552B + 552A | Lincoln Electric LF-72/74 instruction

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F-12	TROUBLESHOOTING AND REPAIR	F-12
	TROUBLESHOOTING AND REPAIR

DIODE BRIDGE TEST

(continued)

FIGURE F.4 – CONTACTOR

552B

+ 552A -

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41

58042

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TEST PROCEDURE

1.Remove the input power from the unit.

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

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

4.Check for the correct input voltage at leads 41 and 42 on the bridge. If the input voltage is not there check the wiring back to the receptacle assembly pins I and K.

5.Check for the proper output on leads 580 negative and 522 positive. The voltage should be 59VDC. If you are only reading 38VDC the control circuit is open. Check the wiring and the connections back to your control board.

LF-72/74

Image 96

Lincoln Electric LF-72/74 service manual 552B + 552A

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 Table of Contents Installation SectionSection A-1 Installation Amp Rating Duty Cycle Safety Precaution LocationMounting Bench Mount Swivel MountBoom Mount Suspended Weld Cable Sizes Coaxial Weld Cables Weld Cable Connection INSTALLATIONA-7 Analog Control CableControl Cable Connections Miller Power Source Lincoln Wire Feeder Analog Miller Control Cable Adapter K2335-1Pin Function Wire Drive Systems Welding GUN/WIRE Feeder Trigger ConnectorRemote Sense Lead Specifications High Frequency Protection Welding GUNS, Torches and ACCES- Sories Magnum GUN and Cable Assemblies Procedure for Changing Drive and Idle Roll Sets Wire Drive ConfigurationRolls.FIGURE A.4 Pressure ARM Adjustment Gun Receiver For use With BushingSet the pressure arm as follows See Figure A.6 Wire Reel Loading Weld Wire Routing Figure A.9 Shielding GAS Connection Installing Electrode To install Lincoln conduit See Figure A.10bConduit Kits 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 Common Welding Abbreviations Product DescriptionRecommended Processes Front Panel Controls and Connections Figure B.1 Case Front Controls Description Burnback and Postflow Timer KIT Cold FEED/GAS Purge SwitchStep Trigger Interlock Switch Remote Voltage Control KIT Wire Feed Speed Knob Trigger Connector 5-PIN AmphenolGUN Receiver Bushing K1500-2 Trigger Interlock Accessories Section Section C-1 Accessories Optional Kits LF-72s Accessories Key LF-72/74 Maintenance Section Section D-1 Maintenance MaintenanceCalibration Specification Routine Maintenance Figure D.1 Figure D.3 Major Component Location Section AA-1 Section AA WFS Range Wire Sizes AA-2Model AA-3 Figure AA.1 AA-4 AA-5 AA-6 Coaxial Weld Cable INSTALLATIONAA-7 AA-7K1797-xx AA-8 Drive Roll Kits Steel or Cored Wires AA-9 AA-10 Figure AA.3 AA-11 Changing the Gun Receiver BushingLation or changing drive rolls and/or 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 BB-5 K2426-1 and K2426-2 modelsK2426-3 model Switch BB-6 Section CC-1 CC-2 CC-3 CC-4 CC-5 CC-6 Section DD-1 Section DD To verify the wire feed speed Nal wiringWhen inching with gun trigger, electrode 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