Re: Awsome first light !! but...

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

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

Hi Kevin,

At 08:21 PM 8/1/2001 -0500, you wrote:
>
>What size primary cap do you have?  I would guess the system is resonant
>and the main gap is having some problem where it's firing voltage is going
>higher as it opperates.
>
>Please don't change the safety gaps since that should not be the problem.
>
>Cheers,
>
>	Terry
>
>
>Primary cap is 9.3 nF, LTR with my 12/30 NST. So a cap safety gap is 
>unnecessary? 

"I" would always use at least a safety gap across the NST no matter what.
If say, the MMC should fail, it will save the NST.  Sort of like seat
belts, 99.9% of the time you don't needed them but...

>And if I use one, I should have a current limiting resistor? 
>What value resistor and what wattage would be good? I’m sure this has been 
>covered, but I couldn’t find any info in the archive. 

I think you are referring to a resistor in series with a safety gap across
the primary cap.  The resistor and safety gap across the primary cap is not
needed with an MMC type primary cap.  Old oil caps could not self heal and
did not have much margin so safety gaps were a good idea "then."  The
series resistor was to limit the short circuit current if the safety gap
fired and directly shorted the cap.  A few systems used to destroy
commercial caps until the resistors were added.  Directly shorting a Tesla
coil cap can draw tens of thousands of amps!!

>How do I go about 
>tuning this thing? Leave the cap safety gap at 12 kV and close the main gap 
>down? Tune, widen main gap slightly, retune, and repeat? When do I stop 
>widening the main gap, when it gets to 12 kV? Although Terry supplied my 
>caps cheaply and quickly (thanks), Id hate to reorder. Thanks for any help, 

With everything disconnected from the NST, it will output it's rated
voltage.  You can then connect "only" the safety gap to the NST and adjust
the gap so it will barely just not fire.  You can also connect "only" the
main gap to the NST and adjust it so it will fire consistently at the
highest gap setting.  Never connect the primary cap to the NST by itself.
Be careful when adjusting the gaps so you don't shock yourself.

Cheers,
	
	Terry

>Kevin
>