| Electronics > Repair |
| Tomahawk 375 Plasma Cutter Failure Analysis |
| (1/1) |
| seancsnm:
My Lincoln Tomahawk 375 plasma cutter recently failed and I'm trying to troubleshoot to see exactly what happened. It had maybe 20 hours on it when it failed. Details surrounding the failure are in the images, but to sum it all up, it looks like a thermistor dropped to a low resistance and failed. I only have a very surface level understanding of how these plasma cutters work - Lincoln or some other source can explain better than I can. But what puzzles me is why a thermistor (presumably NTC) was placed between the ground and pilot arc signals. What purpose does it serve? I can only guess that it provides a failsafe current path for the pilot arc when the air gap between the torch and workpiece is too large. But even that doesn't make a lot of sense. Why not just put an air gap on the PCB in that case? And why a thermistor instead of a standard resistor? So my question is, why a NTC between those two signals, and does anyone have any clue what would make suitable replacement specs? Oh, and what could have caused the failure in the first place? I am new to using plasma cutters and acknowledge that I abused the machine a little with what I did to the air nozzle, but the failure occurred a good bit after I replaced the nozzle with a new one. |
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