In Reply to: RE: "a 1 watt film resistor should do quite well" posted by 1973shovel on July 22, 2012 at 12:29:16:
But just like selecting a real fuse you have to evaluate the circuit!
You have to consider the current capability of the tube. I use 2 watt resistors in the Cit II with the KT-88s - for EL34s I normally use 1 watt. For EL84s or lower wattage tubes you can often get by with 1/2 watt. There is no single hard and fast rule...
But in considering the cathode circuit you must consider all the possibilities - bias current is not the only thing the resistor sees. Put a scope probe on the cathode pin of the power tube when music is playing - you'll see other waveforms too.
Too small a resistor and the resistor will pop unnecessarily.
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Follow Ups
- RE: "a 1 watt film resistor should do quite well" - Jim McShane 13:35:08 07/22/12 (1)
- RE: "Put a scope probe on the cathode pin of the power tube " - 1973shovel 13:59:03 07/22/12 (0)