[RGK20m3]

Speaker is not the issue, as I have substituted another known good pm speaker, using a separate output transformer and a 1200 resistor in place of the field coil, although that was a good thought. B+ doesn’t change when the volume reduction occurs, nor does the screen supply voltage to the 6A8 or 6K7. Nothing changes in the audio voltages.
I am suspecting that there might be some voltage leakage between terminals either on a tube socket or terminal strip; there is a terminal strip adjacent to the 2nd detector that has B+ along with the grid bias reference resistors….