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Lincoln Electric SVM141-A service manual Table of Contents Theory of Operation Section

Models: SVM141-A

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Section E-1

Section E-1

TABLE OF CONTENTS

- THEORY OF OPERATION SECTION -

Theory of Operation	Section E
General Description	E-2
Input Power Circuit	E-2
Output Rectification, Control Board and Feedback	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 - SQUARE WAVE TIG 275 BLOCK LOGIC DIAGRAM

		BY-PASS
		BOARD
	POLARITY	WORK
	POLARITY
	SWITCH	ELECTRODE
		ELECTRODE
MAIN		HI-FREQUENCY
TRANSFORMER		TRANSFORMER

RECONNECT	INPUT
RECONNECT	POWER
PANEL	SWITCH							C
								C
		H1						H
		H1	X1	AC	DC+			O
								O
								K
				SCR				K
				SCR				E
				BRIDGE				E
		H2	X2			SHUNT		HIGH VOLTAGE
			X2	AC	DC-	SHUNT		TRANSFORMER
		H3		AC	DC-			TRANSFORMER
		H3					F	CIRCUIT
							F
		H4					E
		H4	23VAC				E
			23VAC				D
							B
							A
"A"							C
"A"							K
			18VAC					115VAC
			18VAC			CONTROL		MODE
115VAC			18VAC			CONTROL		SWITCH
115VAC			115VAC			BOARD
RECEPTACLE			115VAC
RECEPTACLE								THERMAL
								THERMAL
								LIGHT
		FAN						THERMOSTATS
								THERMOSTATS
		REMOTE
		RECEPTACLE	DOWNSLOPE GAS			POSTFLOW	BALANCE	OUTPUT
			DOWNSLOPE GAS			POSTFLOW	BALANCE	OUTPUT
			CONTROL	VALVE		CONTROL	CONTROL	CONTROL

SQUARE WAVE TIG 275

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Lincoln Electric SVM141-A service manual Table of Contents Theory of Operation Section

