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Re: [TCML] A New Kind of Valve Coil



Steve, I completely agree with you. It is well known there are several nodal points up the secondary and some spots appear substantially better than others. Just the presence of that grid coil affects the behavior of the complete system.

However, no matter where you place the grid coil it is parasitical and energy is removed from the other coils (primary or secondary).

So when you get to the "yet" and remove the grid coil with feedback from the secondary bottom wire that goes to ground or from a primary lead, I suspect that one can exercise control that approaches the solid state coils.

But your work on the streamer production with the modulated supply was excellent. I personally find the physics and modeling of the streamer more interesting. Perhaps without having to concern myself with tenuring faculty, i'll get back to this.
John

John W. Gudenas, Ph.D.
Professor Emeritus of Computer Science



On Jun 23, 2011, at 11:06 AM, Steve Ward wrote:

I'd like to point out that the issue of "feedback" is not trivial. There
are many ways to obtain a self-oscillating system, but you can end up
operating in subtle different modes, particularly with double-resonant
systems like a VTTC or DRSSTC.

John Gudenas suggests using essentially, primary feedback. This works fine for power oscillators, it may or may not deliver power at the best phase
angle to the secondary coil, however, does make sparks of good size.

Phillip is positioning his feedback coil to where the coupling is much
stronger with the secondary flux than the primary, this difference seemed to give his original VTTC quite a performance edge over any other VTTCs (before the HV modulated supply was developed). I suspect that the operating mode is more efficient in Phillips case than Johns case, in terms of providing
power at the right phase to the secondary.

Im not claiming to fully understand these modes (yet) and how to force the system to operate at each of them, but i would encourage you at least do a AC sweep of the system in SPICE or otherwise, and look at where the poles and zeroes (peaks and dips) are in the response, and you will see there are indeed many frequencies where the system should theoretically be a good oscillator and treat the tube kindly, but i think some mode will have better performance than others. And its *not* just an issue of tuning, its an issue of how the feedback is derived. You can play with turn count, grid leak networks, and primary tuning until you've exhausted every combination, and you will not see the operation difference that you do by changing the
feedback coil location.

Steve

On Thu, Jun 23, 2011 at 9:58 AM, Dr. John W. Gudenas <
comsciprof@xxxxxxxxxxxxx> wrote:

Phillip,
as you know I have been following your progress with your coil as well as
Steve's work.
I solved the grid coil issue a few years ago and there should be some
posting in the archives.
Instead of using the secondary as the major feedback source, I put a flat spiral pancake coil under the primary with the inner diameter about the size of the primary. It is also covered by a circular piece of phenolic so no one
can see it.
I have always used a high wattage adjustable grid leak resistor set for the
sweet spot. This system is sound, never any flash over. I used 14 awg
insulated wire because it was easier to make the pancake.

Now, there is no reason why you can't pick up the current from a primary lead with a current transformer, but then you need to get that to control a high voltage with proper timing for the grid. I am not really sure if this
solves problems or adds to them.
But, I guess you will find out. However, if you can, give the pancake grid
coil a try.

John W. Gudenas, Ph.D.
Professor Emeritus of Computer Science





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