20/50/2 EL34 Bias

Power Amps
1

Looking to retube my 2/50/2. What’s the recommended bias range? maybe around 30mA per tube? I obviously require matched pairs correct? I think it’s time for a retube - been about 10 years and just seems like it lost its vicious punch. Thanks!

2

Hello, Here is the info that you requested;

Two/Fifty/Two Bias Procedure

  1. Connect signal generator, scope and 8Ω100W non-inductive load.

  2. With both Standby switches ON, set output tube bias with voltmeter connected

between one output transformer primary plate tap (Blue or Brown wire) and

center tap Red wire).

a) Set Bias to 38mA. Typical voltage from B+ to brown or blue primary wire is

1.45 VDC. Keep sides within 20% of each other. 1.45V / 38.5 Ohms = .038A