I have a 1984 Marshall Lead 100 Mosfet I got used about 2 months ago and I've had a slight problem since I got it. The Gain knob doesn't seem to actually change the gain, it is a push pull knob for two separate types of distortion, pushing it and pulling it changes like it's supposed to, however turning the knob up or down seems to do nothing, the physical knob turns but the amount of Gain stays exactly the same, the sound is distorted when switched to overdrive, but it seems like it's stuck around 7 or so judging from the sound, I know the knob isn't loose because I took it off and tried turning it up and down without it to no avail, any help would be greatly appreciated!
Last edited by pratliff at May 22, 2015,
Spray contact cleaner like DeOxit into the pot. Obviously turn it off and unplug it first.

If that doesn't work take it to a tech.
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TOOOO many T.C. Electronic Pedals. . .
How much would it cost to have that done? I've never worked on an amp before and I'd hate to screw something up