NEED HELP! Something isn't right

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

Original poster: "Andy Cobaugh by way of Terry Fritz <twftesla-at-qwest-dot-net>" <kb3ewy-at-rcn-dot-com>

Hello All,

(bear with me on this slightly long post)

    Let me give you some background on my coil.  Power is from a Jefferson
15/60 NST.  Safety gaps are set at 1/4" to ground on each side.  The main
gap is a "Vortex" gap, constructed exactly the same as Gary Lau's gap.  It
is set at 1/4".  Tank cap is two strings of twelve .15uF 2000V geek gaps
(25nF total) with 10MOhm 3.5KV bleeders across each cap.  Secondary is 4"
diameter PVC wound for 20" with #22 magnet wire.  Topload is one 3" aluminum
duct toroid beneath a 4" drain pipe toroid.  Primary is 14 turns 1/4" Cu
tubing spaced 1/4" with a off-axis inductor used for real-time tuning.

    Now for the problem.  Tonight, after working out all of the bugs, such
as pri-sec flashovers and bad or loose connections, I worked on tuning the
coil.  Best sparks seem to occur between turn 4 and 5.  It seems to be
really sensitive to tuning, more than before.  Once I got everything set
just right I went to fire the coil once more.  OOPS! Forgot to hook the main
gap back up.  Safeties went completely nuts.  The second the safeties
started to fire I hit the off button which disengages the main contactor.  I
hooked the main gap back up.  I powered the coil up.  Nothing, even at 140V
input, not a sound.  The safeties were silent, and the vortex gap couldn't
have been quieter (except for the vacuum motor).  I knew the routine pretty
well by now, having killed two NSTs so far.  I disconnected everything,
turned the variac up half-way and proceeded to attempt to draw arcs from
each leg.  I actually saw the same arc length on both sides!  I then
measured the resistance, both 3K Ohms to ground.  To make sure I wasn't
fooling myself, I drew an arc from one leg to the other, arcs occurred at
about 3/4".  Finally, I used a 25:1 high voltage probe to check the voltage.
Measured 300V on each side, so that means about 7.5KV per side, or 15KV
total.  I also checked the caps, 24.9nF, same as before.  I didn't run it
after that.

    Now here's the dilemma.  It didn't do anything the last time it ran, and
all I did before that was hook the gap up after the safeties fired.  So what
happened?!?  Could the transformer have carbon-tracked, and then through my
testing it warmed up enough to melt out the track?  I am really at a loss as
to what to do now.  Any and all help is appreciated.

Cheers,

Andy C.
Internet Homepage: http://users.rcn-dot-com/tcobaugh/