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arcing before button is pressed

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  • arcing before button is pressed

    I have a 115VAC Handler 135 that I mostly use for flux core and some MIG. Lately it has started to arc the moment the wire approaches the work piece before I press the button on the gun. No small arc either, it actually welds the metal. It's just a short arc, and when it's gone the wire is "cold" again until I press the button. I can then weld as normal. Once I release the button again, it starts over again with a strong arc the moment the wire approaches the work piece next time. Repeat.

    This is what I've done so far:
    - Checked that the resistor R2 reads 50 ohms.
    - Checked with a meter that there's no residual voltage in the wire after that initial arc.
    - Checked continuity of connections to resistor R2 and to the capacitor.
    - Verified with a meter that the switch in the gun is not sticking and that is actually switching off.

    This problem started a couple of weeks ago, and I'm at my ropes end. Hate to have to scrap this machine, but I'm sick of ruining good work pieces.

    Any suggestions what to check next?

    Anybody had this problem before and how did you fix?

    (By the way, I tried contacting Hobart technical support. They haven't bothered to get back to me in over a week.)

  • #2
    How did you reach out to tech support? It sounds to me like the bleed down resistor may be shorted.


    • #3
      The bleed down resistor (R2) measures 50 ohms. I believe that is the correct value.


      • #4
        By the way, I also verified that the contactor CR1 isn't stuck in closed position. CR3 appears to be working correctly as well.


        • #5
          How long are you waiting after welding to weld again, is this happening immediately after stopping welding or minutes later?


          • #6
            In the past it has happened after about a minute or so, so it's not just immediately. Can't test it right now, since the welder is apart now and I'm swapping out all components in that area. (R2, termistor, CR1 etc.)


            • #7
              Just curious, how did that arcing problem finally work out? Is that contactor on your machine a separate discrete component ? From looking at the schematic and the parts illustration for your HH135 It looks like it's part of and integral to the PC1 circuit board. I don't know how possible it is for a contactor to be part of a circuit board since contactors on mig's are usually a high amperage rather sizeable part. Usually contacts in the contactor would wear and mushroom out a bit and make just enough contact to keep the the wire live