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[Fwd: Solid state TC working! But.. (fwd)]




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Date: Mon, 3 Mar 1997 10:18:27 -0700
From: Jeff Detweiler <jd231825-at-engr.colostate.edu>
To: tesla-at-pupman-dot-com
Subject: Solid state TC working! But..

Greetings everyone,

I've been building Duane Bylund's solid state TC featured in the Sept.'91
issue of Radio-Electronics, and I finally have it working! The secondary is
800 turns of 30 AWG wound on a 5-gallon bucket (yes, a 5-gallon bucket!)
base-driven directly by the TC circuit. I got things hooked up just enough
to see if it works, and I get a nice 4-5" discharge from just the bare wire
in the air--haven't had time to make a discharge toroid yet. Duane Bylund
was kind enough to send me some photos of this exact setup producing as
long as 12" sparks, so at least I know what to aim for! I posted the
circuit schematic at the following website and also will send it to Chip:

http://www.engr.colostate.edu/~jd231825/tesla/schematic.gif

OK, here's the catch. The circuit drives a hand-wound ferrite core
transformer T2 (see schematic) that hooks directly to the secondary ala
magnifier fashion, but I would like to be able to interchange this
transformer with a flyback transformer to drive a large plasma globe I have
already built. T2 has a 10 turn primary, so I hand wound 10 turns around
this hefty flyback transformer I have (an older one rated for 25 kV or so)
and hooked it up.

When I turned up the juice with my variac, I got absolutely no output from
the flyback transformer at first. As I varied the frequency of the circuit,
I hit a "resonant" frequency of the flyback somewhere around 100 khz and
the transformer went from dead to producing a crackling 3" output
discharge. But it remained practically dead for all other frequencies.
Also, the spark output at the resonant freq. was the kind of crackling,
pulsed type spark you might expect from a capacitive-discharge TC, but not
the continuous, rather smooth spark I am used to getting from a flyback
transformer. Also, I should mention that I replaced D1 with a full-bridge
rectifier for this experiment so that the power transistors Q3 and Q4 have
continuous 160 VDC power, so I would expect continuous output from the
flyback.

Question is, is this circuit feasible for driving a flyback, and if so, how
should I go about it? Anybody have a good explanation for what is
happening? All comments and suggestions would be greatly appreciated! Also,
I just wanted to thank Malcolm and Bert Hickman again for all their help
already.

Jeff Detweiler


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