Lincoln Electric SVM 117-A service manual Theory of Operation

	THEORY OF OPERATION
TOC	TABLE OF CONTENTS
	- THEORY OF OPERATION SECTION -
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	THEORY OF OPERATION SECTION	Section E
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	Input Line Voltage and Main Transformer	E-1
	Power Supply Operation	E-1
	Output Rectification and Feedback Control	E-2
	Constant Voltage Output	E-3
	Wire Drive Motor and Feedback	E-4
	Thermal Protection	E-5
	SCR Operation	E-6

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Return		WIRE	GAS
		SPEED	SOLENOID
					WIRE
					DRIVE
		ARC			MOTOR
		VOLTAGE
		CONTROL BOARD
			G		TACH
			A
			T		GUN TRIGGER AND THUMB SWITCH
	LINE	MAIN	E
			S
		TRANSFORMER
	SWITCH		I		FEEDBACK
			G
TOC			N
			A
			L
		RECONNECT
Master					POSITIVE
					TERMINAL
				C	CHOKE
				A	F
to
				P	E
				A	E
Return				C	D
		SCR		I	B
		RECTIFIER		T	A
				O	C
		FAN		R	K
				S	NEGATIVE
		MOTORS
					TERMINAL
					SHUNT

	Figure E.1 -Block Logic Diagram
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to	NOTE: Unshaded areas of Block Logic
	Diagram are the subject of discussion
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	WIRE-MATIC 250