I need a small amp for my new workout room. It's a good place to play late at night after the family has gone to bed. Until I can get something for myself, I've been using my daughter's Bad Cat 7.5 watt "Kitty Cat"; a custom amp based on the Alley Cat. It hasn't been played in a year or so but I plugged it in today and L_O_V_E_D the way my Black SE One with Starla and lipstick pups sounded through this little sucker.
But the good time did not last. The dirty channel volume dropped to about 1/3 after about 5 minutes of playing. So... I swapped the two 12AX7's around hoping to isolate the problem and the amp didn't work without both in the circuit so I couldn't (with my limited understanding) isolate the dead tube. I jumped in the truck and boogied out to my local GC for a pair of new pre-amp tubes. After putting them in the amp (which was a pain because the chassis had to come out of the cab) I was back in business - for a whopping 2 minutes. This time the dirty channel died completely. ARGH. I guess it's not the preamp tubes.
It has two EL84 power tubes which I am about to order online. What else could it be, right? Before I head down that path, do any of you tube amp gurus have any thoughts regarding the problem besides power tubes?
Here's a gut shot, if that helps.