Procedure for Replacing PC Boards
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.
When a PC board is suspected to be defective, the following procedure must be followed:
1.Visually inspect the PC board. If the board has fuses, check to see if any are blown. Are any of the components damaged? Is a conductor on the back side of the board damaged? If electrical dam- age is visible on the PC board, inspect the machine wiring for grounds or shorts to avoid damaging a new PC board. Install a new PC board only after a visual inspection of the PC board and machine wiring is satisfactory.
2.If the problem is remedied by a new PC board, install the old PC board and see if the problem still exists. If the problem does not return with the old board:
a.Check the PC board harness plug and PC board plug for contamination, corrosion or oversize.
b.Check leads in the harness for loose connec- tions.
CONNECTING THE REMOTE CONTROL TO THE MACHINE
Extreme caution must be observed when installing or extending the wiring of a remote control. Improper connection of this unit can lead to loss of control and/or poor welding. Only the green lead can and should be grounded to the machine case. When extending the standard remote control, make sure the leads are the same and the splice is waterproof. Be very careful not to ground the cable when in use and don’t let the lugs touch against the case.
OUTPUT VOLTAGE
The open circuit voltage of the machine should be adjustable from 10 to 46 volts. If any other condition exists, refer to the Troubleshooting Guide.
FAULT PROTECTION OPERATION
The overload protection circuit, in the Control Board, will limit the welding current (heat) to approximately 550 amps if a short or overload is applied to the machine.
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CHECKING SNUBBER PC BOARD
In case of an SCR malfunction or failure, the Snubber PC Board should be checked. Turn the machine off and remove the sides of the machine. Board is mount- ed on back of the case front.
1.Visually inspect the Board for overheated compo- nents or damaged components.
CHECKING OUTPUT CONTROL RHEOSTAT ON MACHINE
Turn machine off (“0” position).
Remove the screws from the hinged control panel and open the panel.
Turn the Output Control switch to “Remote”.
Disconnect the harness plug from the Control PC Board.
With an ohmmeter on X1K, connect it to lead 210 and 75 on R4.
Exercise caution to avoid damaging rheostat tabs.
Rotate the Output control rheostat. The resistance reading should be from around zero to 10K ohms. Check the resistance reading between 77 and 75 on the terminal strip. The reading must be 10K ohms. No reading will indicate an open rheostat and a low read- ing will indicate a shorted or partially shorted rheostat; in either case, replace.
POWER “ I/O “ SWITCH CHECK
1.Turn off the machine input power (“0” position). S1 has 115 volts across it when the input power is connected.
2.Isolate the switch to be tested by removing all con- necting leads.
3.Check to make sure the switch is making open and closed connections with a V.O.M. meter. Put ohmmeter on X1 scale. The meter should read zero resistance with switch “I” and infinite with switch “0”.
4.Put the ohmmeter on X1K scale and measure the resistance between the terminal and the case of the machine (touch a
5.If either step (3) or step (4) fails, replace the switch.
