Lincoln Electric SVM169-A service manual DC TIG Mode

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F-34

TROUBLESHOOTING & REPAIR

F-34

TYPICAL OUTPUT VOLTAGE WAVEFORM - MACHINE LOADED

DC TIG MODE

CAUTION

HIGH VOLTAGE / HIGH FREQUENCY can damage test equipment.

•Perform all voltage and waveform checks with high frequency circuit OFF.

•Perform High Frequency Disable Procedure.

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10 V

MACHINE LOADED TO 180 AMPS AT 16VDC.

This is the typical DC (+) output voltage waveform generated from a properly operat- ing machine. Note that each vertical division represents 10 volts and that each horizontal division represents 2 milliseconds in time. The machine was loaded with a resistance grid bank. The grid load meters read 180 amps and 16VDC

Note: Scope probes connected at machine

output terminals: (+) probe to electrode, (–) probe to work.

0 V

2 ms

SCOPE SETTINGS

Volts/Div	10 V/Div.
Horizontal Sweep	2 ms/Div.
Coupling	DC
Trigger	Internal

PRECISION TIG 185

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Contents Precision TIG Safety Electric Shock can kill Safety Welding Sparks can cause fire or explosionPrécautions DE Sûreté Sûreté Pour Soudage a L’ArcMaster Table of Contents for ALL Sections Table of Contents Installation SectionInstallation Input Single Phase onlyModel Height Width Depth Weight K2345-2 Input at Rated OutputSafety Precautions Select Suitable LocationInput Connections Input Reconnect Procedure Output ConnectionsConnections for TIG Gtaw Welding TIG Torch ConnectionRemote Control Connection Work Cable ConnectionShielding GAS Connection Precision TIG Operation Section Section BOperation Product Description Recommended Processes and EquipmentControls and Settings Control FunctionalityWelding in TIG Mode Operating StepsPulse TIG Control Remote Control Operation Benefits of the Precision TIG 185 DesignWelding in Stick Mode Recommended Electrode Amperage Ranges Precision TIGPrecision TIG Accessories Section Accessories Factory Installed OptionsTable C.1 Field Installed Options K2348-1 Under-Storage CartPrecision TIG Maintenance Section Section DMaintenance Routine and Periodic MaintenanceSpark GAP Adjustment Figure D.2 Location of Maintenance Components Return to Section TOC Theory of Operation Section Section EInput Power Circuit Theory of OperationGeneral Description Output Rectification Feedback Control Figure E.3 Control Board and Output Feedback ControlHigh Voltage / High Frequency Circuit Figure E.4 High Voltage/High Frequency CircuitDC Welding Output Figure E.5 DC Welding Current GenerationAC Welding Output Figure E.6 AC Square Wave Welding Current GenerationSCR Operation Figure E.7 SCR OperationProtective Circuits Thermal ProtectionOverload Protection Troubleshooting & Repair Section Section FTroubleshooting & Repair High Voltage / High Frequency can damage test equipmentPC Board Troubleshooting Procedures WorkstationsProblems Possible Areas Recommended Symptoms Course of ActionPossible Areas Recommended Symptoms Problems Possible Areas Check the welding cables and or TIG Mode Problems Troubleshooting & Repair TIG Welding Problems Problems Possible Areas Electric Shock can Problems Possible Areas Recommended Symptoms Stick Welding Problems High Frequency Circuit Disable Procedure Test DescriptionProcedure Figure F.1 Spark GAP AssemblyT1 Transformer Test Test Procedure T1 Transformer TestReturn to Section Section TOC Primary Windings Primary VoltagesPrecision TIG Static SCR Test Static SCR Test Assembly Removal and Replacement Precision TIG Active SCR Test Active SCR Test Figure F.6 SCR Gate Locations Precision TIG 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 180 Amps AT 16VDCDC TIG Mode Machine Loaded to 180 Amps AT 26VDC DC Stick Mode 50 V/Div Precision TIG Troubleshooting and Repair SCR Bridge Assembly Removal and Replacement ProcedureSCR Bridge Assembly ProcedureFront Panel Mounting Screws 42TROUBLESHOOTING & REPAIRF-42 Figure F.9 Plug J2 on Control Board43TROUBLESHOOTING & REPAIRF-43 Replacement ProcedurePrecision TIG Polarity Switch Removal and Replacement Procedure Polarity Switch Removal ProcedureReplacement Procedure Precision TIG High Voltage Transformer Removal and Replacement Procedure High Voltage Transformer Transformer Secondary Leads Precision TIGFigure F.12 High Voltage Transformer Mounting Insulators Precision TIG Nutdriver Wrench Wire cutters Perform the SCR Bridge Assembly Removal Procedure Assembly Replacement Procedure Precision TIG Troubleshooting and Repair Retest After RepairInput Idle Amps Recommended Meters for Machine Output TestsPrecision TIG Electrical Diagrams Section Wiring Diagram Entire Machine G4549 Precision TIGSchematic Entire Machine G4588 G4588Schematic Control PC Board G4550-1B4-1 Schematic Control P.C. Board G4550-1B4-2 Schematic Control P.C. Board G4550-1B4-3 PC Board Assembly Control G4551-1 G4551SVM Error Reporting Form