JTM622 (2x12) transformer hum, physical and through speakers


New Member
Mar 20, 2022
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Hi. I have a JTM622 that I've owned since new.
It recently started to have a loud 'buzzing' sound, that stopped when I pushed down hard on the handle etc.
After opening the unit up and tightening the transformers screws I have greatly reduced it down to a gentle hum, but now I have noticed that this humming is also being transmitted electrically through the speakers.
It's not 'end of the world' as it's at a much lower volume than the actuall guitar, but any ideas what to check or measure to see if something is wrong?

If you Google; Jtm622 wiring diagram

The first thing that appears is the schematic, the second is a picture of the circuit boards etc from a 622.
Sorry, can't post links at the moment as I'm a newbie