Kali_ma_Amar explained this circuit well on page 4 of this topic but there are still a few things I would like to point out, and figure out...
First, the circuit has a bridge rectifier just like the steam resonantor used in the dune buggy. It appears that the rectified output was put through a 12V regulator and a transistor which I think was used to pulse the primary coil in the home heating unit.
Each steam resonator (the home heating unit and the dune buggy) has 2 NPN and 2 PNP transistors.
The steam resonator is not a capacitor, and inductor, or a resistor. I think current is limited by the coil reactance and the high watt resistors only.
(http://i642.photobucket.com/albums/uu141/Hms-776/steamres3.png)
I would like to point out once again using the circuit above that the steam resonator tubes are nothing more than conductive surfaces placed in the water. A current and voltage wave will travel through them, the polarity of the wave depending on the direction of current flow through the conductor. Although there is no voltage build up and a very small voltage drop across the tubes there is still a voltage wave which passes through the tubes. Pulsing this wave back and forth at high speed and switching the direction of the traveling wave is what ultimately causes the water to heat up. I learned when studying transmission lines that voltage waves propogate at the speed of light(1).
(1) Ref http://www.allaboutcircuits.com/vol_2/chpt_14/3.html
Now as far as questions I have is about the coil itself....The dune buggy steam resonator coil has 3 coils (6 wire ends) while the home heating unit looked to have 7 wires coming out of it...Maybe 3 coils, 1 center tap?
So, what I'm wanting to know now is how the coil was designed. I tend to think each had 1 primary coil and 2 secondary coils bifilar wound, but that is a theory I have yet to prove out....