Cox article in TCBA

To: tesla-at-pupman-dot-com
Subject: Cox article in TCBA
From: tweagan-at-maind.dnet.dupont-dot-com
Date: Wed, 19 Jun 96 03:22:46 EDT

<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".

He mentioned discussing this point with Mr.Hull

<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)?

Yes, the gap across the transformer does act like a safety gap reducing
the HV RF that would appear across the transformer if the cap were in its
place.

<2.  Do you agree that the torroid and air-core chokes described are
<appropriate & adequate?

Appropriate as in I believe they belong there but based on the lengthy
analysis and discussion recently regarding the preferred choke size I 
think the "30 turns" even on a toroid core is shy of the 5mH+ range most
of us shoot for.I also think the small air core choke meant for 1Mhz 
filtering is of questionable value.

<3.  Do you agree that additional "safety gaps" (and "capacitors to
<ground") are not needed in the "recommended" circuit?

The chokes, if they were larger, would filter out the hash from the primary
but what about the occasional spike coming back due to a discharge striking
the primary coil or its wiring? This bad boy needs somewhere to go-might
as well be to ground, the extra gap won't hurt.

<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)

This is something that can't be written in stone.Mabe if we were talking a
ridiculous number of gaps...the type of gap, gap distance, etc will shape
the final configuation

<Tedd Payne


<* TCBA NEWS is a nice quarterly publication by Harry Goldman (518) 792-1003. 

With this I whole heartedly agree!

Tom