Re: D.C. Cox TCBA Article
Tesla List wrote:
> >From paynet-at-interaccess-dot-comTue Jun 18 22:13:21 1996
> Date: Tue, 18 Jun 1996 20:12:11 -0500
> From: Tedd Payne <paynet-at-interaccess-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: D.C. Cox TCBA Article
> I've just read the new issue of TCBA NEWS*, and there was an article of
> interest to those like myself who plan to build a smallish neon
> transformer-powered coil. In short, Cox compared (1) a "conventional"
> circuit with its spark gaps in series to the neon transformer secondary
> winding, and (2) a "recommended" circuit with its spark gaps in parallel to
> the neon transformer secondary.
> Also, he explained why the "recommended" circuit doesn't need additional
> "safety gaps" (or capacitors from neon transformer to ground), and described
> suitable torroid and air-core chokes for the "recommended" circuit.
> Finally, he recommended the use of fewer than 5 gaps in series for a 30mA
> transformer, saying that more would result in undesirable "overquenching".
> Since I haven't tried to repeat the details of his article here, I hope some
> of you have read it, and can comment on it.
> MY QUESTIONS:
> 1. Do you agree that the "recommended" circuit (fig. D) is better than the
> "conventional" circuit (fig. A)?
> 2. Do you agree that the torroid and air-core chokes described are
> appropriate & adequate?
> 3. Do you agree that additional "safety gaps" (and "capacitors to
> ground") are not needed in the "recommended" circuit?
> 4. Do you agree that fewer than 5 gaps in series should be used for a 30mA
> transformer, and that "overquenching" is a concern? If less than 5, how
> many? (Cox's article was unclear about this)
> Your feedback will be greatly appreciated!!!
> Tedd Payne
> * TCBA NEWS is a nice quarterly publication by Harry Goldman (518) 792-1003.
I will attempt an answer as best I can. Before I go to specifics, the
most important factor is that all Neon transformers are inherently weak
when consisdered for Tesla service. One should never consider them a
permanent fixture and always maintain 2 spares on hand for any coil
Now to your Questions, in order.
1. In general, yes I believe shunting gaps are better but not the
panacea Mr. Cox believes them to be. When the gaps stop firing, there is
still a load of expanded magnetic energy in the primary tank this will
kick back into the transformer.
2. Wouldn't go back to the air chokes on a dare!! That is old
technology and only a heavy ferrite toroid in the multi-millihenery range
(minimum) will help prevent all kickback. I have used 0.8 henry chokes
in some instances!
3. I have long ago cast the safety gaps aside. They often do as much
harm as good and besides, in the shunted gap mode, the main gap is also
the safety gaps. I still shunt each xfrmer lead to ground with 500pf!
4. This question is a non-issue. We have put on our tapes, for
years, the full scoop on this one. For a given power, toroid size and
input energy, the more gaps, the more quench! The more quench the more
radiation and less spark. Mr Cox may have picked up in this when he
visited our lab last year and I ran a small 50 watt disruptive coil with
a 15 series gap quencher (gaps set at .005" each). The tiny coil (shown
on our tapes) produced no spark whatsoever from its 10 inch toroid and
was absolutely silent (zero audible noise). It would light giant
fluorescent lights at 5 feet and turn light bulbs placed near it into
plasma globes due to the E-field around it.
Gaps and their number are a function of power applied, voltage applied,
the coefficient of coupling, and the desired result from the system based
on the terminal load. We have harped on this for years. There is no
My little "micro" system consisted of a .003ufd cap, secondary coil 2"X5"
using a 4KV 30ma neon (only 40 volts in from the variac- ~50VA) and a
large 10 inch toroid. I wanted and got RF radiation and a large E-field
with 15 gaps. To get longest sparks, I woud have altered the system to
use only 1 to 4 wide set gaps and a 12 KV transformer with a 6" toroid.
At the same time, I use 8 series gaps on our magnifier and get 9.5 times
the resonator length in output spark. So a lot of gaps is no guarantee
that your spark length will be shortened by the number of gaps only.
Generalities have a way of getting stuck in coiling lore and are a snare
to the feet of the advancing coiler. Know what you are after and build
accordingly. Only time in the lab in experiment will advise the best
There is no cure all for creating the "permanent" neon transformer beyond
using it in the service for which it was intended (neon lighting).
If we liken a neon sign transformer to a person and give him a nice 9-5
low stress job (neon service) and good food and recreation afterwards, he
will work out fine and last a long time. Putting a neon sign transformer
in Tesla service is like sending a person to Siberia for hard labor in
the salt mines. It is a death sentence! Do what you will to ensure your
survival there and you may last a little longer, but you will die in that
service, ultimatly and much sooner than the other guy at his 9-5 job.
Hope I have been of some help in clearing up the matter.
Richard Hull, TCBOR