Tektronix 2465B oscilloscope teardown

[med6753]

Uh oh. Possible one of those fakes "built" by that EBay scammer? 

[BravoV]

Uh oh. Possible one of those fakes "built" by that EBay scammer? 

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.

[med6753]

Uh oh. Possible one of those fakes "built" by that EBay scammer? 

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? 

[BravoV]

Dave already aware of this (HERE), also I did remind him to bring this out on his upcoming 2nd part of this 2465B fixing video -> HERE

[mnementh]

Oh gawd... this schizz has infected ANOTHER thread. 

These are JUNKED OSCILLOSCOPES. You can't assume anything about them.

mnem
 

[grbk]

Oh gawd... this schizz has infected ANOTHER thread. 

These are JUNKED OSCILLOSCOPES. You can't assume anything about them.

mnem
 

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).

[mnementh]

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
 

[tggzzz]

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
 

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.

[Satbeginner]

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!! 

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

[BravoV]

Repost here as reference.

A fellow forum member, mnementh was requesting for a confirmation (HERE), 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.

[MarkL]

Repost here as reference.

A fellow forum member, mnementh was requesting for a confirmation (HERE), 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.)

[BravoV]

Repost here as reference.

A fellow forum member, mnementh was requesting for a confirmation (HERE), 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.

[mnementh]

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 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. 

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

mnem

[bdunham7]

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?

[jonpaul]

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

[bdunham7]

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?

[med6753]

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. 

[mnementh]

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*

[WastelandTek]

This thread is huge, and my search attempts are being frustrating.

Can someone point me at a writeup on reading out the Dallas NVRAM?

[Cooler Than I Look]

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

[bdunham7]

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.

[med6753]

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.

[bdunham7]

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. 

[bdunham7]

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.

[WastelandTek]

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 , 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.