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Lincoln LN-742 Service Manual

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LN-742 & LN-742H Wire Feeders
Safety Depends on You
Lincoln arc welding equip-
ment is designed and built
with
safety
in
mind.
However, your overall safety
can be increased by proper
installation ... and thoughtful
operation on your part. DO
NOT INSTALL, OPERATE OR
REPAIR
THIS
EQUIPMENT
WITHOUT
READING
THIS
MANUAL AND THE SAFETY
PRECAUTIONS
CONTAINED
THROUGHOUT. And, most
importantly, think before you
act and be careful.
World's Leader in Welding and Cutting Products
22801 St. Clair Ave. Cleveland, Ohio 44117-1199 U.S.A. Tel (216) 481-8100
RETURN TO MAIN INDEX
For use with machines having Code Numbers:
SERVICE MANUAL
Sales and Service through Subsidiaries and Distributors Worldwide
10027
10028
10048
10049
10238
10239
10240
10241
Premier Manufacturer of Industrial Motors
SVM130-A
February 1997

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Summary of Contents for Lincoln LN-742

  • Page 1 RETURN TO MAIN INDEX SVM130-A LN-742 & LN-742H Wire Feeders February 1997 For use with machines having Code Numbers: 10027 10028 10048 10049 10238 10239 10240 10241 Safety Depends on You Lincoln arc welding equip- ment is designed and built...

  • Page 2: Electric Shock Can Kill

    Miami, Florida 33135 or CSA Standard W117.2-1974. A Free copy of “Arc Welding Safety” booklet E205 is available from the Lincoln Electric Company, 22801 St. Clair Avenue, Cleveland, Ohio 44117-1199. BE SURE THAT ALL INSTALLATION, OPERATION, MAINTENANCE AND REPAIR PROCEDURES ARE PER- FORMED ONLY BY QUALIFIED INDIVIDUALS.

  • Page 3: Safety

    This can create fire hazards or overheat lifting chains or cables until they fail. 6.c. Ground the equipment in accordance with the U.S. National Electrical Code and the manufacturer’s recommendations. 4.h. Also see item 7c. LN-742 & LN-742H...
  • Page 4 ____________________________________________________ 7.h. To avoid scalding, do not remove the radiator pressure cap when the engine is hot. LN-742 & LN-742H...
  • Page 5 à l’interrupteur à la boite de fusibles. de l’huile, tels que les gants en cuir, chemise épaisse, pan- talons sans revers, et chaussures montantes. 4. Garder tous les couvercles et dispositifs de sûreté à leur place. LN-742 & LN-742H...

  • Page 6: Table Of Contents

    Installation ..........Section A Technical Specifications - LN-742 ......
  • Page 7 Installation ..........Section A Technical Specifications - LN-742 ......

  • Page 8: Technical Specifications - Ln-742

    INSTALLATION TECHNICAL SPECIFICATIONS – LN-742 INPUT VOLTAGE 40 to 42V ±10%, 50/60 Hz, 4.0 Amps WIRE FEED SPEED SYSTEM WIRE SPEED RANGE LN-742 50 in. to 770 in. per minute (1.25 to 19.5 m/min) LN-742H 80 in. to 1200 in. per minute (2.00 to 30.5 m/min)

  • Page 9: Mounting Location

    A K178-1 mounting platform is available for mounting Referring to Figure A.1, route the other end of the the LN-742 to the top of Idealarc power sources. Refer electrode cable through the large oval hole in the to Section C, Accessories, for details.
  • Page 10 FIGURE A.2 – STRAIN RELIEF CLAMP. Connect the remaining end of the control cable with the eight-socket cable plug to the mating receptacle on the LN-742. Referring to Figure A.2, install the input cable under the wire reel mounting stand strain relief clamp.
  • Page 11 INSTALLATION FIGURE A.3 – LN-742 WIRE FEEDER TO LINCOLN POWER SOURCE – CONNECTION DIAGRAM. WARNING TURN INPUT POWER OFF BEFORE CONNECTING THE LN-742 WIRE FEEDER. ELECTRIC SHOCK CAN KILL LINCOLN POWER SOURCE 14 PIN AMPHENOL LN-742 WIRE FEEDER TO WORK...

