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Re: Tubes + SCR's has no class!
"More proper"...maybe...!
But I see a potential problem (may not be a practical problem, I don't know)
about putting a gas or mercury tube near a tesla coil circuit. I would think
that RF nearby could ionize it and keep it on, and even if it stays off in the
beginning, as soon as RF is being produced it's held on by ionization. Now I
may completely misunderstand how those tubes function- you have worked with
them, I have not. I recall reading about mercury rectifiers anyway, that said
they were to be shielded extremely well to prevent RF fields from ionizing the
vapor too much. I know that a fluorescent tube lights anywhere near my
circuit, and that implies that mercury vapor would do the same thing. How well
do vapor thyratrons work in strong RF fields?
To make you happy, I have a TUBE pulser unit that I was going to use to operate
an SCR for staccato. I'm too worried about 555's near the coil, at least right
now, but I will try my luck with them too when I am more confident that they
will not be instant toast.
Happy ("tubes only!") coiling-
Carl
>I just read..."An SCR can act as a switch to ground the cathode of the tube,
>thereby turning the oscillator on. They are the preferred device for doing
>this" ?!!!! Sure this might work but it surely is sacrilegious no?
>Wouldn't it be 'more proper' to keep it all half a century old technology and
>all tubes by going to a mercury or gas thyratron tube between the oscillator
>tube cathode and the system ground. Forget the modern SCR. If you think an
833A
>looks more macho than a cold bank of power mosfets, you're gonna absolutely
>love a big thyratron tube plugged in next to it!
>I've experimented along this vein and found the mercury thyratron to be
>extremely easy to implement and trigger, not to mention indestructible.
>You don't need a large one either. One smaller one I tried was the same
>envelope size and shape as an 807 and worked well on the bottom of four
811A's.
>Robert W."You can have my tubes when you can pry them from my cold dead
>fingers" Stephens
Director
AREA31 Research Facility
<<http://www.area31-dot-org>http://www.area31-dot-org>www.area31-dot-org
>
> ----- Original Message -----
> From: <<mailto:tesla-at-pupman-dot-com>mailto:tesla-at-pupman-dot-com>Tesla list
> To: <<mailto:tesla-at-pupman-dot-com>mailto:tesla-at-pupman-dot-com>tesla-at-pupman-dot-com
> Sent: Saturday, September 02, 2000 21:42
> Subject: Re: More tube coil stuff (Carl Willis)...
>
> Original poster:
<<mailto:cwillis-at-guilford.edu>mailto:cwillis-at-guilford.edu>cwillis-at-guilford.edu
>
>
> An SCR can act as a switch to ground the cathode of the tube, thereby turning
> the tube oscillator on. They are the preferred device for doing this, from
> what I have heard. (In Staccato mode, the oscillator is pulsed every few
> cycles to keep duty cycle low.) What is needed is an SCR that can handle
> about
> 20 - 40 amps and 600 volts...that kind of fat. (I don't understand why they
> don't need to stand up to the full plate potential, since it seems to me that
> the floating cathode would lose electrons to the plate until it was at the
> same
> voltage. Can someone explain?) This kind of part is usually a stud-mount
> thing. I tried to order one a while back from a surplus joint, but first
> they
> wanted $17 for it and secondly they didn't have it in stock. They're not
> hard
> to come by, I just don't feel right spending more for the SCR than I did for
> my
> tube (ten bucks).
>
> >>>(One of these days I will get around to putting together a true staccato
> >>>driver and I'll put a big fat SCR in the cathode lead for it.)
>
>
> >I've got a big fat SCR....ideas?
>
> Make a tube coil and use it for staccato. Or, give it to me!!
>
> Christopher A. Boden Geek#1
> President / C.E.O. / Alpha Geek
> The Geek Group
>
<<http://www.thegeekgroup-dot-org>http://www.thegeekgroup-dot-org>www.thegeekgroup-dot-org
> Because the Geek shall inherit the Earth!
>
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