Re: Building a 3-1000z VTTC

At 06:38 AM 9/1/1999 , you wrote:
>Original Poster: Ross <ross-o-at-mindspring-dot-com> 
>I recently came across an unbelievable deal at a local swap meet.  I
>purchased 2 old HAM RF amplifiers and a rack housed HV power supply.
>Each of the RF amplifiers contained tubes and the usual goodies.  One
>tube is a 3-1000z and the other is a large ceramic tube that doesn't
>have any numbers on it.


Ross, I am green with envy! What a score!

>1.  What is the largest diameter secondary that this tube can power?

Six+ inch? I have powered a 6.5 inch coil with two 833's, and know John F
has produced 38+ inches of hell fire from a six inch coil using four 833's.
If I were you I would start with a 4 inch coil.

>2.  Can someone ID that large ceramic tube?  I hope to reverse engineer
>the schematic of the amplifier for additional clues.  It appears that it
>was designed for 40m HAM service.  Looks to be custom built by K2VA
>(call has been reissued, original K2VA is probably a Silent Key)

Some kind of 3CX???? Maybe a 1600?? All markings worn off?

>3.  The tube specs state the the filament needs 7.5V at 21.3A.  The
>filament transformer that came in the box is a 7.5V, 25A.  Is this OK or
>do I need to drop the current somehow (add series resistance?)

I would suspect that the 25 amp rating is just to be conservative. The
filament will not draw more current than it is designed to, just like a
light bulb.

>4.  Any hints on appropriate component values will be greatly

It really depends on what effect you are after. If you want to make a 120
pulse per second coil, then your schematic looks good to me. But, I would
seriously consider using the "Level shifted" approach to feeding this coil,
using just one of the diode stacks, and about 2 to 6 uFd cap at 10KV. This
is detailed by John Freau in his Tesla list post a while back, and at my site:


This method can easily be adapted to any coil realizing that the voltage
will be approximately doubled to the plate, so if you fed your trany with
120 VAC then it would be a good match for the tube. With the 3-1000 tube
and that power supply you should be able to get well more than two foot

Good luck! I look forward to hearing of your progress, and it is good to
see someone who has some web design knowledge working on another Tube Coil


David Trimmell

>Ross Overstreet
>Huntington Beach, CA