primary cap

From:  Bert Hickman [SMTP:bert.hickman-at-aquila-dot-com]
Sent:  Thursday, April 02, 1998 6:57 AM
To:  Tesla List
Subject:  Re: primary cap

Tesla List wrote:
> ----------
> From:  Hollmike [SMTP:Hollmike-at-aol-dot-com]
> Sent:  Wednesday, April 01, 1998 3:00 PM
> To:  tesla-at-pupman-dot-com
> Subject:  primary cap
>      I have tentatively concluded that I could use up to 0.03uF for my primary
> cap, but wanted to first get advice from those more knowledgable than myself
> before jumping in.  My main reason for wanting to increase the primary cap is
> that I just replaced the 4 X 16 toroid with a 6 X 20.  I found that to retune,
> I will have to splice about 1/4 of a turn of tubing to my primary.  This
> wouldn't present a problem, but I would rather increase the capacitance and
> reduce the number of turns.  I just want to get some advice before I decide
> this.
>     Thanks in advance for any suggestions,
> Mike Hollingsworth


Not to worry! The current rating of a neon transformer is not a
particularly precise parameter - identically-rated neons will deliver a
bit more (but usually not less) current than the faceplate rating
depending on manufacturing variations. Also, the "Q" of the tank-neon LC
circuit at 60 Hz resonance is actually fairly low (typically in the 5-10
range), so that you'll still get the benefits of resonant charging even
with a tank cap that's a bit larger than the calculated value. The gap
firing "spoils" this Q a bit, but you'll still see a 2-3X recharge
current multiplying effect.

Now if you go with a cap that's significantly (3X in your case) larger
than the ideal, the recharge current will tend to drop back towards the
faceplate ratings, and the maximum gap voltage and BPS rep-rate (static
gap) will correspondingly decline. The resonant "peak" of the neons-cap
would now be centered at around 43 Hz for your system. Other than
sluggish gap-firing you shouldn't encounter any other problems if your
system is already successfully withstanding the rigors of resonant

Let us know how it works!

-- Bert --