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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.

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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 self-tapping screw). Reading should be infinite.

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.

DC-400

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Lincoln Electric DC-400 Procedure for Replacing PC Boards, Connecting the Remote Control to the Machine, Output Voltage
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DC-400 specifications

The Lincoln Electric DC-400 is a versatile and robust DC arc welding power source designed to meet the demands of various industrial applications. Known for its reliability and performance, the DC-400 is ideal for both professional welders and fabrication shops requiring robust equipment that can handle challenging welding tasks.

One of the main features of the DC-400 is its ability to provide a smooth, stable arc, which is essential for achieving high-quality welds. This welding machine is capable of delivering a wide amperage range, typically from 20 to 400 amperes, making it suitable for various welding processes, including MIG, TIG, and Stick welding. The unit's high output capabilities allow it to effectively weld a variety of materials, such as steel, stainless steel, and various alloys.

In terms of technology, the DC-400 integrates advanced power conversion technology that enhances energy efficiency while minimizing heat loss during operation. This not only contributes to lower operating costs but also ensures a longer service life for the machine. The DC-400 features a durable, rugged design, with a robust steel frame that can withstand the rigors of heavy industrial use while providing an IP23 rating for protection against moisture and dust.

Another notable characteristic of the DC-400 is its ease of use. The intuitive controls allow for quick adjustments to settings, enabling welders to easily adapt to different job requirements. The arc characteristics of the DC-400 can be fine-tuned to optimize performance for different welding applications, ensuring consistent results every time.

Moreover, the DC-400 is equipped with built-in safety features such as thermal overload protection, which prevents damage to the machine in case of prolonged operation under heavy loads. This feature enhances the safety of the operator and extends the life of the welding machine.

Overall, the Lincoln Electric DC-400 stands out as a reliable and efficient welding power source. Its combination of high-performance capabilities, advanced technology, and next-level usability makes it a popular choice in the industry. Whether for heavy fabrication, maintenance, or repair work, the DC-400 continues to prove itself as an indispensable tool for professional welders seeking quality and durability in their equipment.
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