Lincoln Electric SVM 119-A service manual Typical SCR Gate Voltage Waveform

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F-26	TROUBLESHOOTING & REPAIR	F-26
	TROUBLESHOOTING & REPAIR

TYPICAL SCR GATE VOLTAGE WAVEFORM

SCOPE SETTINGS

This is a typical SCR gate pulse voltage
waveform. The machine was in an open cir-	Volts/Div	. .2 V/Div.
cuit condition (no load) and operating prop-
erly. Note that each vertical division repre-	Horizontal Sweep	.5 ms/Div.
sents 2 volts and each horizontal division
represents 5 milliseconds in time.	Coupling	. . . . .DC.
Note: Scope probes connected at Plug J3	Trigger	. .Internal.
on the control board. The (+) probe to lead
G2, and the (-) probe to lead 204.

WIRE-MATIC 255

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Contents Safety Depends on You WIRE-MATICElectric Shock can kill SafetyARC Rays can burn Fumes and Gases can be dangerousWelding Sparks can cause fire or explosion Cylinder may explode if damagedIii Electric and MAG- Netic FieldsMay be dangerous Sûreté Pour Soudage a L’Arc Précautions DE SûretéWIRE-MATIC Table of Contents Table of Contents Table of Contents Installation Section InstallationTechnical Specifications Wire-Matic-255 Select Proper Location Safety PrecautionsInput Connections StackingFuse and Wire Sizes Connect Shielding GAS Figure A.4 Input Gas Supply Connections Reconnect ProcedureFigure A.5 Reconnect Diagram For 208/230/1/60 Machines Connections Connect Output ComponentsGUN and Cable Installation Wire Size Conversion PartsWIRE-MATIC Operation Table of Contents Operation SectionWELDING, Cutting Safety InstructionsGeneral Description Recommended Processes and Equipment Design Features AdvantagesDuty Cycle Amps Volts Machine CapabilityLimitations Figure B.1 Operator Controls Controls and SettingsFigure B.2 Wire Reel Loading Using the Wire Drive RollFeeding Electrode Operating Steps Setting Idle Roll PressureMaking a Weld WIRE-MATIC Table of Contents Accessories Section AccessoriesK672-1 Spool GUN Adapter KIT OPTIONS/ACCESSORIESMagnum GUN Connection KIT Optional K466-6 Making a Weld with the Spool GUN Adapter K672-1 Installed Timer KIT Installation Optional K585-1 Timer KIT K585-164 1.2mm Aluminum Feeding KIT K673-1 Drive Roll KitsK468 8 Spool Adapter K363P READI-REEL AdapterDual Cylinder Mounting KIT K671-1 Table of Contents Maintenance Section MaintenancePerform the following daily Routine and Periodic MaintenanceMaintenance Contact TIP and GAS Nozzle Installation Cable CleaningDrive Rolls and Guide Tubes GUN Tubes and NozzlesFigure D.2 Liner maintenance Liner Removal ReplacementTo open up the handle GUN Handle DisassemblyDescription English Size Metric Size WIRE-MATIC Theory of Operation Table of Contents Theory of Operation SectionTransformer Input Line Voltage and MainFeedback Control Output RectificationFigure E.4 Constant Voltage Output Constant Voltage OutputFeedback Wire Drive MotorThermal Protection Figure E.6 SCR Operation SCR OperationWIRE-MATIC Table of Contents Troubleshooting & Repair Section Troubleshooting & RepairRecommended Course of Action HOW to USE Troubleshooting GuideBoard can be dam- aged by static electricity PC Board Troubleshooting ProceduresElectric Shock can kill Main Transformer Rectifier Assembly Test To Section TOC SCR Rectifier Perform the Wire Drive Motor Trolyte in these capacitors is Liquid elecPerform the Output Rectifier Materials Needed Main Transformer TestTest Description ON/OFF Power Switch will be hot during these tests Main Transformer Test Test ProcedureLead Plug Location Static SCR Rectifier Assembly Test Leads Figure F.4 SCR 1 Test Points Active SCR Rectifier Assembly Test Leads SCR connections Figure F.7 SCR Tester CircuitWire Drive Motor and Tachometer Feedback Test Wire Drive Motor and Tachometer Feedback Test Test Procedure Test for Feedback Voltage to the Control Board Test for Supply Voltage to TachometerNormal Open Circuit Voltage Waveform Scope SettingsTypical 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 & Repair Typical SCR Gate Voltage Waveform Removal and Replacement Procedure Control PC Board Removal and ReplacementRemoval and REPLACE- Ment Procedure Wire Drive Assembly Removal and Replacement Figure F.11 Wire Drive Assembly Removal ProcedureSCR Output Rectifier Removal & Replacement Disconnection Heat Sink Lead Right side heat sink See Figure F.14Capacitor Bank Removal and Replacement Components Bank Removal ReplacementMain Transformer Removal and Replacement Power Switch FAN Motor and FAN Removal and Replacement Figure F.16 Fan Motor and Fan Removal Components FAN Motor and FAN Removal and Replacement ProcedureTroubleshooting & Repair Open Circuit Voltage Wire Speed RangeInput Volts/Hertz 230/60 375WIRE-MATIC Table of Contents Electrical Diagrams Section WIRE-MATIC Wiring Diagram 208/230 Code Electrical DiagramsWiring Diagram 230/460/575 Code Wire Matic 255 230 / 460Control PC Board G2803 Schematic Control PC Board G2803 Layout Wirematic 255 Control