_112524/?visible_params=2%2C173%2C181%2C2699%2C174%2C98%2C179%2C183%2C259%2C120%2C117%2C184%2C68%2C74%2C176%2C536%2C77%2C32%2C175%2C23%2C177%2C1774%2C2546%2C178%2C2190%2C1605%2C82&mapped_params=2%3A391%3B174%3A1439649%3B)


Quote
Tektronix SUCKS!!!!!
Tektronix is trying to manipulate the oscilloscope market. Today I learned from
my local dealership that they are required by contract to destroy every scope
which is traded in for a new Tektronix scope, regardless of age or condition. So
if you decide to trade in that old scope for a Tektronix, know ahead of time
that it is NOT going to end up in the hands of a ham, or of some kid learning
and experimenting in electronics on a tight budget like I was thir... er, twenty
years ago. No, Tektronix needs to raise their profits by destroying every used
scope they can get their greedy little hands on, regardless of who feels the
pinch!
https://groups.google.com/g/rec.radio.amateur.homebrew/c/FfNSJ6Ho50k?pli=1 (https://groups.google.com/g/rec.radio.amateur.homebrew/c/FfNSJ6Ho50k?pli=1)

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on August 31, 2020, 10:03:44 am

p.s.
why they do not tell us how to, or build, make new U800.... i believe on market we heave 1000 units still operate... because of this IC all unit become trash permanently......
I am indignant because of that .. and then I wonder what ecology and consciousness is ...


::)
Google says otherwise:
https://www.eevblog.com/forum/testgear/tek-2400-scopes-have-the-schematics-for-the-modules-been-released/ (https://www.eevblog.com/forum/testgear/tek-2400-scopes-have-the-schematics-for-the-modules-been-released/)
https://www.davmar.org/TE/Tek2465/lafay.html (https://www.davmar.org/TE/Tek2465/lafay.html)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Kartika on August 31, 2020, 11:16:43 am
The “inventor” never proceeded with his design.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on August 31, 2020, 11:24:24 am
The “inventor” never proceeded with his design.
Check the video in this thread:
https://www.eevblog.com/forum/testgear/tektronix-2400-series-scope-u800-replacement/ (https://www.eevblog.com/forum/testgear/tektronix-2400-series-scope-u800-replacement/)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on August 31, 2020, 12:50:01 pm
Hi nice observation but you do not take cost-effectiveness, investment, programmed obsolescence, etc. if the factory meant absolute quality, then it would not install or produce a maxim IC chip that is structural unstable, etc. very bad also RIFA madness :) @ all! and a complete minimum investment / performance calculation for maximum profit.
the goal is to stop the temperature oscillation in order to make us lucky. we should achieve absolutely better cooling, with higher air flow, I found a great replacement.
p.s.
why they do not tell us how to, or build, make new U800.... i believe on market we heave 1000 units still operate... because of this IC all unit become trash permanently......
I am indignant because of that .. and then I wonder what ecology and consciousness is ...

PMD1208PKB1-A 90m3/h
fan dimesion 80x80x20mm

Quote
Tektronix SUCKS!!!!!
Tektronix is trying to manipulate the oscilloscope market. Today I learned from
----[snip]-----

Are we talking about present day tektronix, or when the 2465 scope was still being produced in the late 1980s? I cannot speak for present day, but back when it was certainly a different company with different values, professionalism, and  philosophy. Ask anyone that worked there back then.

RIFA cap failure = normal component aging, and that is well beyond its expected service life. Back then good quality part, probably one of the best given the technology at the time. Nothing to do with Tektronix trying to cut corners with lower quality components to save a few pennies. 30+ year cap subjected to spikes and surges almost every time the scope is operating. Also, back then there was not so much "dirt" on the AC mains. Perhaps rating it at a bit higher voltage margin then 275VAC (I think it is the cap rating) might have helped a bit stave off some degradation to coming close to short out when the scope is operated on 240V mains, but back then Tek figured it would be enough. And again 275V cap on a 240V line still sounds quite ok (its definitively far from blowing up) even today with a new off the shelve good quality AC rated capacitor. And besides Tek never thought that any scope would still be in use after more than three decades, mainly due to mandatory obsolescence rules in most of the companies that where buying these scopes. They never figured the fan base would still keep them alive after so long.

Fan failure = same 30+ years of service life, spinning and spinning.... Also there are two different types of fan depending on the scope version.

MAXIM chip (initial) problems = nothing to do with Tektronix. They sold the chip foundry to Maxim, and it took them a while to get things right so the great majority of the problematic chips where usually related the first few batches. After some time they figured out all the problems and chip production of later samples reliability was comparable to original in house Tek chip. Unfortunately Maxim chip got a bad reputation as a whole due to those early issues.

With all due respect, I think you need to get  your facts straight. I am not anywhere near at the level of Tektronix experience of some of the older guys, but I have read a lot over time, and quietly hung around this thread and at the TekScopes group, so have learned a lot by listening to the knowledgeable people over the past few years since I have been involved with Tek scopes, specially since I got my own 2465B and managed to get it working thanks in a big way due to the information contained in this thread starting from page 1. Perhaps you should try doing the same before trowing out opinions like these that seem to be a bit unfounded, or that perhaps rather apply to more recent times and not directly related to the 2465 family of scopes and what this thread is mostly about.

And please don't feel like I am trying to suppress in any way your opinions and comments. I don't even consider myself to be one of the long time members here, very far from it, but in general I feel everyone here enjoys having these conversations from time to time and learning about other people's experiences and opinions about Tek scopes in general. But at the same time on the other hand we also try to educate people based on facts and hopefully give them some new knowledge and perspective. So please carry on and keep up this discussion alive for as long as you think it will be in your interest to do so.

EDIT: to correct spelling.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mawyatt on August 31, 2020, 05:38:42 pm
AMR,

Agree these 2465 scopes are living well beyond anyones expectations. I have 2 and repaired both, neither has a heatsink on U800, also replaced the electrolytic caps and infamous RIFA types.

How is a manufacture supposed to know a cap type will fail after 30~40 years, as all they can do is the classic high temperature "life test" within a reasonable time frame.

I've used Tektronix and HP equipment my entire career (retired now), and probably purchased over $1M total. Every instrument with the exception of 1 HP generator that was supposed to replace the HP3325, was well designed and constructed and no apparent cutting corners to save a few $, and performed well beyond the specs and the "Intended Spec Use". If anything, they all were well over-designed, and you could bet your career on the results they produced.

The ISU was a very important part of the older Tektronix and HP equipment DNA, they were designed to make complex and accurate measurements, and not just meet some specs for a Product Brochure. Others had equipment that they touted as Better than HP or Tek on some spec, but in actual use were often not up to the task because of inferior ISU..

To bash the older Tek and HP equipment is an insult to the best engineered equipment at the time, and the very foundation for all the nice equipment options we have today IMO.

My two old Tek 2465 scopes still perform (as do my old HP 34401As) and I just used one to verify the output of a new AWG squarewave and compared against my new SDS2102X Plus DSO, they both agree quite well, not bad for a 35 year old scope :-+

Best,
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Kartika on September 01, 2020, 10:27:03 pm
Quote
"dirt" on the AC mains. Perhaps rating it at a bit higher voltage margin then 275VAC (I think it is the cap rating) might have helped a bit stave off some degradation to coming close to short out when the scope is operated on 240V mains, but back then Tek figured it would be enough. And again 275V cap on a 240V line still sounds quite ok (its definitively far from blowing up) even today with a new off the shelve good quality AC rated capacitor.

then or now, it is desirable to have prevention EMI filter and Insulation trasfomator.

question
has any of you had a chance to see the military version .. i think it has a cooling u800

Alan thank you for expressing your opinion, peace
Regards
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Kartika on December 07, 2020, 05:26:53 pm
U800 ic for tektronics 2465b 2467b

Ramkumar Ramaswamy . 14 hours ago Update - Finally got the initial batch of assembled boards this week . Everything has slowed down thanks to that willy virus . I will begin testing and tuning each of them this week , and then list them on eBay .
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Kartika on December 15, 2020, 07:43:13 pm
 :-+  great news U800 replacment

https://youtu.be/nfc_z2FNeb8
The RU800 - A Drop - In Replacement for the Tektronix U800 Hybrid Ramkumar Ramaswamy . 7 views - 14 Dec 2020 This video shows the working of the RU800 - a drop - in replacement for the Tektronix 155-0241 - XX , also called the U800 in Tek schematics , used in the 2400 series oscilloscopes . These chips suffered from field failures , and now being unobtanium , command premium prices on online auction sites . As of Dec 14 , 2020 , an initial batch of ten RU800s has been assembled and is undergoing testing . They will shortly be listed for sale on eBay .


Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on December 15, 2020, 08:15:45 pm
A worthy cause it seems, and please don't think I am trying to discourage anyone.

But I wonder, when was it the last time anyone here needed to actually replace the U800 chip in their scopes that died of "natural" causes?
Just wondering if there is really still a big demand for these, or a substitute replacement. Not too long ago I remember to sometimes see a listing for an original working Tek chip on ebay, at around BIN $125-150, but no takers for weeks or months. I was once close to buying one just as a future rainy day spare, but given the high price and apparent reliability of these chips, never did. If it has been in place for 30+ years and is still working fine, seems unlikely it might suddenly fail out of the blue. Unless of course the scope suffers a fan failure or airflow intake block. Or people insisting on messing around with the chip and damaging it by trying to attach an unneeded heatsink on them. But otherwise these chips appear to me to be pretty stable.

But if anyone has indeed a damaged U800 story, I would certainly like to hear about it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Kartika on December 18, 2020, 10:15:41 pm
Temperature stability and oscillation is most important for prevention future thermal stress that can causes separation...


https://groups.io/g/TekScopes/topic/28139676?p=Created,,,20,2,0,0::recentpostdate%2Fsticky,,,20,2,940,28139676 (https://groups.io/g/TekScopes/topic/28139676?p=Created,,,20,2,0,0::recentpostdate%2Fsticky,,,20,2,940,28139676)
https://www.eevblog.com/forum/repair/tektronix-2467b-display-issues/ (https://www.eevblog.com/forum/repair/tektronix-2467b-display-issues/)
https://www.youtube.com/watch?v=JZJS2ikPjWY&t=140s (https://www.youtube.com/watch?v=JZJS2ikPjWY&t=140s)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: 0culus on December 20, 2020, 06:31:10 am
FWIW, all the damaged hybrid IC stories I have heard about in these scopes stem from disrupted airflow under the case. The vent holes in the bottom are there for a reason. DO NOT block them!!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on December 20, 2020, 07:03:01 am
+1, and at that video, without the cover, the owner should use a fan blowing the board, as the hybrid ICs are heating up that way as no air flow at all.

Ok, maybe its fine for 1 or 2 minutes for the purpose of shooting that video, but say when trouble shooting this scope with that position for hours without cover, the poor hybrids will be overheated.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tautech on December 20, 2020, 07:18:47 am
+1, and at that video, without the cover, the owner should use a fan blowing the board, as the hybrid ICs are heating up that way as no air flow at all.

Ok, maybe its fine for 1 or 2 minutes for the purpose of shooting that video, but say when trouble shooting this scope with that position for hours without cover, the poor hybrids will be overheated.
Maybe he didn't read post #6 from a wise old tech that has worked on these for decades.

Yes it's a poor show and not at all setting a good example to others that might watch that vid.  ::)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: mawyatt on December 20, 2020, 06:23:02 pm
I've repaired two of these Tek 2465 scopes in the past year or so. Good advise to keep an airflow over the hybrids with the scope cover removed, there's considerable difference in the effective thermal impedance of these hybrid heatsinks without any airflow.

Wonderful instruments from back in the heyday of Tektronix and HP :)

Best,
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Kartika on December 23, 2020, 11:05:57 am
Hi. One a modest idea.  placement of tvs diode in power supply. Extra Surge protection is possible?
Thank you in advance?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on December 23, 2020, 12:00:34 pm
Hi. One a modest idea.  placement of tvs diode in power supply. Extra Surge protection is possible?
Thank you in advance?

Not necessary. The PSU in the 2465 is not prone to surge issues.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Miti on December 27, 2020, 06:42:39 am
I just downloaded the latest SW for TL866II Plus from Autoelectric and I was pleasantly surprised to see that now it has support for the FM16W08 FRAM, that can be used to replace the battery backed RAM. I hope this is not old news.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: troth530 on February 09, 2021, 05:24:10 am
I just scored a 2465 (no suffix) with a service manual at a local charity. 
And it's functional except an issue with "beam find" button is flaky but I see it has the original caps. 
I found parts list of replacement caps for the power supply posted by med6753.
Are there any other caps that need to be replaced such as on other boards?
I don't see a battery for the RAM... is that a newer thing (only needed for 2465a and b) and no battery replacement needed for the 2465.

I also got a fully operational 2245a that clearly needs a battery (and recap).  Is there a similar thread to this one for the 2245a?

Appreciate any help.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: philwong5176 on February 09, 2021, 05:35:46 am
"Is there a similar thread to this one for the 2245a?" ---->

https://www.rc-cam.com/forum/index.php?/topic/4165-tektronix-2245a-oscilloscope-smps-repair-re-cap/ (https://www.rc-cam.com/forum/index.php?/topic/4165-tektronix-2245a-oscilloscope-smps-repair-re-cap/)

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: troth530 on February 09, 2021, 05:56:49 am
"Is there a similar thread to this one for the 2245a?" ---->

https://www.rc-cam.com/forum/index.php?/topic/4165-tektronix-2245a-oscilloscope-smps-repair-re-cap/ (https://www.rc-cam.com/forum/index.php?/topic/4165-tektronix-2245a-oscilloscope-smps-repair-re-cap/)
Thanks.  I'm aware of that thread... assumed it was not the preferred way to go as he seemed to be making adjustments for some different type of caps.  Also, I can print ABS.  Haven't done exploratory surgery on the 2245a, but does that power supply not have any paper RIFA capacitors?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: philwong5176 on February 09, 2021, 06:29:56 am
Look here:A

https://bradthx.blogspot.com/2015/05/tektronix-2246-repair.html

The 2246 has the same SMPS as the 2245A.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on February 09, 2021, 08:12:59 am
I just scored a 2465 (no suffix) with a service manual at a local charity. 
And it's functional except an issue with "beam find" button is flaky but I see it has the original caps. 
I found parts list of replacement caps for the power supply posted by med6753.
Are there any other caps that need to be replaced such as on other boards?
I don't see a battery for the RAM... is that a newer thing (only needed for 2465a and b) and no battery replacement needed for the 2465.

I also got a fully operational 2245a that clearly needs a battery (and recap).  Is there a similar thread to this one for the 2245a?

Appreciate any help.

There are a few small electrolytics scattered throughout the instrument but for the most part they can be left alone.

The 2465 uses non-volatile EAROM to store calibration data and does not require a battery backup.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: slburris on March 04, 2021, 04:23:38 pm
Now my own “B” adventure begins.  I also have two 2465’s and I’ve recapped one of them.  I’ve just come into possession of a 2465BDM with intact Tektronix stickers sealing the case.  Oh dear this case hasn’t been opened in a very long time.

First up, the A5 board.  The capacitors leaked of course.  I’ve removed the damaged components and started to clean the mess.  Some of the pads were either eaten away or flaked off as I swabbed them, so this is going to take some work to repair.  And the precision 10K resistor got clobbered as well.  I may measure my stock of 1206 resistors and see if I can find one in tolerance, otherwise I’ll have to order a replacement. 

I didn’t anticipate how hard it was to get the corroded solder to heat up.  I had to do a combo of precleaning and adding new solder to desolder some of the components. 

Then I’ll have to tackle the NVRAM issue and figure out how to get to the power supply.  It doesn’t look as simple as the 2465.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on March 04, 2021, 04:32:23 pm
I'm assuming that a 2465BDM has the DMM option and probably the Counter/Trigger option, correct? If yes the teardown to get to the PSU will be essentially the same as an older 2465DMS. Procedure here:

https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1861713/#msg1861713 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1861713/#msg1861713)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: slburris on March 04, 2021, 04:43:02 pm
Yeah it’s like the CT with the DMM option included.  I have capacitors on order, but I had to split the order between Mouser and Digi-Key, and both seem to be struggling a bit with fulfillment.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on March 04, 2021, 06:40:37 pm
Ever since the ice storm in Texas a few weeks ago Mouser has been struggling with order fulfillment. Not sure about Digi-Key.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: slburris on March 10, 2021, 11:11:27 pm
Well bummer,  I replaced the caps and collateral damage on the A5 board and now instead of powering up normally, it hangs with the add light on partway through self test.  Did a quick check of the voltages at J119 on the main board, and buzzed out continuity of the repairs, but nothing obvious comes up.  Voltages around the DAC resistor repair area look reasonable.

I’m assuming the repair is either incomplete or cleaning it caused another problem.  Off to the archives to study what this particular hang means.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: slburris on March 13, 2021, 05:31:15 am
So one of the precision 10K resistors has magically gone open after I cleaned this.  I unsoldered the resistor and measured it out of circuit to confirm.  Bits of it seem to be flaking off as well.  So I guess the electrolyte plague made it farther than I thought.

I have no 0.1% resistors with a low tempco, so I’ll have to throw some on the next Digi-Key order and regroup.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: slburris on March 13, 2021, 02:50:05 pm
Indeed, replacing that resistor with an ordinary 10K 1206 brought the scope back to life.  Obviously this isn’t the correct repair long term, but it allowed me to run the EXER 02 routine to dump my calibration data.  Looks like the NVRAM is dated 1990, so next step is to unsolder and see if I can extract that data.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: captcha on September 19, 2021, 11:00:57 pm
This forum has done such an awesome job in helping me better understand my 2445B oscilloscope that I wanted to post here that with the help of the many comments and the 2465B bill of materials I was able to recap the A3 and A2A1 boards and eventually fixed a faulty diode that was causing the constantly resetting at power-up (aka 'tick mode') issue.

For those interested I have documented my repairs in this video:
https://www.youtube.com/watch?v=vC9kd6zx5_M (https://www.youtube.com/watch?v=vC9kd6zx5_M)

Hopefully this scope will last another 30 years!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on September 20, 2021, 04:54:25 am
This forum has done such an awesome job in helping me better understand my 2445B oscilloscope that I wanted to post here that with the help of the many comments and the 2465B bill of materials I was able to recap the A3 and A2A1 boards and eventually fixed a faulty diode that was causing the constantly resetting at power-up (aka 'tick mode') issue.

For those interested I have documented my repairs in this video:
.. <snip> ..

Hopefully this scope will last another 30 years!

