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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