Mortal kombat sound board missing speech

AtomicBomb

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I am going nuts over an MK sound board that won't speak! MK y-unit board, seems to work despite being picky about voltage.

In test mode I only get 1 Bong in sound test, but in the sound play test I only get the background midi tracks. In game the midi plays then dies/goes into echo mode after maybe 1 minute.

I have checked or replaced all the caps, re-burned the eproms, replaced the YM3013 and the OKI chip (getting good at smd chips!), and the 8mhz crystal (getting pulses from the other according to my probe).

Ideas?
 
Y-units have incredibly wide voltage operation. I've seen those things run very low and I've also seen them with maroons setting power supplies to 5.9V and it seemingly did no damage! the T-units are the ones that are garbage, they suffer from some loss from powering the sound board and overall have some kind of inferior grounding issue too I think -- they also reset once they approach about 4.9V at the chips. I don't like running power supplies high, but you almost have to set them to 5.2V to get those within operating spec.

you already focused on what I would have suggested, the Oki speech chip. things probably totally worth noting: this sound board model doesn't use -5V, and the capacitors are almost always the first place you should start.

the caps on these are going bad now (JUST this ADPCM sound board type, not the CVSD or DCS [yet]), and it's pretty common to get either a lot of static or entire sounds will cut out.

I don't have the exact values on them off hand, I have a few I need to do soon actually, but Broodwich sells kits for them. I would start there and see where that gets you.
 
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