Re: New TSG results

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Barton B. Anderson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <tesla123-at-pacbell-dot-net>

John -

Thank you for your write up below on the Jon Tebbs circuit. As you know, I
built it
too. It worked excellent up until I fired up the coil and I killed the pnp
tranny
and 555. I've been talking with Jon offline periodically about this
occurance. I
also pulled out the MOT diode and found I had a H.O.T. with an internal damper
which I replaced it with. As I was nearing completing my board check
(scoping out
the signals), the scope went out (it's always done this). I spent the rest
of last
Saturday trying to resolve the scope problem and haven't got back to the
circuit.

I am curious how I killed the components and I'm leaning toward grounding the
board. When I killed it, I had RF ground connected to circuit ground. I've
since
removed RF ground, but I still need to get back out into the garage and get it
running again. Can you let me know how you set up circuit ground? Also, do
you have
the entire circuit at the gap or any part of it at a control panel?

Thanks and take care,
Bart
--
Barton B. Anderson
http://www.classictesla-dot-com

Tesla list wrote:

> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<FutureT-at-aol-dot-com>
>
> Hello all,
>
> Using a modified setup, I had excellent results using the STSG
> today on my TT-42 TC.  In a direct comparison with the sync rotary,
> it was hard to tell the difference.  Both seemed to hit the 40"
> measuring wire with equal ease.  The rotary sparks may have been
> a little stronger and bushier, but it was subjective.  There was not a
> clear-cut nor easy to see difference.  I have a lot of burned spots
> on the secondary from previous TSG tests, so there may be a
> short in the secondary, but I'm not sure.  When I set the
> measuring wire at 42" the rotary setup spark reached the wire
> one time, the TSG sparks did not.  There are probably greater
> losses in such a long gap arc, but it doesn't seem to affect
> the coil's spark streamer length very much.  My gap spacing is
> about 9/16".  I didn't try adjusting it differently, but it's possible
> I may be able to adjust it a little closer.
>
> I had to use a small house fan blowing on the main single static
> triggered gap to prevent power arcing.  Without the fan, the coil
> sputtered and sparks were unsteady and weak.  Even using
> the fan, the coil sputtered occasionally, so it may have needed
> a little more air flow.  I'm still using the heavy copper electrodes
> with thick silver faces as the main static gap electrodes.  The
> spark gap is very bright and gives a white-hot arc.
>
> I built, and am now using John Tebb's phase controller circuit design
> which uses a 555 timer, a zero crossing detector, a few transistors,
> and some other parts.  At first I was not getting a powerful enough
> spark from the HEIC, but it turns out that the microwave oven diode
> I was using in place of the damper diode was reducing the HEIC's
> output.  I didn't try using a different diode, rather I just ran the
> circuit without the diode for these tests.   The HEIC gives about a
> 9/16" maximum length spark with my setup.  I used a rather
> small power transformer but it seems adequate.  I used about
> 1.3 ohms in series with the HEIC.  An 18awg 6 foot zipcord connects
> the  controller to the HEIC.  The controller circuit is built onto a
> 3.25" x 5" perfboard, which is in turn mounted onto a 6" x 8" wooden
> base which also holds the small power transformer and the phase
> control pot and knob.  All the parts run cool or just slightly warm.
> Only the transformer, the input power rectifier (I used half of a
> bridge), the HEIC series resistors, and the H.O.T. run slightly
> warm.  The H.O.T. is mounted onto a nice heatsink.  John's
> design performed excellently overall (thanks John!).
>
> For best results, the phase adjustment is quite critical.  If turned
> one way, the coil stops firing, if turned the other way, the coil
> sputters.  Before when I used the lamp dimmer type controller, I didn't
> have quite enough phase range as I suspected.  The limited
> phase range prevented me from turning up the coil to full power.
> Now, with the John Tebbs controller, I'm able to turn up the
> variac all the way to 140 volts.  I didn't monitor the gap firing
> with a scope, but there should not be much or any jitter.
>
> In future work, I plan to monitor the gap firing, measure the
> quench time, and build a spark gap similar to Gary Lau's vortex
> gap, to use with the trigger electrode.  I want to try to keep everything
> as compact as possible.  Finally, a variable break-rate TSG
> would be an interesting project.
>
> The STSG is clearly an excellent gap choice for many coiling
> situations.  For small coils, no air flow is needed, so the gap
> can be quite compact.  The use of a triggered multiple gap
> also may eliminate the need for cooling/quenching airflow, up
> to some particular power level.
>
> Cheers,
> John