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Lincoln LN-742, Service Manual

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Lincoln LN-742 Service Manual Download Page 50

LN-742 & LN-742H

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TACHOMETER  FEEDBACK  TEST

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. For your safety and to avoid electrical shock please observe all safety
notes and precautions detailed throughout this manual.

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 technical troubleshooting assistance before you proceed. Call 216-383-2531
or 1-800-833-9353(WELD).

TEST DESCRIPTION

The following procedure will help determine if the tachometer circuit is receiving the
correct voltage and also if the tachometer is developing the correct feedback signal.

MATERIALS NEEDED

5/19” Nutdriver 
Volt/Ohmmeter 

WARNING

TEST PROCEDURES

F-10

TROUBLESHOOTING  AND  REPAIR

F-10

Summary of Contents for LN-742

Page 1: ...ve Cleveland Ohio 44117 1199 U S A Tel 216 481 8100 For use with machines having Code Numbers 10027 10028 10048 10049 10238 10239 10240 10241 SVM130 A February 1997 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 T...

Page 2: ...ng or lying if there is a high risk of unavoidable or accidental contact with the workpiece or ground use the following equipment Semiautomatic DC Constant Voltage Wire Welder DC Manual Stick Welder AC Welder with Reduced Voltage Control 1 c In semiautomatic or automatic wire welding the electrode electrode reel welding head nozzle or semiautomatic welding gun are also electrically hot 1 d Always ...

Page 3: ...m to prevent the welding sparks from starting a fire R e m e m b e r that welding sparks and hot materials from welding or cutting can easily go through small cracks and openings to adjacent areas Avoid welding or cutting near hydraulic lines Have a fire extinguisher readily available 4 b Where compressed gases are to be used at the job site special precautions should be used to prevent hazardous ...

Page 4: ...rking near moving parts 7 f Do not put your hands near the engine fan Do not attempt to override the governor or idler by pushing on the throttle control rods while the engine is running 7 g To prevent accidentally starting gasoline engines while turning the engine or welding generator during maintenance work disconnect the spark plug wires distributor cap or magneto wire as appropriate __________...

Page 5: ...u soudage à l aide d écrans appropriés et non inflammables 4 Des gouttes de laitier en fusion sont émises de l arc de soudage Se protéger avec des vêtements de protection libres de l huile tels que les gants en cuir chemise épaisse pan talons sans revers et chaussures montantes 5 Toujours porter des lunettes de sécurité dans la zone de soudage Utiliser des lunettes avec écrans lateraux dans les zo...

Page 6: ...ire Reel Changing B 13 Accessories Section C General C 2 Flux System Components C 3 Power Input Cables C 4 Welding Guns C 4 Spindles Stands and Adapters C 5 Attaching the Wire Reel Stand C 6 Drive Roll Kits C 6 Maintenance Section D Routine Maintenance D 2 Periodic Maintenance D 2 Theory of Operation Section E General Description E 2 Power Input Circuits E 2 Trigger Circuit E 3 Keypad Display Boar...

Page 7: ...ECTION A 1 TABLE OF CONTENTS INSTALLATION SECTION Installation Section A Technical Specifications LN 742 A 2 Mounting Location A 3 Input Cable Connections A 3 Work Cable A 6 Gun and Cable Assemblies A 6 Gun Cable Connections A 6 Water Connections for Water Cooled Guns A 7 Shielding Gas Hookup A 8 LN 742 LN 742H ...

Page 8: ...ETER 0 025 in through 1 16 in 0 6 through 1 6 mm 0 025 in through 0 045 in 0 6 through 1 2 mm 0 045 in through 3 32 in 1 2 through 2 4 mm 0 045 in 1 2 mm TECHNICAL SPECIFICATIONS LN 742 INPUT VOLTAGE WIRE FEED SPEED WIRE DIAMETERS 40 to 42V 10 50 60 Hz 4 0 Amps WIRE SPEED RANGE 50 in to 770 in per minute 1 25 to 19 5 m min 80 in to 1200 in per minute 2 00 to 30 5 m min SYSTEM LN 742 LN 742H LN 742...

