Lincoln Electric SQUARE WAVE TIG 355 Service Manual page 67

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Observe Safety Guidelines detailed in the beginning of this manual.
PROBLEMS
(SYMPTOMS)
Weak high frequency – machine
has normal welding output.
Lack of penetration in 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 spark gap may be misadjust-
ed. Check and reset per mainte-
nance instructions.
2. Improper shielding gas flow.
Adjust for a flow of 10 to 30 CFH
(4.7 to 14.1 l/min.) for most appli-
cations.
3. Work and electrode cables may
be in poor condition, allowing the
high frequency to "leak off." Use
good quality cables with a high
natural rubber content, such as
Lincoln Stable
Cables should be as short as
possible.
1. The AC Wave Balance control
may be set improperly – settings
above 3 give increased penetra-
tion.
CAUTION
SQUARE WAVE TIG 355
RECOMMENDED
COURSE OF ACTION
1. Make sure that 115VAC is being
applied to the primary of the
high voltage transformer (T3).
See Wiring Diagram.
2. Check for an open or arcing
high frequency
Replace
(Examples: R6, C6, C3, R4)
3. If spark is weak at the spark
gap, check or replace the high
frequency circuit.
T3, L4, L5).
Arc Cable.
1. Check the AC Wave Balance
control potentiometer (R12) for
correct resistance and proper
operation. See Wiring Diagram.
2. Check leads #443 and #444 for
continuity from the AC Wave
Balance control potentiometer
to the lower control panel. See
Wiring Diagram.
3. Perform the Static & Active
SCR Bridge Tests.
4. The control board may be faulty.
Replace.
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component.
as required.
(Examples: