Well I hope you are not using EL34s
First, the tubes that have run away are now junk. They may not test that way on a tester, but these amps run a 6L6GC harder than they should be run. If you bias too low, the amp will lose all of its magic. For the fast and dirty bias, powering up the amp, allow 3 minutes for warm up. You will begin the bias process rotating the pots counter-clockwise as necessary for increased bias and vice-versa. Bias 610-615mV. Only allow a seven minute window of adjustment. If the unit is on longer than 10 minutes collectively, shut it off until cool to the touch (about 30 mins.). Try again.
Before doing this, R43 will need to be replaced. It is one of the cathode resistors. You can see it discolored in the photo. That is one of the parts in any of our kits. 5% of the time, the output trans will be lost before the factory resistor gives up. You do not want that. Further, it is not uncommon for them to ignite the circuit board. The numbers you are reading while biasing, are the voltage drop across the cathode resistor. So you have no idea what you are actually biasing V6 to, and the tubes on that side of the amp are heat distressing the output transformer. Personally, I would not continue to run the amp.
All of those electrolytic capacitors are at least 20 years old. The Cathode resistors are over sized. Other resistors are either under sized, over voltaged, or the wrong value. At least two resistors are transposed, and one trace error exists. D9 is a ticking time bomb, and C7, C26, C46, or C48 are likely over voltaged every time the amp is started due to no centering resistors or power supply regulation. The amp is hard to bias with 270 degrees of carbon film on a plastic substrate (the bias pot). Around $150 worth of parts, and a new set of tubes is my recommendation.
