First light and problems

From:  djQuecke [SMTP:djQuecke-at-worldnet.att-dot-net]
Sent:  Friday, June 26, 1998 2:23 PM
To:  Tesla List
Subject:  Re: First light and problems

I have just gotten my first coil up and running and am certainly no expert.
While I have no "suggestions" I will pass along what seems to work for me.

My coil has 4.3" sec., 21.5" high, 22awg. with a 15 turn inverted saucer
pri. 1/4" copper tube, spaced 1/4", currently tapped at 13.7 turns, .0053
cap.  I'm running much lower power than yours, 15kV 30ma NST (soon to be
doubled).  Toroid is 20" diameter.

Spacing between primary and secondary is 1 1/4".  Strike rail is 8 3/4"
spaced from secondary, 2 1/4" above primary, open circle.  After only minor
tuning, I'm getting 25" to grounded object, although free bolts appear much
longer.  I believe length difference with yours is mostly the higher current
you have available.

I have had zero strikes to primary or secondary  from strike rail and zero
strikes between pri and sec.  I get an occasional strike toroid to strike
rail which I hope means its working correctly.  With the power your using,
my thought is you really need to loosen things up a bit.

I view a well defined corona(?) enveloping the complete secondary and
spreading out to the diameter of pri at point of tap.  I got the numbers for
the spacing of my components from several suggestions on the list as well as
the archive, Weaver and Lau.

I'm very happy with performance at this point and can't wait to boost power
and really get this thing tuned up.

Good Luck,


>From:  Marco Denicolai [SMTP:marco-at-vistacom.fi]
>Sent:  Monday, June 22, 1998 12:43 AM
>To:  tesla-at-pupman-dot-com
>Subject:  First light and problems
>Last weekend I got my ground and my first TC ready: I had no variac and I
>it up at full power. I had before measure primary and secondary to resonate
>both at 240 KHz so the primary tap should have been about in the correct
>IT WORKED! I had about 1 meter long sparks running from the toroid into
>air, almost perfectly horizontal. After the first minute I run into
>1. I got 1-2 sparks from the strike rail hitting the middle of the
>I suppose my strike rail was too much near the secondary (the sparks made a
>10" travel from strike rail to the secondary body).
>2. Then I got some sparks from the inner primary turns to the secondary
>and primary to secondary about 3" height from its base. Because it was day
>and I was (safely) far from the coil, I couldn't notice any corona or aurea
>effects near the primary base, but I suppose the problem was the well known
>3. One diode from my MOT doubler blow up twice (always the same one).
>My coil data:
>Secondary 4.33" diameter, 19.7" wind with AWG 26 enamel wire, 7 layers of
>epoxy paint. Toroid 3.15" diameter tube, 11.4" outer diameter, 12.7 pF.
>Mounted 1.6" over the secondary top. The pair resonates at 240 KHz.
>Primary 7 turns of 3/16" copper tube, inner diameter 5.3", turn spacing
>0.3". Flat pancake. Clearance from inner turn to secondary 0.5".
>Secondary capacitor 0.05uF 50KV. Set to resonate also at 240 KHz.
>Primary turns and secondary first turns almost on the same horizontal
>Tank supply made of two MOTs and two voltage doublers, output 8 KVAC,
>almost 0.5A (I believe). A third MOT primary (with shorted secondary)
>was in series with the 2 MOT primaries on the 220V side to work as a shunt.
>Spark gap is a RQ static gap with blower and two series of 3 of 0.275" gaps
>connected in parallel.
>About the following solutions I would like very much some comments:
>Problem 1: I plan to rework my strike rail as an open ring about 3" high
>from the secondary base, about 8" horizontal clearance from the secondary
>4.33" pipe.
>Problem 2: rework the primary, increase the clearance between inner turn
>secondary to 1", make it a 15 degree upside-down saucer to distribute
>it magnetic field and decrease coupling.
>Problem 3: the two MOT employed were a 900W and a huge 1500W. The diode of
>the doubler of the last one keeps on blowing. I replaced the 1500W with
>900W and I hope this will stress less the diode.
>Your opinion is really welcome...
> Marco Denicolai                   Vista Communication Instruments, Inc.
> Hardware Development Manager      www.vistacom.fi
> marco-at-vistacom.fi                 Kaisaniemenkatu 13 A
> fax:    +358-9-622-5610           SF-00100 HELSINKI
> phone:  +358-9-622-623-15         Finland
>   Remember, Murphy was an optimist! I am not...