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:

Determine to the best of your technical ability that
the PC board is the most likely component caus-
ing the failure symptom.

Check for loose connections at the PC board to
assure that the PC board is properly connected.

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-sta-
tic wrist strap. For safety, use a
1 Meg ohm resistive cord con-
nected to a grounded part of the
equipment frame.

• If you don’t have a wrist strap,

touch an unpainted, 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.

• 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.

Test the machine to determine if the failure symp-
tom 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.

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 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.

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.

TROUBLESHOOTING & REPAIR

F-3

PC BOARD TROUBLESHOOTING PROCEDURES

WARNING

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

Reusable
Container
Do Not Destroy

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