I have gleaned 1.5KW commercial microwaves for their transformers (they had
timers which maxed out at 1 hour!), removed the secondary and replaced it
with heavy copper wire to make 13.8 V high amp supplies for mobile linears
converted to shack use.
The ones I have come across--where I bothered to measure the voltage of the
secondary, were 3000+ V, as I remember 3300-3500 V.
Two matched transformers should be able to serve as a center tapped
transformer without much re-engineering.
In amplifier use, a transformers 50% duty cycle specs should be
sufficient--I wouldn't be surprised if they could serve well in amps (and it
never hurts to make sure the xfmr benefits from a fans output.)
The only red flag which pops up in my mind is if there would be sufficient
isolation of the primary from the secondary at low freq. rf., if not,
something there could probably even be worked out (and, my worry may be
false to begin with.)
In extreme cases, a heat sink could be fitted to the exposed section of the
top and sides of the core (heat conductive epoxy would work.)
And, hey, if I guy gets long winded and smokes a xfmr, a trip to the dump
for a replacement is cheap!
Take care, those transformers can pack a lethal wallop!

Regards,
John
--
I would like to point out, I do appreciate the "Been there--done that!"
posts. Indeed, now your observations, comments and discourse should be
filled with wisdom--I am listening!!!
"Dan/W4NTI" wrote in message
news
Does anyone know what kind of AC voltage a Microwave oven transformer
would put out? Are they center taped or just a single coil?

I need a replacement for my homebrew 3-500z single tube amp. I only used
it for low power AM and I don't need "maximum voltage".

Dan/W4NTI