Lincoln Electric SQUARE WAVE TIG 355 Service Manual page 69

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Observe Safety Guidelines detailed in the beginning of this manual.
PROBLEMS
(SYMPTOMS)
Open circuit voltage is present at
the output terminals even when the
Arc Start switch or Amptrol is NOT
actuated.
Arc rectification when AC TIG weld-
ing.
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.
TROUBLESHOOTING AND REPAIR
POSSIBLE AREAS OF
MISADJUSTMENT(S)
TIG MODE PROBLEMS
1. The Arc Start switch or Amptrol
may be defective. There should
not be any continuity between
pins "D" and "E" on the Arc Start
cable connector, unless the unit
is actuated.
1. The tungsten electrode may be
too small for the process.
2. The AC Wave Balance control
may be misadjusted. Adjust for
more penetration.
3. If helium shielding gas is being
used, reduce the percentage of
helium.
CAUTION
SQUARE WAVE TIG 355
RECOMMENDED
COURSE OF ACTION
1. Check the trigger
Perform the Arc Start Trigger
Circuit Test.
2. The control board may be faulty.
Replace.
3. The power board may be faulty.
Replace.
1. Check components R6 and C6
in the high voltage transformer
primary circuit. Replace if nec-
essary.
2. Perform the Static & Active
SCR Bridge Tests.
3. The control board may be faulty.
Replace.
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circuit.