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First light and problems



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From:  Esondrmn-at-aol-dot-com [SMTP:Esondrmn-at-aol-dot-com]
Sent:  Wednesday, June 24, 1998 10:27 AM
To:  tesla-at-pupman-dot-com
Subject:  Re: First light and problems

In a message dated 98-06-23 03:21:30 EDT, you write:

<< 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
fired
 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
 position.
 
 IT WORKED! I had about 1 meter long sparks running from the toroid into free
 air, almost perfectly horizontal. After the first minute I run into
problems...
 
 1. I got 1-2 sparks from the strike rail hitting the middle of the secondary.
 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 base
 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
 overcoupling.
 
 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 plane.
 
 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 and
 secondary to 1", make it a 15 degree upside-down saucer to distribute better
 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
another
 900W and I hope this will stress less the diode.
 
 Your opinion is really welcome...
  >>
Marco,

I would definitely reposition the strike rail so it is slightly outside of the
last turn on the primary and up about 2.0" above the primary (2.0" clearance).
I would open up the primary and allow about 1.0" clearance between the
secondary and the inner turn of the primary.  I would leave it as a flat
pancake.  Space the secondary up about 1.0 or 2.0".  Now put something in
series with the line power to the MOTs to reduce the current, preferably an
inductor like a variac or welder or even resistive ballast.  You need to do
some tuning at lower power to make sure things are tuned properly and to check
the coupling (in the dark) before again applying full power  -- or of course
get a variac to control the beast.

Ed Sonderman