Page 9: ...t be sized according to the current and the duty cycle of the application With input power disconnected at the source install the input cable per connection diagram A 3 and complete the following instructions 1 Connect the end of the control cable with the 14 pin cable plug to the mating receptacle on the power source 2 Connect the electrode lead to the power source output terminal of the desired ...

Page 10: ...hange polarity turn the power source off Reverse the electrode and work cables at the power source and set the wire feeder voltmeter polarity switch on the power source to the proper polarity Pins not listed in the table in Figure A 3 are not connected on the cable If using the K589 1 remote control kit set the power source control switch to the Remote position WIRE REEL MOUNTING ASSEMBLY CONTROL ...

Page 11: ...EQUIPMENT 14 SOCKET BOX RECEPTACLE REAR VIEW AND 14 PIN CABLE PLUG FRONT VIEW 14 PIN AMPHENOL K 42 K 42 I 41 I 41 H 21 H 21 C 2 C 2 G 75 G 75 D 4 D 4 F 76 PIN C 2 TRIGGER CIRCUIT TRIGGER CIRCUIT OUTPUT CONTROL OUTPUT CONTROL OUTPUT CONTROL WORK 42V AC 42V AC 4 77 76 75 21 41 42 LEAD FUNCTION F 76 E 77 E 77 D E F G H I K FIGURE A 3 LN 742 WIRE FEEDER TO LINCOLN POWER SOURCE CONNECTION DIAGRAM LN 74...

Page 12: ...ode type solid Outershield or Innershield and electrode size to be used Refer to Section C Accessories for different gun types GUN CABLE CONNECTIONS Lay the cable out straight Insert the connector on the welding conductor cable through the large hole in the front panel of the LN 7 GMA and into the brass conductor block on the front of the gearbox Refer to Figure A 4 Make sure it is all the way in ...

Page 13: ...ock 1 Using male 5 8 18 UNF left hand thread fittings connect appropriate water hoses to the coolant inlet and outlet on the back of the LN 742 Connect the other ends of these hoses to the appropriate ports on your water cooling units 2 In the event the water line fittings on your water cooled gun are incompatible with the female quick connects on the front of the LN 742 male quick connects are pr...

Page 14: ...g 1 Connect the supply hose from the gas cylinder flow valve outlet to the 5 8 18 female inert gas fitting on the back panel of the LN 742 2 Install the barbed fitting and union nut to the 5 8 18 female inert gas fitting on the front of the LN 742 Connect 3 16 in 4 8 mm I D gas hose from the gun to the barbed fitting When the gun is to be removed this fitting can be easily detached by loosening th...

Page 15: ...tallation B 4 Changing Drive Rolls For Two Roll Wire Feeders B 4 Changing Drive Rolls For Four Roll Wire Feeders B 6 Idle Roll Pressure Setting B 8 Wire Loading B 9 Wire Reel Loading Readi Reels and Spools B 9 Wire Reel Loading 50 and 60 lb Coils K303 or K376 Wire Reel Stand B 11 Wire Loading 13 14 lb Innershield Coils B 12 Making a Weld B 12 Wire Reel Changing B 13 OPERATION SECTION B 1 SECTION B...

Page 16: ...e LN 742H Factory installed gas solenoid valve and gas fittings Wire drive uses a permanent magnet motor and includes tool less quick release idle roll pressure arm outgoing guide tube and gun cable fastening Optional factory installed water solenoid and fittings for use with water cooled welding guns The LN 742 4 Roll is designed to provide the additional feeding force required when using gun cab...

Page 17: ...ime turns off the wire feeder and then the power source after burnback time Releasing the trigger a second time turns off the solenoid after Burnback time The bottom light indicates spot weld trigger mode Closing the trigger allows a single timed weld cycle The duration of the weld cycle is set with the time selection controls The spot on timer starts when welding current flows TIME SELECTION CONT...

Page 18: ...acceleration setting function press both keys a second time or press any other key except for the setting adjustment arrow keys ENGLISH OR METRIC SPEED DISPLAY UNITS Pressing both the Gas Purge key and Timer Selection key causes the speed display units to toggle between inches per minute no decimal point displayed or meters per minute decimal point displayed If the LED display is showing the voltm...

