RE: Repotting NSTs

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Lau, Gary" <Gary.Lau@xxxxxx>

Definitely don't re-use the tar (technically asphalt).  While I can't
say if that would present a functional issue, it just makes the
possibility of future repairs so much more unpleasant.

I re-potted my 15/60 in melted Vasoline petroleum jelly.  It has a low
melting point so it's easy to handle, and has a very low viscosity, so
it gets into all the nooks and crannies.  Note that if you run your NST
long and hard, it may cause the jelly to melt and leak if your case is
not tight.  This has never happened to me, but I thought I'd mention it.

Others have used melted paraffin to re-pot.  Paraffin has a tendency to
shrink as it cools - not sure if this presents an issue or not.

Regards, Gary Lau
MA, USA


> Original poster: "Jonathan Peakall" <jpeakall@xxxxxxxxxxxx>
>
> Hi All,
>
> Well, I finally destroyed an NST. I wouldn't worry about it, except
that it
> is a 12/120, and the 120's are rare. I was using it to power a Marx
bank. I
> get full spark from one side and a wimpy spark from the other. The
good side
> reades a few ohms higher than the bad side, which is probably how it
was
> before. This makes me believe that the cause is carbon tracking.
>
> So yesterday I melted the tar. It was quite easy. I used an old metal
pot,
> the kind used for canning. I cut a hole in the side large enough to
fit the
> barrel of my heat gun in there. Put some old clothes on and around the
pot
> for insulation. Took a few hours to melt the tar, but very little
stink and
> low chance of fire. Anyway...
>
> I let it cool, and while it seems a little improved, it is not fixed.
So I
> have to empty the NST of tar, use solvent to clean it, and then I want
to
> repot it. I don't want to use oil. This NST is going to get moved
around,
> going to school and so on. I don't want to be dragging around a leaky
oily
> mess.
>
> I have concenrns about re-using the tar. First, it will be hard to
keep it
> perfectly clean. And then there is going to be some loss of tar, so
even if
> I tried to save it I might not have enough. Anyone know where to buy
such
> tar?
>
> I am assuming that the NST must be potted. Can they be run dry?
>
> Many thanks,
>
> Jonathan
> www.madlabs.info
>