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Re: magnetrons as diodes

Original poster: "BRIAN FOLEY" <ka1bbg@xxxxxxxxxxx>

Hi, i am interested in this project. leave the heat sink fins and the two
inductors on the filiament leads can be left there, no problem. it probably
will require air cooling with just the filiament running. a computer fan
should be plenty. read the power input with the filiament on and then with
power going thru it as a diode. if the tube is making any microwave output
it should draw more current. worth taking note. not sure it is a perfect way
to measure for microwave output. cul brian f.
----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Wednesday, January 03, 2007 6:50 PM
Subject: RE: magnetrons as diodes

> Original poster: "Breneman, Chris" <brenemanc@xxxxxxxxxxxxxx>
> I got everything removed from the magnetron except the heat sink
> fins, in case it needs cooling, but noticed that there were two small
> inductors, each one in series with the filament leads.  Will these be
> necessary?
> Also, my actions are somewhat controlled by people who don't know
> much about this stuff, but in my opinion, are somewhat overly
> cautious.  They don't want me to try this unless there's some way I
> can prove that there would be no microwave production.  Theoretically
> there shouldn't be, even with some small stray magnetic fields, but
> is there a simple setup that can be used to test this?
> Chris
> -----Original Message-----
> From: Tesla list [mailto:tesla@xxxxxxxxxx]
> Sent: Wed 1/3/2007 2:50 AM
> To: tesla@xxxxxxxxxx
> Subject: RE: magnetrons as diodes
> Chris,
> Magnetrons are a special case of high voltage vacuum tube diodes.  As
> you point out, because of the strong magnets, the electron path is
> bent into a many-turn spiral.  As the electrons speed by the slots
> going into the multiple cavities, they cause a resonant oscillation
> to build up in the phase-locked cavities.  Take away the magnets, and
> the electron path goes straight between the cathode and anode, like
> any other diode, with the added advantage of having a built-on heat
> sink.  There will be zero microwave production.
> A good experiment would be to remove the magnets, hook it up to your
> MOT powered by a variac, feed the rectified output to a load, such as
> a few feet of water-filled hose with electrodes at each end, and
> measure the output voltage and drop across the magnetron.  But BE
> CAREFUL - the voltage and current combination is LETHAL.
> --Steve Young
> ________________________________
> From: Tesla list [ mailto:tesla@xxxxxxxxxx <mailto:tesla@xxxxxxxxxx> ]
> Sent: Tuesday, January 02, 2007 8:26 PM
> To: tesla@xxxxxxxxxx
> Subject: RE: magnetrons as diodes
> I know relatively little about tube technology, so I may well be
> wrong, but I don't see why not.  If you use the original microwave
> oven transformer, you can use the filament winding to heat the
> cathode like in the original configuration, and the case would be the
> anode of the diode.  If the magnets were removed, I don't think the
> cavities inside would resonate, so I don't think microwaves would be
> produced.  Always good to check though.  I don't know what the
> working voltages would be though.  As I said, I know very little
> about tube technology, so I'm not sure what the minimum forward bias
> would be, but I think the maximum voltage across it would be limited
> only by internal arcing between the cathode and case.  This could be
> measured by applying increasing voltages from the cathode to case
> until it started conducting (ie, an arc forms).  This might damage
> the magnetron tube though if there's some insulating material in the
> path.  If I'm not conclusively proven wrong by someone else here, I
> plan to try this soon.  I just finished disassembling a microwave
> oven and (with some difficulty, as I only had some small pliers) the
> magnetron.  If I try it before you do, I'll let you know how it works.
> Chris
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