"cliff wright" wrote in message
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Jimmie D wrote:
"Jimmie D" wrote in message
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"Jimmie D" wrote in message
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"msg" wrote in message
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Jimmie D wrote:


there are appaently 2 types, one is made to run off of 12 volts maybe
24 VDC and the other runs off of 120VAC.
I think the 120VAC initially converts it to 300VDC then aplies it to
the inverter circuit.. Still trying to find a schematic to verify. I
would think this technology could be a major help for amp builders
allowing us to build inexpensive power supplies and easily custom wind
the inverter transformers.

Please dig out the ones you have and take photos, front and rear of the
entire unit and if you don't mind, disassemble and photograph and
components. I can host the photos if you wish (email them to me).
This would _really_ help in the evaluation until any of us find
schematics.

Regards,

Michael
msg _at_ cybertheque _dot_ org

Seems i am going to be looking for a couple more as the wife laid claim
on these.


I did find some info saying the switcher was run using IGBTs.



Rats, service manual just shows it as a box, but I did find some useful
info here

http://fusor.net/board/view.php?site...y=115878692 1

Knowing the freq they switch at would be a big help


Jimmie
I must confess that I'm not familiar with "inverter" type PSU's for
microwaves. However judging by the old type you would literally be
"playing with fire" in using them for a TX PSU.
Based on the "Don't put it in unless it's needed" philosophy it
1. Won't have ANY filtering worth mentioning. In fact the output will
probably be a series of rough square waves giving about +2KV average
voltage.
2. I would be quite sure that an 807 based linear would turn into slag
with 2Kv on the plates, let alone 2KV squarewaves at about 25KHz.

This is based on the fact that microwave ovens use cavity magnetrons.
these need a small heater voltage and a beefy but rough HT supply.
They are just a diode in a powerful transverse magnetic field.
After all your coffee or soup isn't a sensitive soul about signals!

Now if you had a linear needing 2Kv or so (maybe a California Kilowatt!!!)
and a good supply of high voltage caps then you might be getting somwhere.
You would indeed have the advantage of needing less smoothing because of
the high switching frequency of the inverter but any choke would have to
be suitable for 30 KHz at least with powerful insulation.
But with decent TX tubes not being cheap I still reckon I would prefer one
of the old HV transformers with plenty of fuses.
Best of luck!
73's ZL1BDA ex G3NIA.

Basically I want it for educational(my education) purposes. I had to give up
the ovens I got at the goodwill to my wife so I am waiting on another one to
show up..Bsically I want out learn about the design of the power supply. I
figure it can be much improved but dont see why the idea of using a n
inverter would not work for rf amps. I want to learn about the magnetics
used and the operating frequency to hopefully design my own inverter type
power supply. I was thinking of something along the lines of the old 12 to
600volt inverters used by HEath for their old mobile rigs. But I want to use
them off the mains, input 300vdc output up to a couple of KV. Presently I
have a couple of inverter transformers salvaged from some old tube type CB
amps and the plan is drive them with a couple of IGBTs. First I need to get
them operatin as designed so I can figure out for what freq they were
designed.



Jimmie