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Neo Geo MV4 - Corrupted Music?

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xodaraP

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Hi all,
I have a Neo Geo MV4 with what I believe is corrupted music - I do get some music but it sounds like I am missing a channel in some games, and when those channels do kick in all I get is a very loud stacticky version of what I should be getting. Neo Geo tune is fine, sound effects are fine and when there is no music playing, I get perfect sound

I have confirmed all connections on CN 8, 9, 10 and 11 are good and the board has just been recapped

All 4 slots have the same issue which leads me to think it's the bottom board sound section - but I am not 100% sure and don't have a known good top board to test (ironically my other 2 top boards have no sound at all)

I am currently uploading a video of the issue, Sengoku shows it particularly well. Zed Blade sounds like it's missing half the music in the attract mode
 
I was thinking that might be the case, but was hoping it wasn't the top board :(

The exact same issue is across all 4 slots - is that still likely to be the top board?
 
The boot audio uses FM only so thats why it sounds fine, check the SD signal pins on the prog board cart slots and between the audio ics.
 
Yeah the FM audio is fine from carts as well - it is the digital audio giving me trouble and that's why I wasn't sure if it was the DAC on the bottom board or something on the top

I will start beeping out connections on the top. Thank you for your help
 
So I found 2 bad traces and repaired them and it’s lighting up. I now have full sound but it’s corrupted so still missing data somewhere

I’ve beeped out everything related to the sound section going to the interconnects, time to start looking between the ICs
 
Ok this is a difficult one. All 4 slots are having the issue so it has to be a bad trace on a bus

I have beeped out everything from the interconnects back to each IC to make sure everything on the bus is connected and haven’t found anything

It must be a trace that is barely holding on and beeps out but when carrying data isn’t fully working, or one of the line buffers is bad
 
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Ok I have tracked down the issue to the transceivers at D6/H6/M6/S6

Inputs and outputs look the same, unsure where to go from here
 
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