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Re: BIG resonance! - thoughts...
John,
Thanks for your input, a couple more questions....
>
> Jon, all,
>
> The wider gap gives the large cap the extra time it needs to charge up.
> I use a .0147uF which works well. In general, the largest cap you can
> use, and successfully charge to full voltage, will give the best spark
> output. There's a danger though; you might be firing every 60Hz, instead
> of every 120Hz, this might let the voltage build too high and ruin the
NST.
> In general wide gaps tend to destroy NST's.
How do I know when the tank cap has successfully charged to full voltage?
> I had a 12kV, 30ma NST one time that was especially robust; it was
> able to charge a .0087uF cap. THis gave a good output of 40" using
> static gaps. A typical NST of that rating cannot charge the .0087uF
> cap, but only a .0073uF or so. THis reduces the spark output to about
> 36" or so. But by using a sync rotary, I was able to bring the spark back
> up to 42", and also *protect* the NST to some degree in the process,
> and obtain a much smoother and better overall result.
With my main gap at 0.336" it will fire steadily, miss a few firings, then
continue on with no problem. When it misfires it scares the heck out of me
as my first thought is that something died. When it misfires it seems as
though it must miss maybe 10 firings! I would think that the safety gap
would fire when the main gap misfires, but it doesn't. Am I setting my
safety gap correctly? I have two gaps to ground, each gap is 0.312". If I
set the safety to 0.250 once it fires it won't stop.
>
> > It seems like the new toroid, (6" x 28", 35.43pF), is about the maximum
> size
> > that my coil will support. I'm now getting some turn to turn arcs near
the
> >top of the secondary.
>
> Probably. If you're toroid is 3" or more above the secondary, you could
> try lowering it about 1" and it might stop the turn to turn arcs, but it
> might
> reduce your spark output by 1" or so also.
My toroid was about 1.5" above the secondary, I lowered it to where it was
even with the top turn and the turn to turn sparks stopped, but then the
toroid was much to close to my 15 degree primary and I got lots of strikes
to the strike rail. I'm now in the process of rebuilding the primary. A
"pancake" design will give me about 3" more distance to the toroid. Should
help.
Sounds like there is a sync rotary gap in my future.
Jon Rosenstiel