Lincoln Electric SVM170-A service manual Figure F.15 Right Heat Sink Lead Disconnection

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F-47	TROUBLESHOOTING AND REPAIR	F-47
	SCR OUTPUT RECTIFIER REMOVAL AND REPLACEMENT (continued)

FIGURE F.15 — RIGHT HEAT SINK LEAD DISCONNECTION.

SCR DIODE

SCRLEADLEAD #320B

ASSEMBLY

LEAD

#320

LEAD #209S

LEAD

X4

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5.Remove lead #209S and transformer lead X4 from the right side heat sink using a 1/2 in. socket wrench and 1/2 in. open end wrench. See Figure F.15.

6.Unplug the SCR gate leads G1 and G2 (see wire markers and wiring diagram).

7.Remove the four nuts holding the SCR assembly to the floor of the machine using a 3/8 in. nutdriver.

8.Clear the leads and carefully remove the SCR rectifier assembly.

NOTE: When installing the SCR rectifier assembly, apply a thin coating of Dow Corning #340 compound to the electrical connections.

9.Unplug leads 320 and 320B from the SCR heat sink thermostat on the right side at the SCR assembly.

10.Reassemble the SCR assembly in the reverse order.

POWER MIG 255C

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Contents Power MIG 255C California Proposition 65 Warnings SafetyElectric Shock can kill Iii Welding Sparks can cause fire or explosionSûreté Pour Soudage a L’Arc Précautions DE SûretéMaster Table of Contents For ALL Sections Table of Contents Installation Section InstallationTechnical Specifications Power MIG 255C Location Safety PrecautionsUncrating the Power MIG 255C Input POWER, Grounding and Connection DiagramsInstallation Figure A.2 Triple Voltage Machine Input Connections GUN and Cable Installation Auxiliary Power ReceptaclesShielding GAS Operation Table of Contents Operation SectionWear eye, ear and body protec- tion OPERATIONB-2Limitations Product DescriptionRecommended Processes and Equipment Welding CapabilityWire Size Conversion Parts Wire Drive RollDescription of Controls Procedure for Changing Wire Reel Loading Readi REELS, Spools or CoilsDrive and Idle Roll Sets To Start the Welder Feeding Wire ElectrodeIdle Roll Pressure Setting Wire Drive ConfigurationFigure B.4 Making a Weld When Timer Option is not installedInstructions to Enter Slow RUN-IN Instructions to Enter Fast RUN-INInput Line Voltage Protection Avoiding Wire Feeding ProblemsWire Feed Overload Protection FAN ControlOvercurrent Protection Welding Thermal Overload ProtectionTable of Contents Accessories Section AccessoriesDual Cylinder Mounting KIT K1702-1 Drive Roll KitsMagnum GUN Connection KIT K363P READI-REEL AdapterSpool GUN Operating Instructions for Timer KITConnecting the Spool GUN to the Power MIG 255C K1738-1 Spool Gun Hanger AccessoryMaking a Weld with the Magnum SG Spool GUN Making a Weld with the Prince XL Spool GUNSG Spool Gun Wire Feed Speed Power MIG Table of Contents Maintenance Section MaintenanceLiner Removal and Replacement GUN Tubes and Nozzles General MaintenanceGUN Cable Cleaning Contact TIP and GAS Nozzle InstallationTable D.1 GUN Handle DisassemblyEnglish Metric Description MAINTENANCED-4Theory of Operation Table of Contents Theory of Operation SectionMain Transformer Input Line VoltageFeedback Control Output RectificationFigure E.4 Constant Voltage Output Constant Voltage OutputFeedback Wire Drive MotorThermal and Overload Protection Wire Feed Overload ProtectionFigure E.6 SCR Operation SCR OperationPower MIG 255C Table of Contents Troubleshooting and Repair Section Troubleshooting and RepairHOW to USE Troubleshooting Guide 2TROUBLESHOOTING and REPAIRF-2PC Board Troubleshooting Procedures Output Problems Troubleshooting GuideToxic. Avoid contact with any Problems Possible AreasSymptoms Misadjustments Course of Action Trolyte in these capacitors isPerform the SCR Rectifier Function Problems Wire Feeding Problems Welding Problems Welding Problems Materials Needed Test ProceduresMain Transformer Test Test DescriptionON/OFF Power Switch will be hot during these tests Test Procedure16J5 8J5 115VAC206 3J5 Rectifier Diode Bridge Test Figure F.2 G3521 Rectifier Diode Bridge Location 16TROUBLESHOOTING and REPAIRF-16354 206 36 VDC 208 206 28 VAC 209Power MIG 255C Static SCR Rectifier Assembly Test Static SCR Rectifier Assembly Test Active SCR Rectifier Assembly Test Power MIG 255C Active SCR Rectifier Assembly Test Active SCR Rectifier Assembly Test Figure F.7 Location Leads X2 Figure F.8 Wire Drive Motor and Tachometer Feedback Test 4J1 Wire Drive Motor and Tachometer Feedback Test515B 206B 15 VDC 5J1 1J1 Test for Supply Voltage to Tachometer555 206B To 3.5 VDC 6J1 1J1 Test for Feedback Voltage to Control BoardVolts Normal Open Circuit Voltage WaveformTypical Output Voltage Waveform Machine Loaded Machine Loaded to 250 Amps AT 26 VDC Scope SettingsMachine Loaded to 220 Amps AT 22 VDC Scope Settings Troubleshooting and Repair Typical SCR Gate Voltage Waveform Power MIG 255C Component Replacement Procedures Control PC Board Removal and ReplacementDescription Procedure Removal and ReplacementFigure F.11 Control Board Mounting Power MIG 255C Wire Drive Assembly Removal and Replacement Wire Drive Assembly Removal and Replacement Procedure Power MIG 255C SCR Output Rectifier Removal and Replacement SCR Output Rectifier Removal and Replacement Figure F.15 Right Heat Sink Lead Disconnection Power MIG 255C Capacitor Bank Removal and Replacement Capacitor Bank Removal and Replacement Main Transformer and Output Choke Removal and Replacement Main Transformer and Output Choke 52TROUBLESHOOTING and REPAIRF-52TOC Power MIG 255C FAN Motor Assembly Removal and Replacement FAN Motor Assembly Removal and Replacement Input Volts/Hertz Wire Speed RangeRetest After Repair Open Circuit VoltagePower MIG 255C Section G-1 Electrical Diagrams SectionWiring Diagram Entire Machine Code 11192 L12464 Electrical DiagramsWiring Diagram Entire Machine Code 11218 L12506 Schematic Entire Machine G4752 Schematic Control PC Board G4823-2D1 Sheet Electrical Diagrams Electrical Diagrams Item Used with QTY Part Number Description PC Board Assembly Control G4824-2D1Powermig Schematic Display PC Board L10951Lincoln Electric CO PC Board Assembly Display L10952SVM Error Reporting Form