Test Equipment Anonymous (TEA) group therapy thread

[factory]

A 12 - 18 GHz signal generator I got for $10 from a ham radio swap meet a couple months ago. Someone cut off and removed one of the potentiometers for some unknown reason, but it was simple enough to replace. (I had to reverse engineer the schematics just to figure out which wire went where though).
The mechanism is quite cool, the knob rotates both a cam and the readout through a series of gears. The cam controls the size of the resonant cavity, and the readout is mechanically linked to the cam. It is quite accurate (off by <50 MHz at 13GHz, an error of 0.4%). The output power (not counting cable loss which is probably significant at these frequencies) drops off significantly at higher frequencies, but it is above 10dBm at the lower range.

You can see the isolator, PIN modulator, and filter on the side. The PIN modulator allows for AM modulation.

Those are quite nice little oscillators. Typically original use was sources on RF test set-ups with slotted lines etc.
Note the ganged potentiometer on the end of the camshaft. This adjusts the oscillator bias across the frequency range. One thing they are good for in a modern lab is a low phase noise source. As long as the capacitors are OK and there is no mechanical vibration around :-)

Robert.

They look quite nice, if I didn't already have a HP 8620C & several plug-ins I would have considered buying a couple of those.

HP 86290A that I bought for $15.

I didn't have the 8620C (which is where the module plugs into), so I ended up hooking it up to two power supplies to get all the voltage rails necessary to power it. A process meter was used to set the tune voltage.
There was nothing wrong with it apart from a leaky capacitor and some broken lamps (in the front).

There is a 30dB attenuator which is why the spectrum analyzer output looks very low.

I will try to design my own PLL microwave synthesizer using this module (so the 8620C isn't really useful anyways). I will also need to design my own power supply on a PCB.

You did better than I did, I bought a 86290C from the US (parts or not working) and when it arrived I was surprized to find the N connector from the rear attached to the front with no coax attached, another none urgent project to fix at some point.  I did rescue (buy) two 8620C from the forum scrapper, one of which has the scales for that 86290C.

David

[URI]

Ah, page 5370! Hold your breath, here it is: my [hp] 5370B Universal Time Interval Counter...!


..still in my repair stack as its front end is a bit unreliable due to bad joints of a conducting material HP used to mount SMDs instead of solder.

[Vince]

Thanks people for the feedback on the 2465.


OK so worked a bit on it, as a consequence...

1) Downloaded the manual

2) Entered the service menu and wrote down all the cal constants, 100 memory locations. I also filmed a video clip as Tggzzz suggested, not a bad idea.

3) All diagnostic tests pass OK.

4) Cracked it open : indeed no NVRAM and not tants, great.

5) PSU : no need to worry about the RIFA : I pulled the PSU and turns out they had ALREADY exploded before I bought the scope ! One of them even took out some component, impossible to identify any longer if it was not for the service manual : apparently it's (was....) a 68 ohm resistor, mounted in series with the RIFA.
So will recap the PSU. It's bound to be very similar to the 2467 PSU so hopefully I can reuse some or all of the left over caps I had when I recapped the 2467, will save me some money.




6) THE FAN ! OK I see what the fuss is about now... WTF is this design 

3 problems with it no less :

#1 - Motor itself does not spin, so I need to do some electrical troubleshooting on the PSU board.... but there is zero access to it once mounted inside the scope ! 
I can only hope that a visual inspection and buzzing components, will be enough to fix it. 

#2 - The 1/4" nut securing the collet, is missing. Of course I don't live in imperial land so that will cost money to order    Maybe I can salvage one that would fit, from my hollow state Tek scopes.

#3 - Third and last problem... yes, on my scope too the collet is broken     



Tggzzz if you could post or e-mail me your 3D model, I could try to do like you did and order it from this company.... well first check how much they would charge in shipping, then add customs and all that crap. It's gonna be an expensive collet...
BTW how do you handle the metal insert of the collet ? Do you strip it of the plastic remains, then pput a drop of super glue on it the press fit your 3D collet onto it ?

In the meantime I guess I can just try to super glue it back together, might last long enough to let me fix the electrical fault in the fan control circuitry.

I really was not planning on restoring a scope right now, really not, am doing other things. So I will try to expedite these jobs ASAP and move on... if just because the scope is not safe to use, for fear of overheating the precious many ASIC's in there. So the sooner I get all that done, the sooner I can actually use that scope. Isn't it.

