Whistling noise after retubing 50/50

[MP1Freak]

:? I recently installed a new matched quartet of JJ 6l6GC's in my 50/50 poweramp. 2-3 minutes post power up I could hear a high pitched whistling or whining coming from my power amp. It does not get louder with volume increase and stops when the amp is switched back to standby. It is still as audible with the volume turned all the way off on both channels and gets louder the longer the amp is on. Even with my other rack pieces disconnected it is present. I reinstalled the old GT 6l6GE's (rating 6) and the problem goes away. Three of the GC's are rated 20/2.8 and one is 20/2.9. Anybody else experience this with JJ's?
Any help is greatly appreciated.

 

[triodal]

bad JJ.Did you change the preamp tubes?

 

[MP1Freak]

Not yet, would a bad preamp tube cause this to happen? The noise is louder on the front(control side) of the amp.

 

[Octavarius]

Yes, a bad preamp tube would be the most likely source of your problem.

But that doesn't explain why the whistling goes away when you change power tubes. Look at the power tubes when you power up? Does one of them glow hot, more than the others?

Also, is the whistling on both channels? If on only one, try swapping them around and see if that changes something. If on both, I have no idea.

 

[MP1Freak]

All the tubes were glowing orange and appeared to be equally luminous.
The whistling was not channel specific. The whistling sound was coming from within the chassis. The tube supplier has recommended I try GT 6L6CHP's and has shipped them to me. I should receive them next week, I'll report the outcome.

Thanks for the suggestions.

 

[reo73]

A whistling sound is a microphonic preamp tube in the 50/50. Locate the tube and change it and the problem should be solved.

 

[MP1Freak]

Installed new GT6L6CHP, problem solved!! 8) Thanks all for the suggestions!