>:D  :clap:

https://www.youtube.com/watch?v=QuoKNZjr8_U (https://www.youtube.com/watch?v=QuoKNZjr8_U)

Glad to see the final shaking thumb up ... must feel good, thank you for sharing !  :-+
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Old ET on January 11, 2022, 06:59:10 am
HI,
I am a newby so bear with me, I have a 2467B and just got the Caps so I can begin that process. I have the machine disassembled, that was fun as I had no instructions. What I am interested in are replacements for RT1001 and RT1016 as well as the E1001 and E1002, have not had any luck in finding the parts but it sounds like from your post you were well on the way to getting that handled. I am aware that your post is old, but hoped I would be able to make contact and be able to get the info. My scope is over SN B05000 so I have the SMD's. I am going to replace all the can type tantalums as they are starting to leak around the base of the mounting. My scope was working fine and is extremely clean in side and out, but upon closer inspection I have found a few problems with the filter of the line voltage, couple of resistor blew up and I will replace all that as I get the parts. Also the alum can type tantalums are leaking at the base, don't want the pads to be eaten away so will take care of that as well. Any help would be greatly appreciated.

GR
Title: Re: Tektronix 2465B oscilloscope teardown - A1 board removal, Delay line
Post by: tekky on July 26, 2022, 09:04:52 pm
Part way thru a recap of a later model 2465B, and have removed/reworked boards: Regulator_A2A1, Inverter_A2 & Control_A5. The next step is to remove Main_A1. Different writeups suggest the removal of boards: HV_A9, FrontPanel_A6, and some manipulation of the DL100 delay line on A1.

To be clear, do I need to remove the HV_A9 board to remove the Main_A1? It seems the one elect cap on A9 is easily dealt with from the component side without having to deal with fragile CRT connections.

I see discussion but no pics showing the DL100 delay line and what makes it an obstacle. From what I can see peering into the chassis, it connects at both ends to A1. Does it really need to be disconnected during removal of A1 or does it come out with the board?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tekky on July 27, 2022, 04:47:02 am
It was far simpler to remove A1 than I expected, and no, I didn't need to remove A9 or mess with the delay line, which sits coiled in a plastic carrier (see pic). It all comes out together. The trickiest part of the operation is detaching two push pins from the CRT. I believe these are the vertical signals on W916,W917. They are a long reach with needlenose pliers and will need a light touch to reconnect. I possibly could have unsoldered the wires from the exposed ends of the two inline inductors instead and will do that if it proves hard to push the pins back on with A1 in the way. (Update: I was able to reattach the push pins using the same long needlenose pliers, although long tweezers might provide a more delicate touch. Also I had taken a prior pic of these connections to avoid confusing the two connections.)

Note: there are three elec caps whose leads are hidden under the delay line carrier tray. It was not difficult to lift the tray away from the board slightly and replace those caps without unsoldering the delay line.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on July 27, 2022, 09:36:58 am
Thanks for sharing this details, hopefully this will help future owners that going to do the same task.  :-+  :clap:
Title: 2465B implosion shield orientation
Post by: tekky on July 30, 2022, 08:34:43 pm
Is there a preferred orientation to the clear implosion shield? I wasn't paying attention when I took it off and cleaned it, but then noticed it was a sandwich of two or three plastic layers. Does the thin mylar layer face in or out? Replacement bulbs from digikey/mouser will supposedly be in stock by Oct.   
Title: Tektronix Oscilloscope 2465B DAC Problem
Post by: HAF_RIO on August 30, 2022, 09:02:48 pm
Hi everybody,
Typically the DAC problem ( Serial B050000 and above ) cause a mess in all controls.
As everybody knows, the electrolytics leak contaminate the board and need to be cleaned very well.
I used this four step process ( don't be afraid! ).
1) With WD40 keeping the board with the product about 5 hours.
2) Rinse with neutral - detergent, repeat about 3 times.
3) Rinse again with only pure water ( destiled is better ).
4) Drying com hot air.

After the board cleaned, did rigorose inspection with power magnifying lens, better use stereo microscope ( mine case ).
Some corrosion could be remained, and with thin needle, do the job to remove incrustation.
Measure all resistors and capacitors around the area shown in attached -.
( I found the R2013 open ( measured in 20k scale ), replaced.
After that, the voltages 1.36V and 1.25V apears again!
After all, when power on the oscilloscope, the starting process in the LED panel was slow, found two bad potentiometers ( 5k ), replaced.
Start now is very fast! All controls working again!
Only normal error message due lost calibration.
NVRAM replaced too!

Best Regards,
Helcio
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on August 30, 2022, 10:23:28 pm
I would NEVER use, and never RECOMMEND using WD-40 on any circuit board of value.  :palm:
You are changing the capacitance of the board forever. Particularly in any high frequency section.
Use 99% or higher IPA Isopropanol. It may leave some whitish film, but it will evaporate, and won't leach into the board and stay in there permanently in liquid form.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: HAF_RIO on August 31, 2022, 12:06:05 am
Hi,
WD40 is better than the alcohol to remove acid action from the electrolytics! WD40 don't cause any problem in the board with fiberglass epoxy clad. The A5 board don't suffer this problem wits "HF", don't have enough to capacitance to act in low frequebcy pulses.
The microprocessor clock is 20MHz, and working very well after all!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SoundTech-LG on August 31, 2022, 12:09:35 am
Have fun. Maybe WD will hire you!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Dave_CA on September 01, 2022, 05:49:03 pm
I do not care for the fumes (VOCs) given off by WD40.  Plus WD leaves a residue.  That is its purpose... to leave oil behind.  YMMV.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on September 01, 2022, 09:10:49 pm
Hi,
WD40 is better than the alcohol to remove acid action from the electrolytics! WD40 don't cause any problem in the board with fiberglass epoxy clad. The A5 board don't suffer this problem wits "HF", don't have enough to capacitance to act in low frequebcy pulses.
The microprocessor clock is 20MHz, and working very well after all!

That's wrong, simple Fourier Transform theory.

For an introduction with measurements, see https://entertaininghacks.wordpress.com/2018/05/08/digital-signal-integrity-and-bandwidth-signals-risetime-is-important-period-is-irrelevant/

I wouldn't use Water Displacement 40 on a digital PCB. The nearest I use is Craig DeOxit, and I'm careful to use that only on contacts.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on January 29, 2023, 03:22:11 pm
Hi,
WD40 is better than the alcohol to remove acid action from the electrolytics! WD40 don't cause any problem in the board with fiberglass epoxy clad. The A5 board don't suffer this problem wits "HF", don't have enough to capacitance to act in low frequebcy pulses.
The microprocessor clock is 20MHz, and working very well after all!

NO-NO-NO-NOOOOO!!!

ONLY use dishwasher soap and a soft (tooth) brush to remove any cap leakage in the affected areas.
Then rinse off all soap from the board with water and let dry for a couple of hours before testing.
And BTW, IPO will not remove the acidic leakage residue at all, it will only help spread it further.
As for using WD40.... congratulations, you're basically be looking for a replacement A5 board very soon.


Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Mark Krass on March 02, 2023, 12:13:52 pm
Hi,

Has anybody come across this issue - readout display is shifted too far to the right, see photo. The problem is that if you look at the display not directly but from an angle, some characters covered by CRT frame and not visible.

Service manual offers no adjustment to shift readout display horizontally. But must be something in readout schematic to tweak it?

Mark
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on March 02, 2023, 12:51:52 pm
Best if you could provide some history/context of the fault, and on the instrument itself. Is this a scope new to you, or did the fault suddenly appear in a scope you had for some time? if so was the scope in regular use? etc, etc. Are the traces also affected and/or the regular readout displays? What is the exact model you have, plain 2465, A, or B? Anything else that might be relevant to the fault?

If this is a scope that you just purchased, and assuming this is not a plain 2465, and you have a SMD version A5 board I would venture that first thing to check would be for the usual corrosion problems. Or perhaps something going on in the horizontal deflection circuit. Difficult to say what else without more information. I am sure once you provide more details other people here might be able to provide additional useful suggestions.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Mark Krass on March 02, 2023, 01:35:12 pm
Scope 2465B fully re-capped and cleaned.

This is not a fault, I'd say it is a feature relevant to all 2465 models that needs to be tweaked due to the issue I described above.

Somebody who familiar with readout I/O circuitry and horizontal DAC that generates the voltages used to horizontally position dots of the readout display.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: jonpaul on March 02, 2023, 01:53:18 pm
Check A5 for leaking SMD lytics, PCB damage must be corrected,before any other troubleshoot.

Are only the readout characters displace left,or also the scope,traces?
CAL HOR can,adj if both RO and scope traces affected.
RO position cal also in full CAL

Référence to service manual

Jon
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on March 02, 2023, 02:22:49 pm
Hi,

Has anybody come across this issue - readout display is shifted too far to the right, see photo. The problem is that if you look at the display not directly but from an angle, some characters covered by CRT frame and not visible.

Service manual offers no adjustment to shift readout display horizontally. But must be something in readout schematic to tweak it?

Mark

Yes it does. Section 5-13 of the 2465B Service Manual. Read the entire section carefully. It adjusts the horizontal centering which should fix the readout offset.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Zenith on March 02, 2023, 02:35:27 pm

I wouldn't use Water Displacement 40 on a digital PCB. The nearest I use is Craig DeOxit, and I'm careful to use that only on contacts.

There is a WD40 branded contact cleaner which is probably much the same as any other contact cleaner, Servisol etc. That may be the source of confusion here. As for classic WD40, used for cars and lawnmowers etc, it's absolutely the wrong thing thing to use on electronics.

I agree about not spraying contact cleaner about willy nilly, but carefully applying it to contacts only.

IPA used for electronics should be the proper pure grade.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on March 02, 2023, 02:54:28 pm

I wouldn't use Water Displacement 40 on a digital PCB. The nearest I use is Craig DeOxit, and I'm careful to use that only on contacts.

There is a WD40 branded contact cleaner which is probably much the same as any other contact cleaner, Servisol etc. That may be the source of confusion here. As for classic WD40, used for cars and lawnmowers etc, it's absolutely the wrong thing thing to use on electronics.

I'm vaguely aware that the WD40 product has been "diluted" by marketeers -- to the point it is so useless that I don't even consider using it.

"Caig DeOxit" - without specifying which DeOxit - is pretty much the same.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Mark Krass on March 02, 2023, 04:50:54 pm

Yes it does. Section 5-13 of the 2465B Service Manual. Read the entire section carefully. It adjusts the horizontal centering which should fix the readout offset.

That's it! This is what I was needed. Thank you. It's a R801 if somebody will be looking for it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on March 03, 2023, 03:00:19 am

Yes it does. Section 5-13 of the 2465B Service Manual. Read the entire section carefully. It adjusts the horizontal centering which should fix the readout offset.

That's it! This is what I was needed. Thank you. It's a R801 if somebody will be looking for it.

Good deal. Glad I could help.  :-+
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: DavidAlfa on March 10, 2023, 04:33:37 pm
TL; DR, sorry!

About the DS1225Y NVRAM, do we know what else is stored there?
I know cal data is @ 0x1FE00 - 0x1FFFF, but the scope displays a lot of interrogation signs when not programmed properly.

First attempt of preventive maintenance (Adding the battery before it's too late) ended losing the data, although I'm 100% sure I didn't short anything out.

The battery read 3.2V, but just touching the DMM with the fingers dropped to 2.7V, so go figure if only the capacitive kick when touching the + terminal with the earthed iron (Battery not earthed though) was enough to kill the data.

From now I'll use the EXER 02 procedure to manually extract the cal data on still working scopes, before touching anything, hand-copying 512bytes will take 10 minutes, but way less than running a full calibration!

But some 2465B have extra boards on them (I.E. GPIB, TV(?) modules), I have no idea if they're recognized automatically or they need to me added manually in the diagnostic menu?

Cheers!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on March 11, 2023, 01:33:26 pm
The battery read 3.2V, but just touching the DMM with the fingers dropped to 2.7V, so go figure if only the capacitive kick when touching the + terminal with the earthed iron (Battery not earthed though) was enough to kill the data.

The discharge curve of those batteries is pretty steady, so if you are getting 3.2V (and assuming an accurate reading) battery looks to be still quite good. Anything above 3.0 is to be considered OK. Touching the probe is probably upsetting your DMM reading, not the battery voltage.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: DavidAlfa on March 11, 2023, 02:03:30 pm
Why? I would be acting like a parallel resistor.
I later tried soldering a 470K resistor and definitely, the battery dropped quite a lot, while drawing only 6uA, I'm pretty sure the battery was already weak (Dated '88).
My theory is the heat from the desoldering process affected it, batteries don't like heat, while device quiescent and leakage currents increase, sum it all... bang!

Not sure what a brand-new battery should measure, if it's the same chemistry as the LTC-7P modules (3.5V), then 3.2V is already in the dead zone, these batteries seem to die suddenly with little warning.
(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=1735805)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 11, 2023, 04:38:04 pm
...
About the DS1225Y NVRAM, do we know what else is stored there?
I know cal data is @ 0x1FE00 - 0x1FFFF, but the scope displays a lot of interrogation signs when not programmed properly.
At a minimum, the last operating configuration at power down (knob positions, etc.) and user presets are in there.

Quote
From now I'll use the EXER 02 procedure to manually extract the cal data on still working scopes, before touching anything, hand-copying 512bytes will take 10 minutes, but way less than running a full calibration!
You can also just take a video of flipping through the locations and transcribe it later when, or if, you need it (this also avoids transcribing errors).  If you have a GPIB interface, you can dump the NVRAM data directly to a computer (and reload it too).

Quote
But some 2465B have extra boards on them (I.E. GPIB, TV(?) modules), I have no idea if they're recognized automatically or they need to me added manually in the diagnostic menu?
They are recognized automatically.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bud on March 11, 2023, 04:59:54 pm
If you have a GPIB interface, you can dump the NVRAM data directly to a computer (and reload it too).
Can you give a pointer to the procedure?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: DavidAlfa on March 11, 2023, 05:41:58 pm
Thanks Mark, yep, that was my idea, never think you're perfect and no errors will happen.

Bud, "GPIB" search in this thread:
 https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1943710/?topicseen#msg1943710 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1943710/?topicseen#msg1943710)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 11, 2023, 11:37:04 pm
Thanks, DavidAlfa, for posting the initial link.

Those are the basic commands.  It was later confirmed to work on all the models.  Plus, an optional argument was discovered to dump ALL the NVRAM at once:

  https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1618642/#msg1618642 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1618642/#msg1618642)

Since the procedure is somewhat scattered through threads on eevblog and TekScopes, let me try to summarize the essentials here.

In short, the procedure to capture the calibration and other NV data is to send the GPIB commands:

  key 0
  earom? f

The format of the data returned is the starting location in NVRAM (which is 0 in this case), a colon, and then comma separated values from incrementing NVRAM locations.

On models later than the 2445/2465, you're going to get 255 16-bit words (510 bytes), which maps to 0x1E00 to 0x1FFD in the actual NV SRAM chip.  The words are stored in big-endian format.  The address range covers the calibration data and other opaque data currently unknown to us mere mortals.

To restore the data, you need to send it back to the scope one word at a time.  The format of the argument is the location in NVRAM, a colon, and then the value:

  key 0
  earom 0:215;
  earom 1:1908;
  earom 2:1921;
  earom 3:1921;
  ...
  earom 253:16499;
  earom 254:14;
  earom 255:0;

Sending it back en-masse (i.e., replaying the one big line that the scope sent) does not work, at least not for me.

On the 2445/2465, you are only going to get 200 16-bit words, and not 255.  Words 0-99 are from the EAROM on the main processor board, and 100-199 are from the EAROM on the buffer board.

Keep in mind that all numbers for the EAROM command are represented in DECIMAL and not hex, as it appears in the EXER 02 display.

As an example from the dump above, EAROM 1 is 1908 and is shown in EXER 02 as 0774.  This is stored in the actual SRAM as 0x1E02: 0x07 and 0x1E03: 0x74.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Bud on March 11, 2023, 11:42:51 pm
Very useful post, thanks!

Edit: worked on 2467B like a charm, got 255 words (512 bytes)  :-+
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Mark Krass on March 18, 2023, 12:14:15 pm
Hi,

Does anybody know what is the jumper J504 on A5 board 2465B & 2467B? (SN B050000 & above) How it can help in troubleshooting?  No word in forums/service manual about it.

Location 5K in DMUX & analog control schematic.

Mark
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 18, 2023, 04:39:46 pm
...
Does anybody know what is the jumper J504 on A5 board 2465B & 2467B? (SN B050000 & above) How it can help in troubleshooting?  No word in forums/service manual about it.
I've never seen it documented.  J504 allows the -1.25V reference to be provided by an imprecise resistor divider.  The -1.25V reference is usually provided by the DAC.  The jumper allows allows easier troubleshooting of the DAC and associated circuitry by removing dependency on proper operation of the DAC.

If you search for "J504" on TekScopes on groups.io, you can read how people have employed it to help in their troubleshooting.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Mark Krass on March 18, 2023, 06:21:09 pm

I've never seen it documented.  J504 allows the -1.25V reference to be provided by an imprecise resistor divider.  The -1.25V reference is usually provided by the DAC.  The jumper allows allows easier troubleshooting of the DAC and associated circuitry by removing dependency on proper operation of the DAC.

If you search for "J504" on TekScopes on groups.io, you can read how people have employed it to help in their troubleshooting.

Thanks for pointing to TekScopes on groups.io, this is where the information about J504 truly resides. You're right, this jumper provides ~1.25V reference comes from a voltage divider and not the DAC which is used to troubleshoot DAC circuitry, like you said. So I got the answer, thank you!

PS Funny thing is that google "tektronix 2465b j504" did not come up with any links to groups.io
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SynViks on March 29, 2023, 08:32:50 pm
Curious how easy it'd be to add the counter timer option to a unit that doesn't already have one? IIRC those modules are automatically recognized when present. Is it just a matter pulling the PCB and hooking it up?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on March 29, 2023, 09:04:50 pm
Curious how easy it'd be to add the counter timer option to a unit that doesn't already have one? IIRC those modules are automatically recognized when present. Is it just a matter pulling the PCB and hooking it up?

I was able to do just that to my 2465B thanks to a member of Tekscopes that sold me the whole kit and caboodle and had done it himself more than once on other 2465B's, so he knew very well all there was to know about this option add-on.

Basically you will need the CTT card, and several ribbon and coax cables with specific connectors on their ends, plus also the rear Ext Ref and Word Recognizer jacks with their cables. The scope power supply needs to temporarily be removed, and some jumpers need to be taken off a connector where one of the new ribbon cables will plug into.

So definitively you need to make sure that you really have everything that is required, and the correct procedure to install it. And yes, the board will automatically be recognized once it is installed. Lastly you will need an accurate and stable 1MHz source to feed into the scope so the CTT function can be calibrated as explained in the service manual and which is a very short and simple procedure to perform, and also involves moving a jumper position during cal. The seller even threw in a nice TCXO to do just that as part of the package, and even added an original CTT plastic rear panel with the two additional connector holes, so that was pretty much plug and play without any drilling required. Not that it would have been very hard to do, but its definitively nice to have the connector jacks with their original labels in place, which also makes it look like it came with the scope.

BTW the upper frequency limit of the CTT counter is supposed to be 100MHz, but mine counts very reliably to 200MHz, and only stops working at about 230MHz.

