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Lincoln LT-7, Troubleshooting Manual

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Lincoln LT-7 Troubleshooting Manual Download Page 29

TROUBLESHOOTING AND REPAIR

Observe Safety Guidelines

detailed in the beginning of this manual.

Troubleshooting Guide –

See Wiring Diagrams for location of specified

components. See Wiring Diagrams for troubleshooting of specific circuits.

B-20

B-20

LT-7 TRACTOR

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

CAUTION

TRAVEL PROBLEMS

PROBLEMS
(SYMPTOMS)

FIELD
COURSE OF ACTION

RECOMMENDED SHOP
COURSE OF ACTION

The travel motor runs with limited
speed. The control may be erratic.

1. Remove power to unit and

check the resistance of travel
speed control rheostat (R6).
Normal resistance is 5000
ohms. Also check R6 for
smooth operation.

2. Check associated leads

between R6 and the travel
board.

3. The travel board may be faulty.

1. Perform the 

Travel Motor Test.

Summary of Contents for LT-7

Page 1: ...facturer of Industrial Motors IM279 TS JUNE 1995 Safety Depends on You Lincoln arc welding and cutting equipment is designed and built with safety in mind However your overall safety can be increased...

Page 2: ...R WEARERS SHOULD CONSULT WITH THEIR DOCTOR BEFORE OPERATING Read and understand the following safety highlights For additional safety information it is strongly recommended that you pur chase a copy o...

Page 3: ...ical earth ground 3 f Maintain the electrode holder work clamp welding cable and welding machine in good safe operating condition Replace damaged insulation 3 g Never dip the electrode in water for co...

Page 4: ...vent the welding sparks from starting a fire Remember that welding sparks and hot materials from welding can easily go through small cracks and openings to adjacent areas Avoid welding near hydraulic...

Page 5: ...B 4 P C Board Status Lights B 21 Wire Drive Motor Test B 24 Travel Motor Test B 26 Wire Drive Motor Removal and Replacement B 30 Diagrams Section C M15342 Connection Schematic C 1 L7460 Control Box Wi...

Page 6: ...lied to the the variable voltage board and through resistor R1 to the control board The 115VAC is rectified and regulated by the control board which supplies 24VDC to the logic board GLP WELD CURRENT...

Page 7: ...rectly to the control board dictates that the wire drive motor reverse direction and back the electrode wire away from the work piece Travel speed direction and mode either manual or auto are determin...

Page 8: ...kes contact with the work piece this low voltage is loaded down thus signaling the control circuitry to stop the wire feed motor This feature allows the operator to utilize work touch sensing FIGURE E...

Page 9: ...NOTES A 4 A 4 LT 7 TRACTOR...

Page 10: ...the machinery may exhibit Find the listing that best describes the symptom that the machine is exhibiting Symptoms are grouped according to function problems and travel problems Step 2 PERFORM EXTERN...

Page 11: ...ce it directly into the equip ment Don t set the PC board on or near paper plastic or cloth which could have a static charge If the PC board can t be installed immediately put it back in the static sh...

Page 12: ...closed 3 Check the Inch Up Switch S3 Make certain it is not stuck closed 1 If light 1B on the control board is NOT on then the control board may be faulty Replace 2 If lights 1B and 1A are both ON th...

Page 13: ...n and functioning prop erly 2 Check the circuit breaker locat ed on the front cover If tripped reset If circuit breaker repeat edly trips consult appropriate PROBLEMS SYMPTOMS 3 Open the front cover a...

Page 14: ...SYMPTOMS FIELD COURSE OF ACTION RECOMMENDED SHOP COURSE OF ACTION The wire will not feed and the cir cuit breaker trips when the inch or start switches are pressed 1 Reset the circuit breaker and obse...

Page 15: ...MPTOMS FIELD COURSE OF ACTION RECOMMENDED SHOP COURSE OF ACTION The wire will not feed when the start switch is pressed There is not a voltage indicated on the LT7 voltmeter The wire does inch up and...

Page 16: ...ing the inch down switch observe light 2J It should be lit If not the inch down switch S4 or associated wires may be faulty See wiring diagram 2 If the LT7 is in the constant volt age CV mode and ligh...

Page 17: ...2531 or 1 800 833 9353 CAUTION FUNCTIONAL PROBLEMS PROBLEMS SYMPTOMS FIELD COURSE OF ACTION RECOMMENDED SHOP COURSE OF ACTION The wire will NOT inch down but inches up properly When the start switch...

Page 18: ...CTION The wire will not inch down The wire inches up properly When the start switch is pressed the wire feeds up instead of down 1 Check the connections between the power source and LT7 for loose or i...