Page 19: ...MALL RADIUS IDLE ROLL CLAMPING COLLAR SPACER IF REQUIRED OUTPUT SHAFT DRIVE ROLL HALVES FIGURE B 2 INSTALLING DRIVE ROLLS ON A TWO ROLL FEEDER LN 742 LN 742H Return to Section TOC Return to Section TOC Return to Section TOC Return to Section TOC Return to Master TOC Return to Master TOC Return to Master TOC Return to Master TOC ...

Page 20: ... tubes in place Remove the incoming and outgoing guide tubes if installed 5 Remove the hex head screws and clamping collars from the output shafts Remove the drive rolls and middle guide tube 6 The new rolls to be installed are stenciled with the wire size that will be fed An A after the number indicates aluminum wire Remove the rolls from the kit and wipe them clean Wipe the output shafts and loc...

Page 21: ...GOING GUIDE TUBE MIDDLE GUIDE TUBE SMALL RADIUS IDLE ROLL LARGE RADIUS CLAMPING COLLAR OUTPUT SHAFT SPACER IF REQUIRED DRIVE ROLL HALVES LN 742 LN 742H Return to Section TOC Return to Section TOC Return to Section TOC Return to Section TOC Return to Master TOC Return to Master TOC Return to Master TOC Return to Master TOC ...

Page 22: ...y result is drive roll slippage loosen the gun cable clamping screw on the conductor block and pull the gun cable forward about six inches There should be a slight waviness in the exposed wire If there is no waviness the pressure is too low Increase the pressure setting 1 4 turn Lock the gun cable in place and repeat steps 1 and 2 Four roll wire feeders 1 Release the incoming idle roll and perform...

Page 23: ...th the grooves in the adapter 6 Slide the cage all the way onto the adapter until the retaining spring pops up fully Check to be sure the retaining spring has been fully returned to the locking position and has SECURELY locked the Readi Reel cage in place Retaining spring must rest on the cage not the welding electrode 7 To remove the Readi Reel from the adapter depress the retaining spring with t...

Page 24: ...ot properly straightened it may not feed or may not go into the outgoing guide tube causing a birdnest 3 Insert the free end through the incoming guide tube 4 Press the cold inch key or gun trigger and push the electrode into the drive roll ELECTRIC SHOCK can kill Do not touch electrically live parts such as output terminals or internal wiring When inching with the gun trigger electrode and drive ...

Page 25: ...ding 0 030 to 0 045 electrode be certain the coil is placed on the reel so the spring loaded arms are at the center of the slots in the cardboard coil liner This provides the positive compression of the coil sides needed for trouble free wire feeding 6 Put the cover plate on the reel so the four arms of the cover plate straddle and are in line with the spring loaded arms of the reel 7 Tighten the ...

Page 26: ...If the electrode is not properly straightened it may not feed or may not enter the outgoing tube causing a birdnest 5 Thread the end through the canister wire feed liner until about four inches of electrode are exposed 6 Place the coil onto the disc support 7 Replace the front reel cover and center clamping nut Keep the reel from turning and tighten the center clamping nut securely 8 Thread the ex...

Page 27: ...lease the gun trigger and then pull the gun away from the work after the arc goes out WIRE REEL CHANGING At the end of a coil remove the last of the old electrode from the conductor cable Either pull it out at the nozzle or use the following procedure 1 Cut off the end of the electrode at the gun end Do not break it off by hand Breaking by hand puts a slight bend in the wire making it difficult to...

Page 28: ...NOTES B 14 B 14 LN 742 LN 742H Return to Section TOC Return to Section TOC Return to Section TOC Return to Section TOC Return to Master TOC Return to Master TOC Return to Master TOC Return to Master TOC ...

Page 29: ...le C 5 K363P 22 to 30 lb Readi Reel Adapter C 5 K376 and K303 50 to 60 lb Wire Reel Mounting Stands C 5 K377 Small Mounting Stand for Readi Reel Coils and 22 to 30 lb Spindle with 2 in I D C 5 K378 Small Mounting Stand for 13 to 14 lb Innershield Coils C 5 K435 Spindle Adapter for 14 lb Coils C 5 K438 50 to 60 lb Readi Reel Adapter C 5 K445 Mounting Stand for Readi Reel Coils and 50 to 60 lb Spind...

