Lincoln Electric LE31MP Service Manual
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Lincoln Electric LE31MP Service Manual

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LE31MP ™
For use with machines having Code Numbers:
LE31MP: 12662
SERVICE MANUAL
SVM277
| Issue D ate 17-Aug
© Lincoln Global, Inc. All Rights Reserved.

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  • Page 1 LE31MP ™ For use with machines having Code Numbers: LE31MP: 12662 SERVICE MANUAL SVM277 | Issue D ate 17-Aug © Lincoln Global, Inc. All Rights Reserved.
  • Page 2 THANK YOU FOR SELECTING A QUALITY PRODUCT BY KEEP YOUR HEAD OUT OF THE FUMES. DON’T get too close to the arc. LINCOLN ELEC TRIC. Use corrective lenses if necessary to stay a reasonable distance away from the arc. READ and obey the Safety Data PLEASE EXAMINE CARTON AND EQUIPMENT FOR Sheet (SDS) and the warning label DAMAGE IMMEDIATELY...

  • Page 3: Section A: Warnings

    MAGNETIC FIELDS MAY W117.2-1974. A Free copy of “Arc Welding Safety” booklet BE DANGEROUS E205 is available from the Lincoln Electric Company, 22801 St. Clair Avenue, Cleveland, Ohio 44117-1199. 2.a. Electric current flowing through any conductor BE SURE THAT ALL INSTALLATION, OPERATION, causes localized Electric and Magnetic Fields (EMF).

  • Page 4: Electric Shock Can Kill

    S FETY ELECTRIC SHOCK ARC RAYS CAN BURN. CAN KILL. 3.a. The electrode and work (or ground) circuits are 4.a. Use a shield with the proper filter and cover plates to protect your electrically “hot” when the welder is on. Do eyes from sparks and the rays of the arc when welding or not touch these “hot”...
  • Page 5 S FETY WELDING AND CUTTING CYLINDER MAY EXPLODE IF SPARKS CAN CAUSE DAMAGED. FIRE OR EXPLOSION. 7.a. Use only compressed gas cylinders containing the correct shielding gas for the process used 6.a. Remove fire hazards from the welding area. If and properly operating regulators designed for this is not possible, cover them to prevent the welding sparks the gas and pressure used.

  • Page 6: Table Of Contents

    LINCOLN ELECTRIC LE31MP Service Manual LE31MP Service Manual Last update: 2017/08/01 LE31MP ................................. 1 Service Manual ..............................1 Theory of Operation ............................3 INPUT AND INVERTER POWER / CONTROL BOARD ..................3 DISPLAY CONTROL BOARD AND WIRE DRIVE ....................4 OUTPUT CHOKE, FEEDBACK AND CONTROL ....................
  • Page 7 LINCOLN ELECTRIC LE31MP Service Manual WIRE DRIVE REMOVAL AND REPLACEMENT PROCEDURE ................33 OUTPUT CHOKE REMOVAL AND REPLACEMENT PROCEDURE ..............35 GAS SOLENOID REMOVAL AND REPLACEMENT PROCEDURE..............38 RETEST AFTER REPAIR ..........................40...

  • Page 8: Theory Of Operation

    LINCOLN ELECTRIC LE31MP Service Manual Theory of Operation Figure E.1 – Input and inverter power / control board Input And Inverter power / control board The single phase 120 VAC input voltage is applied to the machine’s inverter power / control board via the S1 on/off switch and the CB1 circuit breaker.

  • Page 9: Display Control Board And Wire Drive

    LINCOLN ELECTRIC LE31MP Service Manual Figure E.2 – Display control board and wire drive Display Control Board And Wire Drive The display control board receives 24 VDC from the inverter power / control board. The display control board creates several DC voltage supplies 15 VDC, 5 VDC, 24 VDC and a variable DC voltage to power the wire drive motor.

  • Page 10: Output Choke, Feedback And Control

    LINCOLN ELECTRIC LE31MP Service Manual Figure E.3 – Output choke, feedback and control Output Choke, Feedback and Control The positive DC welding output from the inverter power / control board is applied to the output choke and then to the output terminal. The output choke filters the welding current to provide a more stable and smooth welding arc.

  • Page 11: Insulated Gate Bipolar Transistor (Igbt) Operation

    LINCOLN ELECTRIC LE31MP Service Manual Figure E.4 – Insulated gate bipolar transistor (IGBT) operation Insulated Gate Bipolar Transistor (IGBT) Operation The IGBT is a type of transistor. IGBTs are semiconductors well suited for high frequency switching and high current applications.

  • Page 12: Troubleshooting & Repair

    Troubleshooting & Repair HOW TO USE TROUBLESHOOTING GUIDE Service and repair should be performed by only Lincoln Electric Factory Trained Personnel. Unauthorized repairs performed on this equipment may result in danger to the technician and machine operator and will invalidate your factory warranty. For your safety and to avoid Electrical Shock, please observe all safety notes and precautions detailed throughout this manual.

  • Page 13: Pc Board Troubleshooting Procedures

    ELECTRIC SHOCK can kill. remove them until installation is complete. • If you return a PC board to The Lincoln Electric Company • Have an electrician install and service this for credit, it must be in the static-shielding bag. This will equipment.

