Hello all, I have an older amp MG15CDR. Bit of a problem with it. Crackles when you turn the gain pot or the tone pot. Seems to be worse when just turned on.  Maybe it's the potentiometers need replacing? Anyone else had this problem?  I can't see that Marshall will supply just these parts.

I would like to repair it, as it is a great little amp, suits my needs well.