Fender Bassman 10 issue

[bassisst90]

Hey guys. My Fender Bassman 10 has been acting up in a real weird way lately. After playing for a while, on the second channel of the amplifier, there is a sound of fire crackling/thunder rumbling whenever im not playing, and even while i am playing but not as noticable. I can lower the volume of that channel or the master volume and it goes away but when I turn it back up it comes back. I've tried to spray contact cleaner in the pots, but that didn't work. I then replaced the volume pots. That also didn't work, so I don't know what it could be. Has anyone ever run across this before?

[jjasilli]

1. always suspect tubes first.  If not, then. . .

2. Sounds like the plate resistors need replacement.  If not already done the entire power supply including filter caps, dropping resistors and plate resistors should all be replaced. 

[eleventeen]

When a Fender makes rat-noises that you can't chase down, it's best to just shotgun-replace the 100K plate resistors. That's been my experience. When they are old, they just induce a lot of spurious noise into the amp and nothing short of replacing them solves the issue.

[bassisst90]

O.K. I guess I'll try replacing the tubes and if that doesn't work, I'll replace those resistors, as I've already replaced the filter caps. Thanks guys