Lincoln Electric SQUARE WAVE TIG 255 SVM100-A Service Manual page 49

Observe Safety Guidelines
detailed in the beginning of this manual.
PROBLEMS
(SYMPTOMS)
The control panel displays cannot
be read. The characters run, dis-
play only half characters, or ran-
dom dots may appear on display.
The voltmeter always reads "00" .
The machine output is normal.
The control panel display back-
ground is dark instead of red. The
machine operates normally.
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 216-383-2531 or 1-800-833-9353.
TROUBLESHOOTING & REPAIR
POSSIBLE AREAS OF
MISADJUSTMENT(S)
FUNCTION PROBLEMS
None
None
None
CAUTION
TROUBLESHOOTING GUIDE
RECOMMENDED
COURSE OF ACTION
1. Check for loose connections at
plug J3 on the control board.
2. The display may be faulty.
Replace.
3. The control board may be
faulty. Replace.
1. Check the continuity of leads
#305 and #313C and their con-
nections to the machine output
studs. Refer to wiring diagram.
2. The Control board may be
faulty. Check for machine
"open citcuit voltage" at 5J6
and 12J6 on the Control board.
If open circuit voltage is pre-
sent then replace the Control
board.
3. If open circuit voltage is not
present at 5J6 and 12J6 (see
Figure F.1) then check the
Protection/Snubber board. See
Protection/Snubber Board
Continuity Test.
1. Check for loose connector (P3)
at the Control board.
2. The Control board may be
faulty. Disconnect P3 from the
Control board. Check voltage
from 1J3 to 2J3 on the board.
See Figure F.1. The voltage
should be 15 to 20vdc. If the
voltage is not correct then
replace the Control board.
3. If the Control board is good
then the Display may be faulty.
Replace Display.
SQUARE WAVE TIG 255
F-8