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Re: ignitron tubes
Tesla List wrote:
>
> >From rwstephens-at-ptbo.igs-dot-netWed Jun 26 22:19:07 1996
> Date: Wed, 26 Jun 1996 11:21:25 -0500
> From: "Robert W. Stephens" <rwstephens-at-ptbo.igs-dot-net>
> To: tesla-at-pupman-dot-com
> Subject: Re: ignitron tubes
>
> >>From bigr-at-teleport-dot-comTue Jun 25 22:01:57 1996
> >Date: Tue, 25 Jun 1996 13:29:26 -0700
> >From: bigr-at-teleport-dot-com
> >To: tesla-at-pupman-dot-com
> >Subject: Re: ignitron tubes
> RWS wrote:
>
> Now here's an idea. Get a robust
> triode designed for high pulse power (the plate will be relatively
> small in dissipation because of the low average power, compared to a very
> heavy filament structure which is needed to source lot'sa amps during
> the short on time). Use one of these as your RF oscillator tube. Have your
> Vacuum tube T.C. all hooked up in the normal
> way, but remove the high voltage AC or DC plate power supply and have some
> friends help you push it out of the way. Now, fabricate a line
> pulser type power supply where you will charge a low ESL pulse capacitor
> (perhaps 0.1- 0.5 mfd) from a DC source through a supply protecting choke
> or resistor, and charge that cap up to the voltage rating of the
> pulse triode used (perhaps 7-10KVDC). Use a rotary break, or yes a hydrogen
> thyratron, or yes even a mercury thyratron
> to short the supply side of the storage cap to ground when
> repetitively triggered. The idea is to send stored packages of DC
> energy off to the tube oscillator circuit which is setup to deliver
> punishing peak power when kicked. You will have to figure out how to
> complete the DC circuit around the capacitor for the charging mode to
> operate. You could use a large series choke from the output side of
> the PFN to ground. This choke will be in parallel with the load
> represented by the oscillator and must be capable of surviving the
> repeated high voltage pulses thrown across it. Matching impedances
> here and in the PFN to the load impedance of the oscillator and the
> rep-rate of the pulser will be critical to get acceptable performance. The storage
> capacitor must be sized small enough so that it can dump all
> of its stored energy into the oscillator during the swich commutation
> period. Building up a true line pulser circuit employing several
> capacitors with series inductors will give some waveshape control of
> the tail of the delivered pulse which is necessary in radar
> apllications but I don't think is necessary for making sparks. If
> you have access to real radar PFN's you could try those.
>
> The results should be a much more impressive
> discharge streamer length than is normal for a vacuum tube powered
> T.C. I haven't tried this yet but have had it in the back of my mind
> as a someday project for a while. Bill Henderson, an 18,000 watt
> version of this system as just described ought to be pretty
> impressive!
>
> Comments are welcomed.
>
> Happy Coiling, etc!, rwstephens
Robert, All
BEEN THERE.... DONE THAT....
Well not me exactly, but JOHN FREAU a very good friend and Tesla coil
buddy in New Jersey, who I rate as "THE GURU OF VACUUM TUBE SYSTEMS", has
been doing this for a year or more now. I have about 30 hours of his
work on video (personal collection). We have also put a lot of excerpts
from same on our video reports.
He has been doing exactly what Robert suggests above, and with phenomenal
results. 18" sparks with 500 watt average power from a tube coil. John
has dubbed his system the "staccatto mode tube coil." It is not a CW
type tube coil, but instead is a pulsed system which dumps energy from a
larger than normal cap into the tank circuit via a high power Tetrode.
The tetrode's grid is pulsed and controlled with solid state circuitry
which allows control over the rep rate and duty cycle. He has even run a
rotary gap as part of the switch in a vacuum tube system. This area is
wide open now thanks to John's pioneering efforts in this area of Tesla
coiling.
Before I am inundated for info, I can't answer all the specifics as I
have not assembled one myself. He is not online, either. I personally
see John about 3 times per year and get his videos almost monthly. We
swap one for one and he lets me cull the most interesting of his stuff
for inclusion in our video reports under our "videos from others"
section.
I have seen John run (4) 833's in parallel with a pole pig on a classic
CW tube coil and get 40" arcs!!!!!!! I have never seen this record
equaled much less exceeded by anyone! As we have devoted full time for
years to the refinement of the tesla magnifier, so John Freau has
followed the vacuum tube coil thread, totally on his own with no support
of a group effort as in our case.
Richard Hull, TCBOR