CTT is definitively a very nice option to have on a 2465B, but in my opinion for anything up to or bellow 100MHz, it still does not beat my 2247A, which besides CTT functionality also comes standard with various other very handy and useful waveform voltmeter functions and some other stuff.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: factory on March 30, 2023, 08:58:17 pm
Curious how easy it'd be to add the counter timer option to a unit that doesn't already have one? IIRC those modules are automatically recognized when present. Is it just a matter pulling the PCB and hooking it up?

I was able to do just that to my 2465B thanks to a member of Tekscopes that sold me the whole kit and caboodle and had done it himself more than once on other 2465B's, so he knew very well all there was to know about this option add-on.

Basically you will need the CTT card, and several ribbon and coax cables with specific connectors on their ends, plus also the rear Ext Ref and Word Recognizer jacks with their cables. The scope power supply needs to temporarily be removed, and some jumpers need to be taken off a connector where one of the new ribbon cables will plug into.

...snip...

You also need the option motherboard & frame if not already present, I'm not sure if the boards vary depending on the model (i.e. no letter, A or B).
The control panel labelling has some differences for options too.

Certainly the GPIB board does, older one plugs into option motherboard. Newer scopes with SMT A5 board, the GPIB board goes behind the A5 board (where the readout board is in older scopes).

David
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SynViks on March 30, 2023, 09:44:11 pm
From looking at the price of the parts, sourcing a 2247A or 2252 might be the more practical option vs retrofitting the CCT option to a 2400 series. 

Seems like the ideal combo is to have a 2247A for general purpose and a 2465 for high bandwidth stuff, as the former has a better feature set for general bench stuff.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on March 30, 2023, 10:42:19 pm
...
Seems like the ideal combo is to have a 2247A for general purpose and a 2465 for high bandwidth stuff, as the former has a better feature set for general bench stuff.

In my own experience having both those models, I would have to say: ABSOLUTELY right!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on April 01, 2023, 01:22:48 am
The measurement capabilities, especially the universal reciprocal timer counter, of the 2247A/2252 are very good.  My only experience with the 2465 series is a 2445B without the CCT so I am not entirely sure how their measurement capabilities compare.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: SynViks on April 02, 2023, 09:46:41 pm
https://www.youtube.com/watch?v=5-5PvtZPeOI (https://www.youtube.com/watch?v=5-5PvtZPeOI) <- based on this and other videos, manual, and various comments I've come across, seems like the 2247A/2252 is better featured than the 2465B with the DMM and CT options. 2247A the measurements have real time update and are done with the scope probes.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Runco990 on April 03, 2023, 07:11:00 pm
Great video on the 2247A.  I have both the 2247A and the 2465BDV.  I have to admit, I somewhat like the 2247A a bit better as a bench scope. 
So I have a general question....  which is the last and best digital or digital storage scope Tek made in this family before the TDS and TAS scopes?
Anyone?   Was the 2440 the last?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: DC1MC on April 03, 2023, 07:37:23 pm
Great video on the 2247A.  I have both the 2247A and the 2465BDV.  I have to admit, I somewhat like the 2247A a bit better as a bench scope. 
So I have a general question....  which is the last and best digital or digital storage scope Tek made in this family before the TDS and TAS scopes?
Anyone?   Was the 2440 the last?

2467BHD
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Runco990 on April 03, 2023, 11:15:52 pm
2467BHD

Well, yes, but that's an all analog scope.  I was referring to a digital or digital STORAGE scope.  I could use this function for very slow events, or one-shots.  I have an HP and a Rigol, but really like the classic Tektronix scopes.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: OhmMyWattage on April 04, 2023, 11:32:48 am
Hi guys I’m a noob about to attempt a repair on a 2465b 57xxx. Based on the photo and serial, can someone please save me some time and tell me what caps for A5 I need? It seems a little different from the service manual I have and some of the photos I’ve seen so far, though I haven’t finished reading this thread yet. It’s gonna take some time so I’m hoping to get some parts ordered while I’m making my way through it. Looking for quality parts of course. Also, which suppliers are ideal for these components in Australia or with international shipping?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Mark Krass on April 18, 2023, 08:38:26 pm
Hi guys,

I was searching for the spare CPU for 2465B and a following point has come up:

According to service manual schematic it has Motorola MC68A02 CPU clocked by 5.0MHz source. I looked at MC68A02 datasheet and it says that max crystal freq for MC68A02 is 6.0Mhz. So far so good.

By fact on A5 board I've got MC6802P CPU installed and its datasheet says that max input freq for MC6802P is 4.0MHz. Crystal on board is 10MHz as it should be so a CPU freq input is 5.0MHz. How it could be? Where is a flaw?

Cut from datasheet attached.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: bdunham7 on April 18, 2023, 09:01:55 pm
So I have a general question....  which is the last and best digital or digital storage scope Tek made in this family before the TDS and TAS scopes?
Anyone?   Was the 2440 the last?

AFAIK, the 2440 was sort of the best and last of its type, although I think the reduced-feature 2439 actually came later.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on April 19, 2023, 01:11:42 am
...
By fact on A5 board I've got MC6802P CPU installed and its datasheet says that max input freq for MC6802P is 4.0MHz. Crystal on board is 10MHz as it should be so a CPU freq input is 5.0MHz. How it could be? Where is a flaw?
You're right about the clock speed.  Perhaps your processor is a different manufacturer?  Does it have the Motorola logo on it?

It could the simplest answer that someone who wasn't paying attention to clock speed put the wrong processor in there.

All my 2445x/2465x boards have an A or B processor on them.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Mark Krass on April 19, 2023, 03:34:28 pm

You're right about the clock speed.  Perhaps your processor is a different manufacturer?  Does it have the Motorola logo on it?

It could the simplest answer that someone who wasn't paying attention to clock speed put the wrong processor in there.

All my 2445x/2465x boards have an A or B processor on them.

Yes it does have Motorola logo, see the snapshot. I double checked a soldering and it looks like factory installation. No freaking idea how it could be :) So the CPU is overclocked and works fine. Mistery.

I’d love to buy mil option SC67127P and swap it but no offers on ebay unfortunately.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: BravoV on April 19, 2023, 03:52:50 pm
Mine, a SC67127P.  :P
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on April 19, 2023, 03:54:31 pm
By fact on A5 board I've got MC6802P CPU installed and its datasheet says that max input freq for MC6802P is 4.0MHz. Crystal on board is 10MHz as it should be so a CPU freq input is 5.0MHz. How it could be? Where is a flaw?

You will most likely get an answer to this question by posting on the IO Tekscopes or Tekscopes2 groups. Some members where Tek employees and might know about the CPU/Xtal choice.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on April 19, 2023, 05:58:15 pm
Yes it does have Motorola logo, see the snapshot. I double checked a soldering and it looks like factory installation. No freaking idea how it could be :) So the CPU is overclocked and works fine. Mistery.
...
Interesting.  It does look very factory.

Well, it's not going to stop working at 4.01 MHz, but it may not work properly at some of the operating extremes, such as temperature and supply voltage.

You could double check that pin 39 (EXTAL) is 5MHz, but I can't imagine it would be anything else.

Maybe it's from a mis-labeled batch and Tektronix was told by Motorola?  Or maybe Tektronix qualified them in-house themselves for 5MHz knowing the scope's operating constraints?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: S57UUU on April 19, 2023, 06:02:21 pm
These old Motorola processors could easily be overclocked by a factor of 2. In the 80's I had a Tandy Color Computer, which was based on an 1MHz 6809 chip. Worked with double clock frequency perfectly, never encountered any problem. Probably wouldn't work in the whole military temperature range, but room temp +-10 degrees, not a glitch.
So running a 4MHz type at 5MHz, shouldn't really be a problem.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: DavidAlfa on April 19, 2023, 06:05:29 pm
Found several comments (https://groups.io/g/TekScopes/message/88685) and a PDF repair guide (https://cdn.hackaday.io/files/1638907011869760/Tektronix-2465A-B-Oscilloscope-Restoration-Repair.pdf) stating the -8V cap (C1101) shouldn't be replaced with anything else than 100uF, or the voltage would be affected.

I fully recapped several PSUs (Including C1101) without any issues, had a bag of EEU-FC1E471 caps, which are Panasonic 470uF 25V low-esr, measured~30mOhm, where old ones did ~1ohm.
Replaced all the 20V & 40V caps with these, as highest voltage is 15V, there's plenty of room till 25V.

I only kept the original 100 & 160V caps, also the 100uf one under the big HV ones (At mains side), it only performs a startup delay,  470uF there would make the PSU to delay for 5 seconds.

Additionally, the 15-ohm resistors on the mains input (Paralleled with NTCs/PTCs) were blown in most PSUs, replaced with 2W parts.
Those near a regulator in a corner, also 15R, were ok but toasty, so I replaced them too.

Voltages were perfect afterwards, (7.98 ... 8.02V), with much lower ripple and noise than before.

Did this for 5x 2465A/B, calibrated them all (Most also had dead NVRAM), and returned to work in great shape.

Now I have 2x 2465B and 1x 2465A with poor focusing (Fully recapped, they were non-starters, some caps's legs had dissolved!), but no amount of tweaking will fix it, it's like looking through a misty/foggy window.

One 2465B had the CH1/CH2 preamp hybrid damaged, causing signal distortion, so I removed it from the lower spec 2465A, it was the blurriest one anyways.

Now I have two blurry 2465Bs, one worse than the other, any hints?
Voltages are perfect, so it must be something elsewhere.... tomorrow I'll swap different boards/hybrids, at least I will shorten the search circle.

Obviously, CRT and plastics were thorougly cleaned!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Mark Krass on April 20, 2023, 04:21:03 pm
Interesting.  It does look very factory.

Well, it's not going to stop working at 4.01 MHz, but it may not work properly at some of the operating extremes, such as temperature and supply voltage.

You could double check that pin 39 (EXTAL) is 5MHz, but I can't imagine it would be anything else.

Maybe it's from a mis-labeled batch and Tektronix was told by Motorola?  Or maybe Tektronix qualified them in-house themselves for 5MHz knowing the scope's operating constraints?

Thank you all guys who responded to my question. I checked pin 39, it has 5MHz indeed. Thus MC6802P, at least middle 90s production works fine with overclocked freq 5MHz. Well noted)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Vince on August 19, 2023, 12:45:57 pm
Hello people,

I apologize if my query is out of place here, but I was directed here.

Apparently this thread covers not just the 2465B ?

My question : I recently bought a 2465, a vanilla 2465, not a 'B' or anything.

It's got s strange cooling setup which appears to have many recurrent  / known issues.
I have all of them and I am trying to solve them one by one..

My problem for the day is to replace the dead DIP package transistor array, with discrete transistors (I guess arrays aren't available anymore ? Or at a high cost maybe...).
I gather people do that.
However I don't have any transistors in stock that have the appropriate current rating.

The array was rated at 1.0A which made sense since the control board runs on 15V and the current limiting resistor in series with all the emitters, is specified at 15R hence 1A total short-circuit currente in the motor windings. However the resistor on my board, measures more like 10.5ohms not 15, so I would need transisotrs rated at 1.5A or 2A.... AND that have a pin layout that can work with the board layout, that is with the base being the middle pin.

So to save me time, could someone tell me what transistors people use in this context ?

If that's out of place just tell me, I will create a new thread instead.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: DavidAlfa on August 19, 2023, 01:03:48 pm
Yeah should work. I fixed one of these in a signal analyzer, a relay coil shorted out and burned one of the transistors in the array.
I simply cutted the pins and soldered a 2n2222A.
Any decent npn bjt like bc547 should work, I doubt each transistor in the array can handle 1amp?
Otherwise use a beefier one like the BD137 etc?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Vince on August 20, 2023, 09:55:15 am
Nope the BC547 is a tiny 100mA 1092 jobbie.

BD137 I do have in stock and would be ideal, so I did try to use it but failed because of the base is not the middle pin so it won't fit the board layout.
This style of package does not allow you to swap pins like you can on small signal transistors.

The middle needs to be the base or it just won't fit, hence why I was asking what people have sucessfully used on this particulat application / board, to save me from scouring dozens of random datasheet on-line until I find one with a suitable pinout...

Array : it's a CA3725. Yes the 1A current rating is for each individual transistor. The array is specially designed to handle high currents to drive windings.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: DavidAlfa on August 20, 2023, 10:06:34 am
Ok! The one I fixed driving a 70ohm coil with 5V if I remember correctly, so it was ok for the job.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Mark Krass on September 16, 2023, 07:10:01 am
Hello
Need advise from experienced users.
Tek 2465B along with readout information started to output some artefacts to the display. Can't upload the video right now, but they are clearly seen at photos, attached. They are on signals area and are flickering 3-5 times per sec. When I turn readout intensity knob to the middle position they go away with readout info. Channel independent, even with grounded. Temperature also independent, coming up with cold device and go away with turning off readout only.

Now close to the point. I have another A5 board taken from a scope. When replaced - all is working fine, no problem, no artefacts. So the issue is in A5.
In original A5 board there was well known electrolytic caps leakage. All were replaced, potential damaged areas were inspected, cleaned. Proximate smd resistors, ceramic caps, traces are checked. Tantalum caps checked. Wima caps also checked.

Another point is that when I touch by finger test point TP32 (on readout schematic <7>) artefacts stop flickering and look like exactly at the photo. This is dot cycle generator section in readout schematic.

So this is the situation. What do you recommend to do?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: DavidAlfa on September 16, 2023, 08:34:53 am
Huh never seen that. But check for everything where the leaky capacitors did their thing.
I had found several resistors and caps falling open, their soldering tabs were no longer making contact with the internals after playing with the acid.
You might have missed some.
Also, did you lift all nearby ics? The electrolite will seep under them and dry.
I found lots of deposits under them, also some vias that looked pretty bad.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on September 16, 2023, 10:56:53 am
When you repaired your A5 board, did you wash the (usually two) cap leak affected areas of the board? In most cases there will be some residual electrolyte left from the leaking caps on the board itself, and gently washing with liquid dish soap (Dawn, Palmolive, etc) and a soft tooth brush dipped in water, and then rinsing it off with water afterwards is the only way to effectively remove it. But be very aware that using IPA (70-90% Pharmacy Alcohol) to try and clean the board will only spread the electrolyte further around and it may slowly then over time once again start causing tiny corrosion problems in other nearby areas. I would also look for any signs of blue-green stuff left on or between any IC pins or vias that you may have missed. Use a microscope if you got one. On my board there where plenty of tiny bluish spots on those ICs located on the side under where there is only the one leaking cap. Don't have the SM in front of me so right now can't give specific PNs but I think you will understand what I mean.

Perhaps the problem you are seeing is related to a spot where electrolyte is creating an unwanted conductive leakage path that is causing those "ghost" images of the lower readouts to appear further up on the middle of the screen. One can see their horizontal positions seem to roughly match both lower readout displays. The fact that those ghosts are also flickering may further suggest that some signal from the readout generator is leaking from one area into another causing some sort of conductive bridge that causes this interference, and that still keeps a timing relationship with the actual readouts. But at least you where able to confirm that the problem is on A5, so no elusive wild goose chase on the rest of the scope. That is half the work, just to determine and confirm where inside the scope the problem is actually located.

See attached pics of my own A5 board showing the two main areas (at least in my case) that are usually affected going through the "car wash", and those should ideally be gently scrubbed and washed and then rinsed off (once again only use liquid dish soap) to make sure no electrolyte residuals are left on the board. Perhaps only washing the board if you have not done so already might clear the problem. Shake off any excess water left on the board and in between parts, and then be sure to give the board ample time to dry before trying it out. Here in the tropics I usually just need to put the board out in the sun for an hour. Some people like to "bake" the board in an oven at very low temperature, but in that case be very careful of not overdoing it. Perhaps even a hair dryer, but again, always be very mindful of not applying excess temperature.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Mark Krass on September 16, 2023, 11:38:07 am
Hello guys,
Many thanks for your response! I removed and resoldered a few nearby ICs and have not found signs of acid. I washed these 2 areas in IPA only, and as I can see now that was not enough and was not right at all.
Ok, will wash it liquid dish soap as you suggested. If it does not show results I will start to remove-wash-resolder all nearby ICs.
Will let you know the progress.
 :)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Mark Krass on September 19, 2023, 06:39:23 pm
Hello,
Updates on the issue. I washed the board with water and dish soap. Dried it. Repeat this process 3 times. No effect.
I desoldered U2965, 2970 and 2890 and nearby ceramic caps, cleaned all area, explored with microscope and I can confirm that the tracks and pads there are ok. I replaced these ICs and caps with new ones and soldered them back. Cleaned the whole area one more time. No effect.
At this moment I can confirm that this "ghost leakage path" is not located at top & bottom layers.
I am out of ideas...
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on September 19, 2023, 08:08:52 pm
So perhaps a faulty component then? I am unfortunately not very qualified to give detailed troubleshooting advice on the A5 board, I am not even very familiar with the circuit structure or schematic as I was fortunate not having to dig in very deep into it to get mine working again after clearing all the corrosion. Perhaps some other more experienced members here could give you further advise.

I would also try posting at the Tekscopes and Tekscopes2 IO groups, there are some very knowledgeable people there, some even are ex Tek employees from when some of these scopes where actually manufactured back in the 80s and 90s.

https://groups.io/g/TekScopes2

https://groups.io/g/TekScopes

Make sure to try both groups. Tekscope2 was formed at some point by a bunch of members that where not too happy the way the group was being run and decided to form a separate one. Tekscopes2 is usually my fist go-to place, but both are very good sources of information and helpful people if you ask the right questions and provide ample relevant supporting information so they can try to point you into the correct direction to pinpoint the issue.

And please keep us updated here of any progress.

Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Orange on September 20, 2023, 09:10:09 am
Hello
Need advise from experienced users.
Tek 2465B along with readout information started to output some artefacts to the display. Can't upload the video right now, but they are clearly seen at photos, attached. They are on signals area and are flickering 3-5 times per sec. When I turn readout intensity knob to the middle position they go away with readout info. Channel independent, even with grounded. Temperature also independent, coming up with cold device and go away with turning off readout only.

Now close to the point. I have another A5 board taken from a scope. When replaced - all is working fine, no problem, no artefacts. So the issue is in A5.
In original A5 board there was well known electrolytic caps leakage. All were replaced, potential damaged areas were inspected, cleaned. Proximate smd resistors, ceramic caps, traces are checked. Tantalum caps checked. Wima caps also checked.

Another point is that when I touch by finger test point TP32 (on readout schematic <7>) artefacts stop flickering and look like exactly at the photo. This is dot cycle generator section in readout schematic.

So this is the situation. What do you recommend to do?

Check resistor R2890 on <7> ( on output of gate U2890B) If that one is drifted or open it would explain the 'finger trick' The diagram says 1k for the value.
Perhaps the electrolyte has affected the value

Edit : updated the resistor value to 1k
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Mark Krass on September 20, 2023, 02:45:43 pm
Check resistor R2890 on <7> ( on output of gate U2890B) If that one is drifted or open it would explain the 'finger trick' The diagram says 1k for the value.
Perhaps the electrolyte has affected the value

Edit : updated the resistor value to 1k

Thank you. I checked R2890 when I was resoldering that area, its value is 332 Ohm and match the numbers on it. Mistake in SM.

