SQUARE WAVE TIG 255
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F-2
TROUBLESHOOTING & REPAIR
CAUTION: Sometimes machine failures
appear to be due to PC board failures.
These problems can sometimes be traced
to poor electrical connections. To avoid
problems when troubleshooting and replac-
ing PC boards, please use the following
procedure:
1. Determine to the best of your technical
ability that the PC board is the most like-
ly component causing the failure symp-
tom.
2. Check for loose connections at the PC
board to assure that the PC board is
properly connected.
3. If the problem persists, replace the sus-
pect PC board using standard practices
to avoid static electrical damage and
electrical shock. (Read the warning
inside the static resistant bag.)
NOTE: It is desirable to have a spare
(known good) PC board available for PC
board troubleshooting.
PC BOARD TROUBLESHOOTING PROCEDURES
ELECTRIC SHOCK can
kill.
Have an electrician install and
service this equipment. Turn the
input power OFF at the fuse box
before working on equipment. Do
not touch electrically hot parts.
WARNING
4. Test the machine to determine if the fail-
ure symptom has been corrected by the
replacement PC board.
NOTE: Allow the machine to heat up so
that all electrical components can reach
their operating temperature.
5. Remove the replacement PC board and
substitute it with the original PC board to
recreate the original problem.
a. If the original problem does not reap-
pear by substituting the original board,
then the PC board was not the prob-
lem. Continue to look for bad connec-
tions in the control wiring harness,
junction blocks, and terminal strips.
b. If the original problem is recreated by
the substitution of the original board,
then the PC board was the problem.
Reinstall the replacement PC board
and test the machine.
6. Always indicate that this procedure was
followed when warranty reports are to be
submitted.
NOTE: Following this procedure and writ-
ing on the warranty report, “INSTALLED
AND SWITCHED PC BOARDS TO VERIFY
PROBLEM,” will help avoid denial of legiti-
mate PC board warranty claims.