Marshall jcm 2000 100 watt red channel light is dimly on when green channel is on

[Mick Bailey]

They're Silver-mica designated C19 &C20 located on the preamp board that runs along the front of the amp. I originally replaced the treble pot because it didn't respond to cleaning and it was still very scratchy, along with the channel switching thump. When I measured the leg of the pot there was quite a high DC voltage present which wasn't getting blocked by the cap. Measured at R38 for convenience, I read 230v with the treble pot fully clockwise and 40v with the treble pot anti-clockwise. It may not be the reason for your problem, but if there's a mystery voltage present in your LED switching circuit it could be worth checking.

Edit - easy to check if it is this causing your problem - if you have an unwanted voltage see if lifting one leg of C19/C20 removes it.

[Mikeguitar]

So I turned it back on first and played through it checking all pots and switches,thought my treble was scratchy but it’s not,the only other problem I see beside the dim red led on when green channel is on is when you push the switch to go to green channel there’s a little pop