Earlier in this thread I found an interesting case when electrolyte acid from C2965 has got inside U2890 and damaged its crystal. Not my case since I tried to replaced U2890 with no effect for me.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Mark Krass on September 22, 2023, 05:02:15 pm
Update on 2465B readout problem:
Ghost images start to appear only at the fast sweeps - 1us and less.
Also I've found that on slow sweeps signal trace and readout are alternated, see the shot attached.
No description of these symptoms in SM & charts but may be somebody faced such problem before?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Orange on September 23, 2023, 12:48:29 pm
Update on 2465B readout problem:
Ghost images start to appear only at the fast sweeps - 1us and less.
Also I've found that on slow sweeps signal trace and readout are alternated, see the shot attached.
No description of these symptoms in SM & charts but may be somebody faced such problem before?
Just as a quick test you can try to readjust the CRT GRID bias a bit and see if you can turn away the ghosting...

If that is not solving the problem, I think you need to start probing around on the readout system circuitry. Sometimes by connecting a probe (x10) will give you an indication which part is sensitive for this issue. There is a lot of CMOS on this board, a damaged output can also give you this effect.

Obvious something with the timing of the blanking signals is causing this. I'm afraid there is no easy way to get a simple solution with this problem, other than measuring and trying to nail it down.
The service manual has a decent amount of information in it, but it is very complex......
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on September 23, 2023, 01:51:30 pm
Just a though, if the OP said that replacing the A5 board solves the issue, why would he want at this point to start poking around in other parts of the scope? Just my 2 cents.

PS. I just went by Tekscopes2 group and happy to see that you are getting pretty good engagement specially from Chuck Harris which I would say is the most veteran "fixer" of 2465/67 scopes as has been doing that as a professional service for a very long time so he knows them inside out, and the info you get from him is usually the very best. Other members will also provide good input and ideas, but Harris is the main reason of why I suggested going to Tekscopes2 first.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Mark Krass on September 23, 2023, 08:33:11 pm
Found a bastard!!!
U2965 had unconnected pad. I checked the area under this IC several times with microscope and there was no any signs that the problem was there!!
Today evening I decided to desolder all area around C2965 and check one again everything with tester now. And wow!!! Got it.
After repair this pad scope is running fine, readout is excellent, no flickering, no ghost images!
Interesting thing is that without that connection readout worked few minutes after power up and then dimmed and disappeared. Each time after power up. It looks to me that it was not heat issue, but readout circuit logic shut it down after getting problem with it. Who knows...
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on September 24, 2023, 02:32:40 am
Good job, feels great finding the culprit, doesn't it?
Enjoy your scope.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: calibrationfixture on September 24, 2023, 06:31:42 am
Hi Mark Krass,

Congratulations with your fix. A bit overdue, but U2965 does ring a bell with me and I checked my Repair Log.

Some time ago I replaced the 4 SMD Elco's on the A5 Controller Board of a 2445B (H706020). Before and after this it was working fine. The vast SMD replacement job on SG5030's made me look again to 24XXB Series A5 Controller Boards. On the aforementioned 2445B I noticed corrosion on U2965 and U2890 (74HCT00DT's). With their removal two heavily corroded Pads came loose. U2965 Pad 8 and U2890 Pad 7 (= GND). Based on the Electrical Diagram I made separate Wire Connections. After that Fix the Scope had no Read-Out. The Controller Board of this 2445B has 671-0965-05 as PN. The Service Manual refers to 671-0965-00 as PN and no updated Electrical Diagram as MCI. Comparing the 05 with a 06 Board from a 2467B (B052372) made clear that Pin 8 of the U2965(C) must be connected to Pin 9/10 of U2890(C) and not to Pin 5 of U2890(B) as with the 671-0965-00 Board. After this correction Read-Out was fine again.

Also on Tekscopes there is a Post on this (2465B, U2965, readout).

Calibrationfixture
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Mark Krass on September 24, 2023, 08:06:16 am
Hi Calibrationfixture,
You're absolutely right - pin 8 of the U2965 must be connected to pin 9/10 of U2890. I had to figure it out by myself taking out ICs from a PCB. Mine is SMD 671-0965-00 as well & SN>0500000. However SM for this revision is inaccurate in many areas of A5 schematic.
PS My lesson learned in this troubleshooting is to trust your multimeter, not your eyes!  8)
-Mark
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tonedeak99 on March 11, 2024, 12:52:59 pm
What an informative thread. Thank you Bravo and all the others who contributed here. Im the happy owner a 2465A CT and I wanted to follow the advice of many here and recap the PS. Especially get those RIFAs out before they pop. Not sure if I should replace any other caps besides those. All my J119 DC voltages are within spec. I also have no error messages and scope appears to be working pretty good. My calibration waveform seems a bit noisy at certain timebases since the trace is not a thin line but a thick fuzzy line. Maybe that’s normal. 🤷‍♂️

Also wanted to replace the Keeper II battery. Its reading 3.3v but dont want to risk losing my data.  What’s the best method for attaching a backup battery while doing the replacement?  I found these two online:
https://jestineyong.com/tektronix-2465a-dv-oscilloscope-memory-backup-battery-replacement/
https://cdn.hackaday.io/files/1638907011869760/Piggyback%20batt.JPG

Also I would be using my grounded soldering iron.  Could that be a problem if the A5 board is out of the scope?  Would it be possible that the iron would ground the battery and the EAROM would lose its data? 

Lastly as a backup plan I was thinking of backing up my data with the a GBIP adapter which was mentioned in this thread. Maybe using the NI USB model. Has it been confirmed that it can be used to backup and fully restore the EAROM data in case I accidentally delete it during the battery replacement?

Thank you all!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: factory on March 11, 2024, 01:29:42 pm
The temporary battery question for the NVRAM was asked here too;
https://www.eevblog.com/forum/testgear/tektronix-2455b-ram-battery-replacement-advice-needed/msg5277409/#msg5277409 (https://www.eevblog.com/forum/testgear/tektronix-2455b-ram-battery-replacement-advice-needed/msg5277409/#msg5277409)

The electrolytic caps in the PSU sometimes leak conductive electrolyte over the boards, as well as eating the traces, this can cause expensive failures all over the scope when the PSU malfunctions. YMMV

David
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on March 11, 2024, 02:11:43 pm
The electrolytic caps in the PSU sometimes leak conductive electrolyte over the boards, as well as eating the traces, this can cause expensive failures all over the scope when the PSU malfunctions. YMMV

Been there done that on my 2465B. If I remember correctly the usual leaking caps where the two (blue) 180uF 40V, and the (also blue) 250uF 20V ones, all to be replaced with 330uF 50V. Thing is sometimes you won't see the leakage pooled up under the cap until the cap itself has been pulled, but if the case make sure to clean well before installing the replacement. The green caps are usually still good, but while you are in there...

Also keep in mind the orientation error for one of the caps on the PCB silkscreen, which is reversed. Best to replace only one cap at a time without using the silkscreen as a guide, and making sure to take notes of each cap's orientation before pulling it so as to install it exactly the same way the original was. Also when taking notes don't confuse the 10uF 100V with 100uF 10V (I think it was) as both will look almost identical in size. I did that mistake when I followed my own bad notes and ended up getting a loud POP which was the only thing that finally revealed the mistake, as I was still checking everything against my notes and could not figure out what was wrong. Not sure the silk screen error applies in your case with an earlier 2465ACT, but certainly it does in the 2465B. You can find plenty more information on this error here on this thread, plus recommended capacitor shopping lists, etc.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: Uunoctium on March 11, 2024, 02:18:09 pm
tl;dr ;-)
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on March 11, 2024, 02:20:41 pm
tl;dr ;-)

Those two 290uF 200V high quality SPRAGE brand caps are usually almost always still in perfect condition, but you could also replace them if desired with 330uF 250V. But it will be hard to find those in axial type, so usually a bit of conversion needs to be done to more conventional radial types by extending and insulating one of the leads and bending it upwards over the body of the cap towards the other end to create a quasi-axial cap.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 11, 2024, 02:20:51 pm
What an informative thread. Thank you Bravo and all the others who contributed here. Im the happy owner a 2465A CT and I wanted to follow the advice of many here and recap the PS. Especially get those RIFAs out before they pop. Not sure if I should replace any other caps besides those. All my J119 DC voltages are within spec. I also have no error messages and scope appears to be working pretty good. My calibration waveform seems a bit noisy at certain timebases since the trace is not a thin line but a thick fuzzy line. Maybe that’s normal.
There are plenty of varying opinions on this, but mine is "if it ain't broke, don't fix it".  If your voltages and ripple are in spec, then leave well enough alone.  You can find plenty of posts from people looking for help after "recapping" because they've destroyed their equipment.  The only exception in these scopes is the RIFA caps, as they are a well-known and frequent point of failure.

The trace on this series scopes can look a little fuzzy because of their internal construction.  You can post a photo of yours, or take a look at the many photos in this thread and compare.

Quote
Also wanted to replace the Keeper II battery. Its reading 3.3v but dont want to risk losing my data.  What’s the best method for attaching a backup battery while doing the replacement?  I found these two online:
https://jestineyong.com/tektronix-2465a-dv-oscilloscope-memory-backup-battery-replacement/
https://cdn.hackaday.io/files/1638907011869760/Piggyback%20batt.JPG
Of those two, I like the Jestine approach since he is replacing the dead battery and not stacking a new one on a dead one.  Leaving a dead battery in there is asking for leaks, and there's no guarantee it wouldn't reduce the life of the new battery.

Quote
Also I would be using my grounded soldering iron.  Could that be a problem if the A5 board is out of the scope?  Would it be possible that the iron would ground the battery and the EAROM would lose its data? 
The EAROM is used on 2445 and 2465.  On later A and B scopes, it was replaced with battery backed SRAM , either combined in a single package or as two separate devices.  As long as the board is isolated, soldering should be ok.  Just don't short any pins by accident.

Quote
Lastly as a backup plan I was thinking of backing up my data with the a GBIP adapter which was mentioned in this thread. Maybe using the NI USB model. Has it been confirmed that it can be used to backup and fully restore the EAROM data in case I accidentally delete it during the battery replacement?
Yes.  I can attest the data can be saved and successfully restored with this method.  I have done it about a half dozen times.

Before trying anything with either GPIB or the battery, I would suggest you take a video of flipping through the NVRAM using EXER 02 and record all the values.  While the methods to get that data back in the NVRAM in case of failure will vary depending on what equipment you have at your disposal, at least you have the data.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tonedeak99 on March 11, 2024, 04:36:08 pm

There are plenty of varying opinions on this, but mine is "if it ain't broke, don't fix it".  If your voltages and ripple are in spec, then leave well enough alone.  You can find plenty of posts from people looking for help after "recapping" because they've destroyed their equipment.  The only exception in these scopes is the RIFA caps, as they are a well-known and frequent point of failure.
I come from the same camp. I haven't tested for ripple yet.  but my DC voltages are fine.

Quote
Also wanted to replace the Keeper II battery. Its reading 3.3v but dont want to risk losing my data.  What’s the best method for attaching a backup battery while doing the replacement?  I found these two online:
https://jestineyong.com/tektronix-2465a-dv-oscilloscope-memory-backup-battery-replacement/ (https://jestineyong.com/tektronix-2465a-dv-oscilloscope-memory-backup-battery-replacement/)
https://cdn.hackaday.io/files/1638907011869760/Piggyback%20batt.JPG (https://cdn.hackaday.io/files/1638907011869760/Piggyback%20batt.JPG)
Quote
Of those two, I like the Jestine approach since he is replacing the dead battery and not stacking a new one on a dead one.  Leaving a dead battery in there is asking for leaks, and there's no guarantee it wouldn't reduce the life of the new battery.


The EAROM is used on 2445 and 2465.  On later A and B scopes, it was replaced with battery backed SRAM , either combined in a single package or as two separate devices.  As long as the board is isolated, soldering should be ok.  Just don't short any pins by accident.
I agree I don't want to leave an old dead battery in there.  I was more asking for suggestions on which points to use to attach the temporary battery.  Also @factory added a third option for connection points: https://www.eevblog.com/forum/testgear/tektronix-2455b-ram-battery-replacement-advice-needed/msg5277409/#msg5277409 (https://www.eevblog.com/forum/testgear/tektronix-2455b-ram-battery-replacement-advice-needed/msg5277409/#msg5277409)
Any preferences on which is the safest or best points to use for the temporary battery?  Also thanks for the clarification on the EAROM vs SRAM.

Quote
Yes.  I can attest the data can be saved and successfully restored with this method.  I have done it about a half dozen times.

Before trying anything with either GPIB or the battery, I would suggest you take a video of flipping through the NVRAM using EXER 02 and record all the values.  While the methods to get that data back in the NVRAM in case of failure will vary depending on what equipment you have at your disposal, at least you have the data.
Excellent thanks.  I will follow your advice.  What software do I use to send commands to the scope?

Quote
Been there done that on my 2465B. If I remember correctly the usual leaking caps where the two (blue) 180uF 40V, and the (also blue) 250uF 20V ones, all to be replaced with 330uF 50V. Thing is sometimes you won't see the leakage pooled up under the cap until the cap itself has been pulled, but if the case make sure to clean well before installing the replacement. The green caps are usually still good, but while you are in there...

Also keep in mind the orientation error for one of the caps on the PCB silkscreen, which is reversed. Best to replace only one cap at a time without using the silkscreen as a guide, and making sure to take notes of each cap's orientation before pulling it so as to install it exactly the same way the original was. Also when taking notes don't confuse the 10uF 100V with 100uF 10V (I think it was) as both will look almost identical in size. I did that mistake when I followed my own bad notes and ended up getting a loud POP which was the only thing that finally revealed the mistake, as I was still checking everything against my notes and could not figure out what was wrong. Not sure the silk screen error applies in your case with an earlier 2465ACT, but certainly it does in the 2465B. You can find plenty more information on this error here on this thread, plus recommended capacitor shopping lists, etc.
tl;dr ;-)

Those two 290uF 200V high quality SPRAGE brand caps are usually almost always still in perfect condition, but you could also replace them if desired with 330uF 250V. But it will be hard to find those in axial type, so usually a bit of conversion needs to be done to more conventional radial types by extending and insulating one of the leads and bending it upwards over the body of the cap towards the other end to create a quasi-axial cap.
I will probably leave these alone if they are unlikely to fail.  But great advice.  Also great advice on how to proceed with changing the caps one by one and which ones to change.  Thanks.  Any preferred shopping list?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: med6753 on March 11, 2024, 04:54:23 pm
Here is a complete guide for re-capping the PSU:

https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1658102/#msg1658102 (https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1658102/#msg1658102)

But it does not address changing the memory battery (the 2465 no suffix uses EAROM) nor does it address changing the SMT capacitors on the 2465B A5 board.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: hpw on March 11, 2024, 04:59:27 pm
Btw: my 2465B is on sell as not any longer used ...
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: factory on March 11, 2024, 06:40:45 pm
The worst offenders were the larger radial Sprague caps with the resin bung, these were often found cracked and/or peeing electrolyte. I would give a list of what I used, but most of the caps I used are now discontinued.

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=2065427;image)

Also if you don't have much experience replacing parts on double sided boards, I would suggest practising on something of no value first.

And as your scope has options, take note or pictures of where all the extra connectors are fitted, before removal.

David
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tonedeak99 on March 12, 2024, 12:08:53 am
The worst offenders were the larger radial Sprague caps with the resin bung, these were often found cracked and/or peeing electrolyte. I would give a list of what I used, but most of the caps I used are now discontinued.

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=2065427;image)

Also if you don't have much experience replacing parts on double sided boards, I would suggest practising on something of no value first.

And as your scope has options, take note or pictures of where all the extra connectors are fitted, before removal.

David
Thanks David.  Found a list by CondorAudio in the Tek group.  Unfortunately some caps are not available.  Any recommendations for substitutes?
Part#   Value   Watts         Mouser Part#
C1021   290 µF   200   ELCTLT      647-UPW2E331MRD
C1022   290 µF   200   ELCTLT      647-UPW2E331MRD
C1066   4.7 µF   35   ELCTLT      647-UPW1H4R7MDD
C1112   4.7 µF   35   ELCTLT      647-UPW1H4R7MDD
C1120   10 µF   100   ELCTLT      647-UPW2A100MED
C1130   10 µF   100   ELCTLT      647-UPW2A100MED
C1220   10 µF   100   ELCTLT      647-UPW2A100MED
C1240   10 µF   100   ELCTLT      647-UPW2A100MED
C1400   47 µF   25   ELCTLT      647-UHE1E470MDD
C1402   47 µF   25   ELCTLT      647-UHE1E470MDD
RT1010   7.0 ohm   NTC Thermistor         995-SG210
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on March 12, 2024, 12:41:13 am
Almost all caps on that list have completely standard values and the ones that are not you can choose the closest available one above the original. For example use 330uF 250V for the 290uF 200V ones. It does not have to be exactly that brand and model specified as a Mouser PN either, you could also easily look for similar caps in another (good) brand, or even equivalents at Digikey as well, although personally I always prefer to stay with Mouser. For one the search at Mouser is very useful and usually provides you with a number of options to choose from for each capacitor.

Its been a while since I recapped my scope, but can't remember that thermistor you have on the list, where is it used? Is it really damaged? It rather sounds like something that just deals with cold startups to limit inrush current. (NTC/VDR).
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: factory on March 12, 2024, 11:58:25 am
The worst offenders were the larger radial Sprague caps with the resin bung, these were often found cracked and/or peeing electrolyte. I would give a list of what I used, but most of the caps I used are now discontinued.

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=2065427;image)

Also if you don't have much experience replacing parts on double sided boards, I would suggest practising on something of no value first.

And as your scope has options, take note or pictures of where all the extra connectors are fitted, before removal.

David
Thanks David.  Found a list by CondorAudio in the Tek group.  Unfortunately some caps are not available.  Any recommendations for substitutes?
Part#   Value   Watts         Mouser Part#
C1021   290 µF   200   ELCTLT      647-UPW2E331MRD
C1022   290 µF   200   ELCTLT      647-UPW2E331MRD
C1066   4.7 µF   35   ELCTLT      647-UPW1H4R7MDD
C1112   4.7 µF   35   ELCTLT      647-UPW1H4R7MDD
C1120   10 µF   100   ELCTLT      647-UPW2A100MED
C1130   10 µF   100   ELCTLT      647-UPW2A100MED
C1220   10 µF   100   ELCTLT      647-UPW2A100MED
C1240   10 µF   100   ELCTLT      647-UPW2A100MED
C1400   47 µF   25   ELCTLT      647-UHE1E470MDD
C1402   47 µF   25   ELCTLT      647-UHE1E470MDD
RT1010   7.0 ohm   NTC Thermistor         995-SG210

For the 647-UPW2A100MED, I used 647-UCA2C100MPD for all of them, it's obsolete, but there are still a few thousand in stock.

