[RodB]

If you check all of that and still have a problem (my first inkling would be one of the 6F6s) then look at the 6J5 phase inverter plate and cathode resistors. The 51k plate load should be pretty close to the cathode 50k. Then check the 4 resistors on the grids of the 6F6s. The top pair should should measure the same as the bottom. If any of these are not matching then the amp is doing more pushing than pulling. In addition, the 6F6 grid bias should be closer to -16 volts which could be a problem with the candohm resistor.