No sound on Sega ST-V

[rjosal]

I just picked up one of the good old garbage can STV cabs because it had Terra Diver in it. Tried it in all my other cabs and no sound on JAMMA. If I turn up the volume pot on the board I get fuzz, but it's definitely not game sound. I expect the stereo line out will work but at the moment I don't have a RCA plug for it to test. I want to figure out why mono isn't working though. Any ideas where I should look? Caps look good. Audio amp looks like it has a tiny bit of flux residue on the solder side, but it looks good to me. Any ideas what I should check?