For the 647-UHE1E470MDD, my choice of UPW1V470MED is no longer available, alternates I would choose from are; 667-EEU-FC1V470, 661-ELE-350ELL470MF1, or 232-35YXM47MEFR63X11, these are all 35V, but you could go with 25V as per the originals, I stocked up on the 35V version for various projects.

For the 647-UPW1H4R7MDD, there are some still available under numbers 647-UPW1H4R7MDD1TD (straight leads) and 647-UPW1H4R7MDD1TA (formed leads to 5mm pitch), all are obsolete.

The other parts I didn't replace.

David
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 12, 2024, 02:10:03 pm
Yes.  I can attest the data can be saved and successfully restored with this method.  I have done it about a half dozen times.

Before trying anything with either GPIB or the battery, I would suggest you take a video of flipping through the NVRAM using EXER 02 and record all the values.  While the methods to get that data back in the NVRAM in case of failure will vary depending on what equipment you have at your disposal, at least you have the data.
Excellent thanks.  I will follow your advice.  What software do I use to send commands to the scope?
On Linux, you can use the ibtest utility that comes with the linux-gpib package.  It's somewhat low-level and not the most convenient, but it gets the job done without having to load or make anything extra.

You will need to write the command "key 0" to your scope, followed by "earom? f".  The scope will respond with one or more chunks of data.  Just keep entering the "r" (read) command to ibtest until there is no more data.  The data will end with a ";".  You will end up with 255 16-bit words.

I'm sure there are additional utilities to run a single query more conveniently than ibtest.

If you have windows, I don't know because I don't run it.  Maybe someone else can jump in with a suggestion.

Here's what it looks like with ibtest (includes checking the ID of the scope first):
Code: [Select]
$ ibtest
Do you wish to open a (d)evice or an interface (b)oard?
   (you probably want to open a device): d
enter primary gpib address for device you wish to open [0-30]: 8
trying to open pad = 8 on /dev/gpib0 ...
You can:
    w(a)it for an event
    write (c)ommand bytes to bus (system controller only)
    send (d)evice clear (device only)
    change remote (e)nable line (system controller only)
    (g)o to standby (release ATN line, system controller only)
    send (i)nterface clear (system controller only)
    ta(k)e control (assert ATN line, system controller only)
    get bus (l)ine status (board only)
    go to local (m)ode
    change end (o)f transmission configuration
    (q)uit
    (r)ead string
    perform (s)erial poll (device only)
    change (t)imeout on io operations
    request ser(v)ice (board only)
    (w)rite data string
    send group e(x)ecute trigger (device only)

: w
enter a string to send to your device: id?
sending string: id?

gpib status is:
ibsta = 0x2100  < END CMPL >
iberr= 0

ibcntl = 4
You can:
    w(a)it for an event
    write (c)ommand bytes to bus (system controller only)
    send (d)evice clear (device only)
    change remote (e)nable line (system controller only)
    (g)o to standby (release ATN line, system controller only)
    send (i)nterface clear (system controller only)
    ta(k)e control (assert ATN line, system controller only)
    get bus (l)ine status (board only)
    go to local (m)ode
    change end (o)f transmission configuration
    (q)uit
    (r)ead string
    perform (s)erial poll (device only)
    change (t)imeout on io operations
    request ser(v)ice (board only)
    (w)rite data string
    send group e(x)ecute trigger (device only)

: r
enter maximum number of bytes to read [1024]:
trying to read 1024 bytes from device...
received string: 'ID TEK/2445A,V81.1,SYS:FV08,BB:FV02,CTT:FV05,DMM:FV01,GPIB:FV02;'
Number of bytes read: 64
gpib status is:
ibsta = 0x2100  < END CMPL >
iberr= 0

ibcntl = 64
You can:
    w(a)it for an event
    write (c)ommand bytes to bus (system controller only)
    send (d)evice clear (device only)
    change remote (e)nable line (system controller only)
    (g)o to standby (release ATN line, system controller only)
    send (i)nterface clear (system controller only)
    ta(k)e control (assert ATN line, system controller only)
    get bus (l)ine status (board only)
    go to local (m)ode
    change end (o)f transmission configuration
    (q)uit
    (r)ead string
    perform (s)erial poll (device only)
    change (t)imeout on io operations
    request ser(v)ice (board only)
    (w)rite data string
    send group e(x)ecute trigger (device only)

: w
enter a string to send to your device: key 0
sending string: key 0

gpib status is:
ibsta = 0x2100  < END CMPL >
iberr= 0

ibcntl = 6
You can:
    w(a)it for an event
    write (c)ommand bytes to bus (system controller only)
    send (d)evice clear (device only)
    change remote (e)nable line (system controller only)
    (g)o to standby (release ATN line, system controller only)
    send (i)nterface clear (system controller only)
    ta(k)e control (assert ATN line, system controller only)
    get bus (l)ine status (board only)
    go to local (m)ode
    change end (o)f transmission configuration
    (q)uit
    (r)ead string
    perform (s)erial poll (device only)
    change (t)imeout on io operations
    request ser(v)ice (board only)
    (w)rite data string
    send group e(x)ecute trigger (device only)

: w
enter a string to send to your device: earom? f
sending string: earom? f

gpib status is:
ibsta = 0x2100  < END CMPL >
iberr= 0

ibcntl = 9
You can:
    w(a)it for an event
    write (c)ommand bytes to bus (system controller only)
    send (d)evice clear (device only)
    change remote (e)nable line (system controller only)
    (g)o to standby (release ATN line, system controller only)
    send (i)nterface clear (system controller only)
    ta(k)e control (assert ATN line, system controller only)
    get bus (l)ine status (board only)
    go to local (m)ode
    change end (o)f transmission configuration
    (q)uit
    (r)ead string
    perform (s)erial poll (device only)
    change (t)imeout on io operations
    request ser(v)ice (board only)
    (w)rite data string
    send group e(x)ecute trigger (device only)

: r
enter maximum number of bytes to read [1024]: 2048
trying to read 2048 bytes from device...
received string: 'EAR 0:215,1908,1921,1921,1927,10204,10088,1917,10118,1970,10304,506,522,8715,8712,548,8647,8671,481,8668,508,8318,32,32,8221,28,15534,16052,7414,15560,16299,8099,16299,16292,16309,566,566,8756,8756,7450,7934,7699,4096,16304,16295,8105,16280,8105,743,744,740,740,10078,10334,2140,2133,10304,10340,2120,104,2133,10319,10322,2108,10321,2102,8297,835,820,817,1646,9814,9842,1630,722,752,14501,3762,3781,1840,1878,560,569,8545,314,1377,10238,1015,8970,1'
Number of bytes read: 448
gpib status is:
ibsta = 0xc100  < ERR TIMO CMPL >
iberr= 6
EABO 6: Operation aborted

ibcntl = 448
You can:
    w(a)it for an event
    write (c)ommand bytes to bus (system controller only)
    send (d)evice clear (device only)
    change remote (e)nable line (system controller only)
    (g)o to standby (release ATN line, system controller only)
    send (i)nterface clear (system controller only)
    ta(k)e control (assert ATN line, system controller only)
    get bus (l)ine status (board only)
    go to local (m)ode
    change end (o)f transmission configuration
    (q)uit
    (r)ead string
    perform (s)erial poll (device only)
    change (t)imeout on io operations
    request ser(v)ice (board only)
    (w)rite data string
    send group e(x)ecute trigger (device only)

: r
enter maximum number of bytes to read [1024]:
trying to read 1024 bytes from device...
received string: '261,1948,9614,1975,1586,1349,1832,9242,9710,9014,710,9000,1362,9158,1187,1029,9109,1015,8928,8387,203,8361,20735,57054,57054,57054,57054,199,252,254,4,58,57054,57054,5543,5290,5366,5323,532,5500,5460,5517,5470,5386,8279,8286,8323,8292,8205,8,6359,6382,6484,7034,7110,6649,6612,6741,7291,7354,5525,5537,5509,5181,5535,5570,5575,5549,5221,5608,8292,65246,280,57054,57054,15764,37288,56338,24767,57054,57054,9480,57054,38308,9781,35954,25263,57054,5705'
Number of bytes read: 449
gpib status is:
ibsta = 0xc100  < ERR TIMO CMPL >
iberr= 6
EABO 6: Operation aborted

ibcntl = 449
You can:
    w(a)it for an event
    write (c)ommand bytes to bus (system controller only)
    send (d)evice clear (device only)
    change remote (e)nable line (system controller only)
    (g)o to standby (release ATN line, system controller only)
    send (i)nterface clear (system controller only)
    ta(k)e control (assert ATN line, system controller only)
    get bus (l)ine status (board only)
    go to local (m)ode
    change end (o)f transmission configuration
    (q)uit
    (r)ead string
    perform (s)erial poll (device only)
    change (t)imeout on io operations
    request ser(v)ice (board only)
    (w)rite data string
    send group e(x)ecute trigger (device only)

: r
enter maximum number of bytes to read [1024]:
trying to read 1024 bytes from device...
received string: '4,57054,57054,12168,13935,20320,30175,57054,57054,57054,57054,30465,23778,44986,9647,57054,57054,57054,57054,48387,47423,41792,57871,57054,57054,57054,57054,64452,24830,31824,27670,57054,57054,57054,57054,41740,12751,16266,5113,57054,57054,57054,57054,50098,2404,34593,63623,57054,57054,57054,57054,63304,2170,65206,18463,57054,57054,57054,57054,54824,8886,63400,47442,57054,57054,57054,57054,38880,2266,60688,13813,57054,57054,57054,57054,48872,16499,14;'
Number of bytes read: 455
gpib status is:
ibsta = 0x2100  < END CMPL >
iberr= 0

ibcntl = 455
You can:
    w(a)it for an event
    write (c)ommand bytes to bus (system controller only)
    send (d)evice clear (device only)
    change remote (e)nable line (system controller only)
    (g)o to standby (release ATN line, system controller only)
    send (i)nterface clear (system controller only)
    ta(k)e control (assert ATN line, system controller only)
    get bus (l)ine status (board only)
    go to local (m)ode
    change end (o)f transmission configuration
    (q)uit
    (r)ead string
    perform (s)erial poll (device only)
    change (t)imeout on io operations
    request ser(v)ice (board only)
    (w)rite data string
    send group e(x)ecute trigger (device only)

: r
enter maximum number of bytes to read [1024]:
trying to read 1024 bytes from device...
received binary data (hex): ffffffff
Number of bytes read: 1
gpib status is:
ibsta = 0x2100  < END CMPL >
iberr= 0

ibcntl = 1
You can:
    w(a)it for an event
    write (c)ommand bytes to bus (system controller only)
    send (d)evice clear (device only)
    change remote (e)nable line (system controller only)
    (g)o to standby (release ATN line, system controller only)
    send (i)nterface clear (system controller only)
    ta(k)e control (assert ATN line, system controller only)
    get bus (l)ine status (board only)
    go to local (m)ode
    change end (o)f transmission configuration
    (q)uit
    (r)ead string
    perform (s)erial poll (device only)
    change (t)imeout on io operations
    request ser(v)ice (board only)
    (w)rite data string
    send group e(x)ecute trigger (device only)
:

EDIT: The above example produces the right result, but shouldn't need multiple reads.  See next post for update on using ibtest.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 12, 2024, 05:00:23 pm
Here's a better example of using ibtest to capture the NVRAM data.  Previously I didn't notice that the reason multiple reads were needed was because ibtest does not use the default timeout from the GPIB configuration file (gpib.conf).  Each read got some of the data but then timed out because the scope is so slow.

Here it is again, explicitly setting the timeout to 10 seconds in ibtest so the response is read in one shot.  Also note the larger buffer of 2048 bytes specified for the "r" (read command).

Sorry for the re-do.  I don't usually use ibtest.

Code: [Select]
$ ibtest
Do you wish to open a (d)evice or an interface (b)oard?
   (you probably want to open a device): d
enter primary gpib address for device you wish to open [0-30]: 8
trying to open pad = 8 on /dev/gpib0 ...
You can:
    w(a)it for an event
    write (c)ommand bytes to bus (system controller only)
    send (d)evice clear (device only)
    change remote (e)nable line (system controller only)
    (g)o to standby (release ATN line, system controller only)
    send (i)nterface clear (system controller only)
    ta(k)e control (assert ATN line, system controller only)
    get bus (l)ine status (board only)
    go to local (m)ode
    change end (o)f transmission configuration
    (q)uit
    (r)ead string
    perform (s)erial poll (device only)
    change (t)imeout on io operations
    request ser(v)ice (board only)
    (w)rite data string
    send group e(x)ecute trigger (device only)

: t
enter the desired timeout:
      (0) none
      (1) 10 microsec
      (2) 30 microsec
      (3) 100 microsec
      (4) 300 microsec
      (5) 1 millisec
      (6) 3 millisec
      (7) 10 millisec
      (8) 30 millisec
      (9) 100 millisec
      (10) 300 millisec
      (11) 1 sec
      (12) 3 sec
      (13) 10 sec
      (14) 30 sec
      (15) 100 sec
      (16) 300 sec
      (17) 1000 sec
13
gpib status is:
ibsta = 0x100  < CMPL >
iberr= 0

ibcntl = 0
You can:
    w(a)it for an event
    write (c)ommand bytes to bus (system controller only)
    send (d)evice clear (device only)
    change remote (e)nable line (system controller only)
    (g)o to standby (release ATN line, system controller only)
    send (i)nterface clear (system controller only)
    ta(k)e control (assert ATN line, system controller only)
    get bus (l)ine status (board only)
    go to local (m)ode
    change end (o)f transmission configuration
    (q)uit
    (r)ead string
    perform (s)erial poll (device only)
    change (t)imeout on io operations
    request ser(v)ice (board only)
    (w)rite data string
    send group e(x)ecute trigger (device only)

: w
enter a string to send to your device: id?
sending string: id?

gpib status is:
ibsta = 0x2100  < END CMPL >
iberr= 0

ibcntl = 4
You can:
    w(a)it for an event
    write (c)ommand bytes to bus (system controller only)
    send (d)evice clear (device only)
    change remote (e)nable line (system controller only)
    (g)o to standby (release ATN line, system controller only)
    send (i)nterface clear (system controller only)
    ta(k)e control (assert ATN line, system controller only)
    get bus (l)ine status (board only)
    go to local (m)ode
    change end (o)f transmission configuration
    (q)uit
    (r)ead string
    perform (s)erial poll (device only)
    change (t)imeout on io operations
    request ser(v)ice (board only)
    (w)rite data string
    send group e(x)ecute trigger (device only)

: r
enter maximum number of bytes to read [1024]:
trying to read 1024 bytes from device...
received string: 'ID TEK/2445A,V81.1,SYS:FV08,BB:FV02,CTT:FV05,DMM:FV01,GPIB:FV02;'
Number of bytes read: 64
gpib status is:
ibsta = 0x2100  < END CMPL >
iberr= 0

ibcntl = 64
You can:
    w(a)it for an event
    write (c)ommand bytes to bus (system controller only)
    send (d)evice clear (device only)
    change remote (e)nable line (system controller only)
    (g)o to standby (release ATN line, system controller only)
    send (i)nterface clear (system controller only)
    ta(k)e control (assert ATN line, system controller only)
    get bus (l)ine status (board only)
    go to local (m)ode
    change end (o)f transmission configuration
    (q)uit
    (r)ead string
    perform (s)erial poll (device only)
    change (t)imeout on io operations
    request ser(v)ice (board only)
    (w)rite data string
    send group e(x)ecute trigger (device only)

: w
enter a string to send to your device: key 0
sending string: key 0

gpib status is:
ibsta = 0x2100  < END CMPL >
iberr= 0

ibcntl = 6
You can:
    w(a)it for an event
    write (c)ommand bytes to bus (system controller only)
    send (d)evice clear (device only)
    change remote (e)nable line (system controller only)
    (g)o to standby (release ATN line, system controller only)
    send (i)nterface clear (system controller only)
    ta(k)e control (assert ATN line, system controller only)
    get bus (l)ine status (board only)
    go to local (m)ode
    change end (o)f transmission configuration
    (q)uit
    (r)ead string
    perform (s)erial poll (device only)
    change (t)imeout on io operations
    request ser(v)ice (board only)
    (w)rite data string
    send group e(x)ecute trigger (device only)

: w
enter a string to send to your device: earom? f
sending string: earom? f

gpib status is:
ibsta = 0x2100  < END CMPL >
iberr= 0

ibcntl = 9
You can:
    w(a)it for an event
    write (c)ommand bytes to bus (system controller only)
    send (d)evice clear (device only)
    change remote (e)nable line (system controller only)
    (g)o to standby (release ATN line, system controller only)
    send (i)nterface clear (system controller only)
    ta(k)e control (assert ATN line, system controller only)
    get bus (l)ine status (board only)
    go to local (m)ode
    change end (o)f transmission configuration
    (q)uit
    (r)ead string
    perform (s)erial poll (device only)
    change (t)imeout on io operations
    request ser(v)ice (board only)
    (w)rite data string
    send group e(x)ecute trigger (device only)

: r
enter maximum number of bytes to read [1024]: 2048
trying to read 2048 bytes from device...
received string: 'EAR 0:215,1908,1921,1921,1927,10204,10088,1917,10118,1970,10304,506,522,8715,8712,548,8647,8671,481,8668,508,8318,32,32,8221,28,15534,16052,7414,15560,16299,8099,16299,16292,16309,566,566,8756,8756,7450,7934,7699,4096,16304,16295,8105,16280,8105,743,744,740,740,10078,10334,2140,2133,10304,10340,2120,104,2133,10319,10322,2108,10321,2102,8297,835,820,817,1646,9814,9842,1630,722,752,14501,3762,3781,1840,1878,560,569,8545,314,1377,10238,1015,8970,1261,1948,9614,1975,1586,1349,1832,9242,9710,9014,710,9000,1362,9158,1187,1029,9109,1015,8928,8387,203,8361,20735,57054,57054,57054,57054,199,252,254,4,58,57054,57054,5543,5290,5366,5323,532,5500,5460,5517,5470,5386,8279,8286,8323,8292,8205,8,6359,6382,6484,7034,7110,6649,6612,6741,7291,7354,5525,5537,5509,5181,5535,5570,5575,5549,5221,5608,8292,65246,280,57054,57054,15764,37288,56338,24767,57054,57054,9480,57054,38308,9781,35954,25263,57054,57054,57054,57054,12168,13935,20320,30175,57054,57054,57054,57054,30465,23778,44986,9647,57054,57054,57054,57054,48387,47423,41792,57871,57054,57054,57054,57054,64452,24830,31824,27670,57054,57054,57054,57054,41740,12751,16266,5113,57054,57054,57054,57054,50098,2404,34593,63623,57054,57054,57054,57054,63304,2170,65206,18463,57054,57054,57054,57054,54824,8886,63400,47442,57054,57054,57054,57054,38880,2266,60688,13813,57054,57054,57054,57054,48872,16499,14;'
Number of bytes read: 1352
gpib status is:
ibsta = 0x2100  < END CMPL >
iberr= 0

ibcntl = 1352
You can:
    w(a)it for an event
    write (c)ommand bytes to bus (system controller only)
    send (d)evice clear (device only)
    change remote (e)nable line (system controller only)
    (g)o to standby (release ATN line, system controller only)
    send (i)nterface clear (system controller only)
    ta(k)e control (assert ATN line, system controller only)
    get bus (l)ine status (board only)
    go to local (m)ode
    change end (o)f transmission configuration
    (q)uit
    (r)ead string
    perform (s)erial poll (device only)
    change (t)imeout on io operations
    request ser(v)ice (board only)
    (w)rite data string
    send group e(x)ecute trigger (device only)
:
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tonedeak99 on March 13, 2024, 07:01:53 pm
The worst offenders were the larger radial Sprague caps with the resin bung, these were often found cracked and/or peeing electrolyte. I would give a list of what I used, but most of the caps I used are now discontinued.

