My buzzbox broke. :-(

[The Haymaker]

Yesterday my Miller Thunderbolt died while welding DC. :-( I found the initial problem, the yellow, uppermost, front panel insulator for the AC side failed and grounded the post to the front panel.

So, trying to finish the last 3" of weld on the project I was working on, I pulled the stud from the panel and left it suspended inside. Still no go, unit acts as though there is a dead short.

Here's what else I found that makes me think this rig is done. On that same stud, there are two large conductors that come from the variable transformer. They come out side by side, but appear to be wound in two directions. These two conductors meet at the problem stud and are both clamped down by a nut.

When I fire up the unit, There is a tremendous amount of heat generated at the point of contact between the wires on the stud, making an incandescent light bulb. Remember, this stud is hanging in free space with no load. I'm wondering if the failed insulator was a secondary to the heat caused by something else going on? See picture.

Did my transformer fail? Maybe one side went to ground, the heat I see being generated from one side of the transformer and being pushed back to a shorted winding on the other side?

I thought diode, but would a failed diode affect the AC side?

Thanks in advance,

E

 

[retiredIW]

this may be better ask over on the miller site. there is a lot of miller techs over there

 

[Patches]

Wish mine would break so I could buy a mig :thumbsup:

 

[jmanatee2]

Wish mine would break so I could buy a mig :thumbsup:

I couldnt wait. I bought a MIG before my buzz box quit. I will never be with out one.

As for the as the burnt stud.. Could be a shorted transformer.

 

[sjb]

I would check the diodes, before I tried anything else. It's easy with an ohm meter. The diodes are always connected across the transformer, so if one shorted it would also effect the AC.

I can't be sure without a wiring diagram, but they may be using that yellow terminal as a tie point to connect 2 separate windings in the transformer. That would explain how a shorted diode could cause heat at that point.


Stan