Pc Board Troubleshooting Procedures - Lincoln Electric RANGER 225 Service Manual

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PC BOARD TROUBLESHOOTING PROCEDURES

WARNING
ELECTRIC SHOCK
can kill.
• Have
service this equipment. Turn the
input power OFF at the fuse box
before working on equipment. Do
not touch electrically hot parts.
CAUTION
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.
ATTENTION
- If you don't have a wrist strap,
Static-Sensitive
touch an un-painted, grounded,
Devices
part of the equipment frame. Keep
Handle only at
touching the frame to prevent
Static-Safe
static build-up. Be sure not to
Workstations
touch any electrically live parts at
the same time.
- Tools which come in contact with
the PC board must be either con-
ductive, anti-static or static-dis-
sipative.
TROUBLESHOOTING AND REPAIR
an electrician install and
RANGER
- 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-shield-
ing 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-shield-
ing 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 deni-
al of legitimate PC board warranty claims.
225
®
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