Page 30: ...able 350 Amps K112 Submerged Arc Welding Gun 500 Amps K115 Innershield Welding Gun 400 Amps K126 Innershield Welding Gun 350 Amps K470 Magnum GMA Welding Gun 200 Amps K471 Magnum GMA Welding Gun 300 Amps K497 Magnum GMA Welding Gun 400 Amps K162H Spindle K363P 22 to 30 lb Readi Reel Adapter K376 and 303 50 to 60 lb Wire Reel Mounting Stands K377 Small Mounting Stand for Readi Reel Coils and 22 to ...

Page 31: ... control box cover and gives voltage control at the wire feeder 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 connector adaptor for connection of the plug on the 28 ft 8 5 m control cable of the K857 See the instructions S19103 included with the kit FLUX SYSTEM COMPONENTS The flux system is a...

Page 32: ...400 amps 60 duty cycle and is available in lengths of 10 25 and 50 feet 3 0 7 6 and 15 2 m K592 INPUT CABLE Consists of an eight conductor control cable with 14 pin control cable plug and a 3 0 85 mm2 electrode cable with stud terminals It is rated at 600 amps 60 duty cycle and is available in lengths of 10 25 and 50 feet 3 0 7 6 and 15 2 m K593 10 INPUT CABLE AND GAS HOSE Similar to the K591 but ...

Page 33: ...wire feed unit by following the Attaching the Wire Reel Stand procedure at the end of this section K377 SMALL MOUNTING STAND FOR READI REEL COILS AND 22 TO 30 LB SPINDLE WITH 2 IN I D This assembly includes a wire reel spindle similar to the K162 spindle attached to a small frame The unit is supplied with the K363 Readi Reel Adapter for using the Lincoln Readi Reel Electrode Coils Without the adap...

Page 34: ...he kit ATTACHING THE WIRE REEL STAND The mounting hardware for mounting the stands is included with the LN 742 Screws and washers are inserted in their respective mounting holes To connect 1 Remove the three 3 8 in hex head bolts from the back of the wire feed unit 2 Place the wire reel mounting stand mounting bracket in position against the back of the wire feed unit 3 Replace and tighten the hex...

Page 35: ...D 2 Drive Rolls and Guide Tubes D 2 Wire Reel Mounting D 2 Periodic Maintenance D 2 Wire Drive Motor and Gearbox D 2 Gun and Cable Maintenance D 2 LN 742 LN 742H SECTION D 1 MAINTENANCE SECTION D 1 Return to Master TOC Return to Master TOC Return to Master TOC Return to Master TOC ...

Page 36: ...L MOUNTING 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 No routine maintenance is required for Readi Reels and 10 to 30 lb spools Do not lubricate the 2 in spindles PERIODIC MAINTENANCE WIRE DRIVE MOTOR AND GEARB...

Page 37: ... Description E 2 Power Input Circuits E 2 Trigger Circuit E 3 Keypad Display Board Control Board Reed Switch Drive Motor and Tach Feedback E 4 LN 742 LN 742H SECTION E 1 THEORY OF OPERATION SECTION E 1 Return to Master TOC Return to Master TOC Return to Master TOC Return to Master TOC ...

Page 38: ...eed wire feeder with a gas solenid valve and fittings It also has standard Lincoln gun connector An LED display and a soft touch keypad provide selection of operating mode function selection timer selection and parameter adjustment Two touch keys operate the cold inch and gas purge functions POWER INPUT CIRCUITS The LN 742 receives 42 VAC usually from the welding power source by way of the input c...

Page 39: ...otor and also activates an electronic switch which closes leads 2 and 4 The closure of leads 2 and 4 energize the welding output terminals on the Lincoln power source The gas and or water solenoid are also energized by a solid state circuit on the control board FIGURE E 2 TRIGGER CIRCUIT GUN TRIGGER RECEPTACLE GAS SOLENOID AC AC DC DC TACH DRIVE MOTOR REED SWITCH 42VAC 42VAC CONTACTOR CONTROL INPU...

