[Boatanchors] Potting of old power transformers.

[J. Forster]

If it was potted in tar, it was not real likely to need it for thermal reasons.
Tar conducts heat very poorly. To remove it, heat in an oven at about 150 F for
an hour or three, then pour off the tar. BE CAREFUL. The stuff will burn your
skin and also catch fire. Alternately, chill it and chip it out.

To remove what you can't get at this way, soak it in mineral spirits or kerosene
for a week. Swish often. Drain and repeat. It comes pretty clean.

The varnish can be destroyed by heating in a special oven (burnoff oven) or
dissolved by putting it in a can of paint stripper. Best brand on request. The
transformer can then be dis-assembled. Do it OUTDOORS. Paint stripper is bad
stuff.

Newer potting materials are harder to remove but conduct heat better, giving
better life. Make sure it ca be removed if necessary.

FWIW,
-John

Keith Densmore wrote:

> Im no expert on transformers but I bet they used a high mass potting
> material  to reduce transformer 'chatter',  besides the obvious insulation
> value of it.
>
> BTW Brian, how did you get the old potting out?
>
> Keith,
> ve3ts