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TROUBLESHOOTING & REPAIR
F-5 F-5
TROUBLESHOOTING GUIDE Observe Safety Guidelines
detailed in the beginning of this manual.
POWER MIG 255
CAUTION
If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, con-
tact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call
1-888-935-3877.
PROBLEMS
(SYMPTOMS)
POSSIBLE AREAS OF
MISADJUSTMENT(S)
RECOMMENDED
COURSE OF ACTION
No open circuit voltage output but
wire feeds normally when gun trig-
ger is pulled.
Wire feeds but welding output is low
causing wire to “stub”. Welds are
“cold”. Machine cannot obtain full
rated output of 200 amps at 28 volts.
1. Check the input voltage at the
machine. Input voltage must
match the rating plate and the
reconnect panel.
2. The gun may be faulty. Check
or replace.
1. Make sure that the proper wire
and procedures are being used.
2. Check gun and work cable for
loose or faulty connections.
1. Check for loose or broken con-
nections at the output terminals,
the chokes, the capacitor bank
and all heavy current carrying
leads. See Wiring Diagram.
2. Make sure that the transformer
secondary leads are securely
connected to the SCR rectifier
assembly.
3. Perform the SCR Rectifier
Assembly Tests.
4. Perform Main Transformer
Test.
5. The control board may be faulty.
Replace.
1. Check for loose or faulty con-
nections of the heavy current
carrying leads.
2. The output capacitor bank may
be faulty. Check for loose con-
nections at the capacitors. Also
check for leaky capacitors.
Replace if necessary.
WARNING: The liquid elec-
trolyte in these capacitors is
toxic. Avoid contact with any
portion of your body.
3. Perform the SCR Rectifier
Assembly Tests.
4. Perform the Main Transformer
Test.
5. The control board may be faulty.
Replace.
OUTPUT PROBLEMS (Continued)