  • Page 12: Work Cable

    AMPHENOL The LN-7 GMA can be used with several guns. In most PLUG cases, Lincoln guns and cables are shipped assembled, ready to weld. Use the gun and cable assembly for the electrode type (solid, Outershield , or Innershield) and electrode size to be used. Refer to Section C, Accessories, for different gun types.

  • Page 13: Water Connections (For Water Cooled Guns

    2. In the event the water line fittings on your water cooled gun are incompatible with the female quick NOTE: If not using a Lincoln water cooler, and if your connects on the front of the LN-742, male quick water cooling device is not designed for use with a connects are provided for installation on 3/16 in.

  • Page 14: Shielding Gas Hookup

    SHIELDING GAS HOOKUP Customer must provide a cylinder of shielding gas, a pressure regulator, a flow control valve, and a hose from the flow valve to the gas inlet fitting of the LN-742. WARNING Install per Figure A.6 and the following: 1.

  • Page 15: Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Section B Operating Instructions

    Wire Reel Changing ........B-13 LN-742 & LN-742H...

  • Page 16: Operation

    WARNING • Wire feed control [50 to 770 in./min (1.25 to 19.5 ELECTRIC SHOCK m/min) for the LN-742; 80 to 1200 in./min (2.00 to can kill. 30.5 m/min) for the LN-742H]. • Do not touch electrically live parts •...

  • Page 17: Controls And Settings

    FIGURE B.1 – WIRE FEEDER CONTROLS. COLD PURGE INCH COLD INCH GAS PURGE SETTING ADJUSTMENT DISPLAY ARROW KEYS OLTMETER INCH FUNCTION SELECTION CONTROLS TRIGGER MODE TIME PREFLOW POSTFLOW TIMER LOCK BURNBACK SELECTION TRIGGER CONTROLS SPOT SPOT MODE CONTROLS LN-742 & LN-742H...

  • Page 18: Acceleration Setting

    DECREASE ARROW. This key decreases the setting of the parameter selected to be displayed, using the The LN-742 has solid-state overload protection of the “Quick-Set” feature for fast and accurate setting. wire drive motor. If the wire drive motor becomes overloaded for an extended period of time, the QUICK-SET FEATURE.
  • Page 19 FIGURE B.2 – INSTALLING DRIVE ROLLS ON A TWO-ROLL FEEDER. CLAMPING COLLAR SPACER (IF REQUIRED) DRIVE ROLL HALVES OUTPUT SHAFT LARGE GUIDE TUBE DETAIL RADIUS OUTGOING DRIVE GUIDE ROLL TUBE OUTGOING GUIDE TUBE INSERT INCOMING IDLE GUIDE ROLL TUBE SMALL RADIUS LN-742 & LN-742H...

  • Page 20: Changing Drive Rolls For Four-Roll Wire Feeders

    13. Be certain that the guide tubes do not touch the drive rolls or idle rolls. If they do touch, readjust 3. Open both quick release levers by moving the them and tighten in place. levers outward and pulling them toward you. LN-742 & LN-742H...
  • Page 21 FIGURE B.3 – INSTALLING DRIVE ROLLS ON A FOUR-ROLL FEEDER. CLAMPING COLLAR DRIVE ROLL HALVES SPACER (IF REQUIRED) OUTPUT SHAFT LARGE GUIDE TUBE DETAIL RADIUS OUTGOING GUIDE TUBE OUTGOING GUIDE TUBE INSERT MIDDLE IDLE GUIDE ROLL TUBE SMALL RADIUS LN-742 & LN-742H...

  • Page 22: Idle Roll Pressure Setting

    1 and 2. Four-roll wire feeders: PRESSURE ADJUSTMENT 1. Release the incoming idle roll and perform the KNOB pressure setting procedure for two roll feeders to set outgoing idle roll pressure. LN-742 & LN-742H...

