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RE: LITTLE TC PIX
Original poster: "Lau, Gary by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Gary.Lau-at-compaq-dot-com>
PLEASE keep us posted with your little coil progress. I'm just dying to
start a bug zapper xfmr based TC to further the small end of the coiling
spectrum, and yours seems to be on that same scale. Is that what your
xfmr is? I'll probably be using a single blown static gap, have you
tried adding forced air to your gap?
BTW, is that a gray METAL box that the primary support is resting on?
If so, I suspect it will be robbing a significant portion of the primary
energy as it will appear as a shorted turn closely coupled to the
Regards, Gary Lau
Original poster: "Ed Phillips by way of Terry Fritz
The other day I put some VERY unprofessional JPEG pictures of the
little coil described below in Terry's temp files. They can be found at
under the names "Li'L TC", "Li'l BANJO 1", and "Li'l BANJO 2". For
those who are interested the box in the first file is 6" wide, which
gives the scale of the rest of it. The coil shown is a slightly longer
version of the one below, wound with #34 wire; performance and resonant
frequency are almost exactly the same, but this coil doesn't have the
tendency to break down which the smaller one does. By the way, things
went much faster with the larger wire and the whole winding took only
about an hour and a half.
"Finally have a TC project to report. Built a small coil this weekend
with the following specs:
Secondary winding: 1.75" OD, 5.6" long
Wire size: #36
Top load: "Semi-toroid"*, about 3.5" OD
and 1.5" thick
Approximate turns: 750
Resonant frequency: Approximately 650 kHz
Primary: 3.5" OD x 1.4" long
Primary capacitor: 4 x 1900 uufd, ceramic filter caps in parallel
Primary transformer: 3 kV, 18 ma
Spark Gap: Victoreen SGCA-2500D sealed
Spark Frequency: Not measured yet, probably several
Construction: Rather crummy, I fear. This is the
2-1/2" plus streamers from #26 "breakout wire" taped to top
Without said wire about 4" very hot streamers to a screwdriver in the
hand. Get similar results with a 2" round brass doorknow for upper
terminal, but get a lot of discharge around the top of the winding.
Almost no sound when there are no streamers.
With the Victoreen gap replaced by a static gap set to "just
the capacitor disconnected get significantly greater streamers, but the
gap gets hot and stops quenching well so haven't made any measurements.
Need to make a cylinder gap and give it a try. Also have a problem with
occasional inter-turn arcs. Don't think there are any crossovers in the
winding, but nor sure although I can't see any. Winding this little
secondary by hand took over two hours. #36 wire is strong enough to
handle, but small enough to cause problems when laying it on the form.
All in all, a satisfying effort. I'm sure others have gotten
better performance from little coils, but this one pleases me. One
thing I haven't done is to measure the primary current. Although the
capacitor is well below resonance there must be a fair amount of input
power, as the Victoreen gap gets hot in a few seconds, the the spark in
the open gap is very, very bright.