Lincoln Electric SVM100-A service manual Table of Contents, Troubleshooting & Repair Section

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TABLE OF CONTENTS	Section F
- TROUBLESHOOTING & REPAIR SECTION -

Troubleshooting & Repair Section	Section F
Safety Precautions	F-1
How to Use Troubleshooting Guide	F-1
PC Board Troubleshooting Procedures	F-2
Troubleshooting Guide	F-3 - F-15
PC Board Connector Locations	F-16
Test Procedures
Control Transformer Voltage Test	F-17
Protection/Snubber Board Continuity Test	F-20
Arc Start Trigger Circuit Test	F-23
Static SCR Test	F-26
Active SCR Test	F-28
Oscilloscope Waveforms
Normal Open Circuit Voltage Waveform DC Stick Mode	F-31
Normal Open Circuit Voltage Waveform AC Stick Mode	F-32
Normal Open Circuit Voltage Waveform DC TIG Mode	F-33
Normal Open Circuit Voltage Waveform AC TIG Mode	F-34
Typical Output Voltage Waveform Machine Loaded DC TIG Mode	F-35
Typical Output Voltage Waveforms Machine Loaded AC TIG Mode	F-36
Typical SCR Gate Voltage Waveform	F-37
Abnormal Open Circuit Voltage Waveform DC Stick Mode	F-38
Abnormal Open Circuit Voltage Waveform AC Stick Mode	F-39
Replacement Procedures
Fan Motor and Blade Removal	F-40
SCR Heatsink Assembly Removal	F-42
Retest After Repair	F-44

SQUARE WAVE TIG 255

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Contents Square Wave TIG Electric Shock can kill SafetyARC Rays can burn Fumes and Gases can be dangerousWelding Sparks can cause fire or explosion Cylinder may explode if damagedMay be dangerous Electric and Magnetic FieldsSûreté Pour Soudage a L’Arc Précautions DE SûretéMaster Table of Contents for ALL Sections Installation Section Table of ContentsTechnical Specifications Square Wave TIG InstallationHigh Frequency Interference Protection Safety PrecautionsSelect Suitable Location StackingInput Supply Connections Input ConnectionsGround Connection TIG Torch Connection Reconnect ProcedureOutput Connections Stick Electrode Cable Connection Table A.1Operation Section Operating Instructions OperationGeneral Warnings Fumes and GasesSection TOC While Weld ING TIG Gtaw Single Phase Polarity Do not Switch AC & DC Recti Fier Power SourceWork Connec Coolant Tion OutputOperational Features and Controls Design Features AdvantagesGeneral Description Recommended Processes and EquipmentLimitations Welding CapabilityControl Panel Keys Controls and SettingsLoad Case Front ControlsTable B.1 Recommended Polarity Settings for TIG Welding Accessory Operation TIG WeldingHand and Foot Amptrol Welding Operation TIG Welding GuidelinesSquare Wave TIG 255 12/95 TIG Welding Sequence Operation 2-STEP ModeTable B.2 Typical Current Ranges 1 for Tungsten Electrodes TIG Welding Sequence Operation 4-STEP Mode Advanced TIG Welding Features Auxiliary PowerALL Machines AC Wave Balance and Auto BalanceOverload Protection Square Wave TIG Accessories Section Options / Accessories AccessoriesInstallation of Field Installed Options Undercarriage FunctionMaintenance Section Maintenance MaintenanceRoutine and Periodic Maintenance Safety PrecautionsFigure D.1 General Assembly Exploded View Square Wave TIG Theory of Operation Section Power Supply Block Logic DiagramInput Line Voltage and Main Transformer Theory of OperationOutput Rectification and Feedback Control High Voltage / High Frequency Circuit DC Welding Circuit DC Welding Output AC Welding Circuit AC Welding OutputSCR Operation Square Wave TIG SCR OperationThermal Protection Troubleshooting & Repair Section HOW to USE Troubleshooting Guide 1TROUBLESHOOTING & RepairPC Board Troubleshooting Procedures Troubleshooting & RepairOutput Problems Troubleshooting Guide12/95 Square Wave TIG Troubleshooting & Repair Recommended Course of Action Problems SymptomsPossible Areas of Misadjustments Function Problems Troubleshooting Guide Troubleshooting & Repair TIG Mode Problems Troubleshooting & Repair Troubleshooting Guide TIG Welding Problems Troubleshooting & Repair Stick Welding Problems Figure F.1 Control Board Connectors PC Board Connector LocationsMaterials Needed Control Transformer T2 Voltage TestTest Description Control BOX Test ProcedureFigure F.4 Control Board and Transformer Control Transformer T2 Voltage TestPROTECTION/SNUBBER Board Continuity Test PROTECTION/SNUBBER Board Continuity Test Table F.6 Square Wave TIG Figure F.6 PROTECTION/SNUBBER Board Test PointsARC Start Trigger Circuit Test ARC Start Trigger Circuit Test Figure F.9 PROTECTION/SNUBBER Board Test Points Static SCR Test Figure F.11 Protection Board Plug Locations Static SCR TestActive SCR Test Figure F.13 PROTECTION/SNUBBER Board Plug Locations Active SCR TestSilicon Controlled Rectifier Test Battery TestScope Settings Normal Open Circuit Voltage Waveform DC Stick ModeNormal Open Circuit Voltage Waveform AC Stick Mode Normal Open Circuit Voltage Waveform DC TIG Mode Normal Open Circuit Voltage Waveform AC TIG Mode Machine Loaded to 200 Amps AT 50 VDC Typical Output Voltage Waveform Machine Loaded DC TIG ModeMachine Loaded to 200 Amps AT 46 VAC AC TIG Mode Auto Balance onMachine Loaded to 50 Amps AT 26VAC Typical SCR Gate Voltage Waveform Volts 5msVolts 2ms Troubleshooting & Repair Tools Required FAN Motor and Blade RemovalFAN Motor and Blade Removal Materials Required SCR Heat Sink Assembly RemovalSCR Heat Sink Assembly Removal Recommended Meters for Machine Output Tests Retest After RepairInput Idle Amps Figure F.16 Transformer Lead Test Points Retest After Repair cont’dElectrical Diagrams Electrical Diagrams PTC1,PTC2 THERMISTOR-PTC,56 OHMS,90MA Control Board G2150Control Board G2150 cont’d Square Wave TIG PROTECTION/SNUBBER Board L9255 CAPACITOR-CEMO,4700P,50V,10% Square Wave TIG Wiring Diagram Square Wave TIG 6 a 0 a 7 a 8 a 3 C Machine Schematic Square Wave TIGA C C T G2150Y P a D Control Board Schematic Square Wave TIG 255 cont’d G2150PROTECTION/SNUBBER Board Schematic Square Wave TIG 255 L9255 Keypad LED Board Square Wave TIG 255 L9212