Electronics > Repair

Series defect on agilent 167xx boards?

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nikodem:

--- Quote from: keitheevblog on December 10, 2020, 03:33:13 pm ---Hey there,

Most of the tests that you're running via that GUI interface are the same tests. What you need to do is telnet into the box(Username:root, pw "uh,uhuh", access the shell, and run the pv command. You can hit ? for help, and most of it is self explanatory. You either select a specific module (or have it execute against all of them), and then pick which tests (or all of them) to run.

There are a couple ways to increase the verbosity of the debugging output.

Are you far enough along to know how to do those steps above?

EDIT: And yes, there's a VERY good chance that the test failures are directly related to the corrosion.

Keith

--- End quote ---

Hi Keith!

Thank you for your quick reply. I've connected the device to my networked and connected to it via telnet. I've run the pv without a problem. I will post the test results here as soon, as I finish the tests  :-BROKE.

What I'm more curious is if it is possible to pinpoint the broken trace or at least find a region, where it might be, based on the failed test or info from the pv. For example - my card failed the comparators test (as shown in the photo) and while cleaning the board from the black goo I've found, that two traces from the DAC to the comparators are broken (and I hope that this is the case with them).

keitheevblog:
Hey,

Yeah it's certainly possible, but I don't think a guide exists to help you identify the traces or regions easily.

I'd suggest looking at the service guides and manuals that describe the tests. There's about a paragraph of text per test that describes what the test does. There's also a general theory of operation section that describes roughly how the LAs work. You can use those, in combination with looking at the board, to help you figure it out.

Some tests are more useful than others. For some of the memory tests, for instance, they will identify which chip number is failing a test. That chip number isn't specific as a PCB silkscreen Unit Designator (or whatever the Uxx's are called) --- so you have to count chips to figure it out.

I can't easily look this up at the moment, but turning on enhanced debugging can help. There's switches like "d=9,p=9,r=9" that adjust the verbosity of the debug output. I don't think we've found a guide that describes what they do, but I think we assume 0-9, and I think I've done 255 before because why not? Look back through the previous threads here where they are discussed. You can see them at the command line help.

Sometimes, you can see a particular problem that matches to a trace. For instance if bit6 is always 0, when it should be a 1, then that trace could be cut. If things are intermittent, it's less clear. Now which trace is bit6? It's mostly trial and error. With these custom chips, finding datasheets isn't always possible. But things are logically laid out on the PCB, usually. So if it's an 8-bit bus, and you know it's bit6, then count 6 from the left, and 6 from the right.....it might be one of those!

You need to be able to probe the boards live, while they are plugged in. In order to confirm the right voltages/signals when the board is being tested/used. MarkL on these forums is a super smart guy --- he has techniques like installing the board in the bottom slot, flipping the chassis over, taking off the bottom cover, then probing the board.

For full disclosure, while I know the approximate technique on how to fix this stuff, I've never actually done it. There are physical challenges (access to the board while it's powered up), which also can require small pigtails to be soldered to the chips.... This stuff being SMD can be challenging to avoid shorts. Or you need to use microprobes (really small fine clips for legs of chips) which can be expensive.

I attempted repairing a couple bad boards, but it was pretty obvious it's beyond me -- partially in terms of lack of experience and skill, but mostly in terms of patience and willingness. You might be in a different place with all of that, obviously.

I hope this helps
Keith

nikodem:
Ok, so I've done some more detailed tests over the telnet, and my board failed the following tests:


* anlyBusTest
* clksTest
* measAnlyBusTiming
* cmpTest
* ZoomChipSelTest
Where I can find any info about this tests? I have a service manual from Keysight page, but there is nothing valuable about the these - they just say, thet there is a particular test. What I would want to know, if, based on the above failed tests, do you think the board is worth trying to repair it? I mean - it's fun and all ;) but if this means e.g. an 100% dead important IC then it is not fun any more to waste a lot of time.

So - any ideas about this failed tests?  :-//

MarkL:
Keith definitely has all the magic incantations for the extra debugging tricks.

Despite my obsession with trying to fix these cards, my success rate is only about 1 out of 3.  It's so unfortunate that "pv" and its capabilities is completely undocumented even now when these products haven't been sold for 20 years.

If you haven't found it yet, there's another thread that may be of some help where the DAC and comparators are discussed:

  https://www.eevblog.com/forum/testgear/agilent-16717a-comparator-and-zoomchipseltest-failures/msg3091674/#msg3091674

Even though it's not specifically your card model, it still uses the same DAC and comparators.  Agilent tried to re-use as much of the front-end design (including timing zoom) between the various modules as possible.

MarkL:
On your latest post, try turning on some of the more detailed debugging output, as Keith suggested, and just run that one test from pv.

Some of the tests will print out bit patterns and other things that it's unhappy about which may be able to guide to you tracks that are damaged.  Most of the test routines name the specific chips where the test is failing, but it doesn't mean it's the chip.

Not that I'm saying it's not a bad chip, but of the boards I've repaired, it never required a chip swap (unless you count the ones I blew up by accident myself, but those doesn't count).

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