RE: NST Failure... What happens?

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

Original poster: "Loudner, Godfrey by way of Terry Fritz <twftesla-at-qwest-dot-net>" <gloudner-at-SINTE.EDU>

Hi Bob

If you damaged a few outer layers of one of the secondary coils, you can
unwind a few layers to get below the damage. However when you try to pull
the thin wire free of the epoxy at the edges of a secondary coil, the thin
wire can easy break. The thin wire can even break in between the edges. Once
the wire breaks, its difficult to find the end of the wire. To find the end
of the broken wire, I have used a needle, magnifying glass, and an ohm
meter. I connect one lead from an ohm meter to the bottom lead of the
secondary coil and probe with the surface of the coil with the other lead
from the ohm meter to find the broken lead. Doing some careful digging with
a needle helps to expose the broken end of the wire. A big magnifying glass
is an absolute necessity. If you hit a tough snag during the unwinding, that
is where the wire will probably break. In the past I broke up the epoxy at
the snag with a needle, while viewing through a magnifying glass. I never
tried this, but maybe a few drops of acetone at the tough location will
soften the epoxy. This phase of the operation requires great patience. Much
time is involved if the wire breaks or you hit a tough snag. Some people
might suggest that you unwind a matching number of layers off the other
secondary coil to even the voltage. But I found this to be unnecessary with
all the NSTs I fixed in the past. They seem to be epoxy crazy these days.
When I was a kid, I use to salvage secondary coils from dead NSTs. There was
no epoxy and unwinding was easy. The epoxy messes these days muct be an
example of better living through chemistry. I have never encountered a
broken primary lead. Perhaps constant vibrations fractured the lead. 

Godfrey Loudner   

> -----Original Message-----
> From:	Tesla list [SMTP:tesla-at-pupman-dot-com]
> Sent:	Thursday, March 14, 2002 8:50 AM
> To:	tesla-at-pupman-dot-com
> Subject:	NST Failure... What happens?
>  
> Original poster: "ROBERT L BOZARTH JR. by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <jbdetails-at-prodigy-dot-net>
> 
>     My 15K 30ma NST stopped working suddenly, about 10 seconds after my
> "first
> light". First I was very excited.... Then really bummed.  So I grabbed my
> multimeter and checked the secondary resistance of the NST. I assumed that
> when
> a NST goes that it would be in the secondary windings. However, I got a
> reading
> that seemed normal, so I checked the primary side. Open circuit on the
> primary!
> How? Why?  I depotted the now non functioning transformer in hopes to find
> out
> exactly what happened. It seems that the input to the primaries innermost
> winding was broken off. 
>  
>     It would have been an easy fix but I damaged the "finer than hair"
> secondary wires. I'm still going to try, but I could sure use some
> pointers....
> Anyone?
>  
>  
> Thanks,
>  Bob Bozarth
> 
>