Posted on Dec 11, 2012 8857
Stepdown transformer T1 drops the incoming line voltage to approximately 48 Vac which is rectified by diode D1; the resultant de charges capacitor C1-through current limiting resistor Rl-to a voltage level preset by R4. When the voltage on R4`s wiper reaches about 8.6 V, Q1 begins to turn on, drawing current through R7 and the base-emitter junction of Q2. Q2 turns on and supplies a positive voltage to the gate of silicon-controlled rectifier Q3.
The positive gate voltage causes Q3 to conduct, thereby discharging C1 through the primary winding of step-up transformer T2, which results in a high-voltage arc at output terminal X. The voltage developed at T2"s output is determined by the value of C1, the voltage across C1, and the turns ratio of transformer T2. The frequency or pulse rate of the high voltage is determined by the resistance of T1 "s primary and secondary windings, the value of R1, and the value of Cl. The lower the value of each item, the higher the output pulse rate; the peak output voltage will only remain unchanged if C1"s value remains unchanged.