[yeldarb]

Yeah, I know, this probably isn't vintage, though it isn't being made anymore.  My NORH SE9, single ended pentode makes a little noise in the left channel when I first turn it on.  Sounds like a dirty potentiometer, but the pot is not in use and is blocking all input.  Noise disappears with warm up and then the amp sounds just fine (great, actually).  Do I have a tube going bad or is it possibly a capacitor?

I'll change output tubes from channel to channel to see if the noise moves this evening, but I'm looking for opinions.

[JimJ]

Dirty pins, maybe?

[yeldarb]

I rotated the output tubes to no avail.  Then I rotated the 12ax7 pair and the noise was gone.  So, dirty pins it must be.  I am surprized.  Pleased, but surprized.  I was going to swap out the Mullard 5ar4 rectifier next and I hated to think that was causing problem.