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Re: Help PLEASE! So close.. and yet...

Yuri,

You don't mention if you tried tuning the coil in your post . . .  You
may just be grossly out of tune.

Only five turns in the primary doesn't give you much leeway.  Try 9 - 12
turns if possible.  

Your cap is probably too small.  Tesla coils may not be an exact
science, but there are rules to follow.  How much capacitance do you
have in the Leyden jars?  Calculate the surface area of the glass or
plastic that is covered inside and out and guestimate the thickness and
plug it into a formula with the (right) dielectric constant.  You say A
Leyden jar . . . that's not plural?  If you only have one, you are
probably too low by a factor of ten or twenty.

You want about .009 microfarads for that transformer.

Another thing to look at: there should be a very marked difference
between no cap, and the cap in the circuit.  The spark gap should be
much more noisy and bright with the cap.  (but until you try a few
different caps, you won't be able to judge it)

Put a fluorescent lamp near the top of the coil (don't hold on to the
lamp).  With the gap firing, it should light.  Try it in a dark room if
necessary.  If you get some light, change the tuning slightly.  If you
find you need all five turns for maximum brightness, you need more than
five.

My guess is your cap is too low and your primary is too small (low
inductance).  More turns and/or bigger cap should fix it.

A shorted turn directly under the primary coil will cause it to not
work, but usually there is a little light and smoke, to let you know
about that kind of problem.  Ditto, if the tube is bad.

Be careful
bob

Tesla List wrote:
> 
> Original Poster: "Yuri Markov" <wmondale-at-hotmail-dot-com>
> 
> Well, I fired up my "not shooting for anything glorious" coil for the
> first time. I had a problem. The transformer, capacitor, spark gap,
> and whole tank circuit work perfectly. Real nice, cool sounding
> sparks in the gap, everything perfect. Only one slight detail - the
> secondary coil and discharge terminal did nothing. Absolutely
> nothing. I tried grounding the bottom to a well, and then directly to
> the house ground, to no avail. In case it helps: The power supply is
> 7500 volts at 30 milliamps(that's 220 watts). The capacitor is a
> leydan jar of an unknown capacitance. The primary is about five turns
> of really big fat copper stuff. As I said, that all works fine. The
> secondary is 30 AWG enamled magnet wire (the really thin red stuff -
> it was all I had) wound about 3/4 the height of a thin untreated
> cardbord wrapping paper tube (2 inches diameter). A softball wrapped
> nice and smoothly in aluminum serves as the discharge terminal. What
> is wrong? Is the cardboard conducting all the RF? Is the wire fatally
> thin? Help, please!
> 
> -Yuri Markov, would-be coiler