RE: NST blown

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

Original poster: "Randy & Lori" <rburney6-at-comcast-dot-net> 

If I understand correctly you measured for ohms from one HV terminal to
the other and found that you were open.  The reason that you still get
some kind of spark when you plug it in, is that there are actually 3
coils in the NST.  There is the primary that is plugged into the outlet,
and there are two HV coils that are center tapped to ground.  Each of
the HV coils will put out 4.5KV against ground, and 9KV against each
other.  You have only let the smoke out of one of the two HV coils.  If
you measure each HV terminal against ground, I believe you will find
that one is fine and that the other is open.  For your second question:
To actually repair the coil itself is next to impossible.  The wires are
as thin as a hair, and you have no idea how far into the coil the break
is.  If you were to unpot the transformer, and you had another HV coil
to put in it's place, then that may be possible.  I recently opened a
12/30 and found that the core was welded, unlike my 15/30 which was
bolted(one more obstacle).  Sorry to be the bringer of bad news.

Randy
Savannah, GA

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Wednesday, January 28, 2004 10:14 AM
To: tesla-at-pupman-dot-com
Subject: NST blown

Original poster: Bob81818-at-aol-dot-com

Hi all, I was demonstrating my first coil at school and after running it

for a few minutes (not continuously) the spark gap stopped firing after
taking it home the secondary of the 9/30 nst had no conductivity, so I
just
implied that it destroyed itself. I plugged it in to double check and I
got
less than millimeter sparks when I scraped a wire over the two secondary

electrodes. That kinda puzzled me a bit, would appreciate if someone
could
explain how that happened if the sec is blown. And I was also wondering
if
its possible to fix an nst like this. I'm not surprised that I blew the
xformer cuz I didn't ground the tank circuit, or put in a safety gap, I
guess I just wanted to know if the coil would work before I added all
the
safety stuff, therefore I accept that I am an idiot. A little advise on
this subject would be nice.
         Thanks all,
               Dan