Lincoln Electric SP-250 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 - E-3
	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

TOC			PIEZO	GAS
to Master
		LCD	ALARM	SOLENOID
		DISPLAY				WIRE
						DRIVE
						MOTOR
		KEYPAD
Return			CONTROL BOARD
				G		TACH
				A
				T		GUN TRIGGER AND THUMB SWITCH
	LINE	MAIN		E
				S
		TRANSFORMER
	SWITCH			I		FEEDBACK
				G
				N
				A
				L
		RECONNECT				POSITIVE
						TERMINAL
					C	CHOKE
					A	F
					P	E
					A	E
TOC					C	D
			SCR		I	B
			RECTIFIER		T	A
					O	C
		FAN			R	K
Return to Master					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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	IDEALARC SP-250