While not radio related, it is still vacuum tube related!
After red plating the output tubes in the right channel once too often, today I replaced the bias potentiometer in both channels. They were old and the wiper of one the pots was “lifting up” and allowing the output tubes to “run away”. This does nothing but shorten the life of the output tubes.
I will also be converting the amp to “triode mode” for a more mellow sound at reduced output power. Since I no longer “crank it up”, this is a fine tradeoff.