[Mondial]

Ron, it seems like you have no negative bias at all on the output tubes.

First, check the voltage on the cathodes of the output tubes. You should have +20 to +24 V, measured to chassis.

Then, check the voltage on the points marked A,B, C, D on your schematic. The voltage should vary from about +5 to +15 V to chassis, as the respective bias pot is turned from end to end.

If you don't have these voltages, check your wiring of the bias board and the connections to the output tubes and circuitry.