Lincoln Electric SVM100-A PROTECTION/SNUBBER Board Schematic Square Wave TIG 255 L9255

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ELECTRICAL DIAGRAMS

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PROTECTION/SNUBBER BOARD SCHEMATIC — SQUARE WAVE TIG 255 (L9255)

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NOTE: Lincoln Electric assumes no responsibility for liabilities resulting from board level troubleshooting. PC Board repairs will invalidate your factory warranty. This Printed Circuit Board schematic is provided for reference only. It may not be totally applicable to your machine's specific PC board version. This diagram is intended to provide general information regarding PC board function. Lincoln Electric discourages board level troubleshooting and repair since it may compromise the quality of the design and may result in Danger to the Machine Operator or Technician. Improper PC board repairs could result in damage to the machine.

SQUARE WAVE TIG 255

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Contents Square Wave TIG Fumes and Gases can be dangerous SafetyElectric Shock can kill ARC Rays can burnWelding 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 InstallationStacking Safety PrecautionsHigh Frequency Interference Protection Select Suitable LocationInput Connections Ground ConnectionInput Supply Connections Reconnect Procedure Output ConnectionsTIG Torch Connection Stick Electrode Cable Connection Table A.1Operation Section Fumes and Gases OperationOperating Instructions General WarningsSection TOC Coolant Tion Output Polarity Do not Switch AC & DC Recti Fier Power SourceWhile Weld ING TIG Gtaw Single Phase Work ConnecRecommended Processes and Equipment Design Features AdvantagesOperational Features and Controls General DescriptionLimitations Welding CapabilityControl Panel Keys Controls and SettingsLoad Case Front ControlsTIG Welding Guidelines Accessory Operation TIG WeldingTable B.1 Recommended Polarity Settings for TIG Welding Hand and Foot Amptrol Welding OperationTIG Welding Sequence Operation 2-STEP Mode Table B.2 Typical Current Ranges 1 for Tungsten ElectrodesSquare Wave TIG 255 12/95 TIG Welding Sequence Operation 4-STEP Mode AC Wave Balance and Auto Balance Auxiliary PowerAdvanced TIG Welding Features ALL MachinesOverload Protection Square Wave TIG Accessories Section Undercarriage Function AccessoriesOptions / Accessories Installation of Field Installed OptionsMaintenance Section Safety Precautions MaintenanceMaintenance Routine and Periodic MaintenanceFigure 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 OutputAC 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 Problems Symptoms Possible Areas of MisadjustmentsRecommended Course of Action 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 LocationsControl Transformer T2 Voltage Test Test DescriptionMaterials Needed 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 ModeAC TIG Mode Auto Balance on Machine Loaded to 50 Amps AT 26VACMachine Loaded to 200 Amps AT 46 VAC 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 Retest After Repair Input Idle AmpsRecommended Meters for Machine Output Tests 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