Quoted from metalkatt:
Wondering if anyone ever had problems with their sound board playing the sounds but no music? I have a playboy 35th and can't seem to get any music out of it...i get most of the sounds, though. And the weird thing is, I have a second board and it does the same thing...sound but no game music. I thought it might be the flat cable that runs to MPU but no luck on that, either.
I had exactly the same issue with my Time Machine.... Checked all voltages, changed the ribbon cable, installed new caps, pulled the sound roms etc. In the end it was a problem on the cpu-board. I got a "new" one on saturday, installed it and my problem was gone.
The old cpu board had some corrosion due to battery leakage that somehow affected the correct communication between cpu and sound board.