[tab10672]

Hello, I am helping a friend restore a 511 that needs the large power resistor replaced. Does anyone know the safest, yet minimal wattage usable in order to save space?
Thanks, Todd

[Arran]

Hi;
When you are replacing a power resistor, or any resistor, you want it in a larger wattage then you need for both heat dissipation and durabilty. Power resistors are typically rated in 1 Watt, 2 Watt, 3 Watt, 5 Watt, 10 Watt, 15 Watt, 20 Watt, and 25 Watt sizes. Since most modern resistors are smaller then the 1928-29 variety space isn't really an issue.
Regards
Arran

[Radioroslyn]

I took a quick look at the diagram and it looks like all of the resistors are in series with the HV. The typical set up is the B-C resistor is in parallel with HV and will have a resistor or two to divide up the bias voltages this set doesn't. No bias on the audio stages. Anyway to answer your question I would think 5 to 10wts would be plenty. A lot of times only certain sections are open you only have to replace the open ones.
GL
Terry

[morzh]

----20 Watt, and 25 Watt sizes....

I have just used a resistor that is 200W ....to simulate a filament in my device so I can hit it with 260W of power without bringing an argon bottle along....

[Arran]

There are power resistors larger then 25 Watts but they aren't typically found in old radios, I have some 50 and 60 Watt resistors myself but that isn't the ceiling either.
Regards
Arran

[tab10672]

Thanks for the info, I wired two 5 watt resistors is series to build each of the four sections, the original was missing so now each section equals 10 watts to center 20 across both double sections. If it gets too hot I will use higher wattage resistors.