I just picked up a touchmaster 7000 and it appears when the cooling fan is plugged in there is some electronic interference that is a buzz coming out of the speaker. It isn't crazy loud, but loud enough. Any ideas to filter it maybe?
That's a good idea. Not sure where the sound portion is, I think it's all in one board.
The fan is the main one over by the power switch. I tried switching others in to see if there was improvement, but the interference is still there. It's a merit conversion, so maybe they didn't hook up a ground with the touchmaster kit board?
Possibly. As I'm sure you know, the hum is caused by AC feedback in the sound section, possibly on the +12 line. Usually I see this a lot in old jukeboxes. Attaching a ground wire from the amp to the power supply usually makes it go away.
I think others have dealt with a similar issue on Nintendo games like Donkey Kong by installing a cap across the tabs of the speaker to filter it out, but it can have the side effect of possible changing the game sounds a bit.
You may also look at the board to see if there are any filtering caps near the speaker output connector that you can change out...