Circuit changes resulting from the addition of a gas purge switch.


Additions:
    A relay, pushbutton momentary switch, diode, and several wires were added to the control circuitry.

Operation:
When the button is not pressed the welder operates normally. When the button is pressed the relay coil is energized which causes the relay to switch the connection of resistor R16 from diodes D9 and D11 to the out pin of Voltage Regulator X4. This turns on the Gas Solenoid Control opto-isolator OC11 which then turns on triac TR11. Triac TR11 then energizes the Gas Solenoid.

Circuit Changes:
One lead of resistor R16 was unsoldered from the circuit board trace that connected R16 to diodes D9 and D11. A wire was then soldered from the trace to the NC pin of the relay. A wire was soldered from the free lead of R16 to the COM pin of the relay. A wire was soldered from the OUT pin of Voltage Regulator X4 to the NO pin of the relay. A wire was soldered from the GND pin of X4 to one of the two coil pins of the relay. A wire was soldered from the other coil pin to one of two male spade connectors. Another wire was soldered from the out pin of X4 to the other male spade connector. These male spade connectors connect to the female spade connectors which are soldered to wires from the pushbutton switch. The added diode was soldered reverse parallel across the coil pins of the relay.