Diode Bridge Test | Lincoln Electric LF-72/74 manual

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F-11	TROUBLESHOOTING AND REPAIR	F-11
	TROUBLESHOOTING AND REPAIR

DIODE BRIDGE TEST

WARNING

Service and repair should be performed by only Lincoln Electric factory trained personnel. Unauthorized repairs performed on this equipment may result in danger to the technician or machine operator and will invalidate your factory warranty. For your safety and to avoid electrical shock, please observe all safety notes and pre- cautions detailed throughout this manual.

If for any reason you do not understand the test procedures or are unable to per- form the test / repairs safely, contact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call 1-888-935-3877.

TEST DESCRIPTION

This test will help determine if the diode bridge is receiving the power AC input voltages and is converting them to the correct DC output voltages.

MATERIALS NEEDED

5/16 in. nut driver

42VAC power supply

Volt-Ohmmeter

LF-72/74

Image 95

Lincoln Electric LF-72/74 service manual Diode Bridge Test

Contents

LF-72/74 Safety Electric Shock can kill Iii Welding Sparks can cause fire or explosion Sûreté Pour Soudage a L’Arc Précautions DE Sûreté Master Table of Contents for ALL Sections Section A-1 Table of ContentsInstallation Section Amp Rating Duty Cycle Installation Mounting Safety PrecautionLocation Suspended Bench MountSwivel Mount Boom Mount Weld Cable Sizes Weld Cable Connection Coaxial Weld Cables Control Cable Connections INSTALLATIONA-7Analog Control Cable Pin Function Miller Power Source Lincoln Wire FeederAnalog Miller Control Cable Adapter K2335-1 High Frequency Protection Wire Drive SystemsWelding GUN/WIRE Feeder Trigger Connector Remote Sense Lead Specifications Magnum GUN and Cable Assemblies Welding GUNS, Torches and ACCES- Sories Rolls.FIGURE A.4 Procedure for Changing Drive and Idle Roll SetsWire Drive Configuration Set the pressure arm as follows See Figure A.6 Pressure ARM AdjustmentGun Receiver For use With Bushing Wire Reel Loading Figure A.9 Weld Wire Routing Shielding GAS Connection For Codes 11209, 11210, 11211 and above Installing ElectrodeTo install Lincoln conduit See Figure A.10b Conduit Kits Figure A.12b Aluminum Wire Preparations Base Model Bench Model Standard Duty Bench Model Heavy Duty INSTALLATIONA-18 Cable Typical System Configurations LF-72/74 Section B-1 Operation Section GAS Input Work Connection Operation Recommended Processes Common Welding AbbreviationsProduct Description Figure B.1 Case Front Controls Description Front Panel Controls and Connections Remote Voltage Control KIT Burnback and Postflow Timer KITCold FEED/GAS Purge Switch Step Trigger Interlock Switch Trigger Interlock Wire Feed Speed KnobTrigger Connector 5-PIN Amphenol GUN Receiver Bushing K1500-2 Section C-1 Accessories Section Optional Kits Accessories LF-72s Accessories Key LF-72/74 Section D-1 Maintenance Section Routine Maintenance MaintenanceMaintenance Calibration Specification Figure D.1 Figure D.3 Major Component Location Section AA Section AA-1 Model WFS Range Wire SizesAA-2 Figure AA.1 AA-3 AA-4 AA-5 Coaxial Weld Cable AA-6 K1797-xx INSTALLATIONAA-7AA-7 AA-8 AA-9 Drive Roll Kits Steel or Cored Wires Figure AA.3 AA-10 Guides AA-11Changing the Gun Receiver Bushing Lation or changing drive rolls and/or AA-12 Assembly of Drive Rolls and Wire Guides Set the pressure arm as follows See Figure AA.8 AA-13 AA-14 Loading 16 to 44 lb .3 20kg Spools See figure AA.8 AA-15 Figure AA.11 AA-16 Figure AA.12a AA-17 Figure AA.12b AA-18 AA-19 Common Equipment SET-UPS AA-20INSTALLATIONAA-20 AA-21 Figure AA.15 High Volume Production AA-22 Figure AA.16 Portable Welding Section BB Section BB-1 Fcaw Innershield or Outershield BB-2 BB-3 Required Equipment Figure BB.1 Case Front Controls Description BB-4 K2426-3 model BB-5K2426-1 and K2426-2 models BB-6 Switch Section CC-1 CC-2 CC-3 CC-4 CC-5 CC-6 Section DD Section DD-1 WFS knob setting Could remain energized Several seconds To verify the wire feed speedNal wiring When inching with gun trigger, electrode DD-3 MAINTENANCEDD-3 DD-4 Figure DD.3 Major Component Location Section E-1 Theory of Operation Section Return to Section Theory of Operation Control Board LF-72/74 Section F-1 Troubleshooting & Repair Section HOW to USE Troubleshooting Guide Troubleshooting & Repair PC Board Troubleshooting Procedures Function Problems Function Problems Troubleshooting & Repair Test Description Drive Motor and Tach Feedback Test Test Procedure GAS Solenoid Test Troubleshooting and Repair Figure F.3 Leads 552, 552B Test Procedure Diode Bridge Test 552B + 552A Wire Speed Potentiometer Test 14F-14 Wire Speed Potentiometer Test PC Board Removal and Replacement Removal Procedure Replacement Procedure Control PC Board Removal and Replacement Procedure Troubleshooting and Repair Procedure Wire Drive Motor and Gear BOX Removal and Replacement Procedure Replacement Procedures Operation Verification SET UP LF-72/74 Section G-1 Electrical Diagrams Section LF-72/74 Electrical Diagrams Timer KIT Board Normal Speed Micro Internal panel Motor Connecter Summary High Torque Setting engages Schematic Common Analog Control PC Board G4559 Sheet Electrical Diagrams Electrical Diagrams PC Board Assembly Common Analog Control G4560-2E0