[Hallicrafters] HT-37 low voltage rectifier

[Kenneth Laine Ketner]

Or take the transformer out and haul it to your local electric motor repair
shop where they will shake and bake it professionally for you. However, if
there are shorted or weak windings, those faults could be baked in permanently.
On the other hand, some imported insulating varnish could shore up those weak
zones. The motor shop might be able to diagnose it somewhat. I guess the only
real certain cure is a Peter Dahl replacement xfmr.

--

Ken Ketner
ARS KA5ELD (Extra Class)
  Personal Webpage: http://www.wyttynys.net
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Email:
 home: ketner at arisbeassociates.com
 office: kenneth.ketner at ttu.edu

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Lubbock, TX 79464



"Roger(K8RI)" wrote:

> > Hi Riley,
> >
> > The buzz is most likely coming from loose laminations in the transformer.
> > This is brought about by the increased load of the rectifier filaments
> which is
> > why it s\disappears when you go solid state. You can try to tighten up the
> > bolts holding the transformer together.  This sometimes helps, but does
> not
> > always work.  If you have a horizontally mounted transformer, you will
> have to
> > loosen the mounting bolts below the chassis and use an ignition wrench
> above the
> > chassis to tighten the bolts, then retighten the below chassis hardware.
>
> I know a ham who lives in Saginaw that used to vacuum impregnate
> transformers using transformer varnish, a heavy walled 5 gallon bucket, a
> vacuum cleaner, and much to his wife's displeasure, her kitchen oven to dry
> the thing once done.  I don't know if he's still married or not.
>
> It was a simple process.  Put the transformer in the bucket. Pour in enough
> varnish to cover the transformer by a couple inches.  Hook the vacuum
> cleaner to the top of the bucket (he had soldered a fitting on the lid), run
> the vacuum cleaner for 15 minutes or so, to get the air out of the
> transformer, then disconnect the vacuum cleaner which let the air back in
> the bucket which forced the varnish back in between laminations and
> windings. Let drip for a few minutes, place in oven over cookie sheet (for
> obvious reasons) and bake till dry.
>
> It was not a high vacuum, but according to him it worked quite well even if
> it was messy (and smelled up the whole house)
>
> Roger Halstead (K8RI, EN73 & ARRL Life Member)
> N833R, World's Oldest Debonair? (S# CD-2)
> www.rogerhalstead.com.