(https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/?action=dlattach;attach=2065427;image)

Also if you don't have much experience replacing parts on double sided boards, I would suggest practising on something of no value first.

And as your scope has options, take note or pictures of where all the extra connectors are fitted, before removal.

David
Thanks David.  Found a list by CondorAudio in the Tek group.  Unfortunately some caps are not available.  Any recommendations for substitutes?
Part#   Value   Watts         Mouser Part#
C1021   290 µF   200   ELCTLT      647-UPW2E331MRD
C1022   290 µF   200   ELCTLT      647-UPW2E331MRD
C1066   4.7 µF   35   ELCTLT      647-UPW1H4R7MDD
C1112   4.7 µF   35   ELCTLT      647-UPW1H4R7MDD
C1120   10 µF   100   ELCTLT      647-UPW2A100MED
C1130   10 µF   100   ELCTLT      647-UPW2A100MED
C1220   10 µF   100   ELCTLT      647-UPW2A100MED
C1240   10 µF   100   ELCTLT      647-UPW2A100MED
C1400   47 µF   25   ELCTLT      647-UHE1E470MDD
C1402   47 µF   25   ELCTLT      647-UHE1E470MDD
RT1010   7.0 ohm   NTC Thermistor         995-SG210

For the 647-UPW2A100MED, I used 647-UCA2C100MPD for all of them, it's obsolete, but there are still a few thousand in stock.

For the 647-UHE1E470MDD, my choice of UPW1V470MED is no longer available, alternates I would choose from are; 667-EEU-FC1V470, 661-ELE-350ELL470MF1, or 232-35YXM47MEFR63X11, these are all 35V, but you could go with 25V as per the originals, I stocked up on the 35V version for various projects.

For the 647-UPW1H4R7MDD, there are some still available under numbers 647-UPW1H4R7MDD1TD (straight leads) and 647-UPW1H4R7MDD1TA (formed leads to 5mm pitch), all are obsolete.

The other parts I didn't replace.

David
Thanks for helping with substitutes.  I'm confused on the importance of brand (i.e Nichicon) and ripple. (Nichicon UPW vs UCA).  Do these factors matter?  I'm reading some mixed information.

Here's a better example of using ibtest to capture the NVRAM data.  Previously I didn't notice that the reason multiple reads were needed was because ibtest does not use the default timeout from the GPIB configuration file (gpib.conf).  Each read got some of the data but then timed out because the scope is so slow.

Here it is again, explicitly setting the timeout to 10 seconds in ibtest so the response is read in one shot.  Also note the larger buffer of 2048 bytes specified for the "r" (read command).

Sorry for the re-do.  I don't usually use ibtest.

Code: [Select]
$ ibtest
Do you wish to open a (d)evice or an interface (b)oard?
   (you probably want to open a device): d
enter primary gpib address for device you wish to open [0-30]: 8
trying to open pad = 8 on /dev/gpib0 ...
You can:
    w(a)it for an event
    write (c)ommand bytes to bus (system controller only)
    send (d)evice clear (device only)
    change remote (e)nable line (system controller only)
    (g)o to standby (release ATN line, system controller only)
    send (i)nterface clear (system controller only)
    ta(k)e control (assert ATN line, system controller only)
    get bus (l)ine status (board only)
    go to local (m)ode
    change end (o)f transmission configuration
    (q)uit
    (r)ead string
    perform (s)erial poll (device only)
    change (t)imeout on io operations
    request ser(v)ice (board only)
    (w)rite data string
    send group e(x)ecute trigger (device only)

: t
enter the desired timeout:
      (0) none
      (1) 10 microsec
      (2) 30 microsec
      (3) 100 microsec
      (4) 300 microsec
      (5) 1 millisec
      (6) 3 millisec
      (7) 10 millisec
      (8) 30 millisec
      (9) 100 millisec
      (10) 300 millisec
      (11) 1 sec
      (12) 3 sec
      (13) 10 sec
      (14) 30 sec
      (15) 100 sec
      (16) 300 sec
      (17) 1000 sec
13
gpib status is:
ibsta = 0x100  < CMPL >
iberr= 0

ibcntl = 0
You can:
    w(a)it for an event
    write (c)ommand bytes to bus (system controller only)
    send (d)evice clear (device only)
    change remote (e)nable line (system controller only)
    (g)o to standby (release ATN line, system controller only)
    send (i)nterface clear (system controller only)
    ta(k)e control (assert ATN line, system controller only)
    get bus (l)ine status (board only)
    go to local (m)ode
    change end (o)f transmission configuration
    (q)uit
    (r)ead string
    perform (s)erial poll (device only)
    change (t)imeout on io operations
    request ser(v)ice (board only)
    (w)rite data string
    send group e(x)ecute trigger (device only)

: w
enter a string to send to your device: id?
sending string: id?

gpib status is:
ibsta = 0x2100  < END CMPL >
iberr= 0

ibcntl = 4
You can:
    w(a)it for an event
    write (c)ommand bytes to bus (system controller only)
    send (d)evice clear (device only)
    change remote (e)nable line (system controller only)
    (g)o to standby (release ATN line, system controller only)
    send (i)nterface clear (system controller only)
    ta(k)e control (assert ATN line, system controller only)
    get bus (l)ine status (board only)
    go to local (m)ode
    change end (o)f transmission configuration
    (q)uit
    (r)ead string
    perform (s)erial poll (device only)
    change (t)imeout on io operations
    request ser(v)ice (board only)
    (w)rite data string
    send group e(x)ecute trigger (device only)

: r
enter maximum number of bytes to read [1024]:
trying to read 1024 bytes from device...
received string: 'ID TEK/2445A,V81.1,SYS:FV08,BB:FV02,CTT:FV05,DMM:FV01,GPIB:FV02;'
Number of bytes read: 64
gpib status is:
ibsta = 0x2100  < END CMPL >
iberr= 0

ibcntl = 64
You can:
    w(a)it for an event
    write (c)ommand bytes to bus (system controller only)
    send (d)evice clear (device only)
    change remote (e)nable line (system controller only)
    (g)o to standby (release ATN line, system controller only)
    send (i)nterface clear (system controller only)
    ta(k)e control (assert ATN line, system controller only)
    get bus (l)ine status (board only)
    go to local (m)ode
    change end (o)f transmission configuration
    (q)uit
    (r)ead string
    perform (s)erial poll (device only)
    change (t)imeout on io operations
    request ser(v)ice (board only)
    (w)rite data string
    send group e(x)ecute trigger (device only)

: w
enter a string to send to your device: key 0
sending string: key 0

gpib status is:
ibsta = 0x2100  < END CMPL >
iberr= 0

ibcntl = 6
You can:
    w(a)it for an event
    write (c)ommand bytes to bus (system controller only)
    send (d)evice clear (device only)
    change remote (e)nable line (system controller only)
    (g)o to standby (release ATN line, system controller only)
    send (i)nterface clear (system controller only)
    ta(k)e control (assert ATN line, system controller only)
    get bus (l)ine status (board only)
    go to local (m)ode
    change end (o)f transmission configuration
    (q)uit
    (r)ead string
    perform (s)erial poll (device only)
    change (t)imeout on io operations
    request ser(v)ice (board only)
    (w)rite data string
    send group e(x)ecute trigger (device only)

: w
enter a string to send to your device: earom? f
sending string: earom? f

gpib status is:
ibsta = 0x2100  < END CMPL >
iberr= 0

ibcntl = 9
You can:
    w(a)it for an event
    write (c)ommand bytes to bus (system controller only)
    send (d)evice clear (device only)
    change remote (e)nable line (system controller only)
    (g)o to standby (release ATN line, system controller only)
    send (i)nterface clear (system controller only)
    ta(k)e control (assert ATN line, system controller only)
    get bus (l)ine status (board only)
    go to local (m)ode
    change end (o)f transmission configuration
    (q)uit
    (r)ead string
    perform (s)erial poll (device only)
    change (t)imeout on io operations
    request ser(v)ice (board only)
    (w)rite data string
    send group e(x)ecute trigger (device only)

: r
enter maximum number of bytes to read [1024]: 2048
trying to read 2048 bytes from device...
received string: 'EAR 0:215,1908,1921,1921,1927,10204,10088,1917,10118,1970,10304,506,522,8715,8712,548,8647,8671,481,8668,508,8318,32,32,8221,28,15534,16052,7414,15560,16299,8099,16299,16292,16309,566,566,8756,8756,7450,7934,7699,4096,16304,16295,8105,16280,8105,743,744,740,740,10078,10334,2140,2133,10304,10340,2120,104,2133,10319,10322,2108,10321,2102,8297,835,820,817,1646,9814,9842,1630,722,752,14501,3762,3781,1840,1878,560,569,8545,314,1377,10238,1015,8970,1261,1948,9614,1975,1586,1349,1832,9242,9710,9014,710,9000,1362,9158,1187,1029,9109,1015,8928,8387,203,8361,20735,57054,57054,57054,57054,199,252,254,4,58,57054,57054,5543,5290,5366,5323,532,5500,5460,5517,5470,5386,8279,8286,8323,8292,8205,8,6359,6382,6484,7034,7110,6649,6612,6741,7291,7354,5525,5537,5509,5181,5535,5570,5575,5549,5221,5608,8292,65246,280,57054,57054,15764,37288,56338,24767,57054,57054,9480,57054,38308,9781,35954,25263,57054,57054,57054,57054,12168,13935,20320,30175,57054,57054,57054,57054,30465,23778,44986,9647,57054,57054,57054,57054,48387,47423,41792,57871,57054,57054,57054,57054,64452,24830,31824,27670,57054,57054,57054,57054,41740,12751,16266,5113,57054,57054,57054,57054,50098,2404,34593,63623,57054,57054,57054,57054,63304,2170,65206,18463,57054,57054,57054,57054,54824,8886,63400,47442,57054,57054,57054,57054,38880,2266,60688,13813,57054,57054,57054,57054,48872,16499,14;'
Number of bytes read: 1352
gpib status is:
ibsta = 0x2100  < END CMPL >
iberr= 0

ibcntl = 1352
You can:
    w(a)it for an event
    write (c)ommand bytes to bus (system controller only)
    send (d)evice clear (device only)
    change remote (e)nable line (system controller only)
    (g)o to standby (release ATN line, system controller only)
    send (i)nterface clear (system controller only)
    ta(k)e control (assert ATN line, system controller only)
    get bus (l)ine status (board only)
    go to local (m)ode
    change end (o)f transmission configuration
    (q)uit
    (r)ead string
    perform (s)erial poll (device only)
    change (t)imeout on io operations
    request ser(v)ice (board only)
    (w)rite data string
    send group e(x)ecute trigger (device only)
:

Thanks Mark.  I will see how to run this in windows and report back.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on March 13, 2024, 08:35:59 pm
Thanks for helping with substitutes.  I'm confused on the importance of brand (i.e Nichicon) and ripple. (Nichicon UPW vs UCA).  Do these factors matter?  I'm reading some mixed information.

The capacitance of an electrolytic decoupling capacitor is not critical. Look at the tolerances of the original capacitors: often they were -20% +100%.

Obviously the voltage has to be suitable; don't run anything at the rated voltage!

The more subtle points are all inter-related: ripple current, operating frequency (mains or SMPS), temperature, and lifetime. Higher is better :) Lower will work, but not necessarily as well nor for as long.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: factory on March 13, 2024, 09:09:12 pm
Thanks for helping with substitutes.  I'm confused on the importance of brand (i.e Nichicon) and ripple. (Nichicon UPW vs UCA).  Do these factors matter?  I'm reading some mixed information.

The brand was just my preferred option at the time and some of the parts were changed to what the local suppliers had available in stock at the time. I've used a mix of Rubycon & Panasonic for a couple of these PSUs too.

For the one that is no longer available, I gave similar parts from three other brands. Just make sure you choose reputable brands from reputable suppliers and not some unknown brand or fake crap from ebay/amazon/aliexpress etc. Unrelated to this thread, I did notice Nichicon have EOL'ed lots of their higher voltage capacitors.

David
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: jonpaul on March 14, 2024, 12:33:51 pm
Menachem at Conrad Audio in Isreral has lots of tips, recapping lists and parts for every TEK 246X model

j
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tonedeak99 on March 14, 2024, 09:20:02 pm
Thank you all so much.  I have my order ready.  It's definitely more than I was hoping to spend.  I checked the hours with EXER 05 and the scope has 5000.  Is there a particular point when a full recap is truly necessary?  Or can I get away with just changing the SRAM battery and the RIFA caps?  Is checking the ripple important to make this decision?  I also took a video of EXER 02 as recommended by many here.  Also any help on the proper/best points to attach a temp battery to the SRAM will be greatly appreciated.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tonedeak99 on March 15, 2024, 12:43:10 pm
hi all.  I was trying to understand how to measure the ripple for chart 5-1 in the service manual.  Can someone please explain the difference between total p-p ripple and 2x the line frequency p-p ripple and how each is measured.  I have a 20MHz analog scope I was going to use with a 1x probe grounded to the chassis set to the settings in the manual below Table 5-1.  Also I'm a bit worried about the Tek scope overheating, especially U800.  I've read warnings against running the scope with the cover off for extended periods, but this check requires that you let the scope warm up for 20mins plus the time needed to perform the checks.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 15, 2024, 03:34:18 pm
hi all.  I was trying to understand how to measure the ripple for chart 5-1 in the service manual.  Can someone please explain the difference between total p-p ripple and 2x the line frequency p-p ripple and how each is measured.  I have a 20MHz analog scope I was going to use with a 1x probe grounded to the chassis set to the settings in the manual below Table 5-1.  Also I'm a bit worried about the Tek scope overheating, especially U800.  I've read warnings against running the scope with the cover off for extended periods, but this check requires that you let the scope warm up for 20mins plus the time needed to perform the checks.
Total p-p ripple is letting the measuring scope trigger on whatever it finds and you can measure the p-p on the resulting waveform.  To measure twice the line frequency, you need to synchronize the scope triggering to the incoming AC line by selecting LINE trigger.  Basically you're looking for variation of two peaks spaced 120Hz apart to make sure there's no major imbalance between the positive and negative peak of the incoming AC after it's been rectified.

U800 will be fine with no fan running over it (but not true for some other model Tek scopes, which is where this concern comes from).  There's been much discussion about U800's thermal properties over on https://groups.io/g/TekScopes.  Also, it does not need a heatsink fitted, and don't be tempted to turn the mounting nuts.  Mechanical failure is its downfall.

For a temporary battery attachment point, any ground on the card will do for the battery negative, and the battery positive should go to any point connected to the SRAM Vcc.  The link you posted before from Jestine shows two possible points that would work.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on March 15, 2024, 04:27:50 pm
For a temporary battery attachment point, any ground on the card will do for the battery negative, and the battery positive should go to any point connected to the SRAM Vcc.  The link you posted before from Jestine shows two possible points that would work.

Don't forget to put a small 1N4148 diode in series with the temporary battery, just in case to avoid any current going into that battery while the main lithium battery is still connected, or the power of the instrument is still turned on.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 15, 2024, 05:12:36 pm
For a temporary battery attachment point, any ground on the card will do for the battery negative, and the battery positive should go to any point connected to the SRAM Vcc.  The link you posted before from Jestine shows two possible points that would work.

Don't forget to put a small 1N4148 diode in series with the temporary battery, just in case to avoid any current going into that battery while the main lithium battery is still connected, or the power of the instrument is still turned on.
I was thinking power would not be applied again until this operation was complete, since you don't want to be soldering these wires with the board un-isolated.  But if you did, and the scope was powered on, you're right that the +5V would flow into the temporary battery.  The lithium battery already has a diode which would keep its contribution below the 3V of the temporary battery, so that should be ok.

A series diode could be used for added safety if desired.  A Schottky diode would provide for a lower voltage drop.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tonedeak99 on March 15, 2024, 11:11:58 pm
hi all.  I was trying to understand how to measure the ripple for chart 5-1 in the service manual.  Can someone please explain the difference between total p-p ripple and 2x the line frequency p-p ripple and how each is measured.  I have a 20MHz analog scope I was going to use with a 1x probe grounded to the chassis set to the settings in the manual below Table 5-1.  Also I'm a bit worried about the Tek scope overheating, especially U800.  I've read warnings against running the scope with the cover off for extended periods, but this check requires that you let the scope warm up for 20mins plus the time needed to perform the checks.
Total p-p ripple is letting the measuring scope trigger on whatever it finds and you can measure the p-p on the resulting waveform.  To measure twice the line frequency, you need to synchronize the scope triggering to the incoming AC line by selecting LINE trigger.  Basically you're looking for variation of two peaks spaced 120Hz apart to make sure there's no major imbalance between the positive and negative peak of the incoming AC after it's been rectified.
Thanks Mark.  I tried CH1 trigger and LINE trigger and the waveform is exactly the same.  Also there are tiny spikes in the waveform, do I measure those or just the center band of the waveform?

Attached are some example waveforms and my results below:
J119 Pin    Vdc   p-p ripple (with spikes, without spikes)
1        -14.95   8mw, 4mv
2        4.98   35mv, 20mv
4        9.96   8mv, 4mv
5       -4.96   10mv, 7mv
6       14.92   8mw, 5mv
8        86   10mv, 8mv
9       41.7   8mv, 6mv
11       -7.99   8mv, 4mv
12        4.96   15mv, 5mv
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: add_ocean on March 16, 2024, 09:19:59 pm
About keeper battery replacement.

I was worrying about this 37 year old battery (dated 1987). So have bought new chinese one, manufactured 2023.
But when measured the voltage, both old and new battery measured 3,5V (within few of 1/1000 tolerance).
Who knows which battery will fail first or maybe last for the next 30 years?
This chemistry lasts 100 years in theory, but manufacture culture makes difference in practice.

So, the solution:
Attached new battery without detaching the old one. Each battery is connected via own diode and resistor, so these are isolated from each other.

No need to take the board off and de-solder, no risk of loosing calibration. Double reliability.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tonedeak99 on March 16, 2024, 09:54:07 pm
About keeper battery replacement.

I was worrying about this 37 year old battery (dated 1987). So have bought new chinese one, manufactured 2023.
But when measured the voltage, both old and new battery measured 3,5V (within few of 1/1000 tolerance).
Who knows which battery will fail first or maybe last for the next 30 years?
This chemistry lasts 100 years in theory, but manufacture culture makes difference in practice.

