Weird Noises

[usastrat1985]

I have a Marshall JCM2000 TSL602. It squeals with the gain on the lead channel turned more than 3. Also, when you start it up and take it off standby it makes crackling/popping noises. It is not a microphonic tube. I have tapped all of them and they made no noises. Any ideas? Thanks.

 

[Trick]

Sounds like a preamp tube. Try switching them around or if you have a spare replace them one at a time. As far as that popping is concerned, that can be normal on some amps regardless of brand. You might have a capacitor that has gone out of spec in that part of the circuit that may cause that popping if it wasn't there before.

 

[usastrat1985]

is it normal for it to do it for several minutes? i don't know if it ever stops. also, i don't know much about amps, but how can switching tubes around fix the problem?

 

[Trick]

is it normal for it to do it for several minutes? i don't know if it ever stops. also, i don't know much about amps, but how can switching tubes around fix the problem?

As far as the popping goes it very well could be a bad power tube or a capacitor problem if it's a constant while the amp is on. The squeal on the other hand could be a preamp tube (the smaller ones) by swapping them out one at a time, you'll find the bad one if that's the issue. A preamp tube doesn't have to be microphonic to cause that squeal.

 

[usastrat1985]

well i know i had all the capacitors replaced. so how do i check if if a power tube is bad? also, do i need to get another preamp tube or can i just do like someone above said and switch each of the preamp tubes to a different slot? thanks.