William Sommerwerck wrote:
Some of the older US made units from Litton or Tappan had
a giant reed relay, and the HV was actually switched on and
off for the defrost mode. They made a nice sound switching
on and off.

I'm curious as to how my GE works.

If, at 50% (say) you were full "on" for one minute, then off for one minute,
you'd be running in that first minute at a power level that would cause
localized boiling. (This is a problem with soups and oatmeal.)

I do not see that. Therefore, I have (???) to assume that PWM with a cycle
of less than one second is used.

1 second seems pretty excessive. I don't recall what the timing cycle on
the Tappan ones were, but it was less than a minute for sure, but not
every few seconds.

I really liked those older machines. They were easy to use. I still don't
get why a microwave oven needs multiple buttons pressed to heat food. It
used to just be, turn the timing knob and press start. That's it.