Lincoln Electric SVM100-A service manual SCR Heat Sink Assembly Removal

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F-43

TROUBLESHOOTING & REPAIR

SCR HEAT SINK ASSEMBLY REMOVAL (continued)

SCR Heat

Sink Assemblies

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TEST PROCEDURE

1.Remove main power supply to machine.

2.Remove case sides and top.

3.Locate SCR heat sink assemblies.

4.Remove all gate, snubber and cable leads from the SCR heat sink assembly that is to be serviced.

5.Remove the four 1/4”-20 hex nuts and associated plain and lock washers from the four 1/4”-20x1.75” hex head cap screws. Remove the heat sink assem- bly trying not to disturb the insulating washers and bushings. See figure above.

6.Reinstall the heat sink assembly in the same manner being certain that the insulating washers and bushings are installed correctly. See figure above.

7.Test with an ohmmeter to make certain that the heat sink assembly is electrical- ly isolated from chassis ground by at least 500,000 ohms of resistance.

8.Reconnect the gate leads.

9.Reconnect the snubber and cable leads using a thin coating of Dow 340 heat sink compound on the connection sur- faces. Be sure that the connection sur- faces are clean and free from any dirt or paint.

SQUARE WAVE TIG 255

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Contents Square Wave TIG Safety Electric Shock can killARC Rays can burn Fumes and Gases can be dangerousCylinder may explode if damaged Welding Sparks can cause fire or explosionElectric and Magnetic Fields May be dangerousPrécautions DE Sûreté Sûreté Pour Soudage a L’ArcMaster Table of Contents for ALL Sections Table of Contents Installation SectionInstallation Technical Specifications Square Wave TIGSafety Precautions High Frequency Interference ProtectionSelect Suitable Location StackingInput Connections Ground ConnectionInput Supply Connections Reconnect Procedure Output ConnectionsTIG Torch Connection Table A.1 Stick Electrode Cable ConnectionOperation Section Operation Operating InstructionsGeneral Warnings Fumes and GasesSection TOC Polarity Do not Switch AC & DC Recti Fier Power Source While Weld ING TIG Gtaw Single PhaseWork Connec Coolant Tion OutputDesign Features Advantages Operational Features and ControlsGeneral Description Recommended Processes and EquipmentWelding Capability LimitationsControls and Settings Control Panel KeysCase Front Controls LoadAccessory Operation TIG Welding Table B.1 Recommended Polarity Settings for TIG WeldingHand and Foot Amptrol Welding Operation TIG Welding GuidelinesTIG 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 Auxiliary Power Advanced TIG Welding FeaturesALL Machines AC Wave Balance and Auto BalanceOverload Protection Square Wave TIG Accessories Section Accessories Options / AccessoriesInstallation of Field Installed Options Undercarriage FunctionMaintenance Section Maintenance MaintenanceRoutine and Periodic Maintenance Safety PrecautionsFigure D.1 General Assembly Exploded View Square Wave TIG Power Supply Block Logic Diagram Theory of Operation SectionTheory of Operation Input Line Voltage and Main TransformerOutput Rectification and Feedback Control High Voltage / High Frequency Circuit DC Welding Output DC Welding CircuitAC Welding Output AC Welding CircuitSCR Operation SCR Operation Square Wave TIGThermal Protection Troubleshooting & Repair Section 1TROUBLESHOOTING & Repair HOW to USE Troubleshooting GuideTroubleshooting & Repair PC Board Troubleshooting ProceduresTroubleshooting Guide Output Problems12/95 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 PC Board Connector Locations Figure F.1 Control Board ConnectorsControl Transformer T2 Voltage Test Test DescriptionMaterials Needed Test Procedure Control BOXControl Transformer T2 Voltage Test Figure F.4 Control Board and TransformerPROTECTION/SNUBBER Board Continuity Test PROTECTION/SNUBBER Board Continuity Test Figure F.6 PROTECTION/SNUBBER Board Test Points Table F.6 Square Wave TIGARC Start Trigger Circuit Test ARC Start Trigger Circuit Test Figure F.9 PROTECTION/SNUBBER Board Test Points Static SCR Test Static SCR Test Figure F.11 Protection Board Plug LocationsActive SCR Test Active SCR Test Figure F.13 PROTECTION/SNUBBER Board Plug LocationsBattery Test Silicon Controlled Rectifier TestNormal Open Circuit Voltage Waveform DC Stick Mode Scope SettingsNormal Open Circuit Voltage Waveform AC Stick Mode Normal Open Circuit Voltage Waveform DC TIG Mode Normal Open Circuit Voltage Waveform AC TIG Mode Typical Output Voltage Waveform Machine Loaded DC TIG Mode Machine Loaded to 200 Amps AT 50 VDCAC TIG Mode Auto Balance on Machine Loaded to 50 Amps AT 26VACMachine Loaded to 200 Amps AT 46 VAC Volts 5ms Typical SCR Gate Voltage WaveformVolts 2ms Troubleshooting & Repair FAN Motor and Blade Removal Tools RequiredFAN Motor and Blade Removal SCR Heat Sink Assembly Removal Materials RequiredSCR Heat Sink Assembly Removal Retest After Repair Input Idle AmpsRecommended Meters for Machine Output Tests Retest After Repair cont’d Figure F.16 Transformer Lead Test PointsElectrical Diagrams Electrical Diagrams Control Board G2150 PTC1,PTC2 THERMISTOR-PTC,56 OHMS,90MAControl Board G2150 cont’d Square Wave TIG PROTECTION/SNUBBER Board L9255 CAPACITOR-CEMO,4700P,50V,10% Square Wave TIG Wiring Diagram Square Wave TIG Machine Schematic Square Wave TIG 6 a 0 a 7 a 8 a 3 CG2150 A C C TControl Board Schematic Square Wave TIG 255 cont’d G2150 Y P a DPROTECTION/SNUBBER Board Schematic Square Wave TIG 255 L9255 Keypad LED Board Square Wave TIG 255 L9212