Page 40: ...rent sensing reed switch and sends the appropriate signals to the wire drive motor Thus the wire is fed at the correct speed and at the correct time dependent upon the commands issued from the keypad The display board exhibits the commands set forth by the keypad as well as displays the actual arc voltage FIGURE E 3 KEYPAD DISPLAY BOARD CONTROL BOARD REED SWITCH DRIVE MOTOR AND TACH FEEDBACK GUN T...

Page 41: ...bly Replacement for Two Roll Wire Feeders F 26 Swing Arm Assembly Replacement for Four Roll Wire Feeders F 28 Gas Solenoid and Connections Replacement F 31 Retest After Repair F 34 Check Wire Feed Speed F 34 ELECTRIC SHOCK can kill 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 te...

Page 42: ...ptoms that the machinery may exhibit Find the listing that best describes the symptom that the machine is exhibiting Symptoms are grouped according to function problems feeding problems and welding problems Step 2 PERFORM EXTERNAL TESTS The second column labeled POSSIBLE AREAS OF MISADJUSTMENT S lists the obvious external possibilities that may contribute to the machine symptom Perform these tests...

Page 43: ... directly into the equipment Don t set the P C Board on or near paper plastic or cloth which could have a static charge If the P C Board can t be installed immediately put it back in the static shielding bag If the P C Board uses protective shorting jumpers don t remove them until installation is complete If you return a P C Board to The Lincoln Electric Company for credit it must be in the static...

Page 44: ... replace the gun trigger switch 2 Check the gun trigger recepta cle Check for loose or faulty connections 1 Check for opens or shorts in the control cable 2 Perform the Input Voltage Test 3 Perform the Drive Motor Test 4 Observe LED 1 located on the control board It should blink on and off at a controlled rate of 1 second on and 1 second off If it does NOT the control board may be faulty If LED do...

Page 45: ... The inch and weld speeds may be set to the same value 2 If the display shows the sym bol the inch speed has been dis abled To enable the inch speed press the increase arrow key 3 Check plug J2 on the control board for loose or faulty connec tions 1 The control board may be faulty Replace 1 Perform the Tach Feedback Test 2 Perform the Drive Motor Test 1 Disconnect plug J2 from the con trol board T...

Page 46: ...y switch on the Lincoln welding power source is in the correct position for the welding process 2 Check or replace the control cable Check the continuity zero ohms of leads 21 and 67 1 Check for mechanical restric tions in the wire feed path 1 Make sure the control cable is connected to the welding power source correctly 2 Check the 42 VAC fuse or circuit breaker in the welding power source 1 If a...

Page 47: ... local Lincoln Authorized Field Service Facility 1 Check plug J6 located on the control board for loose or faulty connections 1 Contact your local Lincoln Authorized Field Service Facility 1 If the arc voltage is greater than 44 VDC this is a normal condi tion The voltmeter only reads 0 44 VDC 1 This is an EPROM error The parameter recalled at power up is out of range Press any key to reset unit C...

Page 48: ...ical troubleshooting assistance before you proceed Call 216 383 2531 or 1 800 833 9353 CAUTION 1 Contact the Lincoln Electric Service Department 1 216 383 2531 or 1 800 833 9353 WELD 1 Perform the Drive Motor Test 2 The control board may be faulty Replace The wire is feeding rough or not feeding The drive rolls are turning The drive rolls do not turn when the gun trigger is pressed The gas solenoi...

Page 49: ...g Poor arc striking with sticking or blast offs The weld bead may be ropy and narrow 1 Check the welding cables for loose or faulty connections 2 Make sure the wire feed speed voltage polarity and shielding gas are correct for the process being used 3 Check for mechanical restric tions in the wire feed path 4 Make sure the welding power source is functioning properly 1 Make sure the wire feed spee...

Page 50: ...ty and to avoid electrical shock please observe all safety notes and precautions detailed throughout this manual 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 technical troubleshooting assistance before you proceed Call 216 383 2531 or 1 800 833 9353 WELD TEST DESCRIPTION The followin...

Page 51: ...3 for the presence of 12 8 VDC If this voltage is missing or low the control board may be faulty 8 With the gun trigger activated or the gun trigger terminals jumpered together refer to Section G Electrical Diagrams and the motor running check from the blue lead 2J3 to the black lead 3J3 for the presence of approximately 1 5 VDC Note When the motor is not running the voltage may be from 0 to 2 5 V...

