HELP: Dell Latitude D620 Compal LA-2791 Rev 1.0 UMA not powering

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  • vettouch
    Senior Member
    • Sep 2020
    • 68
    • Nigeria

    #1

    HELP: Dell Latitude D620 Compal LA-2791 Rev 1.0 UMA not powering

    I traced what the fault of the motherboard could be and discovered that PU3 got hot (see attached schematic) when the power button was pressed. Boardview can be of immense help. I appreciate all candid assistance.
    Attached Files
  • Stevedb
    Stevedb
    • Feb 2018
    • 624
    • Belgium

    #2
    Re: HELP: Dell Latitude D620 Compal LA-2791 Rev 1.0 UMA not powering

    If Pu3 get hot then you must check if it outputs are not shorted ld03 , ld05

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    • vettouch
      Senior Member
      • Sep 2020
      • 68
      • Nigeria

      #3
      Re: HELP: Dell Latitude D620 Compal LA-2791 Rev 1.0 UMA not powering

      @Stevedb; I found 4.8v on presumably LDO5 or LDO3 because I don't know how find the exact pin numbers. Also, somewhere on one of the PU3 pins, I measured 3.2v. What can I suspect?

      Comment

      • SMDFlea
        Super Moderator
        • Jan 2018
        • 20705
        • UK

        #4
        Re: HELP: Dell Latitude D620 Compal LA-2791 Rev 1.0 UMA not powering

        Originally posted by vettouch
        @Stevedb; I found 4.8v on presumably LDO5 or LDO3 because I don't know how find the exact pin numbers. Also, somewhere on one of the PU3 pins, I measured 3.2v. What can I suspect?
        The PU3 chip will have a dot in one corner,that means pin 1 starts there. Count the pins counter clockwise

        Datasheet https://cdn.badcaps-static.com/pdfs/...f508d059dc.pdf
        Attached Files
        All donations to badcaps are welcome, click on this link to donate. Thanks to all supporters

        Comment

        • harshana
          Badcaps Veteran
          • Aug 2022
          • 207
          • Sri Lanka

          #5
          Re: HELP: Dell Latitude D620 Compal LA-2791 Rev 1.0 UMA not powering

          Originally posted by vettouch
          @Stevedb; I found 4.8v on presumably LDO5 or LDO3 because I don't know how find the exact pin numbers. Also, somewhere on one of the PU3 pins, I measured 3.2v. What can I suspect?
          You will see a dot on the chip. keep that dot on left bottom corner. then pins starting from that dot. left to right.

          Here I attached the order.

          Comment

          • vettouch
            Senior Member
            • Sep 2020
            • 68
            • Nigeria

            #6
            Re: HELP: Dell Latitude D620 Compal LA-2791 Rev 1.0 UMA not powering

            @SMDFlea & @harshana: I could not find any dot on the PU3. Instead, I discovered that there was a dot on the board signifying pin 1. In the course of my investigations on PU3, pins 7, 9 and few others before pin 14 shorted to ground. I also discovered that on the pins configuration image sent by SMDFlea, GND is on pin 23. I'm confused, someone please help me!

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