Page 19: ...re does not stop feeding when it touches the work piece The wire will not inch up The wire inches down properly 1 Make certain a variable voltage board is installed and connect ed correctly 2 The jump...

Page 20: ...ECOMMENDED SHOP COURSE OF ACTION The wire feeds up with either inch switch The wire feeds down with either inch switch 1 While pressing the inch down switch observe light 2E on the logic board If ligh...

Page 21: ...s at full speed during the inch mode only The wire feeds at full speed during the weld mode only 1 The logic board may be faulty 1 Remove electrode from drive rolls and place a jumper wire from lead 5...

Page 22: ...BLEMS PROBLEMS SYMPTOMS FIELD COURSE OF ACTION RECOMMENDED SHOP COURSE OF ACTION The wire feeds at full speed in both inch and weld modes The wire has limited or erratic speed control in one or more m...

Page 23: ...sources put a jumper from 2 to 4 on the ter minal strip This activates the output from the power source Test for voltage at the output terminals of the power source If no voltage is indicated then th...

Page 24: ...OURSE OF ACTION No control of power source output from LT7 tractor Power source does have output The circuit breaker trips while the LT7 is at idle not feeding wire 1 Check control cable leads for pro...

Page 25: ...urce output contactor does NOT drop out The power source output terminals are always electrically hot The welding and travel do not stop when the stop switch is pressed 1 With the LT7 at idle not feed...

Page 26: ...age is NOT present check the circuit breaker the R5 resistor the travel switch and the associ ated wiring See wiring dia gram 3 If the correct AC voltage IS pre sent at leads 531 to 632 then check the...

Page 27: ...vel switch set to manual The travel motor runs continuously with travel control switch set on automatic 1 Check light 2H on logic board Light 2H should be lit when automaic travel is required If light...

Page 28: ...ed ly trips The travel motor runs at full speed with no control 1 While unit is traveling check the the travel motor armature cur rent Normal current is 0 5 amps DC Note In older units also check for...

Page 29: ...incoln Electric Service Department for electrical technical troubleshooting assistance before you proceed Call 216 383 2531 or 1 800 833 9353 CAUTION TRAVEL PROBLEMS PROBLEMS SYMPTOMS FIELD COURSE OF...

Page 30: ...H DOWN SWITCH PRESSED 2K SIGNAL TO OPERATE POWER SOURCE CONTACTOR 2L WELD VOLTAGE CONTROL OPERATIVE 2M GROUND LEAD PROTECTOR TRIPPED 3A ELECTRODE VOLTAGE OUTPUT FROM VV BOARD 3B ELECTRODE VOLTAGE INPU...

Page 31: ...T 7 TRACTOR FIGURE B 1 Logic P C Board LED Locations FIGURE B 2 Voltage P C Board LED Locations FIGURE B 3 Control P C Board LED Locations L5927 LOGIC 2B 2C 2D 2E 2F 2H 2J 2K 2L 2M L5394 VARIABLE VOLT...

Page 32: ...NOTES B 23 B 23 LT 7 TRACTOR...

Page 33: ...bserve 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...

Page 34: ...r connector See Table B 3 3 Apply field voltage first pins C and D to the motor Then slowly apply the arma ture voltage on pins A and B See Table B 3 4 The motor should run and the speed should vary w...

Page 35: ...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 departmen...

Page 36: ...ce test is good pro ceed to the Motor Applied Voltage Test MOTOR APPLIED VOLTAGE TEST 1 Carefully connect the 110VDC supply SUPPLY TURNED OFF to pins C and D on the travel motor connector See Figure B...

Page 37: ...ING AND REPAIR B 28 B 28 LT 7 TRACTOR A B C 595 594 C B D A 647 646 559 561 FIGURE B 5 Travel Motor Connector Pins FIGURE B 6 Travel Motor Connector Pins Older Units with Powered Field TRAVEL MOTOR TE...

Page 38: ...NOTES B 29 B 29 LT 7 TRACTOR...

Page 39: ...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 procedure...

Page 40: ...and remove the two socket head cap screws mounting the motor to the gear box housing Note The inspection cover plate has to be remove Step 5 to gain access to the two socket head cap screws 7 Careful...

Page 41: ...DIAGRAMS C 1 C 1 LT 7 TRACTOR CONNECTION SCHEMATIC M15342 This diagram is provided for reference only It may not be totally applicable to all machine codes...

Page 42: ...ARM CONTROL CABLE TO POWER SOURCE 2 4 31 32 21 75 76 77 GND 2 4 31 32 21 75 76 77 GND A B C D E F G H I CONTROL BOX GROUND GROUNDING LEAD PROTECTOR 4CR 563 539 541 539 532 TERMINAL STRIP GND 627 626...

Page 43: ...NOTES C 3 C 3 LT 7 TRACTOR...

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