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F-7
TROUBLESHOOTING AND REPAIR
F-7
POWER MIG 255C
Observe all Safety Guidelines detailed throughout this manual.
PROBLEMS
(SYMPTOMS)
POSSIBLE AREAS OF
MISADJUSTMENT(S)
RECOMMENDED
COURSE OF ACTION
No control of arc voltage. Wire feed-
ing is normal.
There is no gas flow when gun trig-
ger is pulled. Wire feeds and weld
voltage is present.
The machine stops feeding wire
while welding.
1. The arc voltage control poten-
tiometer may be dirty. Rotate
several times and check if prob-
lem is resolved.
1. Check gas source and hoses for
leaks or kinks.
1. Check for adequate wire supply.
2. Check for mechanical restric-
tions in the wire feeding path.
The gun may be clogged.
3. Check gun liner and tip are cor-
rect for wire size being used.
4. Check spindle for ease of rota-
tion.
5. If Timer Option Kit is installed,
make sure spot timer knob is
set to OFF.
1. The arc voltage control poten-
tiometer may be faulty. Check or
replace. See Wiring Diagram.
2. Perform the SCR Rectifier
Assembly Tests.
3. The control board may be faulty.
Replace.
1. Check the gas solenoid by dis-
connecting it from the control
board (Plug J8) and applying a
12 VDC external supply to the
gas solenoid. If the solenoid
does NOT activate then it may
be faulty. Replace.
2. The control broad may be faulty.
Replace.
1. Check the motor armature cur-
rent. Normal armature current is
2.0 to 2.7 amps maximum. If
the motor armature current is
normal the control board may be
faulty. Replace.
2. If the motor armature current is
high (over 2.7 amps) and there
are NO restrictions in the wire
feeding path then the motor or
gear box may be defective.
Replace.
FUNCTION PROBLEMS
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 1-888-935-3877.
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