mark IV occasional problem...

[JimAnsell]

my mark 4 occasionally starts to get this loud, annoying, windy/staticy sound goin on when it idles after being on for a long time.
i thought maybe it was my pre amp tubes, so i swapped them out for some other ones, and its still doing it.
it stops temporarily when i smack the cabinet, but then it just comes back.
any ideas?

 

[disassembled]

Might be a cold solder joint or the power tubes. A lot of the JJ tubes I used exhibited noise like this.



Greg

 

[psychodave]

Sounds like tubes to me. Try tapping on a tube when the noise starts...try using a pencil and tap it softly or wiggle it. May possibly be a tube socket :idea:

 

[Tuna141]

My guess would be tubes too - especially a preamp tube.

 

[Boogiebabies]

I had the same thing with a C+. It was a dirty Volume 1 pot.