Microwave Oven Choke (What's it for?)

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Gregory Hunter by way of Terry Fritz <twftesla-at-qwest-dot-net>" <ghunter31014-at-yahoo-dot-com>

Dear List,

A friend gave me an old Amana "Radar Range". It
belonged to his elderly mother. She said it started
making a scary noise, and she didn't want it anymore.
It's not just a cliche when I say they don't make them
like that anymore, because they really don't:

http://hot-streamer-dot-com/greg/amanal.jpg

This thing had at least 50 lbs of steel chassis--built
like a tank. The label says it was manufactured in
February 1977!

Getting back to the actual subject--this thing had an
unusual component in the power supply section--an iron
core choke. Have a gander:

http://hot-streamer-dot-com/greg/amanad.jpg

The rest of the PSU is conventional in every respect.
Big 2300vac MOT on the left, .85uF/2500wvac capacitor
with external bleeder resistor, bloc-style HV
rectifier--the classic half-wave voltage doubler.
Whatever the choke is, it is involved in the HV
circuit. The high tension leads for the magnetron pass
thru it. Oddly enough, I don't see a filament winding
on the MOT. Could this be a filament xfmr, or perhaps
a ballast for a 120vac filament? Any appliance repair
tradesmen out there? What is that thing?

Regards,

Greg
http://hot-streamer-dot-com/greg