Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: ajeffcote on February 10, 2012, 07:44:19 am
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How large of a plate load resistor should I use in my AB763/6L6 build? I have 1/2watt carbon comp an 1 watt carbon film 100K resistors on hand.
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for plate resistors iŽll go with the 1watt (ore 2w)..
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How large of a plate load resistor should I use in my AB763/6L6 build? I have 1/2watt carbon comp an 1 watt carbon film 100K resistors on hand.
Calculate the worst case scenario, you manage to swing the tube all the way open. Vpeak = B+, P = V^2/R. So, if B+ is 200V and your plate load resistor is 100k, then P = 200 * 200 / 100000 = 0.4 watts. Even if you manage to swing the tube all the way open, though, it's going to swing back. You're really concerned with average dissipation. A more realistic scenario is Vavg = B+/2. So P = 100 * 100 / 100000 = 0.1 Watts. 1/2 watt should be good and safe. 1 watt should be foolproof. 1/4 watt would probably work, but it's better to overbuild than underbuild. Redo the calculations with your actual voltages.
Chris
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Although most amps use 1/2 watt plate load resistors, I prefer 1 watt. I replace all half watt in a given schematics by 1 watt anyway. Some say carbon comp are more sensitive to heat and we all know that heat affects the value of resistors. Try to heat a resistor with a heat gun or other mean, and measure it's value, before and after applying heat. See the difference.
Colas
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Thank you! One watt resistors it will be!