[Mondial]

Joe, have you checked the phasing of your negative feedback connection?

In another posting you mentioned oscillations at certain volume control settings. With that replacement output transformer, you have a 50% chance of applying positive feedback as there are no phase markings on the transformer leads.

You can try exchanging the two primary plate leads and see how it affects the oscillation and the operation of the bass and volume controls. If you have a dual trace scope, checking the phase of the feedback signal compared to the volume control input signal should be easy enough.