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Procedure for Replacing PC Boards
WARNING
ELECTRIC SHOCK can kill.
•Have a qualified individual install and service this equipment.
•Turn the power source input power off at the disconnect switch before work- ing on this equipment.
•Do not touch electrically hot parts.
Before replacing a PC board which is suspected of being defective, visually inspect the PC board in ques- tion for any electrical or mechanical damage to any of its components and conductors on the back of the board.
a. If there is no visible damage to the PC board, install a new one and see if this remedies the prob- lem. If the problem is remedied, reinstall the old PC board to see if the problem still exists. If it does no longer exist with old PC board:
1.Check the PC board harness connector pins for corrosion, contamination, or looseness.
2.Check leads in the plug harness for loose or intermittent connection.
b.If PC board is visibly damaged electrically, before possibly subjecting the new PC board to the same cause of failure, check for possible shorts, opens, or grounds caused by:
1.Frayed or pinched lead insulation.
2.Poor lead termination, such as a poor contact or a short to adjacent connection or surface.
3.Shorted or open motor leads, or other external leads.
4.Foreign matter or interference behind the PC boards.
c.If PC board is visibly damaged mechanically, inspect for cause, then remedy before installing a replacement PC board.
If there is damage to the PC board or if replacing PC board corrects problem, return it to the local Lincoln Electric Field Service Shop.
PC BOARD TROUBLESHOOTING PROCEDURES
CONTROL PC BOARD
The Control PC Board controls all machine functions including the thermal protection indicator light and the Meter PC Board. Most problems, if not caused by faulty wiring machine misuse, will stem from a faulty Control PC Board.
Perform the following diagnostic procedure before replacing the Control PC Board.
1.Turn off the input power at the fuse box.
2.Check for loose connections in the PC Board plugs, particularly J3.
3.Disconnect the J3 plug from the Control PC Board. Measure the resistance between the following wire terminals in the plug:
A)Between wire #200 and wire #201.
B)Between wire #202 and wire #203.
Both of these resistances should be less than 1 ohm.
If these resistances are not less than 1 ohm, check the wiring back to the main transformer.
If these voltages are less than 1 ohm, refer to "Procedure for Replacing PC Boards."
METER PC BOARD
When the Meter PC Board malfunctions, first determine if the rest of the machine functions correctly. If so, then the problem is in either the harness between the meter and control boards, or in the meter board itself. Refer to "Procedure for Replacing PC Boards". As a last resort, the Control PC Board may have to be replaced.
CAUTION
If for any reason you do not understand the test procedures or are unable to perform the tests/repairs safely, contact your Local Lincoln Authorized Field Service Facility for technical troubleshooting assistance before you proceed.
