The first coil had a 1000-turn resonator 7 in tall by 3 in across under a 6 by 2 in toroid, with a 25-turn primary 3 by 4.5 in around its foot. Two IRF740s in a half bridge ran straight off the 240 V mains, driven by a TL494 free-running at about 250 kHz through a small ferrite isolation transformer. There was no feedback, and the coil was tuned by hand. Then come the four supplies, with photographs of what each did to the spark. On half-wave rectified mains the sparks come out straight and sword-like, 6 in and unbranched. On full-wave they fatten and branch but grow no longer. On smoothed DC the breakout turns into a hissing cone of corona. With a phase-angle controller firing at the mains peak they go spidery and dance. The ground strikes arched upward in their own heat like a Jacob's ladder and set fire to anything flammable.
Schematics and photos
photo: the coil, annotated by its builder 
diagram: the simplified half-bridge circuit 
diagram: primary voltage (square) and current (sine) at resonance 
photo: half-wave rectified mains, the straight sword sparks 
photo: full-wave rectified, fatter and branched, no longer 
photo: corona from points, dividing into two jets at the breakout 
photo: a fan of corona off the toroid 
photo: smoothed DC, the hissing cone 
photo: phase-angle control, spidery and dancing 
photo: phase-angle control, the branching, with a strike to an unearthed piece of metal 
photo: a ground strike arching upward in its own heat 
photo: another ground strike
Sources
- richieburnett.co.uk: Solid state tesla coil
- Internet Archive: richieburnett.co.uk, what's new (19 Oct 2001, his dated change log)
This is the card from the driver tree, written from what the builder published. Send corrections through the forum.