TROUBLESHOOTING | ||
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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 damage is visible on the PC Board, inspect the machine wiring for grounds or shorts to avoid dam- aging 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 over- size.
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 failure of the output control rheostat or the control circuit. 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 output circuit voltage of the machine should be adjustable from 10 to 46 volts in CV. In the CC mode, the open circuit voltage should be approximately 57 volts (54 volts on 50/60 Hz) except at near minimum settings of the output control where it may be lower. If any other condition exists, refer to the Troubleshooting Guide.
FAULT PROTECTION OPERATION
The overload protection circuit, in the Control PC Board will limit the welding current (heat) to 550 amps if a short or overload is applied to the machine. (Refer to the Machine and Circuit Protection section).
CHECKING SNUBBER CIRCUIT
In case of an SCR malfunction or failure the snubber assembly should be checked. Turn the machine off and remove the sides of the machine. (See the instruction manual parts list for the exact location.)
1.Visually inspect the snubber assembly for over- heated components or damaged components.
CHECKING OUTPUT CONTROL RHEOSTAT ON MACHINE
Turn machine off (“0” position).
Remove the control panel screws and open the con- trol panel (see the section on Terminal Strip Connections for screw locations).
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 POT taps.
POWER “I/0” SWITCH CHECK
1.Turn off the machine power input (“0” position). S1 has 115V across it when the input power is con- nected.
2.Isolate the switch to be tested by removing all con- necting leads.
3.Check to make sure the switch is making connec- tions with an ohmmeter. The meter should read zero resistance.
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.
If for any reason you do not understand the test procedures or are unable to perform the tests/repairs safely, contact your Local Authorized Field Service Facility for technical troubleshooting assistance before you proceed.