Re: First Power Up Test

Tesla List wrote:
> >From ccurran-at-execpc-dot-comWed Jul 31 21:42:01 1996
> Date: Wed, 31 Jul 1996 08:39:49 -0500
> From: Chuck Curran <ccurran-at-execpc-dot-com>
> To: Tesla List <tesla-at-poodle.pupman-dot-com>
> Subject: First Power Up Test
> Hello Group:
>         Well, last night I was able to get enough time to set up and accomplish
> my first test firing of my new coil.  It immediately shot out a 20"
> spark from the toroid to my "test ground" which was simply a chunk of
> #14 wire going from my earth ground to a point within 20" of the
> toroid.  This spark was very thin and blue, but the multiple arcs from
> the outer primary turn to the strike rail mounted about 1 3/4" above the
> outer primary turn were wide and white--there seemed to be 3-4 firing
> almost at the same time.  Apparently my next step will be to get the
> primary and secondary resonant frequencies closer together!  My
> secondary with the toroid resonates at 140 Khz so I then picked a tap
> point to give a primary resonance at 130 Khz to compensate for the
> charge build-up on the toroid which I understand typically drrops the
> secondary resonance point.  My toroid is 48" in diameter using 6"
> aluminum flexible duct as the outer ring.  I had seen up to about 220
> volts going in and 4.5 amps and it was sparking--I stopped watching the
> panel then and just watched the primary arcs!! Any opinions on whether I
> should move my tap to a lower frequency first?  Since I am asking a
> question here I'd better list some system specs too:
> Power Supply: 14,400 VAC 10KVA pole pig limited with a Century Arc
> Welder (set a minimum settings for first test)
> Spark Gap: seven gap 1 1/2" dia. copper tube sytem with fan, in series
> with a  rotary--12 breaks/rev running slow--maybe 1500-2500 RPM???
> Primary:  14 turns of 1/2" copper with 1/2" gap between turns.  About
> 11" I.D. and 40" O.D.------Tapped at 9 3/4 turns.  Condenser Products
> .025 Mfd cap at 20,000 volts same as many in the group.
> Secondary:  8" dia, acrylic form with 28" of #20 wire using a 48" dia.
> toroid.
> I figure if anyone could suggest going up or down in my primary
> resonance point it might save me some time and possibly reduce the risk
> of lots of generating lots of smoke!!  I already have apparently blown
> the free digital volt meter I got!  Tonight I hope to try again so any
> comments about your past efforts and knowledge would be appreciated.
> Thanks
> Chuck Curran


I would make sure that the strike rail wire is indeed open and not a 
shorted turn.  I assume you know this.  I have nevr seen arcs leap from 
the primary to the strike rail!!

First, characterize your secondary in-place, with toroid on.  That is, 
find its frequency of resonance while in the primary system.  Next, tune 
or tap the primary to that frequency and use a small grounded rod to tune 
the system by firing it at reduced power until the sparks hit the 
grounded rod.  Note the variac position when strike occurs.  Now move out 
one turn on the primary tap point.  Next, see if, at the same variac 
position, you get an arc.  If so, move the grounded rod further away and 
do this until you are satisfied you have the longest spark at a given 
setting.  Rarely will more than one turn "out" from "instrument tune" be 

Richard Hull, TCBOR