Re: Tuning help

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

Original poster: Esondrmn-at-aol-dot-com 

In a message dated 8/21/03 7:32:28 AM Pacific Daylight Time, 
tesla-at-pupman-dot-com writes:

John,

I ran some quick calculations on your coil.  If you really have 5 .01 uf 
caps in series, for .002 uf per string, and 25 strings in parallel, you 
have a total of .05 uf.  This is about twice as much as you need to be in 
tune.  When tapped at turn 7, you need only about .017 uf.  When tapped at 
turn 6 (which allows some room for tuning) you need .024 uf.  So - remove 
about one half of the strings, start at turn 6 and tune for longest sparks.

Ed Sonderman

>Hello,
>I'm "kind of a newbie" and I need some serious help with my coil
>I can't seem to tune it. Does anyone have any suggestions.
>The specs are as follows:
>
>Transformer
>120v 60Hz
>2 Mots stacked for 4800vac
>secondaries connected to core- cores grounded
>2400vac relative to ground
>PFC
>No filter
>
>
>   Spark Gap
>Adjustable single half ball gap with fan (65CFM airflow)
>I think I'll try to build a sync gap
>
>Tank Cap
>MMC Type
>5 in series 25 in parallel 125 total
>Each cap 0.01uF 3KV
>0.05 uF 20% tolerance each cap
>Rated 15000 VDC
>Made from ceramic High Q caps
>Cap bank has been checked for damage by visual a multimeter inspection- not
>damaged
>
>Primary
>Type- Flat "pancake" coil
>7 turns
>1/4 inch copper tubing
>1/2 spacing between turns
>1 inch spacing between inner most turn and secondary
>4 inch width of coil
>3/4 of an inch from base
>3.81 uh need to form resonant freq of 363kHz
>14.051uh total -formals used
>Strike rail - open loop, 4inches above primary connected to bottom of
>secondary
>
>Secondary
>aspect ratio of 6:1
>3 inch by 18 inch
>#24 enameled magnet wire
>about 900 turns
>Top load- toroid 16.117pF
>resonant feq at 363kHz with top load -measured
>1/4 inch above primary
>Top load close to secondary for electrostatic shielding - see I do know
>something
>wound on power line grounding insulator
>
>Misc
>When feed from my oscillator at 363kHz and 10 volts
>a voltage of about 400 volts is generated
>All connections have been checked repeatably.
>The ground is good.
>
>I have a Tektronix 533A oscilloscope (still works), oscillator, and a
>multimeter
>
>All comments are welcome - Please help,
>John