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Topics - Marshall_Lead12Guy

Trying to track down the source of 60Hz hum in a Lead 12 I picked up last week. So far, I've not fixed it. So, I could use your help, guys.

Main clue: volume pot all down or all up yields loudest hum; hum nearly disappears when pot is at 2 o'clock.

Here's what I've done so far:
(1) Replaced all electrolytic caps (they were probably over 30 yrs. old.)
(2) Removed volume pot for out-of-circuit check; 1.14M, smooth from 0 to 1.14 through rotation.
(3) Hit the whole board with the soldering iron (in case of a non-visible bad joint).
(4) Re-soldered the ground wire connections (the one from transformer to chassis, and the one from transformer to one of the filter caps).

[Probably not related to the hum, but worth mentioning: the transformer needs a varnish dip, since there's a medium-loud mechanical hum.]

I'd attach an image, but I'm new here and so don't yet have the ability to do so (as far as I can figure, anyway). I can assure you, though, that the internals are clean. All looks as you would expect.

I look forward to hearing from you. I'd love to get this figured out.