Nomen Nescio wrote:

I just got an isolation transformer for restoration of my 1950's RCA Victor
TV. The power cord is non-polarized. Up until now, I've just been using a
Fluke 77, so I didn't bother with the isolation. But I'm now moving into a
phase where I need to view waveforms on an oscilloscope. And from what
I've read, without an isolation transformer, fireworks will be the result
of the first probe. Now that I've explained the scenario, can anybody
explain how I can test the isolation transformer so that I know it is doing
the job it was designed to do? I took some measurements with the Fluke and
this is what I got:

wall outlet: 118VAC
iso: 118VAC
Hot_wall - Hot_iso: 67.5VAC
Neutral_wall - Neutral_iso: 60VAC
Hot_wall - Neutral_iso: 162VAC
Neutral_wall - Hot_iso: 34VAC

With this information, can it be concluded that the isolation transformer
is working as designed?

Hi...

Worked on lots of those sets; wish I had a nickel for
everytime I burned my fingers pulling a 5U4

Anyway, can't help asking... why the fireworks possibility?

All of those old sets had a power transformer connected
straight to the line (except power switch), and nothing
else connected to the line, so....

Take care.

Ken