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TROUBLESHOOTING AND REPAIR F-3
LN-7 GMA WIRE FEEDER
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 trou-
bleshooting 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
properly connected.
3. If the problem persists, replace the
suspect PC board using standard
practices to avoid static electrical
damage and electrical shock. Read the
warning inside the static resistant bag
and perform the following procedures:
P.C. Board can be
damaged by static
electricity.
- Remove your body’s
static 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 un-
painted, grounded, part
of the equipment frame. Keep touching the
frame to prevent static build-up. Be sure not
to touch any electrically live parts at the
same time.
ELECTRIC SHOCK
can kill.
•
Have an electrician
install and service this
equipment. Turn the
input power OFF at the
- Tools which come in contact with the P.C.
Board must be either conductive, anti-static
or static-dissipative.
- 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
failure 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 troubleshooting.
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
reappear by substituting the original
board, then the PC board was not
the problem. Continue to look for
bad connections 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 writing
on the warranty report, “INSTALLED AND
SWITCHED PC BOARDS TO VERIFY
PROBLEM,” will help avoid denial of legiti-
mate PC board warranty claims.
PC BOARD TROUBLESHOOTING PROCEDURES
ATTENTION
Static-Sensitive
Devices
Handle only at
Static-Safe
Workstations
Reusable
Container
Do Not Destroy
WARNING
CAUTION
fuse box before working on equipment. Do
not touch electrically hot parts.