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RE Re: tube advice needed
Subject: RE Re: tube advice needed
Date: Thu, 22 May 1997 05:30:30 GMT
From: robert.michaels-at-online.sme-dot-org (Robert Michaels)
Organization: Society of Manufacturing Engineers
To: tesla-at-pupman-dot-com
Friends -- it is =not= necessary to have a gazillion-watt,
trebillion-kilovolt, multi-megabuck transmitting tube to build a
vacuum-tube Tesla coil (tho -- it helps!).
Low-powered receiving tubes, audio-amplifier types included, can
be paralleled to attain desired power levels.
I wrote a while ago of a long-ago buddy who used 40 audio tubes
(50C5's, I believe) in parallel to build a rather credible coil.
The performance of the coil may not have
been so hot (by the standards of This List),
but the array of 40 tubes glowing in the dark
was.
Also eminently suitable are the tubes (formerly) used as
horizontal output amplifiers in TV receivers. There were
many such type numbers (consult your nearest friendly
neighborhood tube manual -- or olde tyme TV repair shop).
Radio Shack stores took special orders
for receiving tubes in the recent past
and may very well still do so.
- - - - - -
Likewise, and similarly, you do not need a kilo-volt transformer
for tube work (unless you use transmitting tubes such as
those in Mr. Stevens' post). For receiving-tube work, a trans-
former of several hundred volts is fine.
- - - - - - -
It is unnecessary to rectify the transformer voltage. Raw ac
may be applied directly to the plate of a tube for Tesla coil
work. Dc is more efficient, and use of ac will result in 60-Hz.
(in the USA) hum in the Tesla discharge, but ac otherwise works
well.
- - - - - - -
For circuits, design ideas, and tutorial material =older=
editions of the "Radio Amateurs' Handbook" (pub. by the
American Radio Relay League) is a good place to start.
Another standard reference work which has been in print
=forever= is "Electronic Communications" by Schrader
(McGraw-Hill, I think).
A more broadly-based reference on general electronics is (of all
things!) "Electronics", by Horowitz & Hill (Cambridge
University Press, I think). Some consider this the best
book on the subject ever written.
- - - - - - -
Note that as tubes may be parallelled for higher power output
triodes may also be (usually) series-ed for higher voltages --
at some loss of efficiency, tho this is somewhat more
experimental than parallelling.
Just some =more= ideas, from
Detroit, USA
Robert Michaels
[ ... ]
T>For small coils 811-A's are OK. They are slightly too small
[ ... ]
T>810's are great. You can parallel as many of these as you want, and
[ ... ]
T>833-A's are a terrific medium sized vac tube TC tube. Plate voltage
[ ... ]
T>A terrific ceramic tube from the broadcast industry for very high
T>power are the 3CX- series. For example a 3CX10,000 or a 3CX15,000.
[ ... ]
T>A tube that works well at microwave oven transformer voltages is the
T>805. Use one or two in parallel. (I used one in parallel once, this
T>is easy to do actually but hard to picture). Just kiddding. : )
T>One of these daze I'm gonna build a vaccuum tube TC with a tiny tube
T>like a 6SN7 with the two triode sections parallelled. This 7.5 watt
T>tube shud be good for 20 watts in Tesla mode.
T>Just some ideas.
T>rwstephens