Re: troubleshooting tesla coil, continued (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Fri, 14 Sep 2007 19:07:04 -0700
From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: troubleshooting tesla coil, continued (fwd)

Hi Marko,

I was thinking that "you might be thinking" you could increase 
inductance to suit your "as is" cap size.

If for some silly reason you wanted to keep your cap "as is", you could 
increase primary inductance (a lot). 22 turns would be required using 
the same wire size and spacing of your existing primary. This would 
yield the needed 77uH of inductance. But, the primary would have to 
positioned with the top of the primary only 3" above the bottom of the 
secondary with the remaining primary turns below the secondary in order 
to keep coupling to a usable level (0.128). The primary from top to 
bottom would be about 11", so the bottom would extend about 8" below the 
secondary bottom turn.

Yes, all that is doable but a bad idea. You'll be well on the opposite 
side of cap resonance, so there can't be any gap failures or your new 
12/60 NST will be doomed. Also, be aware that with such a small cap 
size, bps will be ridiculously high and each bang will be ridiculously 
low energy. This situation is not good.

You are far better off with a cap size of 0.0185uF or in that range (for 
NST protection and good spark lengths). But even this with your existing 
coil isn't great because you would have only 2 turns of primary 
inductance. The problem is the small topload.

If you throw on a 4" x 16" toroid with a 8" center disc placed center to 
the toroid (using a 0.185uF cap), you can use your existing primary as 
is without change (except slight tuning). That's the ticket for a good 
43 inch sparks!

Here's what your coil could look like as a performer:
http://www.classictesla.com/temp/Marko.gif

Here's Javatc for this particular setup (btw, note the static gap 
dimensions, it's important and air is required):
http://www.classictesla.com/temp/Marko.txt

Just a thought.
Bart

Tesla list wrote:

>---------- Forwarded message ----------
>Date: Thu, 13 Sep 2007 19:19:45 -0400
>From: Marko Ruban <Marko@xxxxxxxx>
>To: Tesla list <tesla@xxxxxxxxxx>
>Subject: troubleshooting tesla coil, continued
>
>Hello guys, I'm back from a long summer vacation.  As per previous 
>suggestions I have acquired an old NST transformer (12kV, 60Hz, 60mA 
>output).  And the spark gap does run now with capacitor/primary in 
>circuit.  However, there's no visible effect on the topload, still.  
>Could it be that badly un-tuned?
>
>Please see the photo of my simple setup and make any suggestions...
>http://marko.dppl.com/TC_setup.jpg
>
>The flat rectangular thing in front, is the capacitor, which should be 
>about 7pF.  Can't make a more specific measurement since my new 
>multimeter is still in the mail.  Spark gap is on top of the NST, and 
>consists of two screws facing each other (about 0.2" adjustable 
>spacing).  Wire running in the back to the right is the ground.
>
>Also, here's a dump of JavaTC for my coil...
>http://marko.dppl.com/coil.txt
>
>Thanks in advance for any assistance.
>
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