Thunderbolt 225V

[skyboss]

Ok, what is wrong with my stick welder? The unit hums and it seems like the fan is running but when I try to strike an arc, nothing happens. No output. Then when I switch it off there is a pretty noticeable flash inside the case. Is that normal? This is a used welder I picked up to play around with. Any thoughts?

[Al T.]

Maybe the diodes or capacitor are shorted. Is this an ac/dc type? Any voltage at the leads at all?

[Ed Heimbach]

A long distance diagnosis is always pretty iffy but it sounds as if the secondary is shorted and the big flash you see is the input line breaking contact.
Normally, when a welder is shut off, the current going in is quite small, and no flash results when the circuit is broken.
However, when a circuit is broken which is carring a lot of current, a large flash will result.
Open up the case and look for any place where the output lines could have worn through the insulation.
Good luck.

[Phil]

Originally posted by skyboss
Ok, what is wrong with my stick welder? The unit hums and it seems like the fan is running but when I try to strike an arc, nothing happens. No output. Then when I switch it off there is a pretty noticeable flash inside the case. Is that normal? This is a used welder I picked up to play around with. Any thoughts?

Skyboss, I would agree with Ed's diagnostic; you have a short on the secondary side. You can still get parts, even the seconday windings. Once you have checked the wiring as Ed suggested, you could also verify the receptacles; they should be isolated from the case. Here's a link to the Thunderbolt 225 manual (not sure what the difference is with the 225V).

http://www.millerwelds.com/om/0100/o116j_mil.pdf