Re: it works!
Subject: Re: it works!
From: Terry Fritz <twftesla-at-uswest-dot-net>
Date: Sun, 25 Jul 1999 18:05:39 -0600
At 03:28 PM 7/25/99 -0400, you wrote:
>Well, my coil finally gets output. I rechecked my wiring and found that
>the secondary ground had worked loose. I seem to get maximum output from
>about 7.2 turns.
Wow! I calculated 7.3 turns from the info you gave before! Nice to know I
got that close...
>I got constant 14"-16" streamers with some
>occassionally going out to 20"ish. I'm currently running a 12/60 NST,
>.0106 EMMC, 16" 22AWG secondary on 4" PVC. Toroid is 19" x 4" aluminum.
>My spark gap is a lame set of two bolts. So now I have some more
>1) how much improvement would a better SG give me? How about going to a
The 15 vs 12 kV transformer will only make a moderate improvement.
>2) how high should my secondary be relative to the primary? What are
>the signs that it's too high or too low?
I would go 6" to 12" from the top secondary winding to the center of the
torroid. Field mapping could tell you exactly but this is close enough for
practical purposes. If it is too low, the output sparks will get shorter.
If it is too high, you will get arcs of the top of the secondary windings.
>3) how wide should I set my spark gap? At what point am I putting my
>NST in danger?
That is very hard to say. Depends on the exact shape and other factors
about the gap electrodes as well as altitude. I would put the gap across
the transformer with NOTHING else in the circuit. The transformer will
then produce its rated voltage across the gap so you can set the gap to
where it just fires. Then the gap will be set to your transformers proper
>4) how should I set my safety gap? Should I short the primary and
>adjust the safety until it just doesn't fire?
Just like the above but set the gap to where it just does NOT fire.
>Thanks to everyone who helped me with questions about getting my coil to
>fire. I took some digital pics of my coil not operating and will post
>them soon. I have an old Pentax K1000 and plan to try some operating
>pics soon too.
>On another note: I have fired my coil for about 60 seconds followed by
>60 secs off and repeated this about 15 times and my EMMC caps were not
>even warm to the touch. I'm using 2 strings of 10 of the .056 1600V
Them are good caps!! Mine stay cold too. With a 12kV transformer you
should be fine. I ordered a thousand of those puppies that I'll sell at
cost ($1.40 each) but they are back ordered for a month or so...
I would say the spark gap should be the first thing you should work on
improving. you may want to consider a fast and easy multi gap like the one
I show at:
A rotary sync gap made from an induction motor is best,but the simple gap
above is pretty fast and easy and should be a big improvement.
Very glad you got your coil working. Have fun!!