Amp Problem

Hi there i recently dug my old Mashall mg15cdfx out of the loft, was thinking abotu selling it off. only to find out that its not working properly! on The Gain setting it works fine, a soon as i switch to the clean setting, it goes all crackley like my lead is broken except its not! Any one got any ideas how to fix this?

Dust in the potentiometer (pot) may be the cause of that. The best way to fix that is to get to the pot with a can of that compressed air they sell at office supply stores for cleaning out keyboards and blast the inside of the pot as you turn it, but don't let too much fluid get in there (cold air condenses the air and will make whatever you spray it on moisten some).

thanks dude ill give it a try!