More study and its a basic early line filter. Intended to clean up the power supply. Something which now is done at the point of generation, but back then wasn't detected until sound equipment came into being.

Perhaps you might remember some amps which gave out a radio signal? Because they picked it up in their circuitry. Such things are rare as rocking horse doodoo now.

Its unlikely now to find a noisy line in the grid. But quite possible in something like a generator if the line filter on that is poor or faulty.


Using: Dell 3268 i3, 8 GB ram, windows 10. Biab version 2017 standard package, no extras.