Re: New coil

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

Original poster: "John Richardson" <jprich-at-up-dot-net> 


Hi DC,

Thanks for the input.  I think I'm going to follow yours and Bart's advice,
and go with a larger cap bank.  I realize that I should have done a scrap
wire primary first, but it was a Saturday afternoon, and I was a little too
anxious to build something.  In the future I will heed your advice.

Thanks,
John Richardson


 > Original poster: "Dr. Resonance" <resonance-at-jvlnet-dot-com>
 >
 >
 > Always start with a "scrap wire" primary --- usually some old 12 AWG house
 > wiring works fine.  Use 20 to 26 turns max so you can find your exact
tuning
 > point before putting the copper tubing in place.  This scrap wire pri has
a
 > bare turn scraped every turn and staggered slightly so they don't arc
over.
 >
 > Keep your total pri spark gap at 0.120 inch maximum while doing initial
 > tuning.  Also, never increase your variac beyond 35-40% max until all
tuning
 > is finished.
 >
 > This tuning should also include raising your sec coil in 1/2 inch
increments
 > to find the best coeff. of coupling match.  This is easy to do.  Use a
small
 > piece of brass attached to the underside of your upper sub-base.  This
brass
 > is drilled and tapped 1/4-20 NC.  Make a long 5 inch 1/4 brass stud coming
 > out of the bottom of your sec coil.  Then you can just screw the sec up
and
 > down until you find the sweet spot.  Later, cut off the excess brass stud
on
 > your sec coil.
 >
 > After all this is done you can bring your variac up to full power ---
never
 > before.
 >
 > It sounds like your NST and pri cap might be resonating --- in which case
it
 > can build up a resonance equal to 2.22 x Erms of the NST.  Be careful as
 > this can blow xmfr and caps.
 >
 > A good value for cap would be equal to 1.6 x resonant value for your xmfr.
 > See the Geek Group charts to find the resonant value for your particular
NST
 > and then use 1.6 x that value.  This insures your xmfr will not be in
 > resonance with your cap.
 >
 > Resonant value does assure max power transfer, but NSTs are not made to
 > withstand the resonance and will blow.  This also applies to MMC type
caps.
 > Set your MMC for approx 2.5 x Erms of the NSTs potential and you will not
 > have overvoltage problems.
 >
 > Dr. Resonance