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Re: Tubes
Tesla List wrote:
>
> Subscriber: FutureT-at-aol-dot-com Tue Jan 21 23:10:35 1997
> Date: Tue, 21 Jan 1997 16:50:44 -0500 (EST)
> From: FutureT-at-aol-dot-com
> To: tesla-at-pupman-dot-com
> Subject: Re: Tubes
>
> > Stephen,
>
> >I am not at all familiar with the nomenclature ECC803S, but I was
> >able to look up a type 803 transmitting tube in the RCA databook.
> >Although this tube is a pentode, at 2000 volt plate rating and 125
> > watt plate dissipation it is a heck of a lot of tube for $15,
> >assuming of course that what you have found is truly an 803. If it
> >is, I'd get one and try it. Tie all three grids together and pretend
> > it is a triode, might work. The filament on the 803 is 10 volts at 5
> > amps. The tube has a plate cap and a giant 5 pin base (same as a
> >4-125A/4D21, with a straight sided diameter of 2-9/16" and an overall
> >length of 9-1/4".
>
> >snip
> >rwstephens
> >>
>
> Steven, Robert,
>
> I also do not know if the ECC803S is the same tube as an 803. I used an 803
> in a tube coil, (found 3 of them at hamfest for $3 each), I connected a 15k
> resistor from the high voltage supply to the screen grid, and a 45k resistor
> from the screen grid to the suppressor grid, the coil gave a 5 to 6" spark.
> By the way, an 845 tube gave a 7" spark, and a 304TL tube gave a 10" spark
> in the same tube coil, which happened to be powered by a microwave oven
> transformer.
>
> John Freau
John -
I just had a flash(?) of inspiration - some fuzzy part of my brain
started screaming "load impedance". Perhaps the 304TL gave maximum
bang due to tube's lower internal resistance???? (plate volt/current)
I recall that there is a bit of an art to matching the plate load
impedance to the tube's internal resistance. Too high a load impedance
and you don't get full poop. Too low a load impedance causes the same
thing, only the excess energy goes into heating the plate in the
tube. This might explain the one post about how the tubes ran nice and
cool with the incandescent (resistive) load and really warmed up with
the Tesla tank circuit (*highly* reactive.)
- Brent