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Re: Still mystified by odd TC behavior, what gives?

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Jonathan,

If you can add another ~0.025 cap in series and it suddenly works, it does
sound like there may be a problem with the first cap.  It may be arcing
over internally or something but it would also be smoking and burning up.
However, if both caps are good, the effective capacitance will be divided
in half to around 0.012 which may simply be a far better point for you
cap/NST combinations to work at.  If the gap fires well with a given cap
but there is no output, that sure sounds like the primary circuit and the
secondary circuit are not tuned together.  I would try getting more turns
on the primary first.

The "sweet spot" should not be all that hard to find.  I wonder if your
primary has too few turns and you are simply not able to tune down low
enough in frequency.  You may want to figure out the primary and secondary
frequencies with one of the programs or equations to see where you are at.
There was not enough info here for me to do it.



At 07:03 AM 5/19/2001 -0700, you wrote:
>Howdy All,
>I have been struggling for over a week to figure out what the heck is
>going on here. If anyone can help me, I'd be soooo happy. Here is the
>Basic coil specs:
>Small secondary, 450 wraps of 22 AWG on a 3.5" form.
>Primary: Either a 12 turns 12 AWG auto wire on a 6.5" form, or 15 wraps
>10 AWG auto wire on a 8" form.
>PSU: Either a 12kv/120ma or 15kv/60ma.
>Vacuum single gap
>RF filter ALA Terry
>I recently got a Resonant Research Inc. .025 (actually tests to .023)
>tank cap. When I try to use it, with either transformer or even with
>both ganged up in parallel, I get no output from the secondary,
>regardless of how I tune the primary or set the SG. I can draw a wimpy
>spark to a ground rod, but that's it. The gap fires fine over a range of
>settings. As soon as I add another cap in series to the .023 and lower
>the capacitance, it fires up. Yet the gap isn't acting as I have seen in
>the past with too large a tank cap, which has always resulted in erratic
>SG performance.
>The only thing I can think of is that the "sweet spot" is really small,
>and as I only have taps on each turn on the large primary I haven't hit
>it right. Is it possible for the tuning to be so sensitive that one gets
>no output unless really close? The gap sounds mean and hot, but is it
>possible that the .025 cap is damaged? It seems unlikely considering the
>fury of the gap.
>If you can help, you're my Hero!
>Jonathan Peakall (The other OTHER Jonathan)