Lincoln Electric SVM169-A service manual Assembly Removal and Replacement

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F-23

TROUBLESHOOTING & REPAIR

F-23

STATIC SCR TEST (continued)

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3.Using an analog ohmmeter test the resistance from anode to cathode of SCR1. Reverse the meter leads and check from cathode to anode of SCR1. See Figure F.4. If a low resis- tance is indicated in either direction SCR1 is faulty. Replace SCR Bridge Assembly. See SCR Bridge

Assembly Removal and Replacement .

5.The further check the SCR’s func- tions use an SCR tester and proceed to the Active SCR Test.

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4.Repeat Step #3 testing SCR2, SCR3 and SCR4.

FIGURE F.4 SCR TEST POINTS

	SCR2 CATHODE
SCR1 ANODE	SCR3 CATHODE
SCR1 ANODE
	SCR4 ANODE

SCR1 CATHODE/SCR2 ANODE

SCR3 ANODE/SCR4 CATHODE

PRECISION TIG 185

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Contents Precision TIG Safety Electric Shock can kill Welding Sparks can cause fire or explosion SafetySûreté Pour Soudage a L’Arc Précautions DE SûretéMaster Table of Contents for ALL Sections Installation Section Table of ContentsInput Single Phase only InstallationK2345-2 Input at Rated Output Model Height Width Depth WeightSelect Suitable Location Safety PrecautionsInput Connections Output Connections Input Reconnect ProcedureConnections for TIG Gtaw Welding TIG Torch ConnectionWork Cable Connection Remote Control ConnectionShielding GAS Connection Precision TIG Section B Operation SectionOperation Recommended Processes and Equipment Product DescriptionControl Functionality Controls and SettingsOperating Steps Welding in TIG ModePulse TIG Control Benefits of the Precision TIG 185 Design Remote Control OperationRecommended Electrode Amperage Ranges Precision TIG Welding in Stick ModePrecision TIG Accessories Section Factory Installed Options AccessoriesTable C.1 K2348-1 Under-Storage Cart Field Installed OptionsPrecision TIG Section D Maintenance SectionRoutine and Periodic Maintenance MaintenanceSpark GAP Adjustment Figure D.2 Location of Maintenance Components Return to Section TOC Section E Theory of Operation SectionTheory of Operation Input Power CircuitGeneral Description Figure E.3 Control Board and Output Feedback Control Output Rectification Feedback ControlFigure E.4 High Voltage/High Frequency Circuit High Voltage / High Frequency CircuitFigure E.5 DC Welding Current Generation DC Welding OutputFigure E.6 AC Square Wave Welding Current Generation AC Welding OutputFigure E.7 SCR Operation SCR OperationThermal Protection Protective CircuitsOverload Protection Section F Troubleshooting & Repair SectionHigh Voltage / High Frequency can damage test equipment Troubleshooting & RepairWorkstations PC Board Troubleshooting ProceduresCourse of Action Problems Possible Areas Recommended SymptomsPossible 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 Test Description High Frequency Circuit Disable ProcedureFigure F.1 Spark GAP Assembly ProcedureT1 Transformer Test T1 Transformer Test Test ProcedurePrimary Windings Primary Voltages Return to Section Section TOCPrecision 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 Scope Settings AC TIG ModeNormal Open Circuit Voltage Waveform DC TIG Mode AC Stick Mode DC Stick Mode Machine Loaded to 180 Amps AT 16VDC Typical Output Voltage Waveform Machine LoadedDC TIG Mode Machine Loaded to 180 Amps AT 26VDC DC Stick Mode 50 V/Div Precision TIG SCR Bridge Assembly Removal and Replacement Procedure Troubleshooting and RepairProcedure SCR Bridge AssemblyFront Panel Mounting Screws Figure F.9 Plug J2 on Control Board 42TROUBLESHOOTING & REPAIRF-42Replacement Procedure 43TROUBLESHOOTING & REPAIRF-43Precision TIG Polarity Switch Removal and Replacement Procedure Removal Procedure Polarity SwitchReplacement Procedure Precision TIG High Voltage Transformer Removal and Replacement Procedure Transformer Secondary Leads Precision TIG High Voltage TransformerFigure 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 Retest After Repair Troubleshooting and RepairInput Idle Amps Recommended Meters for Machine Output TestsPrecision TIG Electrical Diagrams Section Precision TIG Wiring Diagram Entire Machine G4549G4588 Schematic Entire Machine G4588Schematic Control PC Board G4550-1B4-1 Schematic Control P.C. Board G4550-1B4-2 Schematic Control P.C. Board G4550-1B4-3 G4551 PC Board Assembly Control G4551-1SVM Error Reporting Form