Lincoln Electric SVM166-A service manual Trigger and Control Circuits

E-3	THEORY OF OPERATION	E-3
	FIGURE E.3 – TRIGGER & CONTROL CIRCUITS

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ELECTRODE INPUT VOLTAGE

TOROID

ASSEMBLY

FULL

WAVE

BRIDGE

CONTACTOR

	FEED	WELDING
	PLATE
GAS
	M
SOLENOID	O	HALL
	T
"ELECTRODE"	O	EFFECT
FEEDBACK	R	MODULE
VOLTAGE #67

ARMATURE

RPM FEEDBACK

TOC

ON/OFF

SWITCH

MOV

WORK SENSING LEAD

BOOST POWER SUPPLY BOARD

FEED HEAD BOARD SUPPLY

DRIVE MOTOR SUPPLY

FEED HEAD

CONTROL BOARD

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"WORK" VOLTAGE FEEDBACK #21

SPI COMMUNICATIONS

SHIELDED CABLE

COLD	WIRE	TRIGGER	TRIGGER	DISPLAY
		INPUT &	INTERLOCK
INCH	FEED			BOARD
		PROCEDURE	SWITCH
SWITCH	SPEED
	CONTROL

TRIGGER AND CONTROL CIRCUITS

When the gun trigger is closed (activated) the Feed Head Board is “signaled” to apply armature voltage to the drive motor, activate the gas solenoid and close the LN-15 internal contactor. When the con- tactor is closed the welding current path from the electrode cable to the conductor block is completed. This sequence will supply electrode wire, arc voltage and current to the welding gun.

The Cold Inch/Gas Purge Switch allows the user to feed wire without closing the contactor. This feature gives the operator an electrically “cold” electrode even though the power source’s output terminals are electrically “hot”. This switch also allows the user to activate the gas solenoid without feeding wire or closing the contactor.

When activated the Trigger Interlock Switch keeps the gun trigger circuit closed even when the operator releases the trigger. This is useful when making long welds.

NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.

LN-15