Potting Transformers

From kee–(at)–ustin.ibm.com Mon Sep 30 10:41:05 CDT 1996
From: kee–(at)–ustin.ibm.com ()
Newsgroups: rec.audio.tubes
Subject: Re: rewinding transformers
Date: 30 Sep 1996 14:58:33 GMT
Distribution: world
Originator: kee–(at)–een.austin.ibm.com

In article , cign–(at)–elios.phy.OhioU.Edu (Dave Cigna) writes:
> I am planning to rewind a couple of power transformers (I’ll let
> someone else worry about the outputs … for now.) All of the
> references that I have suggest using shellac to bind the laminates
> together. Is something else preferred in this age of magic polymers?
>
> Ditto the above question about potting compounds. The older
> transformers that I have taken apart are filled with what is
> probably tar, but the newer ones use something harder. Any suggestions
> on what to use, and just as important, where to get it?
>
Shellac is preferable. By the way, every mechanical stress on the lamination
causes deformations of the magnetic domain boundaries that decrease the
desirable qualities. Don’t bend them.

Use spar varnish. Get a bucket, dunk the whole transformer in it. Pull a
vacuum on the bucket to get out air bubbles. Once it is fully de-aired,
bake it for a couple of days in a 200F oven.

No, I’m not kidding. I designed transformers for a living at one time, and
this is as close to the actual manufacturing process as you can reasonably
do at home.

R.G.

 

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