Whoa. I just make the simplest crkt possible- EZ80 in series with a relay
coil, 1N4001 and a current limitting resistor. When the relay acts, heater
(also connected in series with a resistor) is switched off and the anode is
connected directly to the cathode of EZ80. The whole thingie is powered from
20V mains transformer winding (I've got a vintage tranny with many windings,
one was 20V and I decided to use it).