Bias adjustement pots.

What is the best way to check the correct performance of the potentiometer(s)?
See the article by Dejan V. Veselinovic
appreciate for interesting article!

less-likely the DC-component may be from the tube amps due to the damaged trim pot since they have an output transformer.
on the other hand I can test the quiescent output directly before the transformer and see if it's present there.