HV PWR XFORMER-gud idea

[Brian Carling]

thanks dOUG - YES, i AM GOING TO HAVE TO GIVE THIS A TRY
(oops) - I have a friend with an old oven for me. I think ONE xfmr
might do it for a medium-power amplifier such as a pair of 811As
or similar, for about 500 watts.

Knock out those magnetic shunts and away we go!

Thanks - Bry

On 22 Jan 98 at 9:44, Doug wrote:


> Hi Bry and the Gang....the piece is called a "magnetic shunt" and is
> fairly obvious as a bar of laminations across the "window" of the
> microwave transformer core.  You can carefully knock it out with
> a punch while supporting the rest of the core on a rest, anvil or
> whatever you've got.
>
> One thing to be aware of is that in most cases, the HV side of the
> transformer has one side grounded to the frame, which would be
> a concern should one want to series a few for more current output.
> I'd recommend mounting them on insulated standoffs...just in case.
>
> I think these might be a real source of low cost Plate supplies, just
> will take some planning to make 'em work like we need.
>
> 73
>
> Doug, K7YD
> Livingston, MT
>
> Brian Carling wrote:
>
> > I heard that this quiescent current draw was due to some
> > electrico-mechanical loading on the transformers to dampen voltage
> > variations as the load is applied, and that there are some little
> > metal pieces that need to be removed.
> >
> > What are they called?
> >
> > Does anyone know how to identify these and remove them from microwave
> > transformers???
> >
> > Bry, AF4K
> >
> > On 21 Jan 98 at 16:57, Richard wrote:
> >
> > > VAN LINCOLN wrote:
> > > >
> > > > Heard a couple hams on 2 meters this morning discussing a really good idea.
> > > > Thought I'd  pass it along on the internet.
> > > >
> > > > One of the hams talking said he found that in OLD MICROWAVE OVEN's, was an
> > > > undiscovered
> > > > resource.  Namely the HV transformer that powers the Magnetron Tube.  He
> > > > has observed that
> > > > most of the transformers have a HV winding of +/- 2000 VAC (single winding)
> > > > @ usually
> > > > about 500 ma. capacity.  AND a 110 VAC primary.   This means that two
> > > > transformers matched of course, and placed in series, will provide 4000 VAC
> > > > centertapped, and 110vac/220vac primarys AT 1/2 an AMP, which is
> > > > more than enough to power that linear amp he wanted to build.  Also, old
> > > > worn out Microwaves can be had
> > > > for free or very cheaply at service dealers, and the local paper want ads.
> > > > FYI from a 'fellow junk collector'
> > > > wd8aam.....this can be copied freely for any use.
> > > >
> > >   I have a friend who works in electronics repair and who investigated
> > > the use of microwave power transformers in amp power supplies....He
> > > found that they draw a rather high no-load current on their primary
> > > windings, around 2.5 to 3 amps, depending on the size of the xfmr. You
> > > can hook up one to 120vac and measure the primary current with a snap-on
> > > type inductive ammeter--I did and confirmed his finding.  If you are
> > > willing to allow that much no-load loss they should be usable.
> > > You will notice that the transformer laminations are welded together,
> > > and this would increase core losses.
> > >
> > > Dick W0EX
> > >
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> > ****************************************************
> > *** 73 from Radio AF4K/G3XLQ Gaithersburg, MD USA  *
> > **  E-mail to:  bry at mnsinc.com                     *
> > *** ICQ 6124470  ***
> > **  http://www.mnsinc.com/bry/                     *
> > ****************************************************
> > AM International #1024, TENTEN #13582. GRID FM19. Using a SWAN 250 on 6m,
> > Other rigs: Valiant, DX-60/HG-10, FT-840, TM-261A, Ameco TX-62, Gonset Comm. III
> > TEN-TEN #13582, DXCC #17,763 Bicentennial WAS
> >
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>
****************************************************
*** 73 from Radio AF4K/G3XLQ Gaithersburg, MD USA  *
**  E-mail to:  bry at mnsinc.com                     *
*** ICQ 6124470  ***
**  http://www.mnsinc.com/bry/                     *
****************************************************
AM International #1024, TENTEN #13582. GRID FM19. Using a SWAN 250 on 6m,
Other rigs: Valiant, DX-60/HG-10, FT-840, TM-261A, Ameco TX-62, Gonset Comm. III
TEN-TEN #13582, DXCC #17,763 Bicentennial WAS

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