Chasing distortion

an auto-bias circuit should also be checked. if you can't do that yourself, you should bring it to tech.

My rig can only handle up to KT 120's (4 per each monoblock), That would be neat if I could go to a 150...anyway, how's your voltage? My voltage is all over the place since we live across the river from a nuclear power plant...some times of the day - usually going into evening, it spikes to about 127v, normally during the day time it's at 120v or 118v. I was blowing tubes regularly, then installed variac transormers at each monoblock and problem solved. no more melting tubes.

^^^This.  Definitely get it serviced, you're wasting your money right now trying to replace tubes.

Get it serviced.  Probably has a blown resistor in the auto bias circuit.  Will just kill more tubes.

It has an auto-bias circuit.  I'm thinking maybe that got fried.

You need to check bias on all tubes. input/driver tubes can also go bad, but my suspicion that bad power tube could "take away" other components so bias checking is essential.