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TRIGGER CIRCUIT
When the gun trigger is activated, the
EPROM which is located on the control
board, signals the motor circuitry to start the
wire drive motor and also activates an
electronic switch which closes leads #2 and
#4. The closure of leads #2 and #4 energize
the welding output terminals on the Lincoln
power source. The gas and or water solenoid
are also energized by a solid state circuit on
the control board.
FIGURE E.2 – TRIGGER CIRCUIT.
GUN TRIGGER
RECEPTACLE
GAS
SOLENOID
AC
AC
DC+
DC-
TACH
DRIVE
MOTOR
REED
SWITCH
42VAC
42VAC
CONTACTOR CONTROL
INPUT CABLE
RECEPTACLE
KEYPAD
CONTROL BOARD
FEEDBACK
DISPLAY
PC BOARD
CURRENT
SENSING
LN-742 & LN-742H
THEORY OF OPERATION
E-3
E-3