Pc Board Troubleshooting Procedures - Lincoln Electric SP-100 Service Manual

TROUBLESHOOTING & REPAIR

PC BOARD TROUBLESHOOTING PROCEDURES

WARNING
ELECTRIC SHOCK can
kill.
Have an electrician install
and service this equip-
ment. Turn the input
power OFF and unplug
the machine before work-
ing on equipment. Do not
touch electrically hot
parts.
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.
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 problem. Continue to look for bad
connections in the control wiring har-
ness, junction blocks, and the termi-
nal 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 writing
on the warranty report, "INSTALLED AND
Switched PC BOARDS TO VERIFY PROB-
LEM," will help avoid denial of legitimate PC
board warranty claims.
F-2
SP-100