Re: More destroyed NST's How do I remove stubborn tar?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-uswest-dot-net>" <evp-at-pacbell-dot-net>

Tesla list wrote:
> 
> Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<FutureT-at-aol-dot-com>
> 
> In a message dated 1/17/01 8:15:46 PM Eastern Standard Time, tesla-at-pupman-dot-com
> writes:
> 
> > Many sources say one can melt out the core and most of the tar by
putting it
> >  into an oven at 200 degrees. Mine sat there for hours at 250 degrees
and it
> >  was still hard as a rock. Nothing even began to melt until 300 degrees and
> >  that was only half. The rest was like concrete.
> >
> 
> Garry,
> 
> If it's a Jefferson NST, they often use a silica filling material in
> the tar.  It tends to not liquify for this reason.  In any case 200
> degrees is not enough.  It's a lot of work depotting those
> beasts.  I did two of them, but I'll probably never do another one.
> 
> I often work them over with a propane torch outdoors to soften
> the tar, which I then remove with a screwdriver (carefully).
> 
> John

	Has anyone ever tried using a heat gun (he-man hot air gun, that is) to
melt the tar away from the ends of the transformer at the point where it
connects to the insulators?  If the failure is indeed due to carbon
tracking, this should allow selective removal of tar without as much
mess and without concern of the transformer dropping out of the case and
pulling out the leads to the windings.  Furthermore, since the melted
tar would be liquid which can be kept hot by the air gun, would think
that it would be a simple matter to keep it flowing into a can from
which it could be trashed or remelting to restore the potting.

Ed