[tautech]

Vince, there is much to be learnt about the 2465 here:
https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/

Especially from posts by some very experienced members.....

[Vince]

Thanks wil have a look... huuuu, wow, 72 PAGES ?! 

I will ask ChatGPB to make me a one page synthesis of the thread with thumbnails I can click to go direct to the most interesting/relevant posts.

[tggzzz]

2) Entered the service menu and wrote down all the cal constants, 100 memory locations. I also filmed a video clip as Tggzzz suggested, not a bad idea.

0x100, of course

5) PSU : no need to worry about the RIFA : I pulled the PSU and turns out they had ALREADY exploded before I bought the scope ! One of them even took out some component, impossible to identify any longer if it was not for the service manual : apparently it's (was....) a 68 ohm resistor, mounted in series with the RIFA.

Yup.

Look at the prepreg under the resistor. One of mine has a 1cm diameter hole in the prepreg.

Tggzzz if you could post or e-mail me your 3D model, I could try to do like you did and order it from this company.... well first check how much they would charge in shipping, then add customs and all that crap. It's gonna be an expensive collet...
BTW how do you handle the metal insert of the collet ? Do you strip it of the plastic remains, then pput a drop of super glue on it the press fit your 3D collet onto it ?

TBH I'd prefer if you made your own, since I would like another iteration before I think it is acceptable to allow it to escape into the wild.

I made a guess as the bolt that threads into the collet, and duplicated that in resin. That didn't work very well, so I allowed the bolt to be a self tapper.

Your thought of reinserting the metal insert into the new collet seems sensible, and you might consider making it in a slightly more flexible nylon material. To nobody's surprise, homebrew PLA printers are useless - the collet instantly cracks along a seam.

This is the total cost from DirtyPCBs:

Item   Description   Price   Quantity   Total   Status
SLA #1300 24x5collet-v2.zip   SLA print: 0.63cm3 / 0.90g / White   $0.95   4   $3.80   In production
Shipping   Hong Kong Post Airmail (1-8 weeks)   $1.00   1   $1.00   
Total            $4.8   

Four off cost $4.80, including shipping in a plastic envelope. It didn't provoke any import duties, but maybe using DHL/TNT/Fedex/etc would.

ISTR seeing other people have made collets; perhaps they would be better.

In the meantime I guess I can just try to super glue it back together, might last long enough to let me fix the electrical fault in the fan control circuitry.

ISTR replacing the quad transistors with individual transistors mounted on a standard IC header. I don't see why they need to be thermally coupled.

I really was not planning on restoring a scope right now, really not, am doing other things. So I will try to expedite these jobs ASAP and move on... if just because the scope is not safe to use, for fear of overheating the precious many ASIC's in there. So the sooner I get all that done, the sooner I can actually use that scope. Isn't it.

There are contradictory statements about the specific overheating IC, U800. I saw no problems in the 24x5, but the A/B variants may be driving it harder. Nonetheless, I had a small (unheated) fan heater playing over the relevant area.

I would definitely not touch the bolts securing U400, since the seriously bad attachment mechanism causes the failures.

[Vince]

2) Entered the service menu and wrote down all the cal constants, 100 memory locations. I also filmed a video clip as Tggzzz suggested, not a bad idea.

0x100, of course

Nope, 100 décimal, 0x63, well at least that's what the service manual says   


- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
EAROM EXAMINE (Exerciser 02).
This routine allows the operator to examine the contents of any or all EAROM locations.
The EAROM has 100 (decimal) locations (63 hexadecimal).
Addresses above 63 (hex) are not defined.
When entered, the Exerciser displays the contents of EAROM location 00 (hex) on the top line of the crt display.
Calibration constants reside between addresses 01 (hex) and 4C (hex)
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

[factory]

5) PSU : no need to worry about the RIFA : I pulled the PSU and turns out they had ALREADY exploded before I bought the scope ! One of them even took out some component, impossible to identify any longer if it was not for the service manual : apparently it's (was....) a 68 ohm resistor, mounted in series with the RIFA.

Yup.

Look at the prepreg under the resistor. One of mine has a 1cm diameter hole in the prepreg.

Mine weren't as bad, some burning with blown RIFAs but no board damage, those were 30Ω & 68Ω.
Also some of the 15Ω had tiny burn marks & were open.

