Keyboard Shortcuts
ctrl + shift + ? :
Show all keyboard shortcuts
ctrl + g :
Navigate to a group
ctrl + shift + f :
Find
ctrl + / :
Quick actions
esc to dismiss
Likes
Search
Re: HP 16500C looking for logic analyser boards that are functional
|
In my experience with these boards, the issues are usually around the edges of where the runners used to be - sometimes even a fair ways away from the edges. I don't know the chemistry of what's going on here, but people have suggested it has something to do with the adhesive and moisture exposure in the air over a long period of time, hence why the damage is around the edges. Any of the vias that are "tented" (aka have solder mask over them) are _usually_ ok, it's the ones that have exposed solder that you need to watch out for. If you heat them, you'll see what I mentioned before about the solder has a very powdery / dry look to it, and a bunch of weird brown goopie chunks will come out of it - it almost looks like flux, but it's not flux. I think the solder actually looks ok-ish, but may not be conductive anymore in some instances. I heat those and reflow fresh solder into them, which helps get all the brown chunks out. Also sometimes the corrosion gets under the solder mask on the traces - the traces will look normal through the solder mask, but if you scrape the mask a little bit, you'll find powdery metal again. Any trace that's suspect, try to find the components it goes to and do an end-to-end continuity check across the whole trace. You'll be amazed at what looks ok, but isn't. My Observations: Picture 1: Reflow the 4 large VIAs to the right of "OK" above where the runner was. Reflow the test pad in the middle of the track to the left of where the runner was (can barely see it in the picture on the left edge). Right at the corner of the right most track below where the runner was, there's a "green crusty" - anywhere you see green crusties, the track may be damaged under the solder mask. It looks like you may have scraped the mask back on another trace down there already, or maybe that's one that has an issue - it's a different color than the others. The 3rd one from the left where it's turning and going at an angle. Also have a look at the very bottom horizontal trace - the one that's parallel to and just outside of the runner area. It looks suspect. Picture 2: Reflow the 3 large vias - the one that's under the runner for sure will produce the brown gunk. Try to flush out as much as possible and fill it with fresh solder. Picture 3: Reflow the 3 large vias - be careful with the one on the right that's copper colored - once they look like that, they are very thin and very easy to lift off the board with too much heat. Also check that one where it transitions from the large via pad to the trace - scrape back the mask a little bit and make sure you get good solder adhesion back into the trace a little bit to that pad. Picture 4: All of those test pads are suspect in the upper right quadrant of the picture - you can see how the ones closer to the runner look grey / have green crusties around them. The ones further away from where the runner is (lower right) look more normal - silvery and shiny. Reflow the suspect ones making sure to be making good contact to the traces on either side of the test pads. Picture 5: Looks like picture 2, but slightly more visible in the picture - same comments Picture 6: All of the large test pads look suspect. All the joints on the component on the very bottom left of the image are suspect (all green and nasty looking). The "brown" look under the solder mask of the trace right in the middle is suspect. There's also a green crustie on the trace to the right of the one with the brown mark - that could be on the surface, or it could be under the mask as well. Picture 7: Basically the same picture as picture 6, but further down - again the component on the very left side of the image all connections are suspect. That's where I'd be checking right at the opening of the solder mask where the track turns into a pad for breaks. Most of the large vias / test point look bad. Did you check into if the 16500 mainframe has self tests with detailed info? Those really help to narrow things down. It's very hard to tell visually what's actually bad and what isn't, and you can spend HOURS cleaning up stuff that looks bad on the board, but probably isn't actually creating any real problems. On Sun, Nov 19, 2023 at 6:42?PM Damien Towning <connolly.damien@...> wrote:
|
to navigate to use esc to dismiss