Bjarney,

The spouse suggested that too. So I plugged in a 60-watt bulb (and then a 100) and measured the voltage across that.

Ditto the 35-watt tube radio I was working on...after it was properly working. It still read 125-127 volts when the entire setup was plugged into a 120 volt outlet (this was actual voltage at the receptacle).

I don't want to spend 50$ on a new isolation transformer if it's going to do the same thing, since the catalog listing for the device I was considering did say +/- 5% tolerance.

The primary and secondary aren't shorted to each other (I did a continuity test) so that's a good thing.

Wonder if I'm just better off plugging a lightbulb in series with the primary to drop the incoming voltage a bit...and save my money for a Variac [Linked Image]