I used ROX05S 0.5W flameproof resistors for replacements (ROX05 would probably have been better, those are slightly larger size, similar to the originals), I disagree with the 2465B thread, these are safety critical parts IMO, I can only imagine the damage with 2W resistors if the the cap in series shorts, or thermistor in parallel goes open  YMMV.

https://docs.rs-online.com/bb13/0900766b816f9bef.pdf

David

[tggzzz]

I used ROX05S 0.5W flameproof resistors for replacements (ROX05 would probably have been better, those are slightly larger size, similar to the originals), I disagree with the 2465B thread, these are safety critical parts IMO, I can only imagine the damage with 2W resistors if the the cap in series shorts, or thermistor in parallel goes open  YMMV.

I tend to agree.

Question for when you've been at the pub for a few hours: is it better to have a small resistor that spontaneously dissassembles itself, or a larger resistor that remains composed but becomes visibly enraged?

[tautech]

Thanks wil have a look... huuuu, wow, 72 PAGES ?! 

I will ask ChatGPB to make me a one page synthesis of the thread with thumbnails I can click to go direct to the most interesting/relevant posts.

Do note some that made comments repaired and calibrated these CRO's from early days so know them well and what they are talking about. 

[TERRA Operative]

What about fusible resistors? Just spitballing....


If someone has accurate dimensions of the collet, I can draw it up in CAD.
Would be interesting to get them made in aluminium, PCBWay could do the manufacture. No idea on cost... But a run of collets could make the per-part cost not unreasonable.

[Vince]

Fusible resistors yes.... maybe Tek MEANT for these resistors to blow, ad a safety device... who knows.
So putting a beefier component would defeat the original intent / safety.

Making the collet out of aluminium I don't know... the screw part of it would just snap.
I think you really need to reuse the existing "screw" part of this part.... but agzain the question is how do you do to attach it solidly to the replacement collet, whatever material you choose to make it out of ?

[wkb]

I'd go for brass, not for aluminium. Or stainless steel, should the intent be to make the Tek survive for another 40+ years.

[Robert763]

I used ROX05S 0.5W flameproof resistors for replacements (ROX05 would probably have been better, those are slightly larger size, similar to the originals), I disagree with the 2465B thread, these are safety critical parts IMO, I can only imagine the damage with 2W resistors if the the cap in series shorts, or thermistor in parallel goes open  YMMV.

I tend to agree.

Question for when you've been at the pub for a few hours: is it better to have a small resistor that spontaneously dissassembles itself, or a larger resistor that remains composed but becomes visibly enraged?

I'd replace them with mains rated fusibles. For example Vishay NFR25H. You could possibly get way with the more common NFR25 which is 0.33W.

Robert G8RPI.

[wkb]

As for intentional fusibility: Would have been nice to put the resistors on ceramic standoffs or similar. Burning holes in FR4 is not really sound engineering practice,

[Neomys Sapiens]

As I have several step attennuators, of which too many extend only to 1GHz and none of which is in a desktop enclosure, I decided to change that!
Won this auction with 90.-, for practicality of use and to end the dry spell.

[factory]

I used ROX05S 0.5W flameproof resistors for replacements (ROX05 would probably have been better, those are slightly larger size, similar to the originals), I disagree with the 2465B thread, these are safety critical parts IMO, I can only imagine the damage with 2W resistors if the the cap in series shorts, or thermistor in parallel goes open  YMMV.

I tend to agree.

Question for when you've been at the pub for a few hours: is it better to have a small resistor that spontaneously dissassembles itself, or a larger resistor that remains composed but becomes visibly enraged?

If photonicinduction is involved, you can have spontaneous dissassembly and visibly enraged at the same time. 

What about fusible resistors? Just spitballing....

Yes fusible resistors would be even better.
https://www.mouser.co.uk/datasheet/2/418/4/NG_DS_1773218_E-717674.pdf
https://www.vishay.com/docs/28737/nfr25.pdf

Having said that, in my days as an apprentice, I tested various low wattage 4.7Ω resistors of wirewound, carbon, metal film, fusible types and they all went open circuit with gradual increasing overload. probably need to repeat this now the parts are mine. 
Higher voltage might cause flash over with some of those, I only used low voltage to test them.

