Electronics > Repair

Series defect on agilent 167xx boards?

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MarkL:

--- Quote from: fpgaarcade on March 22, 2023, 09:52:37 pm ---Thanks for the detailed response.
I can get hold of a working 1680A for a bit which looks to use the same front end? and I can probe around that. I've got access to a decent 'scope at work.
...

--- End quote ---
I don't have a 1680A, but it uses the same 40-pin probing system as the cards mentioned previously.

I was able to find a few teardown photos which show the 1680A acquisition card.  The photos weren't good enough to read the number off the comparator, but it has the right number of pins, and the layout and passives look the same on the input side.  The layout of the test clock area also looks the same.

You'll know for sure when you get it open and can verify if it's using the 1NB4-5036 comparator.

Please post your findings if you can - thanks!

fpgaarcade:
I will!

dorkshoei:
Well that's interesting.

A long time ago I bought my first 16xxxx, a 16700b.  One of the installed cards was a 16534a and it passed all the self-tests and showed valid calibration.  It seemed to work based on some minimal usage but I'd never re-run the calibration.

A year ago I bought a  mint 16702b from a local seller on Craigslist.  He assured me it passed self-tests but it turned out he thought that meant it powered on  :-/O   All three of the 16752a cards failed test (I've got two working since).   The 16720a passed self test (and failed spectacularly a week later, now every test fails).  The 16534a passed self test.

When I got home I happened to notice that C107 on the 16702b/16534a card had imploded (pic).   Given the cap type and location I doubted it was critical but not exactly encouraging.

This week I fixed the damaged pcb/cap and got around to running calibration on both the 16534a cards using a T-cable setup from AliExpress  I expected one card to pass fine and it did.  The other immediately threw "PROBLEM: either the cables are not connected properly or there is a serious problem with this module".  Continuing on only 2 of the 7 tests pass, hysterisis and trigger level.

What was unexpected was that it's the original module from the 16700b that's failing.  The one with the repaired cap is working fine.   Never assume LOL.

Question: So on the working one I'd previously removed the old runners and bought some of the recommended 3M tape.   Before I apply conformant coating and reinstall the runners and bless it good are there any other tests I should run.   I see a bunch of other tests in the service manual (hooking upto multimeter and signal generator).   

[I'll read through this thread for tips, I recall some from MarkL, on fixing the non-working card]


Thanks!

ahakman:
So I've managed to get 2 more 16752A cards working, of 3 more that I bought. After my first round of repair attempts on this batch of 3, I had one working (which I've stacked with my original 2 I repaired before, filling my 16903A chassis - but I have a line on a 16902B so it would still be nice to get all 5 cards working), one failing the ZoomAcq test, and one failing the Memory Unload Modes Test.

The one failing the ZoomAcq test seemed very suspiciously similar to the failing PLL chip problem reported earlier in this thread, so I just swapped the PLLs on the 2 boards that had problems, and now I have one card that works entirely, and presumably one that's failing both memory unloads and the ZoomAcq tests now.

Does anyone still have any "beyond repair" cards they could scavenge a PLL chip from? Or that maybe are not quite as "beyond repair" as they thought?

Does anyone have experience with where the fault would be for the Memory Unload Modes Test? Reading the service manual, that test tests reading the memory data off the card to the backplane (so presumably to the CPLD chips close to the backplane connector). The card that's failing that test had by far the worst corrosion on it. I suspect one of the vias around the middle runner (with the huge parallel bus of tracks that runs up the middle of the card), or the next 2 runners towards the "POD 1/2" side of the card - there was some very nasty corrosion there, but I just can't see anything that looks broken after I cleaned it all up. I tried probing a few of the most suspect vias on a known good card to see if I could find where they went, so I could test which one was broken on the broken card, but I wasn't able to trace some of them (inner layer traces to BGA pads I'm thinking??)

MarkL:

--- Quote from: dorkshoei on March 24, 2023, 08:59:25 pm ---...
This week I fixed the damaged pcb/cap and got around to running calibration on both the 16534a cards using a T-cable setup from AliExpress  I expected one card to pass fine and it did.  The other immediately threw "PROBLEM: either the cables are not connected properly or there is a serious problem with this module".  Continuing on only 2 of the 7 tests pass, hysterisis and trigger level.

What was unexpected was that it's the original module from the 16700b that's failing.  The one with the repaired cap is working fine.   Never assume LOL.

--- End quote ---
Just to be clear, is the 16534A that's failing its cal passing all the self-tests?  If you run it anyway, can you see any traces with a signal applied to one or both channels?


--- Quote ---Question: So on the working one I'd previously removed the old runners and bought some of the recommended 3M tape.   Before I apply conformant coating and reinstall the runners and bless it good are there any other tests I should run.   I see a bunch of other tests in the service manual (hooking upto multimeter and signal generator).   

--- End quote ---
I've never worked through the performance section.  It seems like it's a fair amount of work and wouldn't gain you that much unless you were using the card to produce verifiable test results.

The only thing I thing I think would be useful is to check is that the 50R termination is working on the specified attenuator ranges.  I don't think the 50R terminator is checked in either the self-tests or cal.  I've had attenuators where the the 50R termination relay was flaky, and one where the resistor itself was blown.

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