neo geo 4 slot/general mobo repair troubleshooting

[burgerkingdiamond]

I'm trying to get a 4 slot Neo Geo MOBO for an upcoming cabinet build. I've found a faulty one on ebay for $80 with no working sound. I'm pretty handy with a soldering iron and I have a multimeter and whatnot, but I wouldn't really know where to start on troubleshooting this thing if I were to buy it since I've never repaired something like this (I've fixed stuff that I've fucked up plenty of times, but at least I had a good idea of exactly what I fucked up).

So tips from experienced members would be appreciated. Thanks!

[beatsgo]

Did the seller mention anything about what caused the motherboard to not output sound? One common issue I hear is the LM324 amplifiers might have gone bad. The capacitors or resistors connected to the LM324s might have gone bad too. You can find more detail on this (no pictures though) neo geo thread.

[burgerkingdiamond]

Did the seller mention anything about what caused the motherboard to not output sound? One common issue I hear is the LM324 amplifiers might have gone bad. The capacitors or resistors connected to the LM324s might have gone bad too. You can find more detail on this (no pictures though) neo geo thread.

the guy has several 4 slots for sale. A few have sound issues and there are some other problems too that I don't remember.

thanks for the link. I'll probably get it and just hope for the best. For $80 I think it's worth a shot. After reading about Opt2not's success repairing that Raiden DX board which he got for an obscenely low price I feel inspired to take a chance on it.

I'll post up results.

[burgerkingdiamond]

after some research I'm pretty sure that I know exactly what happened to this board.

Only the single slots are Jamma compatible. The rest are nearly, but they're wired for stereo sound. I read online that plugging an MVS mobo into a Jamma harness can damage the MVS amp. I'd be willing to be that's exactly what happened to all these 4 slots. It should be pretty easy to figure out which components need to be replace. So I'll definitely give it a shot.

[opt2not]

Yay, glad you got inspired from my repair!

My tips are, start off with the standard checks:
- Thorough Physical check. If you have a magnifying glass, or jewelers loop, it would make your life a bit easier. Check the traces around the audio section, caps for bulging (probably just best to replace 'em), any scorching, etc...
- Voltage check for sure. I hear weird issues with sound and video can happen when the voltages are too high on the board. Make sure to check off the board, so that you get the proper reading under load.
- Clean the edge connector traces. I use an eraser.
- If you got a logic probe, might be good to poke around the audio section and see if there's any weird behaviour hanging about. If you can find out the specs on those amp chips, meter them out and see if they're dead or not.

Hopefully it's a simple fix for you. $80 for a 4 slotter is a pretty awesome deal too!