I just restored a Pinbot and I'm having a similar problem. My speach works all the time but my sound fades out. It's not bad but it happens about every 10 games or so. The speach will be fine but everything else is silent. Usually the sound comes back within 2-3 minutes so I haven't even looked into the problem. When I replaced my CPU rom but not my sound rom. I think that's probably my issue. Do you have new sound rom also?