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Lincoln Electric LF-72/74 service manual AA-13, Set the pressure arm as follows See Figure AA.8

Models: LF-72/74

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AA-13	INSTALLATION	AA-13

PRESSURE ARM ADJUSTMENT

WARNING

ELECTRIC SHOCK can kill.

•Turn the input power OFF at the welding power source before installation or changing drive rolls and/or guides.

•Do not touch electrically live parts.

•When inching with the gun trigger, electrode and drive mechanism are "hot" to work and ground and could remain energized several seconds after the gun trigger is released.

•Only qualified personnel should perform mainte- nance work.

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The pressure arm controls the amount of force the drive rolls exert on the wire. Proper adjustment of both pressure arm gives the best welding performance. For best results, set both pressure arms to the same value.

Set the pressure arm as follows (See Figure AA.8):

Aluminum wires	between 1 and 3
Cored wires	between 3 and 4
Steel, Stainless wires	between 4 and 6

FIGURE AA.8

CORED WIRES	1		SOLID WIRES
OUTERSHIELD		6	ALUMINUM
METALSHIELD	5
	3	2	STAINLESTEELSS
INNERSHIELD		4

LF-72/74

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Lincoln Electric LF-72/74 service manual AA-13, Set the pressure arm as follows See Figure AA.8

Contents

LF-72/74 Safety Electric 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 Installation Section Table of ContentsSection A-1 Amp Rating Duty Cycle InstallationLocation Safety PrecautionMounting Suspended Bench MountSwivel Mount Boom MountWeld Cable Sizes Weld Cable Connection Coaxial Weld CablesAnalog Control Cable INSTALLATIONA-7Control Cable Connections Analog Miller Control Cable Adapter K2335-1 Miller Power Source Lincoln Wire FeederPin Function High Frequency Protection Wire Drive SystemsWelding GUN/WIRE Feeder Trigger Connector Remote Sense Lead SpecificationsMagnum GUN and Cable Assemblies Welding GUNS, Torches and ACCES- SoriesWire Drive Configuration Procedure for Changing Drive and Idle Roll SetsRolls.FIGURE A.4 Gun Receiver For use With Bushing Pressure ARM AdjustmentSet the pressure arm as follows See Figure A.6 Wire Reel Loading Figure A.9 Weld Wire RoutingShielding GAS Connection For Codes 11209, 11210, 11211 and above Installing ElectrodeTo install Lincoln conduit See Figure A.10b Conduit KitsFigure A.12b Aluminum Wire PreparationsBase Model Bench Model Standard Duty Bench Model Heavy Duty INSTALLATIONA-18Cable Typical System ConfigurationsLF-72/74 Section B-1 Operation SectionGAS Input Work Connection OperationProduct Description Common Welding AbbreviationsRecommended Processes Figure B.1 Case Front Controls Description Front Panel Controls and ConnectionsRemote Voltage Control KIT Burnback and Postflow Timer KITCold FEED/GAS Purge Switch Step Trigger Interlock SwitchTrigger Interlock Wire Feed Speed KnobTrigger Connector 5-PIN Amphenol GUN Receiver Bushing K1500-2Section C-1 Accessories SectionOptional Kits AccessoriesLF-72s Accessories Key LF-72/74 Section D-1 Maintenance SectionRoutine Maintenance MaintenanceMaintenance Calibration SpecificationFigure D.1 Figure D.3 Major Component Location Section AA Section AA-1AA-2 WFS Range Wire SizesModel Figure AA.1 AA-3AA-4 AA-5 Coaxial Weld Cable AA-6AA-7 INSTALLATIONAA-7K1797-xx AA-8 AA-9 Drive Roll Kits Steel or Cored WiresFigure AA.3 AA-10Guides AA-11Changing the Gun Receiver Bushing Lation or changing drive rolls and/orAA-12 Assembly of Drive Rolls and Wire GuidesSet the pressure arm as follows See Figure AA.8 AA-13AA-14 Loading 16 to 44 lb .3 20kg Spools See figure AA.8 AA-15Figure AA.11 AA-16Figure AA.12a AA-17Figure AA.12b AA-18AA-19 Common Equipment SET-UPS AA-20INSTALLATIONAA-20AA-21 Figure AA.15 High Volume ProductionAA-22 Figure AA.16 Portable WeldingSection BB Section BB-1Fcaw Innershield or Outershield BB-2BB-3 Required EquipmentFigure BB.1 Case Front Controls Description BB-4K2426-1 and K2426-2 models BB-5K2426-3 model BB-6 SwitchSection CC-1 CC-2 CC-3 CC-4 CC-5 CC-6 Section DD Section DD-1WFS knob setting Could remain energized Several seconds To verify the wire feed speedNal wiring When inching with gun trigger, electrodeDD-3 MAINTENANCEDD-3DD-4 Figure DD.3 Major Component LocationSection E-1 Theory of Operation SectionReturn to Section Theory of OperationControl Board LF-72/74 Section F-1 Troubleshooting & Repair SectionHOW to USE Troubleshooting Guide Troubleshooting & RepairPC Board Troubleshooting Procedures Function Problems Function Problems Troubleshooting & Repair Test Description Drive Motor and Tach Feedback TestTest Procedure GAS Solenoid Test Troubleshooting and RepairFigure F.3 Leads 552, 552B Test ProcedureDiode Bridge Test 552B + 552A Wire Speed Potentiometer Test 14F-14 Wire Speed Potentiometer TestPC Board Removal and Replacement Removal Procedure Replacement Procedure Control PC Board Removal and Replacement ProcedureTroubleshooting and Repair Procedure Wire Drive Motor and Gear BOX Removal and ReplacementProcedure Replacement Procedures Operation Verification SET UPLF-72/74 Section G-1 Electrical Diagrams SectionLF-72/74 Electrical DiagramsTimer 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