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Agilent 16717A Comparator and ZoomChipSelTest failures
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keitheevblog:
Hi there,

I've got a misbehaving HP 16717A for my 16700A hp logic analyzer. The module had previously worked fine but has started throwing these test failures lately. I've been carefully removing the plastic runners from all my modules, cleaning them using IPA, applying a conformal coat on the runner areas, and then reapply the runners. Using a 3M ESD-safe electronics vacuum, I vacuumed both sides.

This particular module had the runners and old adhesive removed, and the area cleaned with IPA. A nearby 25 mil test pad looked dull and crusty, so I used a gentle brush with IPA. That didn't really do it, so I applied Deoxit D5 to the area, scrubbed to no real avail. I thought that the cleaning broke the trace on one of the sides of the pad, so I carefully scraped the soldermask off the trace, and measured a good tone between either side. And all the way to the yellow 16-pin (4816P-B07, film resistor, I think) packs. The trace isn't broken.

The blade now fails self-testing with cmpTest (Comparator test), and the zoomChipSelTest (Zoom Acquisition Chip Select Test)

Testing using pv with "debug d=9 r=9"

--- Code: ---pv> x cmpTest
  Check POD1 Thresholds:
    Slot C, Chip 9: B BBBBBBBB BBBBBBBB  B BBBBBBBB BBBBBBBB  Cal Clk No Act.
    Slot C, Chip 8: B BBBBBBBB BBBBBBBB  B BBBBBBBB BBBBBBBB  Cal Clk No Act.
    Slot C, Chip 9: B ....BB.. .B.BBBBB  . BBBB..BB B.B.....  Cal Clk Levels
    Slot C, Chip 8: . BBBB.BBB ........  . B....... ........  Cal Clk Levels
    Slot C, Chip 9: B BBBBBBBB BBBBBBBB  . ........ ........  Cal Clk Activity
    Slot C, Chip 8: B BBBBBBBB BBBBBBBB  B BBBBBBBB BBBBBBBB  Cal Clk Activity
  Check POD2 Thresholds:
    Slot C, Chip 9: B BBBBBBBB BBBBBBBB  B BBBBBBBB BBBBBBBB  Cal Clk No Act.
    Slot C, Chip 8: B BBBBBBBB BBBBBBBB  B BBBBBBBB BBBBBBBB  Cal Clk No Act.
    Slot C, Chip 9: . BBBB..BB B..B..B.  B ........ .BB.B...  Cal Clk Levels
    Slot C, Chip 8: . BBBBBBBB ........  . ........ .BB.BB..  Cal Clk Levels
    Slot C, Chip 9: . ........ ........  B BBBBBBBB BBBBBBBB  Cal Clk Activity
    Slot C, Chip 8: B BBBBBBBB BBBBBBBB  B BBBBBBBB BBBBBBBB  Cal Clk Activity
  Check POD3 Thresholds:
    Slot C, Chip 9: B BBBBBBBB BBBBBBBB  B BBBBBBBB BBBBBBBB  Cal Clk No Act.
    Slot C, Chip 8: B BBBBBBBB BBBBBBBB  B BBBBBBBB BBBBBBBB  Cal Clk No Act.
    Slot C, Chip 9: . BB...... ........  . BBBB..BB ........  Cal Clk Levels
    Slot C, Chip 8: . B...BB.. ....B.B.  B BBBBBBBB BBBBBBBB  Cal Clk Levels
    Slot C, Chip 9: B BBBBBBBB BBBBBBBB  B BBBBBBBB BBBBBBBB  Cal Clk Activity
    Slot C, Chip 8: B BBBBBBBB BBBBBBBB  . ........ ........  Cal Clk Activity
  Check POD4 Thresholds:
    Slot C, Chip 9: B BBBBBBBB BBBBBBBB  B BBBBBBBB BBBBBBBB  Cal Clk No Act.
    Slot C, Chip 8: B BBBBBBBB BBBBBBBB  B BBBBBBBB BBBBBBBB  Cal Clk No Act.
    Slot C, Chip 9: B ........ .BB.BB..  B BBB....B ........  Cal Clk Levels
    Slot C, Chip 8: . BBBBBBBB B..B.BBB  B ........ .B......  Cal Clk Levels
    Slot C, Chip 9: B BBBBBBBB BBBBBBBB  B BBBBBBBB BBBBBBBB  Cal Clk Activity
    Slot C, Chip 8: . ........ ........  B BBBBBBBB BBBBBBBB  Cal Clk Activity
> Slot C: Comparator Test Failed!
Mod   C: TEST FAILED       # "cmpTest" (2, 2, -1)

--- End code ---

So those are U8 and U9, which are the HP 1NB4-5040 ASICS. A normal passing test has "all decimal points." Not sure what the B indicates -- but it sure looks like something's hosed.

