Pc Board Troubleshooting Procedures - Lincoln Electric NA-5N Service Manual

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PC BOARD TROUBLESHOOTING PROCEDURES

_______________________________
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 replacing PC
boards, please use the following procedure:
1. Determine to the best of your technical
ability that the PC board is the most likely
component causing the failure symptom.
2. Check for loose connections at the PC
board to assure that the PC board is prop-
erly connected.
3. If the problem persists, replace the sus-
pect PC board using standard practices to
avoid static electrical damage and electri-
cal shock. Read the warning inside the
static resistant bag and perform the follow-
ing procedures:
ATTENTION
Static-Sensitive
Devices
Handle only at
Static-Safe
Workstations
Reusable
Container
Do Not Destroy
equipment frame. Keep touching the frame to
prevent static build-up. Be sure not to touch
any electrically live parts at the same time.
- Tools which come in contact with the P.C.
Board must be either conductive, anti-static or
static-dissipative.
TROUBLESHOOTING & REPAIR
WARNING
ELECTRIC SHOCK can kill.
Have an electrician install
and service this equip-
ment. Turn the input power
OFF at the fuse box before
working on equipment. Do
not touch electrically hot
parts.
P.C. Board can be dam-
aged by static electricity.
- Remove your body's stat-
ic charge before opening
the static-shielding bag.
Wear an anti-static wrist
strap. For safety, use a 1
Meg ohm resistive cord
connected to a grounded
part of the equipment
frame.
- If you don't have a wrist
strap, touch an unpainted,
grounded, part of the
NA-5
- Remove the P.C. Board from the static-
shielding bag and place it directly into the
equipment. Don't set the P.C. Board on or
near paper, plastic or cloth which could have
a static charge. If the P.C. Board can't be
installed immediately, put it back in the static-
shielding bag.
- If the P.C. Board uses protective shorting
jumpers, don't remove them until installation
is complete.
- If you return a P.C. Board to The Lincoln
Electric Company for credit, it must be in the
static-shielding bag. This will prevent further
damage and allow proper failure analysis.
4. Test the machine to determine if the fail-
ure symptom has been corrected by the
replacement PC board.
NOTE: It is desirable to have a spare (known
good) PC board available for PC board trou-
bleshooting.
NOTE: Allow the machine to heat up so that
all electrical components can reach their oper-
ating 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 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 writing
on the warranty report, "INSTALLED AND
SWITCHED PC BOARDS TO VERIFY
PROBLEM," will help avoid denial of legiti-
mate PC board warranty claims.
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