Good morning everyone. I have a problem with the sound of a Bally black belt, it has the TCS card. The sound goes away after a while of playing. At first it works fine, but after half an hour of playing, the sound goes away, I turn it off and turn it on again, the sound does not return, and if I leave it off for a while and turn it on again, it already has sound, but then it goes away again. If I leave the pinball with the game started, the sound does not go away, it only goes away when a switch is activated, I imagine when the cpu requests some sound or effect from the audio card. I have already cleaned the wiring harnesses, I have already changed the capacitors of the audio card and the power card, resolve all the points of both cards, in the 5v voltage of the audio card, I have 4.9v, the voltage does not vary with or without sound. The VR1 potentiometer is new, the coin door potentiometer is already clean and working well. When there is no sound, with the logic tip verify that if the request for sound from the CPU arrives. I suspect some integrated circuit. Please help!

IMG_20200519_202749 (resized).jpg

Well after going back on the electronic diagram, and thanks to the freezing spray, I discovered the cause of the loss of sound. The processor of the audio card .. mc68b09. I leave the solution for someone else. Greetings.