1957 H Model: After sitting for a few months with the aircraft battery in storage, I reinstalled the battery planning to check out the plane and get back in the air. Plenty of power and the engine started fine, but when I turned on the Radio Master nothing. No popped breakers but under the panel was a large can capacitor that was smoking hot so I shut everything down. The capacitor is marked 20000 MFD 25vdc. What is this for and could it be related to the lack of power to the radios? Thanks

I would guess that it is there for AC interference/noise suppression. It will effectively pass RF AC from the alternator to ground with out passing DC. They are usually on or near the alternator though. If it has failed by shorting internally it will provide a path for DC and overheat. It could drop the voltage of your avionics bus to not actuate the avionics relay and not flow quite enough current to trip the breaker. I suggest removing it and testIng without it. If your avionics powers up but you have radio noise then install a new one.

Thanks for your input Norman, I’ll update you with the outcome of trouble shooting