Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Yosser on May 25, 2026, 09:19:38 am
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This might seem obvious, but are the anode resistors included with the secondary winding resistance in the calculation below?
https://robrobinette.com/How_to_Bias_a_Tube_Amp.htm
The amplifier I wish to bias has 22R resistors in series with the anodes.
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I was thinking that you would have to subract the extra resistance somehow. Probably should use and alternate method like a bias probe or 1 ohm resistors on the cathodes and then subtract a nominal screen current value out of the total tube current to arrive at plate current. I asked AI
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Much easier than AI's response...
All plate current must flow through the 22Ω resistor. So, simply measure the voltage drop across the 22Ω and do the simple math, I=E/R. Then multiply the resulting current times the measured plate voltage to get plate idle dissipation.
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Much easier than AI's response...
All plate current must flow through the 22Ω resistor. So, simply measure the voltage drop across the 22Ω and do the simple math, I=E/R. Then multiply the resulting current times the measured plate voltage to get plate idle dissipation.
"measured plate voltage to get plate idle dissipation" is that the voltage measured at the anode or the voltage drop between the ct and anode?
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"measured plate voltage" is the voltage between anode and cathode. If this is a fixed bias amp with cathode connected to ground, that would be anode to chassis ground.
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"measured plate voltage" is the voltage between anode and cathode. If this is a fixed bias amp with cathode connected to ground, that would be anode to chassis ground.
Ah, thanks