I figured I would use this thread instead of creating a separate thread, to post a repair log. I'm working on a Hook right now, and it had a curious sound board problem. This is the 5050 sound board with the BSMT2000 chip.
You'd get the "hook Hook Hook" start up call out, and you'd get the I hate I hate I hate Peter Pan call out in attract, but when it started advertising "Lethal Weapon 3" in attract, the music would stick, you'd end up with the beginning of the music then a long sine tone would just stay on forever. If you turn it off and back on, it does the exact same thing.
if you go into test mode, the voice rom 1, voice rom 2 would work, the sine test for left/right/both speakers would work... but as soon as you tried Music 1 the music would play for 5 seconds then lock on. If you instead tried to play Music 2, nothing would happen, but the sound would be dead from them on. Music 3, would lock on... Music 4 would do nothing but the sound would be dead. As soon as you played any music, the sound would either lock on or be gone until you reset the game.
If you started a game, you'd instantly have no sound because it would be trying to play music! There's very little info out there about these boards, but the two V roms are just as they are labeled, the call outs. The U7 rom is the music, but also has the software to run the sound board... the sound board will run without the two voice roms but will not run without U7. It will not run without the 6809, and it will not run without the BSMT2000 chip.
Ultimately what fixed it was a new 6264 ram, now all the music works great. If you run into problems where the music hangs or crashes, change the ram!
Hope this helps resurrect some of these sound boards!