Lincoln Electric INVERTEC STT Series Service Manual page 51

F-10
TROUBLESHOOTING GUIDE
PROBLEMS
(SYMPTOMS)
Weld bead appears "cold."
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 216-
383-2531 or 1-800-833-9353.
TROUBLESHOOTING & REPAIR
POSSIBLE AREAS OF
MISADJUSTMENT(S)
WELDING PROBLEMS
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 electrode
wire being used.
CAUTION
INVERTEC STT
Observe Safety Guidelines
detailed in the beginning of this manual.
RECOMMENDED
COURSE OF ACTION
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 associ-
ated wiring may be faulty. See
the Wiring Diagram. The control
PC board may be faulty. Also
check for loose or faulty con-
nections on the heavy current
carrying conductors (i.e., main
transformer, choke,
diodes, Darlington module and
output 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 con-
trol PC board may be faulty.
5. The Darlington module may be
faulty. Check or replace.
F-10
output
DEC 97