01-07-2014, 03:46 PM
How are you measuring the 71A bias voltage? These tubes are biased with a combination of fixed and cathode bias, so you can't measure the grid bias voltage with respect to the chassis. It must be measured from the filament to the grid instead.
Actually, all of the model 20's voltages are measured with the filament as reference, as a tube socket test adapter was used for the measurements.
Actually, all of the model 20's voltages are measured with the filament as reference, as a tube socket test adapter was used for the measurements.
