Re: Vacume tube TC

Tesla List wrote:
> >From DavidF4797-at-aol-dot-com Sun Dec  8 12:00:28 1996
> Date: Sun, 8 Dec 1996 09:46:18 -0500
> From: DavidF4797-at-aol-dot-com
> To: tesla-at-pupman-dot-com
> Subject: Vacume tube TC
> I've been tinkering around with a vaccume tube coil now for several months
> using a pair of 811a's (triodes) and was able to produce a nice 3" brush
> discharge off the top of the coil ( tall thin candlestick variety).  I then
> switched to a 4-500z with the intent to produce greater output....
> Unfortuneately, the same circuit doesn't produce *any* brush output, although
> if I get a flourescent tube near to the primary and secondary it lights up so
> there must be output of a sort.  I have heard it speculated that the extra
> controll grid in the 4-500z is causing the problem and that what I really
> need is a 3-500z triode.
> Does anyone have any ideas or suggestion about this?I just looked in my tube manuals for the 4-500z and it is not listed.  The 
last tube book i bought was 1973.  That tube must be newer that 1973.

The 3-500z is listed and I know a little about it.

Plate voltage on the 3-500z is 4000 volts at 500 watts 116 mhz

Don't connect the screen grid to the control grid.  There are a few tubes 
that are specifically designed for that type of connection but the 3-500z is 
not it.

The screen grid on a tube will usually work connected directly to the plate 
but sometimes it needs a voltage difference between the two of just a few 
volts maybe 50 to 100 volts or so for the 4-500z.

If I had a tube manual with that tube listed I could figure out the exact 
resister value.  So the best thing is to experement with a varable resistor 
or lots of low value resistors.  1 ohm 2 ohms, 5 ohms, 10 ohms.

The plate is 500 watts and the screen will be much lower.  Maybe 10 or 20 

Also some circuits you can put a capacitor in parallel with the screen 
resistor.  Cap voltage rating has to be only larger enough for the voltage 
difference between the plate and screen.  500 volt should be safe.  Try .01 
uf for the 1st experement.

Send me a drawing of your circuit and that might help me figure it out.

Gary Weaver