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My Hobart Handler 120 stopped working during a welding process. Now when I pull the trigger, the 30a 110v circuit breaker trips. The machine can be turned on and the breaker holds (cooling fan in the welder is ON), but as soon as the contacter pulls down, the 110v supply circuit is overloaded and the breaker opens. I was welding at the time in a constricted spot, without the gas cone on using inner-shield wire. My tip touched the work piece (has happened thousands of times before) - I expected to have the wire stick in the tip, but this time the tip and wire appeared to become free just a moment after I lifted the gun from the work and tickled the trigger a couple times. The machine sounded loud when I pulsed the trigger - like it was welding hard, even though there was not arc from the gun... the wire was not feeding - so I pulled all the wire back out of the gun and cable, just to watch the machine with no wire in the liner. Then, when I pulled the trigger to watch the action of the feed motor - the circuit breaker tripped. I reset it and took off the transformer side cover to watch the action of the contactor. The contactor arcs when it is commanded on by the trigger switch and if held more than a second the breaker trips at the shop fuse box. After studying the electrical schematic I suspect the trouble must be in the primary side of the Power Transformer (bad news), but I see some references online to the diodes of the output rectifier being a cause for tripping shop circuit breakers? I am considering disconnecting the two leads from the power transformer to the output rectifier to see if this will allow the wall-breaker to hold when the trigger is pulled.

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Please don't give me a bad rating for this. Its just a little extra info. you didn't mention that may help you find the problem. Depending on your specific model, there should be 1 or 2 breakers on the unit it self. If there is only 1, it will shut down the entire machine when tripped. If there are 2, the top one is for the whole unit and the lower one is for the wire feeder motor only. There is also a thermal overload that will shut down everything except the cooling fan. Secure the trigger closed and let the fan run for a while to see if it re-starts when cooled. If the depth of the weld was stable before the problem occurred, I would suspect a short in the motor and not the rectifier. That is not a sure bet though. If the transformer does not start when it cools, UNPLUG the welder and short the transformer to ground to be sure the capacitor is discharged. Then isolate the feed motor and transformer and use an OHM meter to test them individually to ground for a short. With a little luck, it will be the feed motor. Please let me know if this helped at all. I am new and still learning how to explain what I am thinking. Thanks for writing us.

Posted on Apr 02, 2011


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