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

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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

Image 98

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

Contents

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