500W Tube Coil Takes Off!

To: tesla-at-pupman-dot-com
Subject: 500W Tube Coil Takes Off!
From: Tesla List <mod1-at-pupman-dot-com>
Date: Wed, 15 Oct 1997 11:16:34 -0600 (MDT)
Approved: mod1-at-poodle.pupman-dot-com

---------- Forwarded message ----------
Date: Wed, 15 Oct 1997 00:40:49 -0700
From: "Jeff W. Parisse" <jparisse-at-ddlabs-dot-com>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: 500W Tube Coil Takes Off!

All,

Many thanks to Brent Turner, Mark Rzeszotarski and John Freau (and others
not mentioned) for their help with my first tube coil. I ran it for the first time
tonight and it worked great (for a first try of course). I managed to get
8-10" sparks and a heck of allot of radiated RF.

The coil uses two 250TH tubes in parallel and a 0-4200 Vdc plate supply.
The primary form is 7" dia. and the secondary is 5" dia. x 20". The primary
caps add up to .0021uf to .0022uf (variable) and with a 22 turn primary coil,
resonate near 356 kHz.

Question: The grid resistor, although seemingly overrated, got red hot during
an extended run. Since I had already adjusted it until I got the correct plate
current (700ma), I'm guessing that it was seeing too much voltage from the
grid coil. I started to remove some windings from the grid coil but stopped
after removing two, I thought I should ask the group about this first.

Observation: Using a 10H filter choke to smooth the dc really killed spark
output. From 8" to say, 1". Without the choke, the coil has a 60Hz (120Hz)
hum that I really wanted to filter away. I placed the choke between the 
center tap of the filament transformer and ground. Maybe I should move it
to between the negative side of the full wave bridge rectifier and ground? 

Jeff W. Parisse, Art Director
Digital Design Laboratories
www.ddlabs-dot-com