Re: NST REPAIR

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

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

Tesla list wrote:

> Hi Ed,
> 
> I do nst repairs all of the time.  I think that if you got it working, you
> are in good condition and the repair will last.  

	I hope so!

> Ive only had one bad NST
> repair, where the secondary shorted through itself.  Maybe i will try the
> heatgun, i have one.  Did you leave the rest of the transformer in the tar??


	Yep, just melted the tar around the "inside" of the insulator at the
bad end.  I don't know whether I actually melted the tar around the
insulator, but sure got it warm and the tar just above the insulator
flowed out of the hole under gravity.  If my heat gun hadn't died I'd
have done a more thorough job.

>   It would be better to take the whole thing out of tar to keep it from
> breaking down the tar on the original "good" side.  

	I contemplated doing that, as in the process the core got hot enough to
loosen the tar on top of it, but then I thought about the extra mess and
decided to stay with what I'd done.

> But hey man, cool!  i
> like hearing about people bringing dead transformers back to life,
> especially if you get them for free!

	This was one of several I dug out of the ice plant beside a freeway on
ramp.  Obviously they had slid off the back of a truck as it went around
the bend.  This was the only one of the batch that didn't end up with
mangled insulators, and has just one chip out of the "good" end.  I had
to make new insulators for the rest of the batch, which were all 12 kV,
60 ma Franceformers without PF correction.  I kept some and gave some
away, but they've all kept working.  This particular one wouldn't have
failed if I hadn't run it without a safety gap at the same time that the
spark gap opened way up due to an insulator cracking.  Since I'd set the
gap spacing so it would just breakdown with normal line voltage on the
transformer I thought it would be save.  Stupid stunt I won't repeat.
> 
> Steve Ward.
> 
> PS my repairs can take at least 4 hours!! more like 6-8 hours!!

	If you try a heat gun get the biggest one (guess it's the only one) you
have.  I think that a preheat on a hot plate or "in the oven" would make
matters go better, and would still involve less work than chipping or
melting all of the stuff out.  I also thought of making an aluminum bit
for my 500 watt American Beauty soldering iron and starting the nob with
it.  I think that would go pretty quickly too, but I tried the heat guns
first and I hope now I won't have to do any more.

Ed