Just picked up a used Hobart Handler 120 real cheap. It seemed like it has been sitting outside (without the side covers) for a year or two. It was dirty, but I cleaned it out and everything looks okay and seems like it works okay except one thing.

From the moment I power on the machine, the feed motor is running. The speed control works fine through the whole range. Motor runs whether or not the gun switch is plugged in.

What's wrong and how do I fix it? If I took it to a service center, how much do you think it would be to fix?

Thanks.

well obviously its something in the motor control circuit. If you are capable just trace the power from the motor back to wherever the trouble is. I would bet it is a shorted relay or something similar.

good luck
Matt

If it's similar to a Hobart I fixed for a friend a few weeks ago, yes, it's the motor drive relay, points were badly arced and basically 'stuck'..
It's a relay with a clear plastic case about 1.5 x 1.5 x 2 inches in size..
Can probably be cleaned up for temporary try out use, but should be replaced..
Local Hobart dealer wanted [ I think] around 80- CDN, Digikey has similar units for 'a lot' less.. but will require minor rewiring..

enjoy..