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TROUBLESHOOTING & REPAIR |
LF-72/74
Observe Safety Guidelines detailed in the beginning of this manual.
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| PROBLEMS | POSSIBLE AREAS OF | RECOMMENDED | |
| (SYMPTOMS) | MISADJUSTMENT(S) | COURSE OF ACTION | |
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| FUNCTION PROBLEMS (Continued) |
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| No shielding gas. | 1. No gas supply, or gas supply | 1. | Verify cylinder is not empty and |
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| interrupted. |
| is turned on. |
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| 2. Solenoid not functioning. | Check the hose for cuts or kinks. | |
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| Make sure it is not crushed. | |
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| Verify the hose is connected to the | |
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| gun bushing or welding gun. | |
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| 2. | Perform the GAS SOLENOID |
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| TEST. |
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| Variable or hunting arc. | 1. Bad contact tip | 1. | Check for proper size contact |
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| 2. Possible loose connection in |
| tip. Make sure tip is not worn, |
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| current carrying cables. |
| and is free of spatter. |
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| 3. Set up not correct. | 2. | Clean and tighten all electrode |
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| 4. Problem with shielding gas. |
| and work connections. Verify |
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| the gun bushing is tightly |
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| mounted to the wire drive. |
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| Verify the gun is tightly mounted |
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| to the gun bushing. |
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| 3. | Verify the proper polarity is |
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| being used for the weld proce- |
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| dure. Make sure the proper |
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| electrode |
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| maintained. |
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| 4. | Check the gas flow rate and |
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| mixture. |
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| 5. | Control board may be faulty. |
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| When the trigger is pulled, the | 1. Possible bad gun or faulty con- | 1. | Check all electrode and work |
| drive rolls spin but no arc voltage | nections in the heavy current |
| connections. Verify the the gun |
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| carrying leads. |
| bushing is tight to the wire |
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| 2. Possible faulty control cable. |
| drive. Verify gun is tightly |
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| mounted to the bushing. | |
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| 3. Possible defective power | 2. | Check the control cable and |
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| source. | ||
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| connectors for continuity, cuts, | |
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| or broken pins. |
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| 3. | Verify the power source is oper- |
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| ating properly. |
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| The arc burns back to the tip. | 1. If timer kit is installed, reduce |
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| the amount of burnback time. |
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| The gas continues to flow for a | 2. If the timer kit is installed, |
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| reduce the amount of post flow |
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| long time after the weld. |
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| time. |
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CAUTION
If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, con- tact the Lincoln Electric Service Department at
