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A tragic coil




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From:  Bert Hickman [SMTP:bert.hickman-at-aquila-dot-com]
Sent:  Saturday, February 21, 1998 9:43 AM
To:  Tesla List
Subject:  Re: A tragic coil

Tesla List wrote:
> 
> ----------
> From:  mark [SMTP:moyson-at-tig-dot-com.au]
> Sent:  Saturday, February 21, 1998 4:30 AM
> To:  Tesla List
> Subject:  Re: A tragic coil

<SNIP>

> >
> >Mark,
> >
> >Your primary tank circuit must be tuned to oscillate at the same
> >frequency as your secondary for optimal operation. When you changed the
> >tank cap did you retune the system?
> 
> I recalculated the capacitance and inductance and tried to mach up the
> values as best I could!
> I am having a hell of a time tuning this coil....never before has there been
> so many problems.

>From one of your other posts, it also sounds like your power source (an
ignition coil) may be overloaded by the relatively large size tank cap
you're using (0.01 uF). The ignition coil may not have enough current to
adequately charge the cap. A neon sign transformer would be a better
power source for this size tank cap. To use the ignition coil, you may
want to fabricate some Salt Water bottle caps instead. They're cheap to
make and easy to build. I'd suspect your ignition coil may not be able
to drive much more than about 0.001-0.002 uF properly. What are you
using to drive the primary of the ignition coil?

<SNIP>
> 
> If you have relatively few turns on the secondary,
> >this may be one of the major reasons why the coil is a poor performer. A
> >tight-wound secondary, with moderate gauge (#22-26 AWG) wire will give
> >you better performance.
> 
> This prewound coil looks to have 30AWG wire.

<SNIP>

Sounds like you need rewind the coil with some close-wound magnet wire.
A small (say 2" x 10") toroid at the top will help as well once you get
other parts of the system working properly.

> 
> I am using a bank of 3KV caps....new ones Ive never seen before! They seem
> to be really good but pricy at $1.95 a pop.
> 
> Also I have seen a high pulse discharge cap for strobe lights rated at 7ufd
> and 250VAC. Could you use this in any way??

The 7 uF cap can't be used in a spark-gap type Tesla Coil - it's got too
low an operating voltage. And, because it's probably an electrolytic
cap, it also can't withstand the voltage reversals necessary for the
primary tank circuit to oscillate properly. What do your new caps look
like?

Safe coilin' to you, Mark!

-- Bert --