Lincoln Electric LF-72/74 service manual Function Problems

Page 89

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F-5

TROUBLESHOOTING & REPAIR

F-5

LF-72/74

Observe Safety Guidelines detailed in the beginning of this manual.

 

 

 

 

 

PROBLEMS

POSSIBLE AREAS OF

RECOMMENDED

 

(SYMPTOMS)

MISADJUSTMENT(S)

COURSE OF ACTION

 

 

 

 

 

 

FUNCTION PROBLEMS (Continued)

 

 

No shielding gas.

1. No gas supply, or gas supply

1.

Verify cylinder is not empty and

 

 

interrupted.

 

is turned on.

 

 

2. Solenoid not functioning.

Check the hose for cuts or kinks.

 

 

 

Make sure it is not crushed.

 

 

 

Verify the hose is connected to the

 

 

 

gun bushing or welding gun.

 

 

 

2.

Perform the GAS SOLENOID

 

 

 

 

TEST.

 

 

 

 

 

 

Variable or hunting arc.

1. Bad contact tip

1.

Check for proper size contact

 

 

2. Possible loose connection in

 

tip. Make sure tip is not worn,

 

 

current carrying cables.

 

and is free of spatter.

 

 

3. Set up not correct.

2.

Clean and tighten all electrode

 

 

4. Problem with shielding gas.

 

and work connections. Verify

 

 

 

 

the gun bushing is tightly

 

 

 

 

mounted to the wire drive.

 

 

 

 

Verify the gun is tightly mounted

 

 

 

 

to the gun bushing.

 

 

 

3.

Verify the proper polarity is

 

 

 

 

being used for the weld proce-

 

 

 

 

dure. Make sure the proper

 

 

 

 

electrode stick-out is being

 

 

 

 

maintained.

 

 

 

4.

Check the gas flow rate and

 

 

 

 

mixture.

 

 

 

5.

Control board may be faulty.

 

 

 

 

 

 

When the trigger is pulled, the

1. Possible bad gun or faulty con-

1.

Check all electrode and work

 

drive rolls spin but no arc voltage

nections in the heavy current

 

connections. Verify the the gun

 

 

carrying leads.

 

bushing is tight to the wire

 

 

2. Possible faulty control cable.

 

drive. Verify gun is tightly

 

 

 

mounted to the bushing.

 

 

 

 

 

 

3. Possible defective power

2.

Check the control cable and

 

 

source.

 

 

 

connectors for continuity, cuts,

 

 

 

 

 

 

 

 

or broken pins.

 

 

 

3.

Verify the power source is oper-

 

 

 

 

ating properly.

 

 

 

 

 

 

The arc burns back to the tip.

1. If timer kit is installed, reduce

 

 

 

 

the amount of burnback time.

 

 

 

The gas continues to flow for a

2. If the timer kit is installed,

 

 

 

reduce the amount of post flow

 

 

 

long time after the weld.

 

 

 

time.

 

 

 

 

 

 

CAUTION

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

LF-72/74 SINGLE/DUAL

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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 Section A-1 Table of ContentsInstallation Section Amp Rating Duty Cycle InstallationMounting Safety PrecautionLocation Swivel Mount Bench MountBoom Mount SuspendedWeld Cable Sizes Weld Cable Connection Coaxial Weld CablesControl Cable Connections INSTALLATIONA-7Analog Control Cable Pin Function Miller Power Source Lincoln Wire FeederAnalog Miller Control Cable Adapter K2335-1 Welding GUN/WIRE Feeder Trigger Connector Wire Drive SystemsRemote Sense Lead Specifications High Frequency ProtectionMagnum GUN and Cable Assemblies Welding GUNS, Torches and ACCES- SoriesRolls.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 RoutingShielding GAS Connection To install Lincoln conduit See Figure A.10b Installing ElectrodeConduit Kits For Codes 11209, 11210, 11211 and aboveFigure 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 OperationRecommended Processes Common Welding AbbreviationsProduct Description Figure B.1 Case Front Controls Description Front Panel Controls and ConnectionsCold FEED/GAS Purge Switch Burnback and Postflow Timer KITStep Trigger Interlock Switch Remote Voltage Control KITTrigger Connector 5-PIN Amphenol Wire Feed Speed KnobGUN Receiver Bushing K1500-2 Trigger InterlockSection C-1 Accessories SectionOptional Kits AccessoriesLF-72s Accessories Key LF-72/74 Section D-1 Maintenance SectionMaintenance MaintenanceCalibration Specification Routine MaintenanceFigure D.1 Figure D.3 Major Component Location Section AA Section AA-1Model WFS Range Wire SizesAA-2 Figure AA.1 AA-3AA-4 AA-5 Coaxial Weld Cable AA-6K1797-xx INSTALLATIONAA-7AA-7 AA-8 AA-9 Drive Roll Kits Steel or Cored WiresFigure AA.3 AA-10Changing the Gun Receiver Bushing AA-11Lation or changing drive rolls and/or GuidesAA-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-4K2426-3 model BB-5K2426-1 and K2426-2 models BB-6 SwitchSection CC-1 CC-2 CC-3 CC-4 CC-5 CC-6 Section DD Section DD-1Nal wiring To verify the wire feed speedWhen inching with gun trigger, electrode WFS knob setting Could remain energized Several secondsDD-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
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