Touchmaster 7000 fan interference

ManiN

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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?
 
The big fan on the cabinet or the little one on the processor?

Sounds like a grounding issue. try running a ground jumper from the sound board (if it's separate) to the power supply.

Or maybe replace the fan...
 
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...
 
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