BF Super Reverb Question

[rf7]

I'm working on a Super reverb that is crackling. It seems to originate from the mixer tube V4. I've replaced the plate and cathode resistors and the tube socket for the mixer stage. It's still crackling. Moving the eyelet board does not help either.

I've noticed that the B+ rails are kind of jumpy on the scope. And the jumps seem to coincide with the crackling. I've bridged the filter caps with new ones and I still have this symptom. Could this be caused by a failing rectifier tube?

I need to get a spare one of them and try it.

[Paleo Pete]

Clean the tube socket contacts. My SF Super Reverb just started the same thing not long ago, same tube I think, wiggled the tube and it stopped, which tells me it's a dirty contact. Wiggle your tube, or pull and replace it a few times. I just wiggled each one down the line while it was running, when I did that tube it stopped.

One of the suggestions made here was to spray the tube pins with contact cleaner and plug it in a dfew times to clean the socket contacts without spraying the cleaner into the amp. My original idea was to spray some on a pipe cleaner and use that. It works great on AC adapter plugs on my effects boxes...

[rf7]

I just replaced that socket, hopefully it isn't dirty. I'll wiggle things just to see if anything changes.

[Paleo Pete]

Sorry, my bad, I missed where you said you had already replaced the socket.

Bad tube would be very possible, especially if it's old. Beyond that I'm not qualified to even guess, there are plenty more knowledgeable folks on here who will know of other areas to check.

Arcing maybe? Turn the lights off and see if it makes a visible arc.