Scott,
One of the advantages of running it at a fixed frequency is that you
could use the primary of the 400 Hz transformer as a tuned circuit by
putting an appropriate cap across it. That would cut down on the harmonics
even if its driven with a power MOSFET.

Since no one seems to have built something like this from scratch, I'll
start doing some bread boarding this week. If I'm able to get a good solid
design, I'll post it.

Steve W6SSP
p.s.-keeping the equipment original is certainly one of my goals

Scott Dorsey wrote in message
...
Steve wrote:
Hi Gang,
In the past, when converting equipment from 400 Hz power to 60 Hz power,
I've replace the transformer(s), and increased the size of the filter
caps.
That was many moons ago.

This is the smart thing to do IF you don't care about keeping the
equipment
original.

These days, it seems like it'd be fairly easy to build something like a
switching power
supply but using a fixed frequency at 400 Hz instead. Has anyone done
this
yet, and if so, I'd sure be intersted in the details.

There are switching converters out there. The problem is that if you use
a square wave at 400 Hz, you get all kinds of harmonic trash, so you
either
need to use a class B or better stage and suffer extreme inefficiency, or
use a "modified sine" inverter configuration. I don't think it would be
too hard to hack up some of the cheap truckstop 12V-120V inverters to
produce 400 Hz, though.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."