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TROUBLESHOOTING & REPAIR
F-10 F-10
INVERTEC STT
TROUBLESHOOTING GUIDE Observe Safety Guidelines
detailed in the beginning of this manual.
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
WELDING PROBLEMS
Weld bead appears "cold." 1. One or more of the machine
settings may be wrong. Check
the Background, Peak Current,
Tailout (STT II Only), and Wire
Speed controls for proper set-
tings. Adjust for optimum weld-
ing performance.
2. Make sure the Wire Type and
Wire Size switches are in the
correct position for the elec-
trode wire being used.
1. Check for the correct open cir-
cuit voltage (approximately
85VDC). If the correct open cir-
cuit voltage IS present, the
Background control (R12) or
the Peak Current (R11) and
associated wiring may be faulty.
See the Wiring Diagram. The
control PC board may be faulty.
Also check for loose or faulty
connections on the heavy cur-
rent carrying conductors (i.e.,
main transformer, choke, output
diodes, IGBT module and out-
put terminals).
2. If the correct open circuit volt-
age is NOT present, perform
the Switch Board Test.
3. The output diodes may be
faulty. Check or replace if nec-
essary.
4. The driver PC board and or
control PC board may be faulty.
5. The IGBT module may be
faulty. Check or replace.