Also we did have one product where the gate resistors created tiny flames (self extinguished when power disconnected), with some fake relabelled grey market BUZ64 mosfets, after the load short circuit test, some IRFxxx equivalents passed the test.

David

[Vince]

MEGGER BMM80/F Insulation DMM Repair


Got lucky, after only a couple hours it's all done, working again and buttoned back up ! 

First, got a good news in the first few seconds : the battery (was thinking Lithium something) is not dead, so no worries finding and buying a replacement..... because there is no (rechargeable) battery in there !
Just a 9V connector and a montage of x6 1.5V LR6 non-rechargeable batteries.



Corrosion : zero ! Not a drop... the case is quite well sealed.

Problem was simply the battery connector. It clearly had been worked on past. The negative wire was originally crimped, but it must have broken and the owner tried to fix that by soldering the wire onto the lug instead. Wire broke off of the joint.



Tried to solder it back, no joy : the white plastic of the connector is soooo soft that it melts like butter and falls apart, long before you have time to do any soldering action....

So I replaced that connector altogether, since I have a stock of these.

Meter now powers up ! 

I did a quick sanity check on all the "normal" ranges of the meter, works fine.
Then I tried the insulation testing feature... not knowing how it works.
It can output 50/100/250 or 500V. 500V is a bit much, but up to 250V is safe I though, to scope with a x10 probe, so I did that.

Was hoping the meter would therefore display 10Meg measurement..... But alas no.

The LCD prints an analog scale, but no "needle", no numerical value to be seen.



When I press the "TEST" button, it sounds and looks good : I hear a relay, then a loud beep, and on the scope scree I see a nice DC pulse of roughly the appropriate / expected voltage, which lasts 60= ms or so.



However once the HV pulse is gone, the meter does not display any result on the screen. No needle moving, no numerical value displayed.... nothing.

So I downloaded the user manual and found the problem : one is supposed not just to briefly press the TEST button, but to actually HOLD IT DOWN. The test runs for as long as the user keeps the button pressed.



Doing so, I can now get a measurement displayed on the screen ,and it reads 10Meg as hoped ! It works ! 



My first time with an insulation tester.... it's cool, I want one now 

Before calling it a day, I spent some time trying to fix the positive 4mm  socket, that the juice comes out of. As you can see it's in very bad shape to say the least. The "shell" of the socket , which is supposed to be a part of the casing, had broekn clean off of said casing, so bye bye socket, meter unusable. Guy apparently tried to secure it back to the casing using a mix of folder paper and some glue. Glue has come unstuck and only the paper was keeping the socket very loosely in place, somehow.



So I removed all that crap, scrapped the socket and casing clean, and glued the socket back in place with a ton of hot snot. Sounds nasty but actually the result looks much better than the previous repair / butchery, and it actually hold the socket firmly in place.  It's actually a tremendous improvement both functionally and cosmetically... I am quite happy.

Also, the thick red HT lead that goes to that socket was at the verge of parting with the socket. It was hanging by only a couple strands. I stripped it and soldered it properly. Much safer and reliable now.

The owner will get not a working meter, but a better put together and more reliable one now. All that for free, as per usual 
Hell I will be daring and see if I can extract 30 Euros from the guy, let's give it a try.


Successful repair. 

I can now go back to fixing the 2465 scope....

[Neomys Sapiens]

@Vince: congrats on that repair. The probe which goes into the three-sectored connector is exactly the same which I'm trying to convert into a Data Hold probe for the UDL44 multimeter.

[factory]

Solartron 7081 part 2, removing Schaffner madness...

Mouser delivered a replacement Schaffner fused line filter IEC block, which got fitted yesterday, the original was from 1989, glad I didn't leave it running last weekend, I really didn't enjoy the last one that smoked at work (in Cropico low ohmmeter). 





Some internal pictures, a date of Feb 1991 is printed on the inside of the casing.









I'm not impressed with whoever serviced it last, they did manage to replace the leaked NiCd with a NiMh, but left some corrosion behind. Also one of the board connectors was part way out of the socket. TER void seals from approx 15 years ago were intact before I started.





After replacing the filter block, I was surprized to see it display "resumed" when powered up, this means the NiMh held some charge. It was then left for a few hours with a 10x 100k resistor box attached, spec is supposed to be 0.01%, it's reading a bit low with the 7081 & a HP 34401A.
Note: I haven't done the 24 hour warm up/bake procedure yet, this is recommended if the DVM has been stored for a long time, need to find a blanket as suggested by tggzzz, original procedure involved the packing box, which probably got chucked 30+ years ago. The early manual doesn't have this procedure.







