[Amps] Microwave Transformers?

[KB0NLY]

Just for the fun of it I might tear apart one of these old nukers and 
salvage the transformer.  I have seen other websites where they show the 
removal and rewinding of the secondary to make power supplies for lower 
voltages.  One smart ham made a really nice 13.8v DC power supply with panel 
meters and the whole works using a microwave transformer.  He claims its 
capable of at least 40 amps.  I don't know if he is valid in his claim, but 
its a free transformer if I wanted to work on it!

73,

Scott


----- Original Message ----- 
From: "Steve Thompson" <g8gsq at eltac.co.uk>
To: <amps at contesting.com>
Sent: Wednesday, March 11, 2009 2:49 AM
Subject: Re: [Amps] Microwave Transformers?


> Microwave oven transformers can be very different one from
> another, even when the original appliance had the same nominal rating.
>
> A lot have quite high resistance windings for the power rating, so
> will give poor regulation and run hot on continuous load. Most
> also have too few turns on the primary for continuous
> energisation, and get very hot from that (in most ovens they are
> fan cooled, even though on for only short periods). You can add
> extra primary turns in the space from the heater winding and
> shunts to help with this, but that increases the resistance.
> Measure some and use the Duncan Amps PSU Designer to see what
> performance they will give.
>
> All I've toyed with can be used with the secondary disconnected
> from the frame - one out of eight or nine needed a bit of kapton
> tape for insulation on a hipot test.
>
> Steve
>
>> Ok, after reading some of the excellent links that the reflector members
>> sent me I see that now.  Makes total sense after finding the right info!
>>
>> Hmm, I could scrounge two of them, but I don't know if its worth all the
>> trouble when I can buy a new toroidal transformer off eBay for about $60
>> with a 1a 800v secondary.  That puts me at a lower plate voltage then I 
>> was
>> shooting for but it would still give me a respectable max output.  I'm 
>> only
>> shooting for about 3-400w on 2m SSB which should be easy at that voltage
>> with the GI-7B.
>>
>> 73,
>>
>> Scott
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