Sometimes machine failures appear to be due to PC
board failures. These problems can sometimes be
traced to poor electrical connections. To avoid prob-
lems 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 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:

PC 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.

- Tools which come in contact with the PC board must

be either conductive, anti-static or static-dissipative.

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.

- Remove the PC board from the static-shielding

bag and place it directly into the equipment. Don’t
set the PC board on or near paper, plastic or
cloth which could have a static charge. If the PC
board can’t be installed immediately, put it back
in the static-shielding bag.

- If the PC board uses protective shorting jumpers,

don’t remove them until installation is complete.

- If you return a PC 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.
(Some “test” boards are available to Service
Facilities through the Parts Department).

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 legitimate PC board warranty claims.

PC BOARD TROUBLESHOOTING PROCEDURES

ATTENTION
Static-Sensitive
Devices
Handle only at
Static-Safe
Workstations

WARNING

CAUTION