So, the V4 power tube (KT66) in my JTM45 is redplating pretty badly when I'm diming the amp. Also, the volume has been cutting in and out slightly, but with the redplating, I'm wondering if this is just a case of a bad tube, or a problem with the inner workings of the amp. The bias shouldn't be a problem, I set it a few days ago to an idle current of about 40 mA (I bias my tubes pretty hot). I'm about to leave for school again and won't have much time to trouble shoot this, I was just wondering if anyone had any quick ideas as to what could be causing this.

I know I should switch the power tubes around to check to see if its a tube problem or socket problem, but if its a socket problem, does anyone have any clues as to what could be causing this? Parasitic oscillations maybe? I'm pretty sure my lead dress is ok... I'm not sure, upon looking back in the chassis, I guess there are areas that could be tidied up a bit. But I want to see if there are any other possible causes before I pull out the old soldering iron again. The tubes themselves have already redplated once very briefly (both V4 and V5) when I was first testing the bias circuit, and I know that this puts them on a sure path towards death. But currently, only one of the power tubes is redplating.
Last edited by al112987 at Sep 1, 2008,