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Re: HP 16500C looking for logic analyser boards that are functional
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I recently repaired a handful of 16752 boards that are now in my 16903 mainframe. I repaired 4 out of the 5 boards I have, and just haven't gotten time to find the one last remaining broken track on the last one (and my mainframe only has 3 slots anyway, so I already have one extra working card than I have slots) The issue I saw the most was corrosion right where the track goes to the opening in the solder mask for the pads / pins - especially on the resistor packs that are EVERYWHERE on the card. Even under a microscope, they're hard to tell there's an issue there. If you look at the 2nd and 3rd pictures in that album - the little green blobs of corrosion right at the solder mask openings is what I'm talking about. You can see later where I scraped the blobs away, and the traces are completely open there and the pads are not connected at all. On the worst card, I ended up removing nearly all of the 330 ohm resistor packs and inspecting carefully, fixing tracks, and putting all the resistor packs back. The same is true for any traces that have "testpoints" in the middle of them, like can be seen on the left side of the 2nd and 3rd picture sin that album - there's an opening in the solder mask for the test points, and there can be corrosion there too. And if you reflow those test points, the solder itself is kindof powdery looking, and when you heat it some lumpy brown stuff comes out - I tried to reflow as many of those as possible that didn't look nice and shiny, and sometimes scrapped a little solder mask back on the edges and made sure the solder was making good contact to known good copper in the traces on both sides of the test points. I'm not sure how similar the 165xx cards are to these 167xx cards. In general, you won't find ANY of these cards that don't have some issues - even if you buy cards off of ebay that work now, they might be right on the edge of failing. I definitely did get some steep discounts for buying cards that were "used" (aka should be working) but turned out to be not working and failing the self tests.? The self test with the detailed failure report in the 16700 / 16900 is invaluable for fixing these boards. If the 16500 mainframe has that too, that will definitely help. My one word of caution is if you're testing 167xx cards in a 169xx mainframe, the chip identifiers (U53 etc) DOES NOT MATCH THE BOARDS. I had to inject some of my own faults to figure out the mapping between what the self test was saying and which chip on the board it was actually talking about (the purple wire wrap wire in some of those pictures). I think that's because the 167xx cards that are supported in the 169xx mainframe have equivalent 169xx cards that are similar, but not exactly the same. I'm guessing from the software side, they use the same drivers / same self test, but when they laid out the PCB for the newer 169xx variants of the cards, the chip identifiers were changed, and the self test is only accurate for the newer 169xx equivalent cards. I also bought a new microscope on a boom arm mount to be able to deal with these cards - it was very useful as well - the boards were too big to be able to get to all of it under my old microscope, which has a pedestal stand. On Thu, Nov 16, 2023 at 2:54?PM Damien Towning <connolly.damien@...> wrote:
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