Re: Vacuum Tube Tesla Coil Design (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Fri, 5 Oct 2007 12:22:24 EDT
From: Mddeming@xxxxxxx
To: tesla@xxxxxxxxxx
Subject: Re: Vacuum Tube Tesla Coil Design (fwd)

 
In a message dated 10/5/07 11:30:43 A.M. Eastern Daylight Time,  
tesla@xxxxxxxxxx writes:

---------- Forwarded message ----------
Date: Fri, 05 Oct 2007  13:41:35 +0200
From: Martin Damev <mdamev@xxxxxxxxxx>
To:  tesla@xxxxxxxxxx
Subject: Re: Vacuum Tube Tesla Coil Design  (fwd)

Hello Brad,

Some two weeks ago you posted something  about
building a VTTC with your 4-400 tetrodes.

There is a very  interesting and efficient oscillator
circuit you could use for your VTTC.  If you are
interested I will help you with the necessary  calculations.
I'm talking of the  "push-pull oscillator with  capacitive
dividers for feedback". This design uses two 4-400  tetrodes
but in return you get approx. twice the RF output.
Using  capacitive dividers for feedback you can avoid
the "tickler coil" and you  get better driving conditions for
the tetrodes. The circuit may look   more complex at first
glance, but it is not more difficult to build.  Basically it
is similar to an astable multivibrator circuit.

I  designed such a circuit for a coiler-friend. This small
but very nice VTTC  uses two 7843 tetrodes by RCA that we
pulled out of some military  communication equipment.
These small tetrodes are metal-ceramic design and  conduction
cooled. The VTTC works very well though  it will need  larger
primary capacitance to take full advantage of the tubes  capabilities.

I personally do not recommend using tetrodes as triodes  by
connecting both grids together. First you can be sure that you  will
easily exceed the control-grid's dissipation rating in most  cases
(especially when the oscillator is not loaded). Second a  tetrode
allows you to pulse the oscillator through the screen grid  voltage.
John Freau has shown that there is a lot of potential in using  this
method.

Two 4-400s should give you 25-30 inch sparks in a good  an optimized
setup.

- Martin



Hi Martin,
 
I would also be interested in seeing this circuit and learning more about  it.
 
Matt D.



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