  • Page 14: Troubleshooting Guide

    MIG mode and the wire feed switch is in ‘100L’ position. If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, contact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call 1-888-935-3877.
  • Page 15 & fully inserting gun. If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, contact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call 1-888-935-3877.
  • Page 16 If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, contact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call 1-888-935-3877.

  • Page 17: Test Procedures

    If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, contact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call 1-888-935-3877.
  • Page 18 LINCOLN ELECTRIC LE31MP Service Manual Figure F.1 – Front panel mounting screw locations Figure F.2 – Top mounting screw locations...
  • Page 19 LINCOLN ELECTRIC LE31MP Service Manual Figure F.3 – Case side mounting screw locations...

  • Page 20: Display Control Board Test Procedure

    If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, contact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call 1-888-935-3877.
  • Page 21 LINCOLN ELECTRIC LE31MP Service Manual Table F. 2 – Display control board voltage tests EXPECTED MACHINE TEST DESCRIPTION TEST POINT (+) TEST POINT (–) READING CONDITION INPUT POWER FROM INVERTER PLUG CN304 PIN 8 PLUG CN304 PIN 1 24 VDC MACHINE ON.
  • Page 22 LINCOLN ELECTRIC LE31MP Service Manual Figure F.5 – Display control board LED and plug locations Figure F.6 – Display control board lead locations...

  • Page 23: Inverter Power / Control Board Test Procedure

    If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, contact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call 1-888-935-3877.
  • Page 24 LINCOLN ELECTRIC LE31MP Service Manual Table F. 3 – Inverter power / control board voltage tests EXPECTED MACHINE TEST DESCRIPTION TEST POINT (+) TEST POINT (–) READING CONDITION INPUT POWER 90 – 150 VAC MACHINE ON. POWER OUT TO PLUG J4 PIN 1...
  • Page 25 LINCOLN ELECTRIC LE31MP Service Manual Figure F.7 – Inverter power / control board location Figure F.8 – Inverter power / control board plug and terminal locations...
  • Page 26 LINCOLN ELECTRIC LE31MP Service Manual Figure F.9 – Inverter power / control board lead locations Figure F.10 – Positive and negative output terminal locations...

  • Page 27: Output Choke Test Procedure

    If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, contact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call 1-888-935-3877.
  • Page 28 LINCOLN ELECTRIC LE31MP Service Manual Figure F.11 – Choke and output rectifier connection locations Figure F.12 – Positive output terminal location...

  • Page 29: Gas Solenoid(S) Test Procedure

    If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, contact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call 1-888-935-3877.
  • Page 30 LINCOLN ELECTRIC LE31MP Service Manual Figure F.13 – Gas solenoid locations Figure F.14 – Gas solenoid lead locations...

  • Page 31: Removal And Replacement Procedures

    If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, contact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call 1-888-935-3877.
  • Page 32 LINCOLN ELECTRIC LE31MP Service Manual 6. Perform the Case Cover Replacement Procedure. 7. Perform the Retest After Repair Procedure. Figure F.15 – Control knob location Figure F.16 – Display board plug locations...

  • Page 33: Inverter Power / Control Board Removal And Replacement Procedure

    If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, contact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call 1-888-935-3877.
  • Page 34 LINCOLN ELECTRIC LE31MP Service Manual 10. Using a Phillips screwdriver, remove the four inverter power / control board mounting screws and washers. See Figure F.22. The inverter power / control board can now be removed and replaced. NOTE: Some plugs and leads may need to be salvaged from this board for reassembly.
  • Page 35 LINCOLN ELECTRIC LE31MP Service Manual Figure F.18 – Positive output terminal location Figure F.19 – Inverter power / control board lead locations...
  • Page 36 LINCOLN ELECTRIC LE31MP Service Manual Figure F.20 – Gas solenoid lead locations Figure F.21 – Center panel mounting screw locations...
  • Page 37 LINCOLN ELECTRIC LE31MP Service Manual Figure F.22 – Inverter power / control board mounting screw locations...

  • Page 38: Wire Drive Removal And Replacement Procedure

    If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, contact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call 1-888-935-3877.
  • Page 39 LINCOLN ELECTRIC LE31MP Service Manual Figure F.23 – Wire drive motor location Figure F.24 – Wire drive motor mounting nut location...

  • Page 40: Output Choke Removal And Replacement Procedure

    If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, contact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call 1-888-935-3877.
  • Page 41 LINCOLN ELECTRIC LE31MP Service Manual 5. Using a 11/16” nutdriver, attach the bolt securing the positive output choke lead and the JPO lead to the positive output terminal. See Wiring Diagram. 6. Replace cable ties as necessary and position the case front onto the machine.
  • Page 42 LINCOLN ELECTRIC LE31MP Service Manual Figure F.26 – Output choke mounting screw and lead connection locations...

  • Page 43: Gas Solenoid Removal And Replacement Procedure

    If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, contact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call 1-888-935-3877.
  • Page 44 LINCOLN ELECTRIC LE31MP Service Manual Figure F.27 – Gas solenoid lead and gas hose connection locations Figure F.28 – Gas solenoid mounting hardware location...

  • Page 45: Retest After Repair

    LINCOLN ELECTRIC LE31MP Service Manual RETEST AFTER REPAIR Should a machine under test be rejected for any reason requiring the removal of any mechanical part that could affect the machine’s electrical characteristics, or if any electrical components are repaired or replaced, the machine must be retested.

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12662

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