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Re: [TCML] Tesla Coil not working (probably primary/secondary/top load issue)

Comments interspersed:

On Sat, Aug 14, 2010 at 1:39 AM, Ray Whiteside <rs.whiteside@xxxxxxxxxxx>wrote:

> I apologize for what is probably the most typical topic you guys usually
> get
> here, but after quite a bit of troubleshooting and personal research you
> guys have been the best source I have found by far.
> I am not going to dig up all the specs for things I don't think are
> particularly important, but of course I can provide them on request.
> I am in the U.S. so this is all hooked up to 120 V at 60 Hz.
> This is hooked up in parallel to a set of PFC caps, in parallel with my
> 9kV/35mA center tapped NST, in parallel with a Terry Filter.

I assume the PFC caps to the primary and the Terry filter to the secondary?
35mA seems like an odd current rating, typically it's 20, 30, or 60 mA.

> I then have a
> static spark gap hooked up in parallel. Then 8 .15 micro farad 942C caps in
> series in series with my primary coil, which is all again in parallel with
> the spark gap. To my understanding this is pretty standard. Along the lines
> of my email earlier today my primary is a little over 9 turns of 10 AWG
> wire, not copper pipe. I then have 800ft of 24 gauge magnetic wire wound
> around a 3 inch diameter PVC pipe with a cap with a bolt through the top on
> which I plan to mount a dual pie plate/4inch aluminum ducting top load on
> it. I have not made the top load yet.

So you're running your coil, but without the top load?  Kind of like driving
a car that you plan to put wheels on to someday?  ;-)

> When I say "not working" I specifically mean there are no sparks coming off
> of the top load that I can see in the dark. The spark gap is firing many
> times a second (I assume 120 times a second) as it should be. I originally
> had a problem in which I was using a tank cap that had a capacitance value
> that was much, much too low, and while the spark gap was still firing the
> difference when I put in the correctly sized caps was staggering.
> Considering the size of my coil there is a LOT of power being put through
> that spark gap. I think it is reasonable to say that given that, everything
> behind the spark gap seems to be working. That leaves the capacitors, the
> primary, the secondary, and the top load. Because of the difference in the
> spark, it seems the capacitors are charging to a significant value, though
> it is difficult for me to test what value they are actually getting to. But
> then electrically, I don't know how the primary or secondary could be
> "wrong" - they are just coils of wire. As was brought up in the other email
> there could be losses because I am using a stranded wire (thanks Gary Lau
> in
> particular), but would these losses be significant enough to make the coil
> not spark off the top load at all?

The difference between stranded and solid wire probably isn't
earth-shattering.  Just something for perfectionists trying to squeeze out
the last inch of spark to obsess about.

The secondary is grounded to a large
> metal plate sitting on concrete in the driveway. I can go buy a copper pipe
> and drive that sucker into the ground without too much trouble, but again I
> find it difficult to believe this is the root of the issue.

The quality of the RF ground won't make a difference in spark length; it
will affect only how much RF garbage gets into your power mains.

> I have a fluorescent bulb that is clearly glowing when placed around the
> secondary, and is much brighter the closer it is. It is also glowing but
> not
> nearly as bright when the coil is in operation but the primary is not
> hooked
> up. From this I know that energy coming from at least the primary and I
> would assume the secondary (because again they are merely coils of wire
> that
> should follow very basic physical principles). Again though, no sparks at
> all off the top. I have also tried tapping the primary at 4 different
> points
> a total of about 3/4ths of a winding apart, there seemed to be little if
> any
> difference in the bulb at these different tap points.
> I have not actually built the top load yet, that is the first thing on my
> list tomorrow. I have had a single aluminum pie plate bolted to the top and
> hooked up to the secondary for the majority of this testing. Towards the
> end
> I took off the pie plate so that there was only a bolt connected to the
> secondary left at the top. I know this does effect the resonance value, but
> again is the difference on such an order of magnitude that it would go from
> not working at all to functional? And I was trying to tune the coil, but it
> seemed to have no effect.

Unless you haven't mentioned it, it's not clear that you've made any effort
to tune your primary to the same frequency as your secondary.  The
difference between using and not using a topload is huge and would require a
significantly different primary configuration.  Sounds like you need to use
a TC design program that calculates the various primary & secondary
component values.

> ...must finish before I have to go back to school in a week. Any insight
> you
> guys have to offer as I beat my head against my desk after another session
> of fruitless google/mailing list searches is greatly appreciated. :)
> --
> Raymond Whiteside

Regards, Gary Lau

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