Lincoln Electric SVM169-A service manual Theory of Operation Section, Section E

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Section E-1	TABLE OF CONTENTS	Section E-1
	- THEORY OF OPERATION SECTION -

Theory of Operation	Section E
General Description	E-2
Input Power Circuit	E-2
Output Rectification and Feedback Control	E-3
High Voltage/High Frequency Circuit	E-4
DC Welding Output	E-5
AC Welding Output	E-6
SCR Operation	E-7
Protective Circuits	E-8
Thermal Protection	E-8
Overload Protection	E-8

FIGURE E.1 – PRECISION TIG 185 BLOCK LOGIC DIAGRAM

					BY-PASS
					BOARD
		POLARITY			WORK
		SWITCH			ELECTRODE
	MAIN				HI-FREQUENCY
	TRANSFORMER				TRANSFORMER
INPUT
POWER
SWITCH BYPASS					C
ASBLY
					H
	H1
		AC	DC+		O
	X1
					K
		SCR
		BRIDGE			E
	H2			SHUNT	HIGH VOLTAGE
	X2
		AC	DC-		TRANSFORMER
	H3
				F	CIRCUIT
				E
				E
				D
				B
				A
				C
				K
	18VAC				115VAC
	18VAC		CONTROL		POWER
FAN	115VAC		BOARD		"ON"
					DIGITAL
					DISPLAY
					MODE
					SWITCH
	REMOTE			THERMO-
	RECEPTACLE	THERMAL	GAS		OUTPUT
				STATS
		LIGHT	VALVE		CONTROL

AUTO	PULSE TIG	STICK	AC	PULSE POSTFLOW
BALANCE FREQ. LED		LED	BALANCE	CONTROL CONTROL
LED	LED		CONTROL

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