Electrical – How to diagnose voltage fluctuations that affect the receiver

If you're just using a regular outlet as you suggest behind the TV, then my suggestion would be to supply it like a regular outlet.

If there is another outlet nearby (directly below would be ideal), fish a wire to it, and attach it to that circuit.

If there is unfinished space below, you can get a wire down there (use a long "installer's drill bit") and then it should be relatively easy to find a circuit to attach it to (or just run it back to the panel).

I'd be nervous about any contraptions that attempt to get power to this circuit otherwise. You absolutely need to have a male end in the wall, as a male-to-male extension cable is dangerous to have.

The best thing I can think up totally as a DIY without requiring real hard-wiring would be to get a blank faceplate, and put a square hole in it, and then mount an IEC 320-C14 connector in it (eg. from digikey).

Then you can just use a standard C13 cord (like the kind used to connect most computers, TVs, etc) and plug it into a surge protector or UPS or whatever.

From all this, I conclude the following is likely:

• Only the outlet in the kitchen next to the sink is properly wired.
• All other outlets have hot and neutral reversed.
• There is no ground connection.
• Unexpected observed voltages (mostly 60 volts) are caused by stray capacitance.

I'll mark it accepted when I get complete confirmation.

Outlets need to have their hot and neutral corrected. Outlets need to be grounded or labelled as "GFCI protected" and "no equipment ground."

Fluctuating voltage from the actually hot line to true ground (the water pipe) is caused by current flow reducing the electrical resistance of the line. Voltage is otherwise high and stable for the capacitive currents as they don't induce enough flow.