RE: Question on Variac lighting

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Lau, Gary" <Gary.Lau@xxxxxx>

The best cap size is the one that makes the best sparks; it doesn't
matter at what point of the Variac the gap begins to fire.  That you
have control between 55% and 100% rather than 25% and 100% is just the
way it is for your coil.

Remember, the spark gap is supposed to be set to fire at the peak
unloaded voltage of the NST.  The fact that your gap fires at 25% or 55%
Variac means that some degree of mains resonance is occurring with the
NST secondary and your cap.  At 50% Variac, this allows the NST with an
open circuit secondary voltage of only half the gap breakdown voltage to
resonate with the cap to ring up on multiple mains cycles to the
breakdown voltage.  I think that in going to the bigger cap, you have
moved the NST/cap resonance further away from 60 Hz - actually a good
thing.

Hearing the hissing with no visible artifacts is normal.

Regards, Gary Lau
MA, USA


> Original poster: "JT Bowles" <jasotb@xxxxxxxxxxx>
>
> I had a 7.4(about) nF  MMC in my tesla coil. The spark gap would
> light at about 25% on my variac.
>
>
>
> After some issues, I now have a 10 nF MMC. But now, my spark gap
> lights at 55%! I have lost much, much control of power of my coil.
>
>
>
> *Before 55% on the variac, i can clearly hear hissing and high
> voltage corona coming from the coil, but in pitch dark, i see NO
> sources for the sound
> *Coil starts up at 55% power.
> Can somebody help me. I want to regain the ability to controll the
> coil. Any suggestions or solutions?
>
> Please respond ASAP. I am using my coil for my "Senior Success
> Seminar" for my high school(need to pass to graduate)
>