PROCEDURE FOR REPLACING PC BOARDS
WARNING
ELECTRIC SHOCK CAN KILL.
BEFORE PERFORMING ANY MAINTE-
NANCE THAT REQUIRES OPENING
THE CASE OF THE POWER SOURCE:
•Disconnect input power to this machine at the Disconnect switch.
•Do not touch electrically live parts or internal wiring.
•Only qualified personnel should service this machine.
Before replacing a PC board which is suspected of being defective, visually inspect the PC board in ques- tion for any damage to any of its components and conductors on the back of the board.
If there is no visible damage to the PC board, install a new one and see if this remedies the problem. If the problem is remedied, reinstall the old PC board to see if the problem still exists. If it does no longer exist with the old PC board:
1.Check the PC board harness conductor pins for corrosion, contamination or looseness.
2.Check leads in the plug harness for loose or intermittent connection.
If PC board is visibly damaged electrically (compo- nents burned, copper traces opened or damaged), 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.Two or more leads shorted together.
4.Foreign matter or interference behind the PC boards.
If PC board is visibly damaged mechanically (such as a part vibrated off or was crushed), inspect for cause, then remedy before installing a replacement PC board.
If there is damage to the PC board and if replacing PC board corrects problem, return it to the local Lincoln Electric Field Service Shop.
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