  • Page 23: Wire Loading

    Do not remove the adapter from the the slot in the retaining spring tab. spindle. FIGURE B.5 – INSTALLING A 30 LB READI-REEL PACKAGE. 2 IN. O.D. SPINDLE ADAPTER RETAINING SPRING BRAKE HOLDING GROOVES READI-REEL INSIDE CAGE WIRES THREADED LOCKING COLLAR LN-742 & LN-742H...
  • Page 24 “birdnest”.) little or no overrun when wire feeding is stopped. Do not overtighten. 3. Insert the free end through the incoming guide tube. LN-742 & LN-742H...

  • Page 25: Wire Reel Loading - 50 And 60 Lb Coils (K303 Or K376 Wire Reel Stand

    6. Put the cover plate on the reel so the four arms of SPRING LOADED the cover plate straddle and are in line with the spring loaded arms of the reel. 7. Tighten the cover as much as possible by hand. DO NOT hammer on the spinner nut arms. LN-742 & LN-742H...

  • Page 26: Making A Weld

    1. Remove the snap-on lid from the plastic canister. 5. Use the Function Selection key and Selection 2. Remove the center clamping nut and the cover Setting arrow keys to set the desired Inch and plate from the wire reel. Weld Feed speeds. LN-742 & LN-742H...

  • Page 27: Wire Reel Changing

    Hold the gun so the contact tip 5. Load a new reel of electrode per the instructions to work distance gives the correct electrical for the specific reel type given previously in this stickout as required for the procedure being used. section. LN-742 & LN-742H...
  • Page 28 B-14 B-14 NOTES LN-742 & LN-742H...
  • Page 29 Drive Roll Kits ......... . . LN-742 & LN-742H...

  • Page 30: Accessories

    ACCESSORIES GENERAL The following is a list of the accessories that can be A detailed description of each item is given later in this used with the LN-742 wire feeder. section. TABLE C.1 – LN-7 GMA ACCESSORIES. Product Number Name...

  • Page 31: Flux System Components

    ACCESSORIES K163 UNDERCARRIAGE K857 can be installed on the LN-742 when it is used with newer Lincoln power sources that are equipped with a 6-socket ms-type receptacle or K864 14-pin The undercarriage includes casters, wheels, a handle, connector adaptor for connection of the plug on the 28 and related hardware.

  • Page 32: Power Input Cables

    Similar to the K591, but includes a gas hose with a 5/8- tank cap and let the air in the tank escape in the holes 18 male fitting for the LN-742 inlet, and water hoses in the side of the cap. After pressure has been with 5/8-18 left-hand male fittings to connect between released, remove the cap from the tank.

  • Page 33: Spindles, Stands, And Adapters

    K438 50 TO 60 LB READI-REEL ADAPTER ADAPTER Adapts Lincoln Readi-Reel coils of 50 to 60 lb (22.7 to Adapts Lincoln Readi-Reel coils of 22 and 33 lb (10 27.7 kg) to a 2 in. (51 mm) spindle. (Included with and 14 kg) to a 2 in.

  • Page 34: Attaching The Wire Reel Stand

    The mounting hardware for mounting the stands is Permits 8 in. (203 mm) O.D. spools to be mounted on included with the LN-742. Screws and washers are 2 in. (51 mm) O.D. spindles. For K377 and K445, or inserted in their respective mounting holes. To connect: K303 and K376 with optional K162H adapter.

  • Page 35: Routine Maintenance

    Wire Drive Motor and Gearbox ......Gun and Cable Maintenance ......LN-742 & LN-742H...

  • Page 36: Routine Maintenance

    To prolong the life of the reel shaft on the 50 to 60 lb coils, periodically coat it with a thin layer of grease. No maintenance to the two position brake is required. If the brake shoe wears through to metal, replace the brake assembly. LN-742 & LN-742H...
  • Page 37 Keypad, Display Board, Control Board, Reed Switch, Drive Motor and Tach Feedback ......LN-742 & LN-742H...

  • Page 38: General Description

    THEORY OF OPERATION GENERAL DESCRIPTION POWER INPUT CIRCUITS The LN-742 receives 42 VAC (usually from The LN-742 is a semiautomatic constant the welding power source) by way of the speed wire feeder with a gas solenid valve input cable connector.

