Voltage – Stepping Down Voltage from 120 VAC to 110 VAC or 117 VAC


I'm a vintage radio collector and I have on my benchtop a Variac that I use for testing out radios. I wonder if there's a way I can put together something that I can either put inside the radio chassis or in the cabinet area of the radio that would allow me to take the 120 V AC mains and drop it down to either 110 V AC or 117 V AC.

I know there are buck/boost transformers out there but nothing that seems to quite fit what am looking for.

They either allow for other types of voltage reduction that would not be applicable for these radios.

I estimate that the amperage would be probably at least one amp and maybe 1.5 when I turn up the volume on some of the sets. Usually the AA5 would draw probably less than one amp while the other larger vacuum tubes complement radios would probably draw more than 1 amp. I also have discovered that some vintage radio restorers use wire wound resistors that give off wattage and heat and I don't know how to calculate what I would need those resistors to be.

I appreciate any recommendations that may be sent my way.

Best Answer

First, in general your radios should work OK at 120VAC. Mains voltage has always varied, which is why the power company could get away with bumping it up over the years.

Second, you can install a filament transformer with the correct secondary current rating, set up to buck the AC. It should be fairly small. While you're observing all due safety precautions, also check that you're bucking the AC voltage, and not boosting it. A 6V filament transformer should get you from 120V to 114V, which ought to be in the neighborhood you want.


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