Re: 811A first light

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Brent, all,
                There is an interesting variation which I recently 
read about in a book on SMPS design which no-one seems to have 
mentioned on the list. This is class F and is considerably more 
efficient than class C. At this stage, I'm not sure whether it is 
applicable to TCs but looking at the circuit configuration suggests 
it is. The author was discussing resonant SMPS topologies and looking 
at RF circuits. There is an interesting catch to it though. 
      The nub of the idea is to run an oscillator (in the author's 
case it was a solid state device) in what looks like class C with a 
resonant tank drain (plate) load but with a 1/4 wave delay line run 
between the drain and the tank. The line is used as a PFN and allows 
the power device to run with squarewaves rather than haversines. 
Basically the line is loaded with a high end impedance (parallel 
tank) and as we all know, a quarterwave line has resonances at f/4, 
3f/4, 5f/4 and so on (I know that the tssp modelling gives slightly 
different values for a TC resonator) with the result that the line 
presents a more-or less constant impedance to a squarewave source at 
the driven end. Something I'll look into one day if I ever get the 
time.

Regards,
Malcolm
  

On 10 Jul 01, at 8:08, Tesla list wrote:

> Original poster: "Brent Turner by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <bturner-at-apc-dot-net>
> 
> Hi -
> 
> Having built a VTTC myself (pair of 805's), I used a MOT from an
> industrial oven. Had two 1100 volt windings in series which paralleled
> quite nicely for 500mA output. Drives my 805's directly with no current
> limiting.
> 
> You shouldn't need current limiting in the transformer anyway. The
> grid-leak bias (variable resistor across a capacitor, whole thing in
> series with the grid) establishes not only a slight phase delay, but
> also limits the plate current.) is adjusted so that plate current falls
> within the tube's plate spec's. The tubes are not driven into full
> class-C operation in the classic VTTC circuit.
> 
> - brent
> 
> 
> 
> Tesla list wrote:
> > 
> > Original poster: "Dr. John Gudenas by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <comsciprof-at-ameritech-dot-net>
> > 
> > James
> > The 811A can only handle 175 mA on the plate -at- around 1500 volts. If
you use
> > a MOT with out any current limiting device you will likely melt the plate.
> > Check out my triple 811A coil on:
> > www.scifair-dot-org/hvdata
> > 
> > John W. G.
> > 
> > John W. Gudenas, Ph.D.
> > Department Chair of Computational and Natural Science
> > Aurora University
> 
> 
> 
>