After going round & round with this damn sound issue I finally got it solved . Not only was this thing humming loudly with the attract lights, but also found the sound would not go low either. I would turn the sound potentiometer all the way down , but this thing would stay loud. If I unplugged the connector for the volume, it would go quiet and the humming would go way down, so it's got to be a bad potentiometer right? Ran off to Pinball Life and got a new 10K volume potentiometer. Installed it and NO change. WTF???? Clay has written quite a bit on this issue on system 11 A's sound, so I decided to fire an email off to him. As I was writing and describing my issues it dawned on me that it had to be in the volume control circuit. I almost ran back to the machine and decided to pull each of the 3 pins in the molex connector and there it was, a cracked connector pin. I re-pinned all three wires and like magic, the hum was gone and my volume control is perfect!
How many times must the obvious be overlooked.....re-pinning connectors!