Lincoln Electric LN-25x Service Manual page 18

LINCOLN ELECTRIC
3. Locate the wire drive motor, on the rear of the wire drive panel, and plug P53. See Figure F.5. See
Wiring Diagram.
4. Carefully apply the correct input voltage (15 – 110 VDC) to the LN-25x.
5. With the gun trigger activated and the motor running check the motor armature current. Normal
armature current is less than 3 amps. If the armature current exceeds 3.2 amps for 8 seconds the
motor will be disabled. See Wiring Diagram.
6. If the motor current is normal and the motor still shuts down the flexible power supply board may
be faulty. Perform the Flexible Power Supply Board Test Procedure.
7. If the motor current is high, check for restrictions in the wire feeding system. These possible
restrictions can be caused by a clogged gun liner, spindle tightness, drive rolls are too tight or a
motor or gear box.
TACHOMETER TEST PROCEDURE
1. Remove the input power to the LN-25x wire feeder.
2. Perform the Wire Drive Assembly And Control Box Cover Removal Procedure.
3. Locate the wire drive motor, on the rear of the wire drive panel, and plug P53. See Figure F.5. See
Wiring Diagram.
4. Carefully apply the correct input voltage (15 – 110 VDC) to the LN-25x.
5. Using a volt/ohmmeter, check for approximately 15 VDC on plug P53 pin 3 (positive red lead #531)
to pin 5 (negative black lead #534). See Figure F.6. See Wiring Diagram. This is the supply voltage
from the flexible power supply board to the tachometer.
6. With the gun trigger activated and the motor running check for approximately 5 VDC at plug P53 pin
4 (positive blue lead #537) to pin 5 (negative black lead #534). This is the feedback signal from the
tachometer to the flexible power supply board.
NOTE: If the tachometer is faulty the motor will run at a constant speed with approximate 10 VDC
applied to the motor armature from the flexible power supply board.
7. If the tachometer passes the above tests, perform the Wire Drive Assembly And Control Box Cover
Replacement Procedure.
8. If the tachometer does not pass the above tests, it may be faulty.
9. If faulty, perform the Wire Drive Motor Removal And Replacement Procedure.
LN-25x™ Service Manual
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