  • Page 39: Trigger Circuit

    TRIGGER CIRCUIT electronic switch which closes leads #2 and #4. The closure of leads #2 and #4 energize the welding output terminals on the Lincoln When the gun trigger is activated, the power source. The gas and or water solenoid...

  • Page 40: Keypad, Display Board, Control Board, Reed Switch, Drive Motor And Tach Feedback

    The display board exhibits the The control board receives commands from commands set forth by the keypad as well as the keypad via the display board. The control displays the actual arc voltage. board compares these commands with the LN-742 & LN-742H...

  • Page 41: Troubleshooting And Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Section F How To Use Troubleshooting Guide

    • Never work on the inside of the machine without turning off the input power. You can receive a life threatening electrical shock if you fail to do this. Only qualified technicians should perform installation, maintenance, and troubleshooting work on the machine. LN-742 & LN-742H...
  • Page 42 HOW TO USE TROUBLESHOOTING GUIDE WARNING Service and Repair should only be performed by 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 43: Troubleshooting And Repair

    CAUTION is complete. Sometimes machine failures appear to be - If you return a P.C. Board to The Lincoln due to PC board failures. These problems Electric Company for credit, it must be in the can sometimes be traced to poor electrical static-shielding bag.

  • Page 44: Troubleshooting Guide

    Replace. CAUTION If for any reason you do not understand the test procedures or are unable to perform the tests/repairs safely, contact the Lincoln Electric Service Department for technical troubleshooting assistance before you proceed. Call 216-383-2531 or 1-800-833-9353. LN-742 & LN-742H...
  • Page 45 Replace. CAUTION If for any reason you do not understand the test procedures or are unable to perform the tests/repairs safely, contact the Lincoln Electric Service Department for technical troubleshooting assistance before you proceed. Call 216-383-2531 or 1-800-833-9353. LN-742 & LN-742H...
  • Page 46 CAUTION If for any reason you do not understand the test procedures or are unable to perform the tests/repairs safely, contact the Lincoln Electric Service Department for technical troubleshooting assistance before you proceed. Call 216-383-2531 or 1-800-833-9353.
  • Page 47 CAUTION If for any reason you do not understand the test procedures or are unable to perform the tests/repairs safely, contact the Lincoln Electric Service Department for technical troubleshooting assistance before you proceed. Call 216-383-2531 or 1-800-833-9353.
  • Page 48 Replace. CAUTION If for any reason you do not understand the test procedures or are unable to perform the tests/repairs safely, contact the Lincoln Electric Service Department for technical troubleshooting assistance before you proceed. Call 216-383-2531 or 1-800-833-9353. LN-742 & LN-742H...
  • Page 49 CAUTION If for any reason you do not understand the test procedures or are unable to perform the tests/repairs safely, contact the Lincoln Electric Service Department for technical troubleshooting assistance before you proceed. Call 216-383-2531 or 1-800-833-9353. LN-742 & LN-742H...

  • Page 50: Test Procedures

    TEST PROCEDURES TACHOMETER FEEDBACK TEST WARNING Service and repair should only be performed by Lincoln Electric factory trained personnel. Unauthorized repairs performed on this equipment may result in danger to the technician or machine operator and will invalidate your factory warranty.
  • Page 51 6. Apply input power to the wire feeder (42 VAC). 7. Check from the red lead (+) (1J3) to the black lead (-) (3J3) for the presence of +12.8 VDC. If this voltage is missing or low, the control board may be faulty. LN-742 & LN-742H...

  • Page 52: Drive Motor Test

    TROUBLESHOOTING AND REPAIR DRIVE MOTOR TEST WARNING Service and repair should only be performed by Lincoln Electric factory trained personnel. Unauthorized repairs performed on this equipment may result in danger to the technician or machine operator and will invalidate your factory warranty.
  • Page 53 6. Carefully apply the variable DC voltage source to the black (+) (1J5) lead and 10. Install plug J5 into the control board. the white (-) (2J5) lead. 11. Install the left side cover assembly using screws and the 5/16" nutdriver. LN-742 & LN-742H...

