Marshall G80RCD Loud Squeal OD1 and OD2

[misterc57]

Hey Folks

Just installed a new proper 6 pin input jack on this amp.

Clean channel works fine. OD2 has a horrible squeal as the Gain Pot is turned up. OD1 also but not as bad as OD2.

Any suggestions?

Thank you, MC

Marshall+G80RCD-G100RCD.pdf

[Jon Snell]

There is a possibility that the jack socket has a bad ground or even inserted 180° the wrong way around. (Yes, I've seen it a few times).

[misterc57]

Turns out the main issue is a bad Gain pot. A lot of dead spots even after disassembly and cleaning.

A few other pots need to be replaced as well.

Thank you!