Nexus NXM 300 Flashing

[WDC19]

Hello I'm new here but could really do with some expert help.
I have been asked to looked at a friends nexus NXM 300 mig set. The fault was unknown to us both but just told it wasnt working, possibly overheating.

You can power the set up but as soon as you press the trigger on the gun it sparks and flashes at the windings and drops the breaker out. I have looked for an earth fault but can find one. I was wondering if it was overheating could the thermal cut out not worked and burnt the windings out?

Has anyone seen anything like this before and could point me in the right direction or is it a scrap job?


Attached is a screen shot of a video I recorded when trying it. Not sure if it helps or can upload the video.

 

[eddie49]

That's quite an impressive flash! It does look as if the main transformer has a short on the primary winding.

It may be possible to confirm this by tracing the mains input wiring through the Contactor ( heavy-duty relay ) to the transformer, and measuring the resistance of the primary. It should be 2 or maybe 3 Ohms, but not zero and not open-circuit.
With power off and the machine unplugged, check if the Contactor has a manual push-in button. If so, measure resistance across the live and neutral of the mains plug with the main power switch on. Pushing the Contactor button should show the low resistance quoted above.

Alternatively, with a flash like the one you pictured, there must be visible damage and burning on the main transformer windings. There's normally no economic way of fixing a burnt-out transformer.