Page 52: ...actory warranty For your safety and to avoid electrical shock please observe all safety notes and precautions detailed throughout this manual 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 technical troubleshooting assistance before you proceed Call 216 383 2531 or 1 800 833 9353 WELD ...

Page 53: ...t slow speed with approximately 1 5 VDC applied As the variable DC voltage is increased to 23 VDC the drive motor should increase to maximum speed 8 If the motor does not run or varies in speed the motor brushes gearbox or motor may be faulty Check each and replace as needed 9 Check the resistance from each of the motor leads on plug J5 to the motor case The resistance should be very high at least...

Page 54: ...For your safety and to avoid electrical shock please observe all safety notes and precautions detailed throughout this manual 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 technical troubleshooting assistance before you proceed Call 216 383 2531 or 1 800 833 9353 WELD TEST DESCRIPTION...

Page 55: ...2 VAC at the red AC terminals of the input rectifier bridge shown in Figure F 3 5 Carefully check for approximately 56 VDC from the white DC to the blue DC terminals of the input rectifier bridge 6 Check for approximately 56 VDC from plug J1 1J1 to plug J1 7J1 on the control board If the 56 VDC is present and any or all of the following test voltages are not correct the control board may be faulty...

Page 56: ...lation to get good contact at the test points in steps 8 and 9 7 Check for 12 8 VDC from plug J3 1J3 to plug J4 6J4 Figure F 4 8 Check for 5 VDC from Test Point A on the control board to plug J4 6J4 on the control board Figure F 5 FIGURE F 4 12 8 VDC TEST POINTS PLUG J3 1J3 PLUG J4 6J4 CONTROL BOARD PLUG J4 6J4 CONTROL BOARD TEST POINT A C16 FIGURE F 5 5 VDC TEST POINTS F 16 TROUBLESHOOTING AND RE...

Page 57: ...control board to plug J1 7J1 on the control board Figure F 6 10 If any of the previous voltages in step 7 8 or 9 are incorrect or missing the control board may be faulty and should be replaced 11 Install the left side cover assembly using screws and the 5 16 nutdriver PLUG J1 7J1 CONTROL BOARD TEST POINT B T1B F 17 TROUBLESHOOTING AND REPAIR F 17 INPUT VOLTAGE TEST continued FIGURE F 6 12 8 VDC TE...

Page 58: ...invalidate your factory warranty For your safety and to avoid electrical shock please observe all safety notes and precautions detailed throughout this manual 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 technical troubleshooting assistance before you proceed Call 216 383 2531 or 1 8...

Page 59: ...ve input power to wire feeder 2 Using the 5 16 nutdriver remove the screws from the left side cover assembly 3 Remove the left side cover assembly 4 Carefully remove plug J11 from the display board shown in Figure F 7 NOTE Once the display board is free from the mounting posts do not try to remove the display board because the keypad plug J10 will limit the travel distance 5 Very carefully pry the...

Page 60: ...UBLESHOOTING AND REPAIR F 20 7 Measure the resistance of each key at plug J10 on the keypad The resistance measurements are taken from the pin locations on plug J10 shown in Figure F 8 8 If any of the resistance tests are not correct per Table F 1 the keypad is faulty and should be replaced PLUG J10 PIN 1 1J10 PIN 8 8J10 KEYPAD RESISTANCE TEST continued FIGURE F 8 KEYPAD RESISTANCE TEST POINTS ...

Page 61: ... the display board onto the four mounting posts 11 Connect plug J11 into the display board 12 Install the left side cover assembly using screws and the 5 16 nutdriver TABLE F 1 KEYPAD RESISTANCE TESTS COLD INCH GAS PURGE UP ARROW DOWN ARROW METER FUNCTION TRIGGER MODE TIMER 100 OHMS 30 TYPICAL 100 OHMS 30 TYPICAL 100 OHMS 30 TYPICAL 100 OHMS 30 TYPICAL 100 OHMS 30 TYPICAL 100 OHMS 30 TYPICAL 100 O...

