Frogger sound question.

I have a Frogger machine with a bizarre sound issue. The board was tested on another machine and seemed to be fine (cant guarantee though as i wasnt there). On my machine when I power up and put credits in, the sound works. I can put 100 credits in and it plays a sound each time. As soon as I press player 1 or 2 the sound quits. There is no sound during game play. Reboot the machine and repeat, same deal.

Any ideas where to start or what to look at?

Thanks