Marshall JCM800 Ground Issue

[louierock]

I have a 1979 Marshall JCM800 1X12 Combo Amp. It sounds amamzing. However, I have been getting some annoying grounding problems. First I thought it was my guitar but it's the same problem with all of my guitars. Unfortunately, there are no ground switches on these amps like the Fender tube amps have. Can one of these be installed, or is there another mod that can be made to fix this? It already has a 3-prong plug.

Thanks for any help. Please email louierock@optonline.net

[phsyconoodler]

You likely have other issues.Did you check the house wiring where you live?What about the power tube bias?
You can get a wall socket checker at Home Depot for a few bucks and it will tell you if the wiring in your house is correct.
The ground switch on fender amps was for when you have more than one amp plugged into the same socket.You lift the ground on one amp to stop the buzzing noises.It was not designed to replace an improper wall socket ground.Lots of other things can introduce noise into an amp,like dimmer switches,flourescent lights,computer monitors and poor guitar cables.And of course,was the amp serviced in the last 10 years?

[louierock]

Thanks. The wiring in the basement is new. It does have dimmer switches though. I'll try to take it to another house to see what happens.

[mc5nrg]

Just turn the dimmer switch off.

[RedMan]

What makes you think its a grounding problem?