Page 62: ...feeder Only qualified technicians should perform installations maintenance and troubleshooting work on the machine TOOLS REQUIRED 5 16 in nutdriver 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 WARNING COMPONEN...

Page 63: ...r securing the toroid assembly to the side of the wire drive compartment 8 On two roll feeders use a 3 8 in open end wrench and remove the mounting screw located beneath the reed switch energizer and mylar insulation On four roll feeders use a 3 8 in socket with extension and remove the two mounting screws and washers located beneath the reed switch energizer and mylar insulation Refer to Figure F...

Page 64: ...CEMENT MOTOR FLAT WASHER RING MAGNET PINION GEAR ROLL PIN MOTOR INSULATOR GEARBOX TACHOMETER MOUNT TACHOMETER RETAINING NUT MOTOR MOUNTING SCREW UPPER INSULATOR SHEET LOWER INSULATOR SHEET GEARBOX MOUNTING PLATE GEARBOX COVER LOCATOR INSULATOR BUSHING BENT J BOLT WIRE LEAD 67 REED SWITCH REED SWITCH ENERGIZER CONTACTOR BLOCK MOTOR MOUNTING SCREW WIRE DRIVE ASSEMBLY AND COMPONENTS REPLACEMENT conti...

Page 65: ...17 Install the tachometer mount using a slot head screwdriver 18 Gently screw the tachometer into the tachometer mount until it bottoms out 19 Back the tachometer out 1 2 turn and tighten the locknut using a 9 16 in wrench 20 Install wire lead 67 onto the contact block using the slot head screw 21 Position the wire drive assembly in the center of the wire drive compartment and line up the mounting...

Page 66: ...Y REPLACEMENT FOR TWO ROLL WIRE FEEDERS ELECTRIC SHOCK can kill 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 WARNING F 26 TROUBLESHOOTING AND REPAIR F 26 LN 742 LN 742H ...

Page 67: ... that attaches the swing arm to the gearbox Remove the swing arm and flat washer from the wire feeder Remove the pivot spacer from the swing arm This step is not necessary if you are not replacing the quick release assembly 3 Pry the speed clip off of the groove pin and lift the idle roll assembly from groove pin 4 Place the new idle roll assembly into the groove pin Secure in place with a speed c...

Page 68: ...REPLACEMENT FOR FOUR ROLL WIRE FEEDERS ELECTRIC SHOCK can kill 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 WARNING F 28 TROUBLESHOOTING AND REPA...

Page 69: ...ost of the wire drive assembly See Figure F 12 2 Using a pair of pliers pull the hinge pin up and out of the wire drive assembly 3 Note the position of the two spacers Carefully pull the two swing arms out of the wire drive compartment Ensure that the two spacers are not lost 4 Remove the two socket head cap screws and flat washers from the swing arm assembly Remove the idle roll shaft pin Slide t...

Page 70: ...e up to accept the hinge pin Do not use excessive force when installing the hinge pin If hinge pin does not go in remove it and try again 8 Slide the hinge pin into the hinge pin opening in the center post Use a rubber mallet to drive the hinge pin in if necessary Drive the hinge pin in until the detente in the pin is visible in the setscrew hole 9 Install the setscrew and tighten until snug SWING...

Page 71: ...can kill 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 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 WARNING F 31 TROUBLESHOOTING ...

Page 72: ... to Master TOC Return to Master TOC Return to Master TOC GAS SOLENOID AND CONNECTIONS REPLACEMENT continued FIGURE F 16 GAS SOLENOID DISASSEMBLY GAS OUTLET FITTING GAS TUBING GAS TUBING TUBE SLEEVE SOLENOID OUTLET FITTING GAS SOLENOID GAS INLET FITTING FILTER SCREEN GAS SOLENOID MOUNTING PLATE F 32 TROUBLESHOOTING AND REPAIR F 32 ...

Page 73: ...enoid 8 Remove the solenoid from the solenoid mounting plate by removing the two phillips head screws from the bottom of the mounting plate 9 Remove the tubing from the gas and solenoid outlet fittings A knife may be required to cut the tubing 10 Mount the new solenoid to the solenoid mounting plate using two phillips head screws 11 Apply thread sealant Loctite 592 to the threads of the gas inlet ...

