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