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Re: tube advice needed
Subject: Re: tube advice needed
Date: Tue, 20 May 1997 10:41:08 -0400 (EDT)
From: FutureT-at-aol-dot-com
To: tesla-at-pupman-dot-com
>snip
>Could tube guru's list their all time favourite tubes, valves,
> triodes, tetrodes etc.? I am especially interested in devices
> which will not require too much additional circuitry, i.e. direct
> replacements for spark gaps (thyratrons?).
> Thanks for your help, I'll let you know what this yields
> steve crawshaw
>>
Steve,
That is quite a treasure trove of tubes! You're right, there are two
approaches to using tubes in a Tesla coil, the usual way is to build a
modified Armstrong oscillator which uses a vacuum tube, which is used to
supply power to a parallel tank circuit. This approach does require
extra
components. These coils are also "inefficient" in producing long sparks
--
sparks tend to be flamelike or torchlike, and are typically 6" to 12"
long,
but can be up to 3 feet or more if enough power is used. Tubes such as
the
3-500Z, 304TL, 833A, 4-250A, 811A, etc, are good. But just about any
transmitting triode, tetrode, or even pentode, will work. But the
tetrodes
and pentodes require extra components. Most people probably stick to
triodes.
The other method; the direct replacement of the spark-gap with a
thryratron
or other low impedance switch is very good from a theoretical point of
view,
but is tricky to "pull off".
Happy tube coiling!
John Freau