[Milsurplus] Design for a cheap 400Hz power supply

[Marty R's GI-stuff haunt]

I did one years back w. a Exar2206 sin-wave-strapped function chip,
a NE570 variable gain cell, & a 50W Sanken hybrid audio chip.  Ran
on + & - 14VDC from 24vac-ct 2A rad shack xfrmr.

Amp output thru surplus 400hz fil xfrmr & rectified then divided down
so NE570 could regulate output

There were no UPS beached wrecks then & I think "re-timing one" may
be just the ticket... with only knock being those square waves... but 
then some make an effort to minimize that via "low harmonic distortion" 
claim

Say the implicit low-pass filtering done by an output xfrmr amy make
ups sets containing output xfrmrs more desireable.