4" x 24" Coil Back Up & Running

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

Original poster: "Gregory Hunter by way of Terry Fritz <twftesla-at-qwest-dot-net>" <ghunter31014-at-yahoo-dot-com>

Dear List,

I finally got off my duff and reconstituted my old 4"
x 24" New & Improved Junkbox Coil. I built a new MMC
for it using fifty 68nF/1600V polypropylene film caps
that Michael Tucknott was kind enough to ship to me
from the UK. I used 5 parallel strings of 10 caps to
achieve 34nF, which is resonant with my 9kV/120ma NST
farm. I know reso caps are out of fashion these days,
but I just couldn't resist the urge to try it again. I
used a bizarre mounting scheme, which results in a
cheap, simple, sturdy, but hideously ugly MMC. I have
dubbed it the "cactus cap". Sorry, no pictures yet.

For the gap I used a new perpendicular flow air blast
gap based on a very powerful 120V centrifugal blower
quenching a single gap made from 1" copper pipe and
caps, and PVC fittings. This is such a simple, cheap,
robust design, I could kick myself for not thinking of
it sooner. Sorry, no pictures of that yet either. I've
got to get one of those digital cameras.

For first light I ran the NSTs wide open (protected
with an RC filter). I used the 12" sphere top load,
which broke out beautifully. However, the top-turn
corona was so intense I had to shut down to save my
secondary. Next, I tuned up with the 4" x 20"
drainpipe toroid.  I was instantly rewarded with
white-hot 45-48" streamers and plenty of hits to the
strike rail. Spectacular! Not insane, like the
original MOT coil, but still very pleasing for "only"
1080VA.

I'm guilty of several sins here, including trying two
new, untested components at the same time (the cactus
cap and the air blast gap), and using resonant
operation. I mostly got away with it, except that I
did get a racing spark near the bottom of the
secondary and also a couple of secondary-to-primary
arc-overs near the same spot. I'll need to do
something about that. Otherwise, the performance was
stellar, and the ugly new MMC cap never warmed above
room temperature. How did this hobby ever get by
without the MMC?

I'll get the pictures posted as soon as I have them.

Regards,

Greg
http://hot-streamer-dot-com/greg

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