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F-8 TROUBLESHOOTING AND REPAIR
LN-7 GMA WIRE FEEDER
PROBLEMS
(SYMPTOMS)
Wire feed speed adjustment is
rough. Works only at certain
portions of the speed range.
Ground Lead Protector circuit
tripping.
POSSIBLE AREAS OF
MISADJUSTMENT(S)
1. Ensure setscrew on the
potentiometer knob is tight.
2. Check for a clogged gun liner or
a mechanical restriction in the
wire feeding path.
1. Ensure all work lead
connections to the work make
tight metal-to-metal contact.
2. Ensure that excess work and
input cables are stored more
than 3 ft (1 m) from the wire
feeder.
3. Is input cable coiled next to the
work cable? Uncoil and loop
back and forth in 3 to 6 ft (1 to
2 m) straight lengths to elimi-
nate the coil.
RECOMMENDED
COURSE OF ACTION
1. Check the resistance of the
potentiometer over the entire
range of travel. The potentio-
meter should adjust from 0 to
10K Ohms. If adjustment is not
smooth and linear, replace per
Wire Feed Speed Potentio-
meter Replacement procedure.
2. The motor or motor brushes
may be faulty. Check the motor
brushes length, and replace
them if they are less than 1/4 in.
in length.
Check for grounded leads in the
wiring harness. Pay particular
attention to the leads connecting
the input cable connector (J101) to
the Control PC board. See Wiring
Diagrams in the Electrical Diagrams
Section.
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.
FUNCTIONAL PROBLEMS (Continued)
CAUTION
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.