So, the solution:
Attached new battery without detaching the old one. Each battery is connected via own diode and resistor, so these are isolated from each other.

No need to take the board off and de-solder, no risk of loosing calibration. Double reliability.
Thanks for your advice but if you look at the data sheet you will see that the Keeper II batteries die abruptly. Also lithium batteries can leak acid and destroy the board. Therefore I’d rather not take a chance and remove the old one and replace it with the same brand and model.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: calibrationfixture on March 17, 2024, 06:38:35 am
Hi,

I agree, replace them notwithstanding the voltage. Done that myself several times. No problems. Mouser doesn't deliver these Timekeeper Batteries to Europe, but Conrad has the same Battery (LTC-7PN). Same Pin-Out. This time without its casing.

https://www.conrad.com/en/p/eve-ef651625-non-standard-battery-ltc-7pn-u-solder-pins-lithium-3-6-v-750-mah-1-pc-s-650799.html (https://www.conrad.com/en/p/eve-ef651625-non-standard-battery-ltc-7pn-u-solder-pins-lithium-3-6-v-750-mah-1-pc-s-650799.html)

Calibrationfixture
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 17, 2024, 02:46:10 pm
...
Thanks Mark.  I tried CH1 trigger and LINE trigger and the waveform is exactly the same.  Also there are tiny spikes in the waveform, do I measure those or just the center band of the waveform?

Attached are some example waveforms and my results below:
J119 Pin    Vdc   p-p ripple (with spikes, without spikes)
1        -14.95   8mw, 4mv
2        4.98   35mv, 20mv
4        9.96   8mv, 4mv
5       -4.96   10mv, 7mv
6       14.92   8mw, 5mv
8        86         10mv, 8mv
9       41.7   8mv, 6mv
11       -7.99   8mv, 4mv
12        4.96   15mv, 5mv
On your photo of pin 2, it looks like about 30mV p-p total ripple and maybe 10mV 2x line ripple.  On pin 4, about 7mV total and I can't see any 2x ripple.

The total p-p ripple would have components from the AC line and also the switching power supply which runs at approx. 20kHz.  The tiny spikes in your pin 4 photo don't correspond to that, or 2x the line frequency.  But even if you count them, you are still well under the total p-p ripple.

It's a somewhat subjective series of tests, as you are trying to visually average the trace on the screen.  A digital scope could do it for you now-a-days, but I don't think that's what the authors had in mind.

Another approach is to use a DMM set on AC volts.  This will measure the total p-p ripple up to the frequency limit of the DMM.  As long as that's 20kHz or higher, it will catch any poorly performing filter caps that are need of replacement.

The tiny spikes might be common mode noise.  You can check by probing pin 7 or 14 on J119.  This is GND and if you still see the same noise, it's going to be visible in all your measurements.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 17, 2024, 04:44:38 pm
I said:
...
Another approach is to use a DMM set on AC volts.  This will measure the total p-p ripple up to the frequency limit of the DMM.  As long as that's 20kHz or higher, it will catch any poorly performing filter caps that are need of replacement.
A clarification on this... The DMM on AC will remove the DC and show you a measurement of the remaining AC signal which would be the total ripple and noise, but it will be displaying the RMS of that AC signal (assuming a true RMS DMM), and not the p-p value that you would get off the scope screen.  The p-p value would be 2.8 * DMM reading for an ideal sine, which admittedly this is not, but it would at least provide a ballpark estimate to compare with the table and tell you if something was radically wrong filter-wise.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tonedeak99 on March 17, 2024, 10:46:15 pm
...
Thanks Mark.  I tried CH1 trigger and LINE trigger and the waveform is exactly the same.  Also there are tiny spikes in the waveform, do I measure those or just the center band of the waveform?

Attached are some example waveforms and my results below:
J119 Pin    Vdc   p-p ripple (with spikes, without spikes)
1        -14.95   8mw, 4mv
2        4.98   35mv, 20mv
4        9.96   8mv, 4mv
5       -4.96   10mv, 7mv
6       14.92   8mw, 5mv
8        86         10mv, 8mv
9       41.7   8mv, 6mv
11       -7.99   8mv, 4mv
12        4.96   15mv, 5mv
On your photo of pin 2, it looks like about 30mV p-p total ripple and maybe 10mV 2x line ripple.  On pin 4, about 7mV total and I can't see any 2x ripple.

The total p-p ripple would have components from the AC line and also the switching power supply which runs at approx. 20kHz.  The tiny spikes in your pin 4 photo don't correspond to that, or 2x the line frequency.  But even if you count them, you are still well under the total p-p ripple.

It's a somewhat subjective series of tests, as you are trying to visually average the trace on the screen.  A digital scope could do it for you now-a-days, but I don't think that's what the authors had in mind.

Another approach is to use a DMM set on AC volts.  This will measure the total p-p ripple up to the frequency limit of the DMM.  As long as that's 20kHz or higher, it will catch any poorly performing filter caps that are need of replacement.

The tiny spikes might be common mode noise.  You can check by probing pin 7 or 14 on J119.  This is GND and if you still see the same noise, it's going to be visible in all your measurements.

Thanks Mark. Unfortunately I still don’t understand how to make the proper measurements but on the bright side if I overestimated and still within spec of the p-p then Im a happy camper.  I guess Ill pass on the 2x line test.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: factory on March 18, 2024, 01:19:35 pm
Thank you all so much.  I have my order ready.  It's definitely more than I was hoping to spend.  I checked the hours with EXER 05 and the scope has 5000.  Is there a particular point when a full recap is truly necessary?  Or can I get away with just changing the SRAM battery and the RIFA caps?  Is checking the ripple important to make this decision?  I also took a video of EXER 02 as recommended by many here.  Also any help on the proper/best points to attach a temp battery to the SRAM will be greatly appreciated.

The problem with the electrolytic caps in these is their age, seals can still perish if they are unused parts that are have been stored for 25+ years, this affects many well known brands of capacitor, dating from the 80s & 90s.

Someone I know on another forum bought a supposedly recapped scope from an ebay crook, then it failed some time after, because only the RIFAs had been changed.  :palm:
The PSU failure damaged many parts on several boards, including some expensive hybrids and corrupted the contents of the EAROM, it was repaired but it cost quite a bit for the parts and a lot of time to fix.
Of course your scope might last many years before this happens, or it could fail quickly. It may cause no damage, or could write it off.

David
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tonedeak99 on March 18, 2024, 02:39:42 pm
Thanks factory.  Decisions...decisions....

I am very confident I can replace the caps and do a good job, but you hear so many horror stories of working scopes that then die after recapping.  Just trying to weigh the pros and cons.  Which brings me to a story.  After doing the ripple and Vdc checks I put the scope case back on and left it at that.  The next day I turn on the scope and I get a dreaded error message: CT TEST 84 FAIL 0C.  I didn't even touch or disconnect any components.  All I did was remove the case, probe J119, and put the case back on.  Even with the case off I had a fan blowing on the A1 board the whole time.  Luckily I powered it down and back up and the error went away, but it does concern me that something as trivial as removing the case could trigger an error.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on March 18, 2024, 07:34:12 pm
....I get a dreaded error message: CT TEST 84 FAIL 0C.  I didn't even touch or disconnect any components.  All I did was remove the case, probe J119, and put the case back on.

The "CT" part in the error message indicates this is coming from the Counter-Timer option of the scope. You can look it up in the 2465 options service manual where the CT option is also included. In the past I've heard about others resolving this error by replacing the CAL jumper and doing the CT calibration only, and this did resolve the problem. CT cal procedure is also explained in detail in the same options manual, and if I remember correctly all that is needed is a known accurate 1MHz or 10MHz signal to be fed into CH1 input and follow the procedure. Its been a while since I fitted the CTT board into my 2465B. The error you got might be due to a marginal CT calibration that may be drifting in and out of spec just on the limit, hence you only got the error once, but doing the cal should get you back on spec and get rid of that error for good.

Can't remember now if your scope is a 2465B, in which case this is the options manual that you want:
https://w140.com/tekwiki/images/1/17/070-6864-02.pdf

If its a 2465A version use this options manual:
https://w140.com/tekwiki/images/3/36/070-5857-00.pdf

Otherwise for the plain 2465 this is the options service manual:
https://w140.com/tekwiki/images/8/88/070-4632-00.pdf
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tonedeak99 on March 19, 2024, 02:11:12 pm
Hope this isn’t too much of a newbie request but Im having a hard time finding any good instructions online with videos or pictures on how to check p-p ripple and 2x line frequency ripple using an analog scope. I think the p-p ripple is just the measurement of the max top and min bottom of the waveform across the screen. See my zoomed in picture of pin 2 with annotations. But I can’t seem to figure out the 2x line frequency number which is a very small number for most pins in table 5-1. I also did check the ground pins 7 and 14 for noise and here is the result.  Seems like minimal noise of less than 1mv.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tonedeak99 on March 19, 2024, 02:29:06 pm
Took another shot of pin 4 but increased the timebase so the waveform wouldnt flicker.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on March 19, 2024, 07:13:12 pm
Use line triggering to make the ripple measurement.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 19, 2024, 08:06:30 pm
Hope this isn’t too much of a newbie request but Im having a hard time finding any good instructions online with videos or pictures on how to check p-p ripple and 2x line frequency ripple using an analog scope. I think the p-p ripple is just the measurement of the max top and min bottom of the waveform across the screen. See my zoomed in picture of pin 2 with annotations. But I can’t seem to figure out the 2x line frequency number which is a very small number for most pins in table 5-1. I also did check the ground pins 7 and 14 for noise and here is the result.  Seems like minimal noise of less than 1mv.
I think it's a good question.

It's difficult to make good 2x line measurements with an analog scope and no filter to eliminate or reduce frequencies higher than 120 Hz.  I can't argue with the numbers in the table, but I'm actually not in agreement with Tek's measurement technique for this.  I think the best that can be done when following their instructions is to look for 120 Hz variations in the overall envelope of the mess on the screen.

Below is a screen shot of J119.2 on a 2465 using a DSO and a lot of averaging to filter out the other noise.  This is what you're trying to measure.  If the 2x ripple is low, like this 2465 (approx 0.625mV), it's going to be impossible to see on an analog scope when mixed in with the other noise.  So, I'd say if the 2x ripple doesn't make itself obvious, it's probably ok.

I've also included some shots of the same pin on an analog scope (actually the same 2465 measuring itself).  It's a subjective call where to place the p-p cursors and I'm not including the extreme outliers.  For the 2x line ripple, it may help to set up the cursors as shown for 120 Hz, so you know what periodicity you're looking for in the envelope.

Everything is line triggered.  Sorry for the shaky photos; I didn't get out the tripod.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tonedeak99 on March 19, 2024, 10:00:52 pm
Use line triggering to make the ripple measurement.
Thanks and yes all my tests were done with the LINE trigger per the service manual.

Hope this isn’t too much of a newbie request but Im having a hard time finding any good instructions online with videos or pictures on how to check p-p ripple and 2x line frequency ripple using an analog scope. I think the p-p ripple is just the measurement of the max top and min bottom of the waveform across the screen. See my zoomed in picture of pin 2 with annotations. But I can’t seem to figure out the 2x line frequency number which is a very small number for most pins in table 5-1. I also did check the ground pins 7 and 14 for noise and here is the result.  Seems like minimal noise of less than 1mv.
...I've also included some shots of the same pin on an analog scope (actually the same 2465 measuring itself).  It's a subjective call where to place the p-p cursors and I'm not including the extreme outliers.  For the 2x line ripple, it may help to set up the cursors as shown for 120 Hz, so you know what periodicity you're looking for in the envelope.
Wow thank you so much for the explanation.  I'm almost there.  Would my attached picture be a proper yet subjective interpretation of your 2x frequency ripple?  I added two black lines comparing the two peaks at 120hz apart.  They are about <1mv apart.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 19, 2024, 10:25:04 pm
...
Wow thank you so much for the explanation.  I'm almost there.  Would my attached picture be a proper yet subjective interpretation of your 2x frequency ripple?  I added two black lines comparing the two peaks at 120hz apart.  They are about <1mv apart.
You're welcome!  Sorry I didn't get a chance to post back sooner.

I think that's a good call (and verified by the DSO).  The 120 Hz period is definitely visible in that photo.  And in this instance for pin 2, you're looking for 2x line ripple >30mV, so it would be quite visible.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tonedeak99 on March 20, 2024, 12:14:41 am
You're welcome!  Sorry I didn't get a chance to post back sooner.
I got it!!! You are a great teacher Mark!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 20, 2024, 10:39:46 am
I've been thinking more about the measurement specification "p-p Ripple at Two Times Line Frequency".  I've been interpreting that very literally in that it's asking for the maximum difference in peaks of the waveform spaced 120Hz apart.  And that's the example I posted.

While some problems may manifest themselves that way, such as a weak half in the AC rectification stage, they may be asking for the p-p ripple *OF* two times the line frequency.  I would interpret that more broadly as any AC line related ripple, and would encompass failures in the output filter capacitors.

In other words, the measurements table for each rail is asking for the peak low frequency ripple (AC line related) and also the total ripple, which includes both the low frequency ripple and the high frequency ripple from the switcher stage.

In this case, I want to amend what I posted about the "2x line" measurement points.  Using the 2465 from before on J119.2, below is the averaged waveform on the DSO, and how that appears on an analog scope.  In the case of the analog display, instead of picking out two peaks, you're trying to pick out a consistent peak and a trough on one side (upper or lower) of the waveform envelope, and as before with the scope line triggered.

Again the measurement on the analog scope is very subjective, but in the photo it's in the right ballpark and maybe the upper cursor should be a little higher.  If the ripple was near the limit, in this case 30mV, you would clearly see the deviation in the envelope.  With some of the other rails on J119, it's just going to be impossible to see their limits of a mV or two.

It would have been nice if Tek provided more than a half a sentence or an example of what they intended.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tonedeak99 on March 20, 2024, 01:48:16 pm

...Again the measurement on the analog scope is very subjective, but in the photo it's in the right ballpark and maybe the upper cursor should be a little higher.  If the ripple was near the limit, in this case 30mV, you would clearly see the deviation in the envelope.  With some of the other rails on J119, it's just going to be impossible to see their limits of a mV or two.

It would have been nice if Tek provided more than a half a sentence or an example of what they intended.
I too have been thinking about this test and what the Tek engineers really wanted.  I want to propose another interpretation.  Could they have wanted us to measure the p-p ripple at 2 points 120hz apart and subtract the two voltages?  See the pic attached.  Point A has a p-p of 24mv.  Point B (120hz later) has a p-p of 23mv.  So the p-p ripple at 2x the line frequency would be 24-23=1mv. 
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tonedeak99 on March 20, 2024, 02:04:27 pm
Here is the parts list for a 2465A A2A1 and A3 boards.  This list was originally compiled by Condor Audio over on the Tek group, but I updated the OOS parts and some capacitors for ones that were closer to the original specs.  Mouser part # was the one provided by Condor Audio.  An "x" under available means I replaced that part with another.  The BOM column is the final Mouser part#:
Resistors               Yachad's recommendation      
Original ---------------------------------------                     
Part#   Value   Watts         Mouser Part#   available   BOM
R1010   15 Ω              0.5         660-PCF2C150K              660-PCF2C150K
R1019   15 Ω       0.5         660-PCF2C150K              660-PCF2C150K
R1020   270K Ω      0.5         594-5093NW270K0J      594-5093NW270K0J
Capacitors                     
Part#   Value   Voltage   Type            
C1016   .068 µF   250   PLSTC      594-222233810683       594-222233810683
C1018   .068 µF   250   PLSTC      594-222233810683       594-222233810683
C1021   290 µF   200   ELCTLT      647-UPW2E331MRD   x   232-200TXW330MEFR18X
C1022   290 µF   200   ELCTLT      647-UPW2E331MRD   x   232-200TXW330MEFR18X
C1025   100µF   25   ELCTLT      647-UHE1E101MED      647-UHE1E101MED
                     
C1034   4.7 µF   10   TANT            505-MKS2B044701KJC00      505-MKS2B044701KJC00
C1020   .0022 µF   250   PPR           594-2222-336-60222      594-2222-336-60222
C1051   .0022 µF   250   PPR            594-2222-336-60222      594-2222-336-60222
C1052   .01 µF   250   PAPER      594-2222-336-60103      594-2222-336-60103
C1066   4.7 µF   35   ELCTLT      647-UPW1H4R7MDD   x   647-UPW1H4R7MDD1TD
C1065   .056 µF   250   MTLZD      594-2222-372-41563      
C1072   3.3 µF   350   ELCTLT      647-UPW2V3R3MPD      647-UPW2V3R3MPD
C1112   4.7 µF   35   ELCTLT      647-UPW1H4R7MDD   x   647-UPW1H4R7MDD1TD
                     
C1101   100µF   25   ELCTLT      647-UHE1E101MED      647-UHE1E101MED
C1102   100µF   25   ELCTLT      647-UHE1E101MED      647-UHE1E101MED
C1110   250 µF   20   ELCTLT      647-UHE1H331MPD      647-UHE1V271MPD
C1111   250 µF   20   ELCTLT      647-UHE1H331MPD      647-UHE1V271MPD
C1113   180 µF   40   ELCTLT      647-UHE1H331MPD      647-UHE1H181MPD
C1114   250 µF   20   ELCTLT      647-UHE1H331MPD      647-UHE1V271MPD
C1115   250 µF   20   ELCTLT      647-UHE1H331MPD      647-UHE1V271MPD
C1116   180 µF   40   ELCTLT      647-UHE1H331MPD      647-UHE1H181MPD
                     
C1120   10 µF   100   ELCTLT      647-UPW2A100MED   x   647-UPW2C100MPD
C1130   10 µF   100   ELCTLT      647-UPW2A100MED   x   647-UPW2C100MPD
C1132   10 µF   160   ELCTLT      647-UPW2C100MPD      647-UPW2C100MPD
C1220   10 µF   100   ELCTLT      647-UPW2A100MED   x   647-UPW2C100MPD
C1240   10 µF   100   ELCTLT      647-UPW2A100MED   x   647-UPW2C100MPD
                     
C1260   100 µF   25   ELCTLT      647-UHE1E101MED      647-UHE1E101MED
C1280   100 µF   25   ELCTLT      647-UHE1E101MED      647-UHE1E101MED
C1300   100 µF   25   ELCTLT      647-UHE1E101MED      647-UHE1E101MED
C1330   100 µF   25   ELCTLT      647-UHE1E101MED      647-UHE1E101MED
C1350   100 µF   25   ELCTLT      647-UHE1E101MED      647-UHE1E101MED
                     
C1400   47 µF   25   ELCTLT      647-UHE1E470MDD   x   647-UPV1H470MGD
C1402   47 µF   25   ELCTLT      647-UHE1E470MDD   x   647-UPV1H470MGD
C1274   1 µF   50   nonplzd      505-MKS2C041001FJC00   x   505-MKS2D041001KKI00
C1291   1 µF   50   nonplzd      505-MKS2C041001FJC00   x   505-MKS2D041001KKI00
C1292   1 µF   50   nonplzd      505-MKS2C041001FJC00   x   505-MKS2D041001KKI00
                     
RT1010   7.0 ohm   NTC Thermistor         995-SG210   x   
RT1016   5.0 ohm   NTC Thermistor         995-SG200      995-SG200

Also I'm still debating if I should replace the 100uf capacitors with 150uf as done by @FireDragon earlier in this thread to improve PS ripple and noise.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 20, 2024, 10:57:48 pm

...Again the measurement on the analog scope is very subjective, but in the photo it's in the right ballpark and maybe the upper cursor should be a little higher.  If the ripple was near the limit, in this case 30mV, you would clearly see the deviation in the envelope.  With some of the other rails on J119, it's just going to be impossible to see their limits of a mV or two.