Next, the Zoom test fails spectacularly, seeing lines like


--- Code: ---      Actual = 0x8808, Expected = 0xadff
      Actual = 0x8808, Expected = 0xadff
      Actual = 0x8808, Expected = 0xadff
     Slot E: FISO #2 failed.
    Slot E: Checking FISO #1...
      Actual = 0x808, Expected = 0xad5a
      Actual = 0x808, Expected = 0xad5a
      Actual = 0x808, Expected = 0xad5a
      Actual = 0x808, Expected = 0xad5a
      Actual = 0x808, Expected = 0xad5a

--- End code ---

and


--- Code: ---      Actual = 0x808, Expected = 0xad5a
      Actual = 0x808, Expected = 0xad5a
      Actual = 0x808, Expected = 0xad5a
      Actual = 0x808, Expected = 0xad5a
      Actual = 0x808, Expected = 0xad5a
     Slot E: FISO #3 failed.
    Slot E: Checking FISO #2...
      Actual = 0x8808, Expected = 0xff5a
      Actual = 0x8808, Expected = 0xff5a
      Actual = 0x8808, Expected = 0xff5a
      Actual = 0x8808, Expected = 0xff5a
      Actual = 0x8808, Expected = 0xff5a
      Actual = 0x8808, Expected = 0xff5a
      Actual = 0x8808, Expected = 0xff5a
      Actual = 0x8808, Expected = 0xff5a

--- End code ---

While sadly I think I broke my kind-of-expensive board, what the heck do you think I did? Did some part fail? Deoxit get stuck underneath a chip?

I don't have the skill or experience (access, or tools, honestly) to probe this board live. I'm just about ok writing this thing off, but wouldn't mind learning from my mistake.

I use a 3M mat with wriststrap religiously, careful with how I hold the board, what I touch.....I don't think it was ESD, but who knows?

Thanks for any guesses or manageable next steps.
Keith
MadTux:
Those Deoxit sprays are cancer to electronics. The acid in these first dissolves oxide layer and then eats away good material.

I'd put that board into dishwasher or otherwise clean it with plenty of water and blow it dry afterwards with compressed air to get rid of any Deoxit residues
keitheevblog:

--- Quote from: MadTux on June 09, 2020, 10:04:04 am ---I'd put that board into dishwasher or otherwise clean it with plenty of water and blow it dry afterwards with compressed air to get rid of any Deoxit residues

--- End quote ---

Sounds like a good idea. I was using IPA after the deoxit, but even the smallest spray on the lightest setting it goes all over.
MarkL:
Hi Keith,

Does the self-test result in the same failed bit pattern every time?  Just wondering if something might be floating and settling to random values during each test.

It's been my experience that the first thing "pv" reports is bad is the thing to go after first.  The tests displayed after that could be a consequence of the first failure.

If it's the comparator test, you might want to look closely around U34, which is on the top side near the bottom edge.  It's an AD7841AS octal DAC (44-pin QFP) which provides the threshold voltages to the 1NB4-5036 comparators near the connectors.  It's parallel load, so perhaps something has happened to nCS, or the bus/address lines leading to the chip.  Also verify power and ref input pins are sane.

Could be anything with these boards, but at least it's a place to start.

EDIT: Fixed minor typo.
keitheevblog:
Thanks much for chiming in Mark! I was about to ping @doricloon or @docben or some of those guys in the other thread, too!

Yes, the comparator test is the first one to fail. I'm almost certain that the Zoom test is failing as a result: from the service guide 16715-97003,


--- Quote ---"Zoom Acquisition Test. The Zoom Acquisition Test verifies the data inputs to the 2GHz TimingZoom acquisition memory and that the TimingZoom acquisition clock is at the correct sampling frequency. Test data is created by clocking the comparators test port. "
--- End quote ---

So if comparators are failing, then this test would fail as well.

Maybe this naive question, but what's the best way to measure these voltages live? I've got some wirewrapping wire(AWG30) that I could solder to the pins in question on the DAC, and then run them out the side of the chassis. I don't see any other way to probe them in-situ.

There's nothing obviously wrong at first glance but I have to dig in. I'll rerun some tests and get some more data points.

Thanks
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