Re: Interesting thing about Tube Coil oscillators...

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

Original poster: "Bert Hickman by way of Terry Fritz <twftesla-at-uswest-dot-net>" <bert.hickman-at-aquila-dot-net>

David,

Interesting experiment! Even though you didn't have a primary tank
circuit, you STILL have a high Q secondary LC circuit that's transformer
coupled back to your primary, and a grid coil to provide feedback that's
180 degrees out of phase. So you still have all the elements of an
oscillator, just not as efficient because of the loose coupling to the
secondary. It would be interesting to see if you could significantly
improve the output by tightening the coupling coefficient... 

-- Bert --

Tesla list wrote:
> 
> Original poster: "David Trimmell by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <davidt-at-pond-dot-net>
> 
> Hello all,
> 
> I was doing some testing of various VTTC configurations last night, and
> thought I would try a "tankless" configuration. Running the output from
> the Level Shifter (normally the B+, but in this case we are using the tube
> to self-rectify HV AC) into the base of my solenoid Primary (23 turns of
> PVC insulted #12 on 6" form 79uH measured), the top of the primary was
> connected to the plate of a single 833C. Grid coil with 22 turns of PVC
> insulted #22 wire is 3/4 inch above secondary, with 4 to 25 K resistance
> for bias, 0.001uF mica cap in parallel. Using this configuration the coil
> will oscillate, producing 3-4" discharge with 4800V on the plate. Power
> consumtion was high ~25 Amps from wall at 40 volts into the PT (60:1), but
> grid current was low, even with only 4 K resistance, less then 30 mA. It
> is quite intesting how I can get a coil that is self resonant at around
> 380KHz to produce this discharge. I am asuming the parasitic capacitance
> in the primary is working here? BUT that would put the Fr0 in the many
> Megahertz range!?
> 
> Anyone have agood explaination of what is really going on here?
> 
> Regards,
> 
> David Trimmell

-- 
Bert Hickman
Stoneridge Engineering
Email:    bert.hickman-at-aquila-dot-net
Web Site: http://www.teslamania-dot-com