Crackling is usually a dirty pot. Sometimes you can clean 'em by rotating it lock to lock a few thousand times, hosing it out with some electronics cleaner, or it may need to be replaced. If you don't know your way around the inside of an amp, have a pro give you an estimate. There are things inside that box that hold large amounts of electricity for a very long time. It's not worth risking it.
Was I the only kid that charged up capacitors with a few hundred volts then:
- Leave them on the work bench, or
- Put them away.
