Pc Board Troubleshooting Procedures - Lincoln Electric SAE-300 HE Service Manual

LINCOLN ELECTRIC

PC BOARD TROUBLESHOOTING PROCEDURES

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.
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 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.
ATTENTION
• Tools which come in contact with the
Static-
PC board must be either conductive,
Sensitive
anti-static or static-dissipative.
Devices
• Remove the PC board from the
Handle only
static-shielding bag and place it
at Static-Safe
directly into the equipment. Don't set
Workstations
the PC board on or near paper, plastic
or cloth which could have a static
Reusable
charge. If the PC board can't be
Container
installed immediately, put it back in
Do Not
the static-shielding bag.
Destroy
SAE-300® HE Service Manual
• 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.
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.
12