A 10X probe will be fine for that 'scope.

Pete Stanaitis

P.S. Talk about Old scopes: I still have a 422 that works.
-------------------

Chuck Sherwood wrote:

The safe way to do this is to make sure your generator is grounded
because the ground lead on your scope will be grounded and you
don't want current flowing in the ground lead or you will burn up
something or shock yourself. Unless you REALLY know what you are
doing you should not float the scope or alternator and obviously
you would not be asking how to do it here if that was the case.

Next is to use a 10x or 100x probe and connect it to the alternator
output. The probe choice will depend on the max input voltage of
your scope. Read the manual to make sure that you don't overvoltage
the input, lest you fry it. My guess is you will need a 100x probe.
Even then, you need to be careful that you do not exceed the max
rating of the probe. There are two little tiny resistors in there
that are used as a voltage divider. If you exceed the power dissapation
of the resistors, they burn out and your probe is now worthless.

This will allow you to check one leg. If you want to make leg to
leg measurements, you will need a two channel scope and two identical
probes. Put one probe on each leg and invert one channel and put the
scope in ADD mode. Now you can safely look at the combined voltage.

chuck