Jukebox Machines

Rock-ola Jukebox Audio Hum Help?
This is a Model #481The jukebox works completely, but whenever it isn’t playing a record (which is most of the time) it emits a hum. It’s not “loud”, but it disrupts a room’s quietness enough that I turn it off every time it’s not in use, which is a hassle and makes it feel less authentic/vintage, since jukeboxes in the 80’s didn’t Vintage Jukebox need to be constantly powered on and off.I’ve inspected the amplifier, and the Muting & Squelch board looks fine, with nothing blown. The power supply board in the amplifier also looks okay, but has some apparent burn marks behind several resistors. The appropriate resistors still have the right impedance though, and all the diodes are working. My guess is that the power isn’t being rectified or filtered properly, but since I have no means to test capacitors, I’m at a loss. I’ve already redone the grounding, to no avail, and tried a noise filter on the 120V input. Any ideas?I’m very comfortable with testing and/or replacing circuit components, so don’t hesitate to recommend it. You don’t have to “dumb down” your answer either.
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