Lincoln Electric SVM128-A service manual PC Board Troubleshooting Procedures

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F-3 F-3

TROUBLESHOOTING & REPAIR

PC BOARD TROUBLESHOOTING PROCEDURES

WARNING

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ELECTRIC SHOCK can kill.

Have an electrician install and service this equipment. Turn the machine OFF 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.

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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 elec- trical damage and electrical shock. Read the warn- ing inside the static resistant bag and perform the following procedures:

•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 prop- er failure analysis.

4.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 electri- cal 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

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

Reusable

Container

Do Not Destroy

PC Board can be damaged by static electricity.

•Remove your body’s static charge before opening the static-shield- ing 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 unpainted, grounded, part of the equipment frame. Keep touching the frame to pre- vent static build-up. Be sure not to touch any electrically live parts at the same time.

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.

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.

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•Tools which come in contact with the PC Board must be either conductive, anti-static or static-dissipative.

SA-250