Arc when powered off?

[RTWigley]

I am trying to figure out why when the machine (125 handler) is switched off, it is still getting an electrical current in the tip of the gun. Has anyone else ever had this problem or know how to fix it?
Thanks.

[Jim-Tx]

I'm not familiar with that machine, but I do know that my MM 210 will spark when the wire contacts the grounded surface. Not sure it it will do it when it's off though. From what I understand, it has something to do with capacitors and starting the arc. This is just a guess, but I'm going to say that what you are experiencing is just a capacitor(s) that are discharging when grounded.

[walker]

Just a little spark, or welding current? If it is just a little spark it is from the capacitor bank, perfectly normal.

[Roger]

Large capacitors in welder smooth out AC ripples left after diodes change AC to DC welding current. They do this by very quickly storing and releasing electricity. This changes 1/2 sine wave pulsating DC from the diodes to a smoother DC current.

http://en.wikipedia.org/wiki/AC/DC_conversion

Sometimes a bleeder resister is used to slowly drain capacitor charge to reduce shock hazard from charged capacitor.

[RTWigley]

It is more of a welding current than a little spark. The machine is completely turned off. It has never done it before.

[Zrexxer]

This is a recurring issue with some of the Handlers. In a previous case Darrell with Hobart said:

"The contacts of the relay on the control board that breaks the primary circuit to the power transformer have welded shut. This will allow the contact to stay hot. The welder won't weld, because the wire won't feed, it'll still spark though. Either the control board needs to be replaced or the the relay on the board needs to be replaced."

read this thread and see if it helps:
http://www.hobartwelders.com/weldtalk/showthread.php?p=296507