I just picked up a 85 Gottlieb Rock and put in the Rock Encore sound roms, worked fine then I shut it off and next time I turned it on I increased the volume a bit and now it will only play the drum track but no bass line, the SFX for the switches/targets are all there and the melody in the main theme but the Bass line is gone which sucks as its great. Is it the volume pot or the roms? Any advice is appreciated.