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IO power board, mosfet leak ?

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    IO power board, mosfet leak ?

    Hello, I have a basic power board (from DSLR camera), this board convert 12v in some other voltages (there is no charging chip). This board is disconnected to other, so it feed nothing, the outputs should be open lines.
    When I plug the battery (12v), I measure a weird behavior…
    I found a mosfet , with 12v at source and gate, and the voltage decrease very slowly at drain : 8v… 7v… 6v… I measured with meter source-drain : 45KOhms, so can I deduce surely the mosfet has a leak (and it is dead) pls ?
    The mosfet datasheet, but it's basic one.
    https://pdf1.alldatasheet.com/datash.../TPCP8106.html

    #2
    Re: IO power board, mosfet leak ?

    Desoldered, and shorted, so I will replace it.

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      #3
      Re: IO power board, mosfet leak ?

      Did the fix work? Sometimes also the drive circuit needs to be reviewed.

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        #4
        Re: IO power board, mosfet leak ?

        Since this is a P-channel mosfet, if you have +12 at S and +12 at G (i.e. source and gate are connected), the transistor should be off, and the drain should be floating. A floating drain would mean the voltage there is indeterminate. Any charge there will eventually leak away.

        If you have G-S shorted, and you have the positive of your meter on S and the negative on D, yes this should show up as an open circuit (infinite resistance). If you connect it the other way, it will depend on your meter what reading you'll get but usually you'll get something due to the body diode in the mosfet. In diode check mode you'll see the diode drop of ~0.6V.

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