Lincoln Electric LF-72/74 service manual Wire Speed Potentiometer Test, 14F-14

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F-14F-14

TROUBLESHOOTING AND REPAIR

WIRE SPEED POTENTIOMETER TEST (Continued)

Figure F.5

577		WIRE FEED
576	10K/2W	SPEED
576	10K/2W	CONTROL
575		POTENTIOMETER

0 VDC MIN. WFS

5 VDC MIN. WFS

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TEST PROCEDURE

1.Remove the input power from the unit.

2.Using 5/16 nut driver remove the 5 screws holding the cover.

3.Apply the correct input voltage (42VAC) to the LF72/LF74 unit.

4.Locate the P8 plug (see wiring diagram) going to the potentiometer.

5.Check for 0VDC minimum to 5VDC maximum between wires 575 and 576. If the voltage is not there, check the wires for continuity back to the control board. If the wiring checks out good, the control board may be faulty.

6.The potentiometer can also be checked by unplugging the P8 connection (see wiring diagram), and checking for 0 to 10k ohms between leads 575 and 576 (as pot is located).

7.Reconnect the disconnected leads and reassemble the cover.

LF-72/74

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Contents LF-72/74 Safety Electric Shock can kill Welding Sparks can cause fire or explosion IiiPrécautions DE Sûreté Sûreté Pour Soudage a L’ArcMaster Table of Contents for ALL Sections Section A-1 Table of ContentsInstallation Section Installation Amp Rating Duty CycleMounting Safety PrecautionLocation Boom Mount Bench MountSwivel Mount SuspendedWeld Cable Sizes Coaxial Weld Cables Weld Cable ConnectionControl Cable Connections INSTALLATIONA-7Analog Control Cable Pin Function Miller Power Source Lincoln Wire FeederAnalog Miller Control Cable Adapter K2335-1 Remote Sense Lead Specifications Wire Drive SystemsWelding GUN/WIRE Feeder Trigger Connector High Frequency ProtectionWelding GUNS, Torches and ACCES- Sories Magnum GUN and Cable AssembliesRolls.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 Weld Wire Routing Figure A.9Shielding GAS Connection Conduit Kits Installing ElectrodeTo install Lincoln conduit See Figure A.10b For Codes 11209, 11210, 11211 and aboveAluminum Wire Preparations Figure A.12bINSTALLATIONA-18 Base Model Bench Model Standard Duty Bench Model Heavy DutyTypical System Configurations CableLF-72/74 Operation Section Section B-1Operation GAS Input Work ConnectionRecommended Processes Common Welding AbbreviationsProduct Description Front Panel Controls and Connections Figure B.1 Case Front Controls DescriptionStep Trigger Interlock Switch Burnback and Postflow Timer KITCold FEED/GAS Purge Switch Remote Voltage Control KITGUN Receiver Bushing K1500-2 Wire Feed Speed KnobTrigger Connector 5-PIN Amphenol Trigger InterlockAccessories Section Section C-1Accessories Optional KitsLF-72s Accessories Key LF-72/74 Maintenance Section Section D-1Calibration Specification MaintenanceMaintenance Routine MaintenanceFigure D.1 Figure D.3 Major Component Location Section AA-1 Section AAModel WFS Range Wire SizesAA-2 AA-3 Figure AA.1AA-4 AA-5 AA-6 Coaxial Weld CableK1797-xx INSTALLATIONAA-7AA-7 AA-8 Drive Roll Kits Steel or Cored Wires AA-9AA-10 Figure AA.3Lation or changing drive rolls and/or AA-11Changing the Gun Receiver Bushing GuidesAssembly of Drive Rolls and Wire Guides AA-12AA-13 Set the pressure arm as follows See Figure AA.8AA-14 AA-15 Loading 16 to 44 lb .3 20kg Spools See figure AA.8AA-16 Figure AA.11AA-17 Figure AA.12aAA-18 Figure AA.12bAA-19 AA-20INSTALLATIONAA-20 Common Equipment SET-UPSFigure AA.15 High Volume Production AA-21Figure AA.16 Portable Welding AA-22Section BB-1 Section BBBB-2 Fcaw Innershield or OutershieldRequired Equipment BB-3BB-4 Figure BB.1 Case Front Controls DescriptionK2426-3 model BB-5K2426-1 and K2426-2 models Switch BB-6Section CC-1 CC-2 CC-3 CC-4 CC-5 CC-6 Section DD-1 Section DDWhen inching with gun trigger, electrode To verify the wire feed speedNal wiring WFS knob setting Could remain energized Several secondsMAINTENANCEDD-3 DD-3Figure DD.3 Major Component Location DD-4Theory of Operation Section Section E-1Theory of Operation Return to SectionControl Board LF-72/74 Troubleshooting & Repair Section Section F-1Troubleshooting & Repair HOW to USE Troubleshooting GuidePC Board Troubleshooting Procedures Function Problems Function Problems Troubleshooting & Repair Drive Motor and Tach Feedback Test Test DescriptionTest Procedure Troubleshooting and Repair GAS Solenoid TestTest Procedure Figure F.3 Leads 552, 552BDiode Bridge Test 552B + 552A Wire Speed Potentiometer Test Wire Speed Potentiometer Test 14F-14PC Board Removal and Replacement Control PC Board Removal and Replacement Procedure Removal Procedure Replacement ProcedureTroubleshooting and Repair Wire Drive Motor and Gear BOX Removal and Replacement ProcedureProcedure Replacement Procedures SET UP Operation VerificationLF-72/74 Electrical Diagrams Section Section G-1Electrical Diagrams LF-72/74Timer 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