I am in the middle of modding a Fender Bandmaster to accept EL34's. It is a '71 Bandmaster Reverb that has already been black faced. I have taken the mod from Ken Fischer (Trainwreck) referenced in Aspen Pittman's Tube Amp Book. I've completed the whole mod except one resistor and the biasing of course. My problem is that the article says, "Increase the value of the resistor in series with the bias diode to reduce the bias voltage to obtain proper bias. This will vary from amp to amp..." So, does anyone have an acceptable value for a black face Bandmaster/Super Reverb, etc. that would save me much time from guessing?