Re: troubleshooting tesla coil, continued (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Fri, 14 Sep 2007 10:49:05 -0400
From: Marko Ruban <Marko@xxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: troubleshooting tesla coil, continued (fwd)

Yes, you're right, I meant to say 7nF, not pF (those damn units ;)

Initially, I built the cap to be 30nF, but then I would need a bigger
topload to balance it out.  So I took some plates out.  The capacitance
was measured with a home-built (calibrated) meter.  I'm waiting to get a
multi-meter now, then I can verify that value.  Capacitor construction is
sheets of 10mil copper foil separated with 10mil Mylar sheets, 1 inch
insulator margin on the sides.

So, as it is now, I should be able to see some sparks on the topload, IF
properly tuned?

I definitely intend to build a cooler spark gap later, but first I want
to get the coil running.


Tesla list wrote:

---------- Forwarded message ----------
Date: Thu, 13 Sep 2007 22:30:03 -0400
From: "Lau, Gary" <Gary.Lau@xxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: RE: troubleshooting tesla coil, continued (fwd)

I think you meant to say that your cap should be about 7nF (not pF).  I
can't tell how it is constructed, but it doesn't look nearly large
enough to be 7nF.  JavaTC  suggests an optimum value of 20nF for best
results, though you can certainly expect some reasonable sparks at 7nF.

Once you get your cap construction right, I'd suggest going for a larger
topload (a toroid is better than a sphere).  Also I strongly recommend a
better spark gap.  Two nails or screws arcing on a small surface with no
airflow is about as bad as it gets.  You really want to spread the
arcing surface out so no point gets too hot - parallel copper pipes.
And any forced airflow through the gap helps (you don't need heroic
measures; a small, focused fan is OK).  Both of these improvements
should bring considerable performance gains, after the tuning is
straightened out.  

Regards, Gary Lau
MA, USA

  

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.