prophei said:As far as I had read someplace, I am accounting for the load of the microphone by a resistor at the output of the board that would go to the mic. The resistor I am using at the B+ output is a 270K resistor.
Quick calc from Dany's values on the mic schematic I got 213,333k ohms for a B+ dummy load resistor. A incorrect dummy load value may throw you for a loop. Maybe your 270k isn't enough load. If I had time, I'd measure mine with your 270k dummy load and see what mine does but unfortunately I'm busy. 17 ohms for H+ (2 watts!). Don't worry to get exact numbers here, just ballpark. Every tube will be different. I set up my PS with a load resistor to get close-ish but definitely not exact. If I can't dial H+ or B+ in precisely, I then change PS components to get where I need to be.