I did take more readings of the resistor box & Time millivolt source last weekend with a HP 34401A, but sods law the page of notes has since vanished. 

Next will be finding a RS232 lead and seeing if any of my old laptops will communicate with the 7081. In the 7081 brochure a Commodore PET is shown in one picture, something like this one.



David

[wkb]

Interesting to see a real cpu, Motorola M6809, paired with an Intel 8291 GPiB chip. I am pretty sure Motorola also did a GPIB, M68488 I think?

[RikV]

I have one of thes too. Unfortunately without the Ohms or AC options.
You don't happen to have a usable manual on the 3480B and 3484A you can share? I am unable to find something usable.

[tggzzz]

Solartron 7081 part 2, removing Schaffner madness...
...
I'm not impressed with whoever serviced it last, they did manage to replace the leaked NiCd with a NiMh, but left some corrosion behind. Also one of the board connectors was part way out of the socket. TER void seals from approx 15 years ago were intact before I started.

Would "aggressively" removing that corrosion have caused more problems?

And this is the connector that seems to need to be pushed in ridiculously hard on my 7081...

After replacing the filter block, I was surprized to see it display "resumed" when powered up, this means the NiMh held some charge. It was then left for a few hours with a 10x 100k resistor box attached, spec is supposed to be 0.01%, it's reading a bit low with the 7081 & a HP 34401A.

I always forget when the definition of the ohm and volt changed by 9ppm.

In my experience it needs ~200 measurements (54s each for voltage) or 3 hours to become stable. The recommended "True  " measurements take twice as long, so only 100 are necessary.

I did take more readings of the resistor box & Time millivolt source last weekend with a HP 34401A, but sods law the page of notes has since vanished. 

Next will be finding a RS232 lead and seeing if any of my old laptops will communicate with the 7081. In the 7081 brochure a Commodore PET is shown in one picture, something like this one.

I'm not a fan of Time mV sources, but I would trust the 34401.

The PET would have used HPIB, not RS232. I was always amazed that the HPIB was standard; I wonder how many PETs were sold because of it.

ISTR managing to get my ethernet-GPIB working with the 7081.

[TERRA Operative]

Nice work on the megger!

I have a Fluke 1587 that I bought years ago (not the newer FC model) when I was an electrician, good for popping apprentices with the 1000V setting.

[AVGresponding]

Getting somewhere with Kicad and the TE related Panaplex footprints (need to double check the NPTH size), going to build a test board.

Very good !  Thanks, now I fdo'nt have to mess around doing the same thing, you can just send me your Kicad file ! 

.. and I will just add a DIL footprint to it, wire up the traces and call it a day...

That's one messed up footprint those things have....

One must wonder what kind of a pre patent application pin arrangement study group was formed.

Very messed up datasheets too, it seems.

Datasheet I used last week;
http://www.tube-tester.com/sites/nixie/dat_arch/Sperry_01.pdf
Found another datasheet;
https://www.waynekirkwood.com/images/pdf/Sperry_Information_Displays_Catalog_1973.pdf
Oddly this datasheet gives 0.025-0.028 hole diameter for the pins, the one I used before gives 0.028-0.031. 
And fill tube dimensions are different on both datasheets, need to check which matches the devices I have, it's not the only difference in the two datasheet, display height & fill tube dimensions are also different.



Seems the large hole is not centred on the fill tube, in the Anadex counter, possibly due to datasheet error. 



Will have to finish the Kicad footprint sometime next week, hopefully I can add it here.

Close up of the slightly faulty NOS display, seems to have uneven/missing plating on the bottom segment. 



Used working one in the Anadex counter for comparison.



P.S. Friday evening was a bit of a disaster, had about 1/2" deep of water, in the workshop after heavy rain. It took several hours to clear the water, with a dumpster dived mini wet vacuum cleaner (part of carpet washer) and a mop for the rest, Saturday the roof drain was cleared of accumulated sandy mud. No TE casualties thankfully, as I know not to leave them directly on the floor, have been using wood blocks for years to prevent corrosion issues. 

David

Only just noticed that the pinout errors on my datasheet are different to the pinout errors on the datasheets you showed...