  • Page 54: Input Voltage Test

    Call 216-383-2531 or 1-800-833-9353(WELD). TEST DESCRIPTION This test will determine if the LN-742 is receiving the correct input voltage and also if the control board is developing the correct regulated DC voltages. MATERIALS NEEDED 5/16”...
  • Page 55 Apply the correct input power (42 VAC) replaced. and check for the presence of 42 VAC at the (red) AC terminals of the input rectifier bridge, shown in Figure F.3. LN-742 & LN-742H...
  • Page 56 8. Check for 5 VDC from Test Point "A" (+) on the control board to plug J4 (-) (6J4) on the control board, Figure F.5. (1J3) CONTROL BOARD FIGURE F.5 – 5 VDC TEST POINTS. PLUG (6J4) CONTROL TEST POINT BOARD "A" LN-742 & LN-742H...
  • Page 57 5/16" nutdriver. 10. If any of the previous voltages in step 7, 8, or 9 are incorrect or missing, the FIGURE F.6 – -12.8 VDC TEST POINTS. PLUG (7J1) CONTROL BOARD TEST POINT "B" LN-742 & LN-742H...

  • Page 58: Keypad Resistance Test

    TROUBLESHOOTING AND REPAIR KEYPAD RESISTANCE TEST WARNING Service and repair should only be performed by Lincoln Electric factory trained personnel. Unauthorized repairs performed on this equipment may result in danger to the technician or machine operator and will invalidate your factory warranty.
  • Page 59 3. Remove the left side cover assembly. 6. Remove plug J10 from the display board. 4. Carefully remove plug J11 from the display board, shown in Figure F.7. LN-742 & LN-742H...
  • Page 60 J10 on the keypad. The resistance correct per Table F.1, the keypad is measurements are taken from the pin faulty and should be replaced. locations on plug J10 shown in Figure F.8. FIGURE F.8 – KEYPAD RESISTANCE TEST POINTS. PLUG (1J10) (8J10) LN-742 & LN-742H...
  • Page 61 11. Connect plug J11 into the display 9. Connect J10 plug to the display board. board. 10. Carefully mount the display board onto 12. Install the left side cover assembly the four mounting posts. nutdriver. using screws and the 5/16" LN-742 & LN-742H...

  • Page 62: Component Replacement Procedures

    Wire cutters 3/8 in. wrench 3/8 in. socket and extension 9/16 in. wrench Slot-head screwdriver Lubricant (part no. E2322) (Century Lubricants A-29) Grease (part no. E2164) (Universal Oil) Sealant (part no. E2225) (General Electric RTV 123) Torque wrench LN-742 & LN-742H...
  • Page 63 7. Remove the cable hanger securing the toroid assembly to the side of the wire drive compartment. 1. Remove input power to the LN-742. 8. On two-roll feeders, use a 3/8 in. open- 2. Using the 5/16 in. nutdriver, remove the...
  • Page 64 MOTOR INSULATOR GEARBOX REED LOCATOR/INSULATOR SWITCH REED BUSHING ENERGIZER TACHOMETER SWITCH BENT MOUNT J-BOLT TACHOMETER WIRE RETAINING LEAD MOTOR MOUNTING CONTACTOR GEARBOX SCREW BLOCK COVER MOTOR UPPER MOUNTING INSULATOR SCREW SHEET LOWER INSULATOR SHEET GEARBOX MOUNTING PLATE LN-742 & LN-742H...
  • Page 65 18. Gently screw the tachometer into the tachometer mount until it bottoms out. 28. Reinstall the cover on the control box using four hex head screws. LN-742 & LN-742H...

  • Page 66: Swing Arm Assembly Replacement For Two-Roll Wire Feeders

    • Observe all safety precautions detailed throughout this manual. Turn off input power to the wire feeder. Only qualified technicians should perform installations, maintenance, and troubleshooting work on the machine. TOOLS REQUIRED 7/16 in. wrench Straight blade screwdriver LN-742 & LN-742H...
  • Page 67 3. Pry the speed clip off of the groove pin and lift the idle roll assembly from groove pin. LN-742 & LN-742H...

