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Melted Mosfet on HP Pavilion ZE4500

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    #1

    Melted Mosfet on HP Pavilion ZE4500

    Today I have opened a notebook HP Pavilion ze4500 because suddenly it doesn't work anymore both with battery and external PS.

    I found a melted Mosfet or at least I think it was a Mosfet: the marking type is P31AJ and it should be from Fairchild.
    The problem is that I have not found the datasheet so I don't know which are his characteristics.
    I was not able to remove completely the board from chassis so I don't know if on the other side of the board there are more damaged components.
    I think this Mosfet is a part of step down regulator with synchronous rectification because there is another Mosfet connected which is in parallel to 2 diodes before an SMT inductance.

    I hope someone here has experience on this notebook and can give me some suggestion about this part of the circuit.

    I found a screw dancing free inside this notebook so I think it has caused the short circuit on the Mosfet.

    Ciao
    Gianni
    Attached Files
    "In the confrontation between the stream and the rock, the stream always wins...Not through strength, but through persistence."
    H. J. Brown
    Tags: None
    #2
    Re: Melted Mosfet on HP Pavilion ZE4500

    I found a cross reference from P31AJ to LM358D but I have no idea if that's correct.
    Mann-Made Global Warming.
    - We should be more concerned about the Intellectual Climate.
    -
    Be who you are and say what you feel, because those who mind don't matter and those who matter don't mind.
    - Dr Seuss
    -
    You can teach a man to fish and feed him for life, but if he can't handle sushi you must also teach him to cook.
    -

    Comment

      #3
      Re: Melted Mosfet on HP Pavilion ZE4500

      LM358 is op amp. Not the one u want. :O

      That will show me as "old school" but op-amp stuff is still used!

      Note the leads goes to these pads. See the one side have 3 all connected while one pin is base or gate while other 4 pins are all connected. Definately a transistor of either type. You will need to find another board that has the exact same IC part number and use it to cross to suitable subsititute and replace both to keep it matched.

      Fairchild starts this off with FDSxxxx or FDDxxxx on the IC. Read off the intact IC for us or more clearer pic with dirt cleaned up off the top of IC please. I feel this is like pair in totem pole fashion.

      I usually find that happen when the PWM IC controller that runs these is also bad, holding one of them on and frying.

      Cheers, Wizard
      Last edited by Wizard; 12-29-2008, 08:58 PM.

      Comment

        #4
        Re: Melted Mosfet on HP Pavilion ZE4500

        How do you know burned chip is not an Op-Amp ??
        MOSFET was a guess.
        Mann-Made Global Warming.
        - We should be more concerned about the Intellectual Climate.
        -
        Be who you are and say what you feel, because those who mind don't matter and those who matter don't mind.
        - Dr Seuss
        -
        You can teach a man to fish and feed him for life, but if he can't handle sushi you must also teach him to cook.
        -

        Comment

          #5
          Re: Melted Mosfet on HP Pavilion ZE4500

          LM358D is available in same 2x4 pin package type as in photo.
          Mann-Made Global Warming.
          - We should be more concerned about the Intellectual Climate.
          -
          Be who you are and say what you feel, because those who mind don't matter and those who matter don't mind.
          - Dr Seuss
          -
          You can teach a man to fish and feed him for life, but if he can't handle sushi you must also teach him to cook.
          -

          Comment

            #6
            Re: Melted Mosfet on HP Pavilion ZE4500

            Hi Wizard and PCBONEZ

            I am convinced it is a Mosfet because it has four pin connected together on one side, and on the other one there is a pin alone (probably GATE) and 3 together.

            See the new attached pics, you can read the marking type.
            The marking on melted Mosfet was clearer before I cleaned the board, now only "31A" is still visible; part of the body was so burnt that fall away when I touched it, but the marking was readable.
            Another curios thing is the date code, 9435A, if I am correct, this components was produced in week 35 in 1994, ten years before the notebook was assembled. If this is right, this is an obsolete device and could explain why it is hard to find the datasheet.

            Originally posted by Wizard
            You will need to find another board that has the exact same IC part number and use it to cross to suitable subsititute and replace both to keep it matched.
            Well it will be hard to find another board, me and my brother repair PC just for hobby, we like to fix thing, so it is very low the opportunity to find a similar board.
            If we ran a shop or a PC business than we would see a lot of PC but doing it based on friend's "order passed by word of mouth" give us few chance.
            As you wrote "PWM IC controller that runs these is also bad, holding one of them on and frying" I think the Mosfet is not the only dead component.
            Unfortunately yesterday my brother was in a hurry, so we couldn't check the bottom side of the board so I don't know what was there.
            If the owner of the notebook will trash it, I keep it in the junk pile, maybe I can find something about it or I can take some components for other repairs.
            I don't think it is worth to bring it back to official assistance because they will charge a lot for this kind of problem AFAIK, this notebook is 5 years old.

            Thanks for your help
            Gianni
            Attached Files
            "In the confrontation between the stream and the rock, the stream always wins...Not through strength, but through persistence."
            H. J. Brown

            Comment

              #7
              Re: Melted Mosfet on HP Pavilion ZE4500

              Everyone, guy was using date code. :o

              The part number is NDS9435A, Fairchild have data sheet up on their website so you can pick out suitable substitute from junk boards and replace BOTH and try.

              Cheers, Wizard

              Comment

                #8
                Re: Melted Mosfet on HP Pavilion ZE4500

                That makes more sense.
                Only "P31A" string I could find at Fairchild was a TO-220 package.

                .
                Mann-Made Global Warming.
                - We should be more concerned about the Intellectual Climate.
                -
                Be who you are and say what you feel, because those who mind don't matter and those who matter don't mind.
                - Dr Seuss
                -
                You can teach a man to fish and feed him for life, but if he can't handle sushi you must also teach him to cook.
                -

                Comment

                  #9
                  Re: Melted Mosfet on HP Pavilion ZE4500

                  Thanks Wizard

                  I was so stupid to think the type was the first string and I didn't try to search for what I thought was the date. At least I identify correctly the manufacturer.
                  Thanks very much, now I can look for suitable replacement.

                  @ PCBONEZ: yes, I was only able to find a transistor with that marking but obviously it was the wrong match.
                  Thank you for trying.

                  Ciao
                  Gianni
                  "In the confrontation between the stream and the rock, the stream always wins...Not through strength, but through persistence."
                  H. J. Brown

                  Comment

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