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Millermatic 175 Trips CB1 when Trigger Switch is pulled

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  • Millermatic 175 Trips CB1 when Trigger Switch is pulled

    I have a Millermatic 175 that I am having issues with.
    Serial number: LC678420 Stock No. 907020

    I was welding and stopped to start another piece. When I moved the Ground clamp to the new piece and tried to weld I didn't get any wire feeding from the machine. I opened the machine up and found that the fan was still running but I did not have any lights on my control board. I checked the output from the fan to the control board to find I was not getting 24 volts from the control board. I replaced the fan motor. Now I have lights on the control board and the wire will feed. However it will only feed for a couple seconds before tripping CB1. I check the amp load on these lines to find that it was spiking when I actuated the trigger switch. I have checked the following items to try to isolate the problem:
    1. I have disconnected the lead from the front of the machine and jumped it with the same result.
    2. I have release tension on the drive rolls with same result.
    3. I have dis connected the drive roll motor and actuated the trigger switch with same result.
    4. Installed another breaker with same result.

    My gut feeling is that I have a bad control board.
    Any input or thoughts here would be greatly appreciated.

  • #2
    CB1 is protecting the input power circuit so the cause is significant.

    Could be a shorted weld output diode or transformer T1.

    As far as there being a board problem, any failed component should be easy to identify if it's tripping CB1.
    Last edited by duaneb55; 08-29-2016, 05:21 PM.
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