It would have been nice if Tek provided more than a half a sentence or an example of what they intended.
I too have been thinking about this test and what the Tek engineers really wanted.  I want to propose another interpretation.  Could they have wanted us to measure the p-p ripple at 2 points 120hz apart and subtract the two voltages?  See the pic attached.  Point A has a p-p of 24mv.  Point B (120hz later) has a p-p of 23mv.  So the p-p ripple at 2x the line frequency would be 24-23=1mv.
I think the end result of that measurement would be the variation in the high frequency amplitude.

By subtracting the top point from the bottom point, you're left with just the amplitude of the high frequency component at that point in time.  And when you do  it at two different times, you get two high frequency amplitudes that you're then subtracting.  The low frequency information has been subtracted out, so I don't see how it relates back to the table.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tonedeak99 on March 21, 2024, 02:51:08 am
Thanks Mark.

Ive come across 3 new issues with my scope that I wanted to share with everyone:

1.  The voltage readings appear a bit off from my other scope and a tektronix signal generator I have. If I set the generator for a sine or square wave with 20v amplitude (the max for the generator) my other scope reads them as 20v but the 2465A reads 21.5V. Unfortunately the 2465A doesn’t have the cool measurement function that the 2465B has to double check the voltage reading.  Btw any way of adding that feature to a 2465A?

2. The trace comes and goes as the unit warms up. Sometimes it disappears completely. This seems to fix itself after it warms up. Still testing to make sure. Adjusting the readout knob doesn’t help.

3. My focus knob is set to 3 oclock in order to be in focus. I would think a properly functioning scope would be closer to 12 oclock.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 21, 2024, 07:49:36 pm
...
Ive come across 3 new issues with my scope that I wanted to share with everyone:

1.  The voltage readings appear a bit off from my other scope and a tektronix signal generator I have. If I set the generator for a sine or square wave with 20v amplitude (the max for the generator) my other scope reads them as 20v but the 2465A reads 21.5V. Unfortunately the 2465A doesn’t have the cool measurement function that the 2465B has to double check the voltage reading.  Btw any way of adding that feature to a 2465A?
Have you checked the other vertical ranges for accuracy?  Are they ok or off by the same percentage?  Do the cursor readings match the graticule?

I have not heard of any way to upgrade an A to a B.  The A1 board in the B has some additional hardware dedicated to the parametric measurements.

Quote
2. The trace comes and goes as the unit warms up. Sometimes it disappears completely. This seems to fix itself after it warms up. Still testing to make sure. Adjusting the readout knob doesn’t help.
Is it fading out and then back in, or does it suddenly disappear and reappear?

The readout knob?  Does the readout fade, or did you mean the trace intensity knob?  Or do you mean everything disappears?

Maybe it's heat related?  Perhaps a session with a can of freeze spray (or inverted canned air) might provide some clues.

Quote
3. My focus knob is set to 3 oclock in order to be in focus. I would think a properly functioning scope would be closer to 12 oclock.
I have a 2465 and a 2445A and neither of my focus knobs sit at 12:00.  They're both around 2:00.

There are additional adjustments you can try, and all in combination with each other because they interact.  The front panel ASTIG for one, and on the HV board there is HIGH DRIVE FOCUS, and depending on your serial number, there might be an EDGE FOCUS.  This is covered in the adjustment procedure.

It takes some patience to iterate for the best focus.  I've found it difficult to get everything on the screen in perfect focus and it usually ends up being a compromise.

I'd recommend marking the current pot positions with a fine Sharpie before tweaking.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tggzzz on March 21, 2024, 09:38:34 pm
I have not heard of any way to upgrade an A to a B.  The A1 board in the B has some additional hardware dedicated to the parametric measurements.

There's a fleabay seller that allegedly converts 2445b into 2465b. Allegedly comes complete with "do not tamper" stickers, so that if you spot his perfidy he can refuse to refund money.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 21, 2024, 09:59:05 pm
I have not heard of any way to upgrade an A to a B.  The A1 board in the B has some additional hardware dedicated to the parametric measurements.

There's a fleabay seller that allegedly converts 2445b into 2465b. Allegedly comes complete with "do not tamper" stickers, so that if you spot his perfidy he can refuse to refund money.
Yeah, he's still selling on ebay, and even more is that the "conversion" is not 100%, as unhappy buyers found out way after the purchase.  Have a read:

  https://groups.io/g/TekScopes/topic/7658884#140202
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tonedeak99 on March 21, 2024, 10:48:44 pm

Have you checked the other vertical ranges for accuracy?  Are they ok or off by the same percentage?  Do the cursor readings match the graticule?
The generator is a Tek CFG250.  It was a switch for either (i) up to 2V or (i) up to 20v amplitudes, so I tried both and maxed the anplitude setting in hopes it would read exactly 2V and 20V.  Both voltages have the same problem by the same percentage and even across different vertical ranges of the scope.  If it wasn't for my other scope reading the generator as accurate at 2v and 20v, I would probably assumed it was the generator that was off.  The cursor readings match the graticle.  To make matters more confusing the calibration point on the scope does read accurately at .4v.
Quote
Is it fading out and then back in, or does it suddenly disappear and reappear?

The readout knob?  Does the readout fade, or did you mean the trace intensity knob?  Or do you mean everything disappears?

Maybe it's heat related?  Perhaps a session with a can of freeze spray (or inverted canned air) might provide some clues.
The trace dims in and out many times in no discernable pattern.  Sometimes the dimming is light, sometimes it is accompanied by a slow flicker while dimming and then other times it continues until it's disappeared.  Mostly happens during warming up but I have also noticed it after the 20min warm up cycle.

I meant that when adjusting the readout intensity knob it didn't affect it.  The trace intensity knob does correct it temporarily, but it then corrects itself.  Meaning if the trace starts dimming and/or disappears
 if I immediately set the trace intensity knob to compensate for the dimming it will brighten up, but then in a few seconds it corrects itself and become super bright.  Maybe the pot for this knob needs to be cleaned?  With regards to your recommendation what components do you recommend I freeze?

Quote
I have a 2465 and a 2445A and neither of my focus knobs sit at 12:00.  They're both around 2:00.

There are additional adjustments you can try, and all in combination with each other because they interact.  The front panel ASTIG for one, and on the HV board there is HIGH DRIVE FOCUS, and depending on your serial number, there might be an EDGE FOCUS.  This is covered in the adjustment procedure.

It takes some patience to iterate for the best focus.  I've found it difficult to get everything on the screen in perfect focus and it usually ends up being a compromise.

I'd recommend marking the current pot positions with a fine Sharpie before tweaking.
If your scopes are also in this position then I will just let it be.  Thanks.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: alan.bain on March 21, 2024, 11:10:40 pm
Have you checked the voltage on the screen electrode around the distributed Y-plates? If this drifts (it is regulated by a simple zener circuit) then the focus position also drifts and ultimately getting a very good sharp focus becomes impossible.  As I recall it should be around the output level from Y amps with no signal, but think it is marked in the SM around 30V I think (no SM here!)

Alan
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on March 21, 2024, 11:14:18 pm
I meant that when adjusting the readout intensity knob it didn't affect it.  The trace intensity knob does correct it temporarily, but it then corrects itself.  Meaning if the trace starts dimming and/or disappears
 if I immediately set the trace intensity knob to compensate for the dimming it will brighten up, but then in a few seconds it corrects itself and become super bright.  Maybe the pot for this knob needs to be cleaned?

Be aware that all rotary controls on this scope are "fly by wire" meaning there is only a plain DC voltage on them that gets "Muxed" over to an ADC, which I believe is what then actually talks to the CPU, which in turn then carries out the desired action. But the CPU itself is grossly under powered for all the stuff it has to constantly handle.  This sometimes, depending on the CPU load, makes some controls feel like they are slow or sluggish to react, or don't react at all until one reaches past the intended point in their range and then suddenly things jump to a new value, and which to some extent might be what you are seeing. Lubing of the pots will never hurt, and would after all this time even be recommendable, however I understand it is not so trivial to get to the back of some of those controls. I've been lucky in that sense and so far never had to actually try to get to them, so this might not apply to all of them. Even pulling some of the knobs might require carefully heating them up a bit with a hot air gun so allow them to come off without breaking. Not even sure if all the pots actually have openings that would admit some fluid into them, but others here will know for sure. In any event use only Deoxit Fader Lube (green fluid), and not the cherry red one which is meant for mechanical switch contacts. If nothing else I'd try some 70-90% alcohol, but Deoxit is king.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 21, 2024, 11:37:54 pm

Have you checked the other vertical ranges for accuracy?  Are they ok or off by the same percentage?  Do the cursor readings match the graticule?
The generator is a Tek CFG250.  It was a switch for either (i) up to 2V or (i) up to 20v amplitudes, so I tried both and maxed the anplitude setting in hopes it would read exactly 2V and 20V.  Both voltages have the same problem by the same percentage and even across different vertical ranges of the scope.  If it wasn't for my other scope reading the generator as accurate at 2v and 20v, I would probably assumed it was the generator that was off.  The cursor readings match the graticle.  To make matters more confusing the calibration point on the scope does read accurately at .4v.

I would make sure the CFG250 was accurate before diving in.

I would start with the scope and set up a stable DC power supply for 2V, as measured by a DMM.  Then probe it with the scope directly using either no probe or a 1x probe and see if you get the expected voltage for both polarities.  Then repeat for 20V.

As for the CFG250, there's several ways to check it.  Probably the easiest is to set up a sine wave output of 2V or 20V, say at 100Hz, and then measure it with your DMM.  If you're saying it's supposed to be outputting +/-2V (4V pk-pk), then your meter should be reading the RMS of that which would be 2V / sqrt(2) = 1.41V.  You can repeat that for 20V.

This looks like a 100% analog function generator, so I wouldn't be surprised if it was off.


I will look into some possibilities for the dimming.  As AMR points out, the CPU is in the middle of the intensity control (and most others), so the issue could be in a number places.

EDIT: Sorry, you said 2V and 20V *amplitude*.  So the RMS calculation is the same, but use 1V and 10V for the peak, so you should get 0.707 volts and 7.07V on the DMM.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tonedeak99 on March 22, 2024, 12:55:45 am
Thank you AMR for the info. Ill see if I can lube it next time I take it apart.

Mark your suggestion was genius. My DMM is only accurate at 60hz so I set the generator to that frequency and immediately noticed that with the amplitude maxed out it was over 7.07v. So I lowered it to give me that value and the waveform was spot on 20v on the scope!  Im thrilled that my scope is well calibrated but Im mindblown that my generator and other scope were both uncalibrated in voltage by the exact amount.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: AMR Labs on March 22, 2024, 01:58:42 am
Mark your suggestion was genius. My DMM is only accurate at 60hz so I set the generator to that frequency and immediately noticed that with the amplitude maxed out it was over 7.07v. So I lowered it to give me that value and the waveform was spot on 20v on the scope!  Im thrilled that my scope is well calibrated but Im mindblown that my generator and other scope were both uncalibrated in voltage by the exact amount.

As a future reference, and as a quick test, I would think that you should be able to use DC voltage all the same to check the accuracy of the vertical inputs. Just switch input mode to GND, center the trace on the middle (or bottom) baseline, select the appropriate V/div range that will give you best resolution, then switch input mode to DC and apply the known accurate DC voltage measured with your DMM, and count the number of divisions the trace goes up or down the screen from the baseline depending on the applied polarity. If for example you chose 5V/div (with a x1 probe) then inputting 20V DC should raise the trace by exactly 4 divisions. Just make sure that you really switched to DC (1Mohm input), and NOT the 50-Ohm input option (also DC coupled) as the input current could blow or overheat the internal load resistor. 20V/50R = 0.4A ^2 x 50R = 8W = PUFF!!
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 22, 2024, 03:16:13 pm
Ok, I have some ideas for you to check for the dimming.  It could be the intensity pot input which goes to the CPU, something in the CRT circuitry, or something in between which includes the DAC and display sequencer.

I would suggest looking at two different points to figure out which section to concentrate on.

1) The first is to verify the INTENSITY input control  This is fairly easy and you can do it from the front panel.  Get into Exerciser 01 and turn the INTENSITY knob so that the INTENSITY knob status line is displayed (should start with "17").  See table 6-9 for the meaning of these fields, but what you're looking for is any variation in the displayed numbers as the dimming is occurring.  If there is, the CPU thinks it's reading changes coming from the INTENSITY pot and the problem is on that side.  Hopefully the problem with dimming will not get in the way of seeing the status display.

I'd suggest reading the section on DIAGNOSTIC ROUTINES starting on 6-10 through (at least) Exerciser 01 to learn how to operate the diagnostic menus.


2) The second place to check is after the CPU, DAC, and display sequencer to see if the CRT is being instructed to dim.

Set up the scope for the test waveforms for the A1 board, which immediately precedes the A1<6> schematics in the manual.  Make sure the readout is completely off.  There is a very small range at 12:00 that this occurs.  If it's not off you'll see lots of junk on the test waveforms as the beam turns on and off when the CRT makes dots on the screen to form the characters.

Check signal VZ on the anode of CR966 (diode further from back edge), schematic <6> loc 8L, waveform [65].  The upper level of VZ is the brightness.  Watch this to see if it correlates to the dimming.

Check signal VQ on the anode CR972 (diode closer to back edge), schematic <6> loc 8L, waveform [66].  This is related to the brightness, but is probably not the cause.  Check for correlation here.


3) (Ok, so I added a third test..)  If you find that VZ or VQ correlates to the dimming, you can take a look at the output of the DAC on the cathode of CR354.  It has a range of about 0 to 2.5V which you should be able to verify as you turn the INTENSITY knob.  The DAC and associated sample and hold circuitry are a known source of problems.  You could even do this test before #1 or #2 since it's easy and targets a known problem area.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tonedeak99 on March 24, 2024, 04:25:23 pm
Thanks AMR for the tip in Vdc amplitude testing. I think that’s how I checked my other scope when I got it.

Mark sorry for the delay in testing but for some strange reason the scope wasn’t dimming. Today it finally started acting up again and I tried your first test. It passed. The EXER 01 values for pot 17 never changed. Unfortunately I couldnt tell if the trace was dimming since the trace disappears once you enter diagnostics. But I tried to go into your test once I noticed the trace acting up and dimming or disappearing.

Sorry if this question is a dumb one but for test 2 do I use a second scope or the same scope to see the waveforms?
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: David Hess on March 24, 2024, 05:42:42 pm
The z-axis hybrids which control intensity are known to fail, but it could be a different problem so exclude everything else.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 24, 2024, 06:08:11 pm
Thanks AMR for the tip in Vdc amplitude testing. I think that’s how I checked my other scope when I got it.

Mark sorry for the delay in testing but for some strange reason the scope wasn’t dimming. Today it finally started acting up again and I tried your first test. It passed. The EXER 01 values for pot 17 never changed. Unfortunately I couldnt tell if the trace was dimming since the trace disappears once you enter diagnostics. But I tried to go into your test once I noticed the trace acting up and dimming or disappearing.

Sorry if this question is a dumb one but for test 2 do I use a second scope or the same scope to see the waveforms?
Sometimes it's ok to use the same scope to measure itself, but given the issues with dimming which may blank the display just when you need it, I would use a separate scope to observe #2.  #3 is the DAC brightness output and would normally be a static DC voltage when the INTENSITY knob is not being moved, so you could either watch it on a DMM or on a second channel on the other scope.

Because the symptom is now occurring more infrequently, you should monitor both points (VZ and DAC output) at the same time to increase your chances of seeing it.

Test #2, monitoring VZ and VQ, is directly after the z-axis hybrid (U950) that David mentions.  If it's bad you should catch it misbehaving, but the display sequencer (U550) precedes it and could also be involved, so you'd have to narrow it down a little further before reaching any conclusions.

I should also mention that you should be very careful probing around the hybrids.  Some of the pins have higher voltages than just plain TTL, and they are very unforgiving if you accidentally short the wrong two adjacent pins with a probe.  If possible, it's safer to probe a thru-hole component on the same node, or if your probe comes with those little protector caps that only allow you to contact one pin at a time, I recommend you use it.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tonedeak99 on March 25, 2024, 06:59:38 pm
Ive been ready to do test 2 and 3 but the trace has been working fine. I think it’s related to the ambient temperature. Lately it’s been warmer outside and therefore inside too.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tonedeak99 on March 26, 2024, 12:29:15 am
Test #3 passed with flying colors.

test #2 created the 2 expected waveforms but the trace never dimmed so test was inconclusive.  I adjusted the intensity and noticed the amplitude changing accordingly.  Even opened the window right next to scope to let in some cooler air.   Not sure what could be the cause yet but will try again tomorrow.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: MarkL on March 26, 2024, 05:53:14 pm
Test #3 passed with flying colors.

test #2 created the 2 expected waveforms but the trace never dimmed so test was inconclusive.  I adjusted the intensity and noticed the amplitude changing accordingly.  Even opened the window right next to scope to let in some cooler air.   Not sure what could be the cause yet but will try again tomorrow.
On test #3, meaning the dimming issue occurred but no changes in the intensity DAC output?  I guess you didn't get a chance to probe VZ at the same time.

If the DAC output remained fixed during the dimming issue, we're left with: display sequencer (U650) --> z-axis hybrid (U950) --> CRT driver board.  I'm not saying those chips are necessarily to blame; just that those are good places to divide the problem.

I prefer to catch a problem red-handed, but if you want to jump ahead a little and it appears to be temperature related, one thing to try is to reseat the z-axis hybrid.  Remove it, clean the contacts gently with isopropyl, and put it back.  Make sure it's lined up exactly before tightening the nuts; you don't want to crack the ceramic.
Title: Re: Tektronix 2465B oscilloscope teardown
Post by: tonedeak99 on March 27, 2024, 12:48:41 am
Hey Mark.  Actually it hasn't dimmed again. Sorry if I wasn't clear but it didn't dim during my Test #3 either.  I have had all 3 tests going on simultaneously.  CH1 on the VZ, CH2 on the VQ and DMM probes on test #3.  I called #3 a pass because it was a range b/w 0 and 2.5 and changed smoothly and linearly as I turned the intensity knob.  Sorry wasn't aware that for test #3 I also needed to check it during dimming.  Will repeat it if this dimming ever comes back.  I'm dealing with the anti-murphy law.