X-Men no sound, then cap replacement, now sound + static

cr4zymanz0r

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X-Men no sound, then cap replacement, now sound + static

So, I took a gamble and bought a 4 player X-Men PCB that was known to not have sound. The sound board had not been tampered with, so I cleaned off the paint with q-tips and rubbing alcohol. Some traces definitely looked corroded.

I removed all the old caps, cleaned everything up the best I could, tested all the traces on top with a multimeter and found around 9 traces that did not have a connection. I got some new caps (non-surface mount for easier installation), repaired the traces, then tested all the connections on the top of a chip with a multimeter. Everything seemed good at that point.

Next I went to test and at first the static was so loud that I couldn't hear any of the game sounds, but after a minute or so nearly all of the static was gone, then after a couple of more minutes came back, but the game sounds were still audible at this point. I poked around at the chip and capacitors with a toothpick while it was running, but that diddn't really seem to change the behavior.

Here's a video I recorded so you can hear for yourself https://www.youtube.com/watch?v=hlDp3euolX4
It sounds more annoying in person than it does in the video.

I know sound issues with these boards are common, but it seems like the main remedy is replacing the leaking caps. Has anybody experienced these static/popping issues after a cap replacement? i'm hoping someone can help pinpoint me to a point of interest such as "oh, that definitely sounds like a loosely connected trace" or "yep, the ____ component is to blame when it sounds like that".
 
You might have to desolder the chip and look at the bottom to see if the chips/traces on the bottom ones are fine. (That's if all the traces/capacitors are correct on the top)
 
You might have to desolder the chip and look at the bottom to see if the chips/traces on the bottom ones are fine. (That's if all the traces/capacitors are correct on the top)

this. that chip is unique. it actually isn't solid to the base of the board, it's like a double-sided chip hovering in the middle of 2 pillars. that said, if the caps leaked through the traces they can spread down there too. then it gets really nuts.
 
Now i'm really confused after more testing.

(Note: When I first got the board I tested it to make sure everything but sound worked. Everything else appeared fine, and the sound was silent.)

I decided to start removing capacitors in groups and test after each removal to see if it was any particular set completing a circuit that was causing that static in the sound.
Static remained after each test, even after all the caps were gone. I even removed the wires and such I used to patch the traces. So with no caps it has no regular audio, but still has static hissing and such. Now I'm really confused since that wasn't present when I tested the board prior to removing the caps.

I don't know if the rubbing alcohol toothbrush scrubbing action grazed the bottom of the board a bit too and disturbed a trace that was barely hanging on or what. If anyone knows why it's acting this way let me know

In the mean time, I guess I'll have to start working on the tedious task of desoldering the board. It'll probably be a day before I really have time to start on that task.

EDIT: For clarification, the static only starts once the game has booted past the initial ROM check screen.
 
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Ok, I desoldered the sound board and sure enough there was some corrosion on the underside as well. Luckily it's not near as bad as the top.

Does anybody have a pinout of the bottom of the 054544 sound board? I could've swore I saw one somewhere a week or two ago, but now I can't find it again. I need to verify these traces around the corrosion, but it's not obvious where all of them go just looking at it.

EDIT: Found the pinout I saw before: http://forums.arcade-museum.com/attachment.php?attachmentid=219905&d=1430472756
Tested and found 2 bad traces, and 2 more that had about 10 ohms resistance (not sure if that's enough to be considered bad).
I'll get around to doing the repairs tomorrow, but I debating if I should wait until I get a socket to put the sound board back on the PCB. I'd hate to directly solder all 64 pins back in and possibly still have issues.
 
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FIXED IT!

Repaired the 2 bad traces on the bottom, and went ahead and patched the two with a slight bit of resistance just to be safe.
I got impatient and didn't want to wait for the socket to come in, so I went ahead and soldered the sound board back in since I couldn't find anything else wrong with it. Works fine now :)

Here's some pics I took of the board after the repair. Tiny surface mount soldering is not my strength. http://imgur.com/a/whA12
 
people on here told me I was a jerkoff for using radial caps.

I was able to save myself the trouble of jumper wires on a Lethal Enforcers I fixed though, using the legs of the caps I went straight to the pins on the edges. the 6-player X-Men (!!!) I did I had no problems with traces. that one went a lot smoother. once again however, radials.

I'm about functionality over aesthetics any day. so sue me. good job fixing it.
 
FIXED IT!

Repaired the 2 bad traces on the bottom, and went ahead and patched the two with a slight bit of resistance just to be safe.
I got impatient and didn't want to wait for the socket to come in, so I went ahead and soldered the sound board back in since I couldn't find anything else wrong with it. Works fine now :)

Here's some pics I took of the board after the repair. Tiny surface mount soldering is not my strength. http://imgur.com/a/whA12

It looks cool, I like it. Nothing beats the feeling of actually fixing something yourself, especially when you think you're gonna accidentally fuck it all up even worse than when you started.
 
It looks cool, I like it. Nothing beats the feeling of actually fixing something yourself, especially when you think you're gonna accidentally fuck it all up even worse than when you started.

that's 98% of the thrill of the job.
 
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