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Re: MicroWave oven Transformer
> Date: Sun, 5 Jan 1997 21:25:09 -0700
> From: Tesla List <tesla-at-poodle.pupman-dot-com>
> To: Tesla-list-subscribers-at-poodle.pupman-dot-com
> Subject: MicroWave oven Transformer
> Reply-to: tesla-at-pupman-dot-com
> Subscriber: pylon-at-nwlink-dot-com Sun Jan 5 20:46:33 1997
> Date: Sat, 4 Jan 1997 19:45:16 -0800 (PST)
> From: James <pylon-at-nwlink-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: MicroWave oven Transformer
>
> I just recently disassembled an old microwave (circa 1983?) and I got an
> old 15+ lb transformer out of it that is used to drive the magnetron. It
> has two secondaries, one for the magnetron filament, the other for the
> magnetron drive. I don't know what the exact outputs are, but I also took
> out a 1 MFD, 2000V oil-filled cap (Yes, i discharged it before i touched
> it...;) that the Drive section of the secondary was connected in series
> with. The wire in the secondary is fairly heavy (~16 ga on the filament
> winding, ~22ga on the drive winding) My question is: Since this is a fairly
> low-voltage transformer (i guess about 1000-1500V), but the current rating
> must be fairly high, because of the size of the wire in the secondary,
> would it be suitable for a tesla coil? It doesn't have any current limiting
> shunts on it, so would I have to put something on it to limit the current?
> Also, would the cap I retrieved from the oven be suitable for
> pulse-discharge experiments? If the x-former isn't suitable for tesla work,
> could I use it for a pulse-discharge supply?
>
> Thanks,
>
> James.....
>
>
James,
The transformer you have just salvaged probably outputs about 2000
VAC with 120 volts input. With a variac on the input it would be a
marvelous transformer to power a vacuum tube Tesla coil employing an
833-A,single or pair of 810 triodes or a pair or three of smaller 805's etc. More
easily available 811-A's could also be paralelled, perhaps four
units but you would be stressing their voltage rating (this is known
as pushing the outside of the envelope!) : )
The filament winding of your transformer is too low to be suitable
for any of the popular above mentioned tubes which you may try to
employ. You will need a separate filament transformer. I don't have
my toob manual handy but I know the 833-A, 810's and 805's require 10 V.
The 811-A may be 6.3 volts. If you require this info just ask and
I'll be happy to look it up.
You can run the tube directly off the transformer through the Tesla
primary tank circuit without rectifier diodes or filter cap. This
arrangement actually gives you longer streamers by pulsing the tube
oscillator at 60 times a second with half the time (when the 60 Hz
sinewave is negative) cutting off conduction and allowing the tube to
rest just over half the time.
The neat result is that when it does conduct, for a given AVERAGE
power level which equates closely to the tubes actual specified power rating,
you can hammer the tube at nearly twice its rated power level safely. : )
This trick gives you an effective peak power of more than twice the average
power level of the tube, while costing less in circuitry and components.
Brent Turner has a nice twinned 805 vacuum tube TC on his home page
which looks like it is powered by just such a transformer. This is
also a configuration well explored by an experienced newcomer most
welcomed to this list, John Freau.
rwstephens