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Welder failure to power on

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  • #16
    Dread, just my thoughts as I am looking at pictures and you have a better perspective with the board right in front of you. I think that component you had outlined before is more likely linked to the auxiliary power supply. It could be used to rectify the input voltage to somewhere between ~140V - ~360V DC (input voltage tolerances on 120V - 240V input circuits) though I am not seeing the electrolytic capacitors for that circuit (would be close to the rectifier). If you can do diode tests on the transistors with the red dots (I think those are your input rectifier diodes), as well as the Emitter to Collector diode test for the transistors with the green dot (appear to be N channel mosfets but a search for the component datasheet will confirm it), and a diode test for the transistor with the yellow dot) we can start to rule those out as the issue.