How to troubleshoot dead power brick

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  • stj
    Great Sage 齊天大聖
    • Dec 2009
    • 30923
    • Albion

    #21
    32ohm between gate and source.
    lets see, source voltage is 170v
    max gate voltage on most mosfets is 30v
    chip is bad and mosfet is in question and where is the 10k coming from?

    Comment

    • CapLeaker
      Leaking Member
      • Dec 2014
      • 7977
      • Canada

      #22
      mmartell
      that sounds to me the OB2269 is fubar. Even so the pads measure up without the chip, recheck the whole gate drive and the mosfet. Usually the mosfet fails and dumps high voltage to the gate drive. But sometimes the IC fails and everything else is o.k. Not sure where the 10k come from either.
      Kinda on the rare scale, but seen it before.

      Comment

      • mmartell
        Badcaps Legend
        • Oct 2013
        • 3189
        • Canada

        #23
        See pic - R5 is a 10k resistor between Gate and Source that's where it's coming from. I also measure 13.6 ohms between pins 6 and 8 on the power ic itself now that it's out of circuit.

        Not sure how to test the mosfet it's not shorted in any way at rest but could be open I guess ? Reads as a transistor from D to S with my meter but that's all I get out of it.

        Can this power ic be substituted with something more common ?
        Attached Files

        Comment

        • CapLeaker
          Leaking Member
          • Dec 2014
          • 7977
          • Canada

          #24
          The OB2269AP is actually quite common. Even LCSC and many others have it, just not Mouser or Digi.
          Pin 6 is the sense pin and pin 8 is the gate pin. That’s why I am saying check out the whole gate drive circuit!

          Comment

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