2.Turn off welding power source.

3.Turn off shielding gas supply at the source, if applica- ble.

6-8. Overheating Protection

If the unit overheats, the weld sequence goes to postflow and the contactor is deenergized. The user relay contacts stay in the state they were in before postflow was entered and remain that way until postflow ends. The following repeating displays are shown:

P O W E R S O U R C E

T H E R M A L O V E R L O A D

A L L O W T O C O O L

B E F O R E C O N T I N U I N G

The ammeter and voltmeter displays flash until one of the fol- lowing events takes place:

1.The thermostat resets (indicating the unit has cooled down).

2.The operator turns the unit Off and then On again.

3.The operator moves the Program/Run/Reset keyed switch to the Reset position, then to either Run or Pro- gram, as applicable.

If the operator carries out items 2 or 3 above, the program pa- rameters can be viewed or modified, but the unit output contactor cannot be energized. If the operator tries to energize the contactor, the unit goes to postflow and repeats the dis- plays shown above.

If the unit overheats, wait until the unit cools down before start- ing to weld.

SECTION 7 – DIAGNOSTICS

7-1. Introduction

A. General

The diagnostics program allows the following to be tested:

1.Internal RAM memory

2.Front panel programming push buttons

3.Run and Program positions of the keyed switch

4.Output selector switch

5.Mode selector switch

6.Purge push button

7.Analog output circuitry

8.Output contactor

9.Background relay

10.Gas solenoid relay

11.Arc starter relay

12.User relays, which include the following: Initial Time relay

Initial Slope relay Weld Time relay Final Slope relay Final Time relay

Postflow relay

Wire Feed Time Delay relay

Pulse Signal relay

13.Remote Pendant

14.Current detection circuitry

15.Input contactor

The RAM test and the programming push button tests are car- ried out each time the diagnostics program is started. The remaining tests can be performed in sequence, or the Right/In- crease or Left/Decrease push buttons can be used to access a desired test. Refer to the subsections in this section for infor- mation on each test.

B. Running The Diagnostics Program

To carry out the diagnostics program, proceed as follows:

1.Follow the directions in Section 2-4 for choosing the diagnostics program on DIP switch SW1.

2.Place Program/Run/Reset keyed switch in Run position.

3.Energize the unit.

C. Stopping The Diagnostics Program

To stop the diagnostics program, follow the directions in Sec- tion 2-4 for choosing program execution on DIP switch SW1.

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Miller Electric OM-842 manual Diagnostics, Overheating Protection, Introduction
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OM-842 specifications

The Miller Electric OM-842 is a versatile and powerful multi-process welding machine designed for professional welders who demand efficiency and reliability on the job. This industrial-grade welder is capable of handling various welding processes, including MIG, TIG, stick, and flux-cored welding, making it an ideal choice for a wide range of applications.

One of the standout features of the OM-842 is its robust output capability. With a maximum output of 400 amps, it can tackle thick materials with ease while maintaining exceptional arc stability. This output range allows for adaptability in different welding scenarios, whether working on heavy fabrication projects or lighter home repairs.

The OM-842 is also equipped with advanced inverter technology. This technology enhances the machine's efficiency and reduces energy consumption. Inverter machines are known for their lightweight design compared to traditional transformer welders, which makes the OM-842 more portable and easier to transport between job sites.

User-friendliness is paramount in the design of the OM-842. Its intuitive control panel features a digital display that provides real-time information on parameters such as voltage and amperage. This allows users to make quick and precise adjustments on the fly, enhancing productivity and ensuring optimal welding results.

Additionally, the OM-842 offers sophisticated weld control features, such as Auto-Set, which simplifies the setup process for beginners and experienced users alike. This technology automatically selects optimal parameters based on the material type and thickness, minimizing trial and error during welding.

The machine also includes a durable and rugged design, suitable for tough working conditions. The protective case and high-quality components ensure longevity and reliability even in adverse environments.

Safety is another critical aspect of the OM-842, with features such as over-temperature protection and a built-in fan to prevent overheating during extended use.

With its powerful performance, advanced technology, and robust design, the Miller Electric OM-842 stands out as an exceptional choice for welders seeking reliability and versatility in their welding operations, ultimately creating high-quality welds across various applications. Whether in a shop or on a construction site, the OM-842 is engineered to deliver outstanding results every time.
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