"Nomen Nescio" wrote in message
...
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?


Very likely the voltages you see are just capacitive coupling from
Primary to secondary.
The impedance of a Fluke 77 is so high it will see all sorts of stray
voltages.
The only simple way to test the isolation is to measure the resistance
between the primary and secondary with a high voltage Megger or similar
insulation tester.
--
John G

Wot's Your Real Problem?