Re: troubleshooting tesla coil, continued (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Sun, 16 Sep 2007 16:43:56 -0400
From: Marko Ruban <Marko@xxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: troubleshooting tesla coil, continued (fwd)

As I mentioned a bit earlier, I made an error in units, my cap was an
estimated 7nF (not pF).  I finally got the multimeter, and that value was
confirmed since initial post.

Capacitor is constructed with 4 pairs of 10mil copper sheets (6" x 8")
separated by 10mil Mylar sheets with 1" margin on the sides.  I picked
Mylar because it has a high dielectric value and high breakdown voltage.
10mil sheet is rated at 70kV.


Tesla list wrote:

---------- Forwarded message ----------
Date: Fri, 14 Sep 2007 18:17:24 -0700
From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: troubleshooting tesla coil, continued (fwd)

Hi Marko,

Your inserting 0.007uF into Javatc so the frequency's do match as they 
should at that capacitance. However, your "saying" 7pF and that is way 
off from both Javatc and what the plate cap really is. Judging by your 
plate cap configuration, it is about 0.7nF (not 7nF) if your using glass 
as an insulator. If air is your insulator, then it's down to 0.1nF.

So you are way out of tune. The fix is the cap. For a plate cap using 
glass with about 0.2" spacing, you would need a plate surface area of 
900 square inches (30" x 30").


If your going to use a plate cap, you might want to consider Castor oil 
which has a high dielectric of 5. About 15 plates (8" x 11") with a 0.2" 
spacing between plates would yield near 7nF (which is 0.007uF). Plate 
caps are fun to play with, but when you start building to a capacitance 
such as this, it can get bulky and messy. I of course recommend an MMC 
for performance.

Take care,
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.