Contents

Square Wave TIG Safety Depends on YouSquare Wave TIG SafetyElectric Shock can kill ARC Rays can burnFumes and Gases can be dangerous Iii Cylinder may explode if damagedSûreté Pour Soudage a L’Arc Précautions DE SûretéMaster Table of Contents for ALL Sections Table of Contents Installation Section Technical Specifications Square Wave TIG InstallationSafety Precautions Figure A.1 Input Supply ConnectionsReturn to Section TOC To Section TOC Input Reconnect ProcedureOutput Connections User Supplied ConnectorsWork Cable Connection Table A.1Cylinder could explode if damaged TIG Torch ConnectionTWIST-MATE Adapter for LW-18 and LW-20 TIG Torch TWIST-MATE Adapter for LA-9 and LA-17 TIG TorchCompleted Assembly Square Wave TIG Table of Contents Operation Section Electric Shock can kill OperationFumes and Gases can be dangerous Welding Sparks can cause fire or explosionDesign Features Advantages General DescriptionRecommended Processes and Equipment Limitations Welding CapabilityFigure B.1 Control Panel Controls and SettingsTIG Welding Welding OperationTIG Welding Guidelines Twist Mate ElectrodeTIG Welding Sequence of Operation 2-Step TIG Mode Table B.2 Recommended Polarity Settings for TIG WeldingTIG Welding Sequence of Operation 4-Step TIG Mode Advanced TIG Welding Features Hand and Foot Amptrol OperationAC Wave Balance and Auto Balance Stick Welding Auxiliary PowerHertz Domestic Machines 50/60 Hertz European MachinesSquare Wave TIG Section C-1Section C-1 Table of Contents AccessoriesAccessories Included with Machine Optional AccessoriesK963-1, -2 Hand Amptrol Table of Contents Maintenance Section Maintenance Routine and Periodic MaintenanceOverload Protection Spark GAP ASSEMBLY, High Voltage Transformer Component Location and AccessControl PC Board Display PC BOARD, ARC STARTER/BYPASS PC BoardFigure D.2 Major Component Locations Table of Contents Theory of Operation Section Theory of Operation Input Power CircuitFigure E.3 Output RECTIFICATION, Control Board and Feedback Output Rectification Control Board and FeedbackFigure E.4 High Voltage / High Frequency Circuit High Voltage / High Frequency CircuitFigure E.5 DC Welding Output DC Welding OutputFigure E.7 AC Welding Output AC Welding OutputFigure E.9 SCR Operation SCR OperationProtective Circuits Thermal ProtectionOverload Protection Table of Contents Troubleshooting & Repair Section HOW to USE Troubleshooting Guide Troubleshooting & RepairDisable Procedure High Voltage / High Frequency can damage test equipmentPC Board can be damaged by static electricity PC Board Troubleshooting ProceduresTroubleshooting Guide Observe Safety GuidelinesDetailed in the beginning of this manual Perform the SCR Bridge Test Troubleshooting & Repair Connections Troubleshooting Guide Troubleshooting & Repair TIG Welding Problems Can Kill Electric ShockTroubleshooting & Repair To Technical Specifications Stick Welding Problems 15F-15 Function ProblemsFunction Problems Installation Troubleshooting & Repair High Frequency Circuit Disable Procedure Test DescriptionMaterials Needed Procedure High Frequency Circuit Disable ProcedureT1 Main Transformer Test T1 Main Transformer Test Test ProcedureReplace the case side covers Primary WINDINGS1 Test PointsGAS Water Solenoid Test Figure F.3 GAS Solenoid Location GAS Water Solenoid TestStatic SCR Test Figure F.4 Plug J1 Location on Control Board Static SCR TestAssembly Removal and Replacement Description Active SCR TestFigure F.6 Plug J1 Location on Control Board Active SCR TestFigure F.7 Active SCR Test Setup SCR Bridge Assembly Removal and Replacement AC TIG Mode Scope SettingsNormal Open Circuit Voltage Waveform DC TIG Mode AC Stick Mode DC Stick Mode Typical Output Voltage Waveform Machine Loaded Machine Loaded to 255 AmpsAT 30 VAC AT 31 VDC Machine Loaded to 275 AmpsAC Stick Mode DC Stick Mode 50 V/Div High Voltage Transformer Removal Replacement Replacement Removal ProcedureHigh Voltage Transformer Removal Figure F.10 High Voltage Transformer Mounting Insulators Replacement ProcedureSCR Bridge Assembly Removal and Replacement Using the 3/8 nut driver, remove the case SCR Bridge Assembly Removal and ReplacementFigure F.13 SCR Bridge Connections Refer to Figures F.11 F.13 Polarity Switch Removal and Replacement Allen Screw Control Knobs Polarity Switch Handle Polarity Switch Removal and Replacement253 POS Micro Switch Leads Square Wave TIGFigure F.16 Polarity Switch Wiring Diagram For Steps 9--17, see Figure F.15 and F.16 Replacement ProcedureDescription Removal and Replacement Main Transformer and Output Choke AssemblyFigure F.18 Transformer Connections POS Micro Switch Leads Figure F.19 Polarity Switch Connections Choke NEGRefer to Figures F.17 F.19 Reassembly ProcedureRetest After Repair Minimum Acceptable Output Voltage AT Maximum Output SettingInput Idle Amps Open Circuit VoltagesSquare Wave TIG Section G Diagram L10747 WiringElectrical TIGSquarewave Diagram L10747-2Control Board Schematic G3358-1 Electrical DiagramsOCI4 TRI3 MT2 Control Board Schematic G3358-2Return to Section Return to Section TOC To Section TOC Display Board Schematic L10768Bypass L10770-17-24-98 Display Board Layout L10770-1XXX 10G-10 Bypass Board Layout L10121-1Square Wave TIG