Trying to fix MK1 Sound board.

[DCrosby]

So I got the sound board, with a sticker (Y1 Crystal Bad Replace <1h) so someone had done some diagnostics before I got to it, and found that the crystal was bad. Which it looked like it had got knocked around, and I don't have a function Generator to check if it was still oscillating at 3.58mHz. So I ordered a new one, and replaced it, and nothing. So I did the test on the amp to see if I could find sound on the legs.. and I did it was quite low, but I didn't hear any "Game Related Sounds" just noise from my fingers over the contacts... I then took a serious look at the contacts of the amp, and sure enough the amp had some damage on the first leg, it looks like when the caps started leaking they ate through the first leg, thankfully I was able to bridge the connection with some solder.

After which it started working... sort of.. it depended how I held the board... so I suspected more issues possibly where some of the other damage occurred some of the solder points on the top of the board are pretty bad, and are breaking away, most likely from the electrolyte... so the question I have is, how do I clean the board, so that I can re-flow solder, as when I heat the crumbly traces they just turn / tarnish, and then won't take any solder...

 

[Asure]

Rinse board with vinegar and toothbrush, then clean up with plenty of alcohol. Use plenty of flux when resoldering components, hope it sticks etc.

 

[DCrosby]

So to help others out, it was that general area around the big capacitor under the amp heat sync, and a lot of those solder points were crusty/brittle... I de-soldered the two coils and all 4 tantulum capacitors around the coils .1uf I believe, and cracked one into two pieces.. I had a spare, not a barrel but a tantulum .1uf and soldered it in, and wouldn't you know it, it worked... I don't have the "Dong" at the beginning but that's also because I got a new battery and it no longer goes through the test to test each ram chip, because it remembers from the last time. It also doesn't complain about cmos coinage anymore.

So it's working I power cycled and tried to touch the chips and twist the board a bit, no change... so for me that's a fix. And I'm happy. Thank you @Asure for the tip, it helped a little neutralize the acid, in the end I just de-soldered, then cleaned with isopropyl alchohol, then went over the pad with a fiberglass pen, and then tinned the hole, and soldered the components back on.