Page 74: ...ess the Inch key Check that the direction of rotation of the drive roll shaft is correct to feed wire out of the front of the machine Check that the drive roll shaft stops abruptly when the key is released 4 Press the Increase Arrow key The number displayed should increase 5 Press the Decrease Arrow key The number displayed should decrease 6 Press the Function Select key The LEDs should toggle thr...

Page 75: ... LN 742 LN 742H TABLE OF CONTENTS ELECTRICAL DIAGRAMS Electrical Diagrams Section G WIRING DIAGRAM G 2 G2615 CONTROL BOARD SCHEMATIC G 3 G2615 CONTROL BOARD LAYOUT G 4 L9122 DISPLAY BOARD SCHEMATIC G 5 L9122 DISPLAY BOARD LAYOUT G 6 SECTION G 1 ELECTRICAL DIAGRAMS SECTION SECTION G 1 ...

Page 76: ...LN 742 LN 742H Return to Section TOC Return to Section TOC Return to Section TOC Return to Section TOC Return to Master TOC Return to Master TOC Return to Master TOC Return to Master TOC NOTES ...

Page 77: ...5K 518 516 L L L P9 518 J11 P8 PIN NUMBERING SEQUENCE P9 PIN 1 J9 J8 L R F CHOKE 5 1 7 5 1 8 B W R F TOROID ASSEMBLY J11 5 1 2 A W F S VOLTAGE 5 1 2 A TACH B U R ELECTRICAL SYMBOLS PER E1537 N A PRESENT ONLY ON THE LN 742H MODELS P8 R R R F TOROID ASSEMBLY R R 41 42 A B C D E GUN CONTROL CABLE W F S POT CONNECTOR AND VOLTAGE POT CONNECTOR OPTIONAL REMOTE WIRE FEED SPEED VOLTAGE POT ASSEMBLY CURREN...

Page 78: ...2901 X5 3 12 2614 488 500 500 500 J6 6 7 12 1 J2 J3 MOLEX CONNECTORS 4 1 2 3 ELECTRICAL SYMBOLS PER E1537 NUMBER N B PRESENT ONLY ON THE LN 742H MODELS ONLY NOT SHOW THE EXACT COMPONENTS OR CIRCUITRY OF CONTROLS HAVING A COMMON CODE WITHOUT AFFECTING THE INTERCHANGEABILITY OF A COMPLETE BOARD THIS DIAGRAM MAY N A SINCE COMPONENTS OR CIRCUITRY ON A PRINTED CIRCUIT BOARD MAY CHANGE NOTES BLUE R LABE...

Page 79: ...D9 D13 D14 D16 D15 D20 D17 D18 D19 D30 D31 D23 X6 X10 X5 X2 X3 X4 X1 X11 X8 LED1 TP1 J1 J6 J7 J2 J3 J5 J4 OCI1 R50 R76 R31 R19 R59 R69 Q 4 X7 Q5 Q 2 Q 3 T1 Y1 C7 G2615 X X X X X X X X X X X X X X XXXX X X X X X XXXX G 4 Return to Section TOC Return to Section TOC Return to Section TOC Return to Section TOC Return to Master TOC Return to Master TOC Return to Master TOC Return to Master TOC NOTE Lin...

Page 80: ...RY OF CONTROLS HAVING A COMMON CODE WITHOUT AFFECTING THE INTERCHANGEABILITY OF A COMPLETE BOARD THIS DIAGRAM MAY N A SINCE COMPONENTS OR CIRCUITRY ON A PRINTED CIRCUIT BOARD MAY CHANGE 8 16 F C B 74HC165 CLK1 H Vcc GND SA QH SS PL D A E CLK2 G QH X2 1 2 9 7 15 10 6 5 4 3 14 13 11 12 DR J10 4 J10 8 1 00K R1 1 00K R 3 475 R15 J10 5 J10 3 475 R10 1 00K R 2 1 00K R 4 LED9 INCREASE PURGE COLD INCH D C...

Page 81: ... Section TOC Return to Section TOC Return to Master TOC Return to Master TOC Return to Master TOC Return to Master TOC 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 r...

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