This is a Weber kit amp. It’s a copy of a Marshall JCM800. Unfortunately expensive repair because the power transformer was shorted.
Also two of the four red JJ EL34 labels were blackened. It’s pretty normal for amps to run one side of the output section harder than the other when pushed into clipping but it seemed excessive in this case. I thought there must be some sort of bias problem. Eventually I realized the 82K and 100K phase inverter plate load resistors were reversed, so it was actually making the phase inverter drive more uneven instead of evening it out, so that would do it.