  • Page 68: Swing Arm Assembly Replacement For Four-Roll Wire Feeders

    • Observe all safety precautions detailed throughout this manual. Turn off input power to the wire feeder. Only qualified technicians should perform installations, maintenance, and troubleshooting work on the machine. TOOLS REQUIRED 3/32 in. Allen wrench 9/64 in. Allen wrench Adjustable pliers Rubber mallet LN-742 & LN-742H...
  • Page 69 6. Install the idle roll shaft pin and the Carefully pull the two swing arms out second socket head cap screw and flat of the wire drive compartment. Ensure washer. that the two spacers are not lost. LN-742 & LN-742H...
  • Page 70 CAUTION 9. Install the setscrew and tighten until snug. Do not use excessive force when installing the hinge pin. If hinge pin does not go in, remove it and try again. LN-742 & LN-742H...

  • Page 71: Gas Solenoid And Connections Replacement

    Turn off input power to the wire feeder. Only qualified technicians should perform installations, maintenance, and troubleshooting work on the machine. TOOLS REQUIRED 5/16 in. wrench Wire cutters 3/4 in. wrench 7/16 in. wrench Phillips screwdriver Knife Thread sealant (part no. E-2442) (Loctite #592) Tie wraps LN-742 & LN-742H...
  • Page 72 F-32 F-32 TROUBLESHOOTING AND REPAIR GAS SOLENOID AND CONNECTIONS REPLACEMENT (continued) FIGURE F.16 – GAS SOLENOID DISASSEMBLY. TUBING OUTLET FITTING SOLENOID MOUNTING TUBING PLATE TUBE SLEEVE SOLENOID OUTLET FITTING SOLENOID FILTER SCREEN INLET FITTING LN-742 & LN-742H...
  • Page 73 9. Remove the tubing from the gas and solenoid outlet fittings. A knife may be required to cut the tubing. LN-742 & LN-742H...

  • Page 74: Retest After Repair

    Check that the LN-742 2 roll ..50 through 770 in./min. drive roll shaft stops abruptly when the LN-742H 2 roll . . . 80 through 1200 in./min.
  • Page 75 L9122 DISPLAY BOARD SCHEMATIC ......G-5 L9122 DISPLAY BOARD LAYOUT ....... .G-6 LN-742 & LN-742H...
  • Page 76 NOTES LN-742 & LN-742H...

  • Page 77: Electrical Diagrams

    ELECTRICAL DIAGRAMS Wiring Diagram WIRING DIAGRAM LN-742 C U R R E N T S E N S I N G INPUT ELECTRODE CABLE R E E D S W I T C H O P T I O N A L...

  • Page 78: G2615 Control Board Schematic

    Lincoln Electric discourages board level troubleshooting and repair since it may compromise the quality of the design and may result in danger to the Machine Operator or Technician. Improper PC board repairs could result in damage to the machine.

  • Page 79: G2615 Control Board Layout

    NOTE: Lincoln Electric assumes no responsibility for liablilities resulting from board level troubleshooting. PC Board repairs will invalidate your factory warranty. Individual Printed Circuit Board Components are not available from Lincoln Electric. This information is provided for reference only. Lincoln Electric discourages board level troubleshooting and repair since it may compromise the quality of the design and may result LN-742 in danger to the Machine Operator or Technician.

  • Page 80: L9122 Display Board Schematic

    NOTE: Lincoln Electric assumes no responsibility for liablilities resulting from board level troubleshooting. PC Board repairs will invalidate your factory warranty. Individual Printed Circuit Board Components are not available from Lincoln Electric. This information is provided for reference only. Lincoln Electric discourages board level troubleshooting and repair since it may compromise the quality of the design and may result LN-742 in danger to the Machine Operator or Technician.

  • Page 81: Electrical Diagrams

    NOTE: Lincoln Electric assumes no responsibility for liablilities resulting from board level troubleshooting. PC Board repairs will invalidate your factory warranty. Individual Printed Circuit Board Components are not available from Lincoln Electric. This information is provided for reference only. Lincoln Electric discourages board level troubleshooting and repair since it may compromise the quality of the design and may result LN-742 in danger to the Machine Operator or Technician.

This manual is also suitable for:

Ln-742h

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