Amiga 600 Recap Project - Trace Gone!

[cbmeeks]

Hello all. Today I'm finally getting around to starting my Amiga 600 restoration and re-cap project.

Restoration isn't totally accurate because it's actually in somewhat good shape.

The biggest issue (so far) is that at least one electrolytic cap has leaked and it appears to have destroyed a trace.

The cap is C822 and a little bit of C821. Pictures attached below.

So, my main question is where to find some good tutorials or info on repairing the PCB trace. Sorry for the quality of the scan below. I only have an iPhone and this is the best zoom I can get.

I'm going to trace the pads to see what kind of continuity I have but it's pretty safe to say one of the pads is gone.

Thanks for any suggestions and wish me luck!

https://dl.dropboxusercontent.com/u/...%20HD/C822.jpg

https://dl.dropboxusercontent.com/u/...%20HD/C821.jpg

[talybont]

Here's a video:

[ Show youtube player ]

But looking at your pictures maybe you can solve it by using a small piece of wire? But then there would be nothing holding the cap firmly in place.

[idrougge]

Just use wire.

And do note that sometimes, the trace may appear to be gone but can still be recovered underneath all the corrosion. Try to clean up with a glass fibre brush.

[cbmeeks]

Thanks for the suggestions. I haven't had a moment to watch the YouTube video from talybont but I will soon.

Last night I tried to flow some solder into the "hole" that once held the pad. I couldn't get any to go in despite using some flux.

Probing around, I could sometimes find continuity with a nearby via but it was difficult. There really isn't much left. I was able to re-tin the other four pads and check continuity. Despite scrubbing with IPA and a brush, I cannot get it any cleaner. When I put an iron to it I can immediately smell that "fishy" smell. Which tells me there is still electrolyte in there. I may take a dental pick and see if I can scrape some more but I'm concerned with doing more damage.

I might break down and buy a cheapo USB microscope. But, I'm still not sure how I'm going to repair this. This is pushing my technical limits on this kind of repair.

[talybont]

You might need to scrape off some of the coating to expose the copper underneath, for instance with a glass fibre brush as idrougge suggested.

Here's a page with some pictures and animations of how it can be done:

http://www.circuitrework.com/guides/2-3-5.html

I've had some success making a new pad with this stuff:

https://www.sparkfun.com/products/10561

In a nutshell, cut a piece that is roughly the size and shape of the missing pad (with a tiny bit extra on the sides) and then press it into place with something pointy but not sharp (like a Q-Tip). It's got a conductive adhesive on it but when you solder the new cap onto the repair pad, you really should bridge it to the trace that the original pad was connected to.

If you notice the cap doesn't feel like it's sticking, you can put a *small* amount of hot glue on the side of it so it won't wiggle. When I say small, I mean small. Don't pot the area with the glue. Just put a small dab on the side of the cap so it doesn't cover the exposed solder on the pads (not only so your future self with thank you in case you have to change that cap in the future, but also because the glue can be slightly capacitive).