Lincoln Electric SVM157-A service manual PC Board Troubleshooting Procedures

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F-3 TROUBLESHOOTING AND REPAIR F-3

PC BOARD TROUBLESHOOTING PROCEDURES

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WARNING

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.

CAUTION

Sometimes machine failures appear to be due to PC board failures. These problems can sometimes be traced to poor electrical con- nections. 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:

	PC	board can be
	damaged		by	static
	electricity.
	- Remove		your	body’s
ATTENTION	static	charge		before
	opening		the	static-
Static-Sensitive	shielding bag. Wear an
Devices	anti-static wrist strap. For
Handle only at	safety, use a 1 Meg ohm
Static-Safe	resistive cord connected
Workstations	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.

-Remove the PC board from the static-shield- ing bag and place it directly into the equip- ment. 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.

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 PROB- LEM,” will help avoid denial of legitimate PC board warranty claims.

POWER MIG 200