RE: Coil Frustration

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

Original poster: "Lau, Gary by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Gary.Lau-at-compaq-dot-com>

Some quick observations:

Your caps look like they may be Mylar types, which have high losses, and
are physically much too small to be pulse-rated caps.  They may work for
short intervals, but will quickly get hot.  Your stated voltage rating
of 1500kV can't possibly be right.  Do you mean 1500V?  If so, the two
in series will be good for 3000V, much lower than your power supply
voltage.

Your 0.50" spark gap is probably too wide.  With my 15kV NST, I use a
gap of less than 3/8".  Most spark gaps will perform much better if air
is blown across the gaps.  Mine is positively worthless (~80% shorter
streamers) without airflow.

I would loose the RF chokes, which are ineffective by themselves without
bypass caps, or make matters worse with their own resonance with bypass
caps.

I didn't attempt to see if your pri/sec are in tune.  Is there a best
primary tap to indicate it being in tune?

With the transformers, hook up the two primaries in parallel, and the
same for the secondaries.  You have a 50-50 chance of getting it right.
It it's wrong, you'll get nothing (i.e. less that what you report).

A 9" diameter secondary is on the large side to be powered by OBITs.  It
may work, but may not be optimum, and this is uncharted territory.  The
reason is that you want most of the secondary capacitance to come from
the toroid, and not the self-capacitance of the coil.  It sounds like to
get yours to tune, you had to use just a small copper sphere.

And it's hard to tell from your photos, but your pri-sec coupling may be
on the low side.

Gary Lau
MA, USA


Original poster: "CJ Moore by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<wizard1234-at-home-dot-com>

I am somewhat of an amateur builder. I have made 2 coils. 1) was
horribly
pathetic and I won't even discuss it 
however, the second was in my opinion a decent small coil.
 
Powersupply - 2x Ignition transformers 10 kv 23 ma (in parallel_
Spark gap - series 4 bolts total gap of about .5 inches
Capacitor - 2x .02 uf 1500 kv
Primary - 7 turns of 3/4 inch copper refrigerator tubing (rising pancake
form)
Secondary - 26 inches high 9 inch diameter wound with 22 gauge wire
Toriod - Ventilation Duct (didn't work at all) just went with a copper
terminal.
2 RF Chokes which were just pieces of pipe with about 200 turns of 22
gauge
wire on them. 
 
With this system running, I would get a faint (really really faint)
corona
around the terminal, and if I put a grounded wire near it, maybe a 4
inch arc. 
 
I have seen other coilers pages and pictures and some people have built
coils
very similar to mine, but with much much better results, please tell me
what I
am doing wrong!
 
Here's a link to some pictures of my coil.
I have made some modifications (but don't have pictures) This is my
first spark
gap, not the one I use now. Don't think the transformers are hooked up
correctly. 
Just for a general idea. 
<http://members.home-dot-net/fredmoore/>http://members.home-dot-net/fredmoore/