Re: tesla coil

["Tesla list" <tesla-at-pupman-dot-com>]

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

Hi Josh,

A common problem with first coils :-)  Don't worry, we'll figure it out.

I think you meant a 5 inch center primary taped at 3 turns and a 1.75 inch dia.
secondary with 680 turns of wire.

The cap size for a 9/30 is 8.842uF resonant at 200 BPS and the LTR (static gap)
size is 12nF.  So you should be fine using a 12nF cap.  If your NST is only
20mA instead of 30mA that may be a bit of a problem but I think something else
is wrong.  Info on this is in the tables at:

http://hot-streamer-dot-com/TeslaCoils/Misc/NSTStudy/NSTStudy.htm

My first guess would be that the primary and secondary are not tuned to the
same frequencies.  I don't have enough information to calculate the frequencies
here but If you let me know I can run the numbers.  I need to know the missing
info below:

Transformer voltage: 9kV
Transformer current: 30mA

Primary coil inner diameter: 5 inches
Primary coil turns: 3
Primary coil distance between turns: ??

Primary cap size : 12nF

type of spark gap: ??

Secondary coil diameter: 1.75 inches
Secondary coil turns: 680
Secondary coil length: ??
Height of first turn of secondary coil above primary coil: ??

Terminal diameter (side to side): ??
Width of donut section if it is a toroid: ??
Height of terminal (center) above primary coil: ??

I think that is everything :-)  With this data I can pretty much figure
everything out.  A 9kV/30mA NST should do about 25 inch arcs if everything is
just right, so something must be wrong.

Cheers,

        Terry


At 09:05 PM 1/1/2001 -0700, you wrote: 
>
> Hi I am new to tesla coils. I recently built a TC with a 1.75 diameter, 680
> turn primary and a 5 inch helical sec taped at 3 turns. Im using a 9-10kv
> 20-30?ma NST and a home rolled .012uf poly cap in mineral oil.  I was able to
> get 3 inch arcs out of the secondary. what would you sugest that I do to
> increase arc legnth? could the problome be my cap? (the equations and tesla
> softwair originaly called for .0079uf caps but the capacity on my cap went up
> to .012uf after I put it in a PVC pipe and filled it with oil) 
>  
> thanks,
> Josh