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Single 833A VTTC

Original poster: "Cameron B. Prince" <cplists@xxxxxxxxxx>

Hi again,

One other thing I wanted to share with you all is my recent success with my
VTTC. John Freau, Steve Ward and Christopher Hooper have all helped me very
much and I certainly learned a lot from them. John asked me to share the
results with the list because I may have stumbled on to something that might
help everyone achieve higher efficiency with their VTTC's. The breakthrough
I've had has been related to moving the grid coil way up on the primary
form. Most plans I've seen recommend about 1 inch between the primary and
the grid coil. My coil has closer to 6 inches and my output improved
drastically. I'm getting 30 inch sparks with around 17A current draw with a
120V input. The coil actually runs best with the variac at about 75-80%.

You can see the coil running here:


It's powered by two MOT's in series, not parallel. The secondary is #28
wound on a 3.5 inch O.D. PVC form. The winding is about 17 inches. The
primary is about 28 turns of 10 AWG wound on 6 inch thin wall PVC. This is
basically the design shown on Steve Ward's page with a longer primary form.
A close up of the coil is here:


I'm using 10K of grid resistance with a 2700pF cap and the main tank cap is
about 2400pF.

I plan to put up a page with full construction details once I finalize the
design, but I'll be glad to answer questions if I can help anyone.

Comments are welcome.