pfm wrote:
Many advocate the use of an isolating transformer. The oscilloscope
probe and ground are then used like multimeter leads. Tektronix and
others maintain this is a dangerous practice and may result in
cumulative damage to the oscilloscope. Differential probes are one
answer, though quite expensive.

Comments please. Thanks

BobH

I have used differential probes and battery operated scopes. That's the
only thing I would recommend.

Unless it's a specific service mans isolation transformer, most every
commercial isolation transformer is NOT isolated from ground. Ground
isolation is often what you after because neutral is tied to ground. Using
complete isolation through a service mans isolation transformer still
passes a low level capacitive ac line connection to the circuit, and
measuring high impedance circuits can throw you off. Using a battery
operated scope still connected to the charger will also pass capacitive ac
line coupling.

Greg