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Re: Protecting Small Transformers




At 06:52 AM 24/04/00 -0600, you wrote:
>Original Poster: "Alexander Rice" <alexjrice-at-hotmail-dot-com> 
>
>Hi All!
>
>I recently built my first coil, it runs on a pair of OBIT's and will
>produce 1' streamers.
>
>Unfortunately I am suffering a rather high transformer kill count.
>
>I need some kind of filter network, but what exactly am I filtering
>and how should I go about doing it?
> 
>Thanks very much, Alex.
>
>
Hello Alex:

Welcome to the wonderful world of coiling!  I'm running a similar setup
to yours, so here's my recommendations.  Build yourself a safety gap to
put directly across the OBIT's.  I used a piece of 1/2 inch copper pipe
as my ground electrode, and two L brackets fitted with bolts and acorn
nuts as the two hot electrodes.  This allows easy adjustment, which you
should do with nothing but the safety gaps connected to the OBIT's.

For a filter, I have a 500 pF., 30 KV "doorknob" cap from each hot leg
to ground, essentially in parallel with the safety gaps.  Each hot leg
connects to the main spark gap thru a 1 K ohm, 30 watt resistor, which
forms the filter in conjunction with the bypass caps.  My main gap is
a RQ type like yours, with 7 segments.  The main capacitor and the TC
primary are connected in series, then paralleled across the main gap.

To keep the load balanced between your two OBITs, connect them in the
usual way for paralleling, but bring one lead to the safety gap and
filter off of each transformer, rather than both leads off of one.
Good luck with your coil.  Keep us posted on your progress.


73, Weazle, VE3EAR/VE3WZL

Listening: 147.030+ and 442.075+
E-mail:    weazle-at-hurontel.on.ca
           or ve3ear-at-rac.ca
Web site:  www.hurontel.on.ca/~weazle