Plate Load Resistors

[ajeffcote]

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.

[chocopower]

for plate resistors i´ll go with the 1watt (ore 2w)..

[spacelabstudio]

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

[Colas LeGrippa]

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

[ajeffcote]

Thank you! One watt resistors it will be!