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First light and problems
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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 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...
________________________________________________________________________