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Dell Laptop Inspiron 13 5379 shuts down at start up

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    #1

    Dell Laptop Inspiron 13 5379 shuts down at start up

    Anyone here specialized in Dell Laptop Inspiron 13 5379 ?

    I'm working on a laptop that when powered on , shuts down after 5 seconds and repeats this each time it's powered up. You can hear the HD spinning until the lap shuts down. The fan doesn't spin at all. VCC_CORE , +VCCGT , + VCCSA remain 0V and PWM's at pin 4 PU4701, PU4702 , PU4801 (NCP81382) is 2.0V (Mid state) for 5 seconds at power on and drop to 0V and PWM at pin 2 PU5001 (NCP81253) remains 0V. What I noticed is that CPU pin E32 line which is VCC_SENSE connected to pin 47 from PU4601 (NCP81218) measures 3.5R to GND and if I split the line the short remains at CPU side. Can I conclude that CPU has a short ? Need to figure this out because a new mb is about $350. Thank you.

    Numbers on motherboard :
    DP/N
    00KJ0J
    cn-00kj0j-wsc00-7aj-12bc-a00
    MO : 28852572 Ver : 1C
    P/N : 4550CF010003
    Tags: None
    #2
    Re: Dell Laptop Inspiron 13 5379 shuts down at start up

    up-lode the schematic & check all coils resistance to GND , 3/5ALWS & 3/5VS voltages are OK or not ?

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      #3
      Re: Dell Laptop Inspiron 13 5379 shuts down at start up

      Originally posted by techtiger View Post
      up-lode the schematic & check all coils resistance to GND , 3/5ALWS & 3/5VS voltages are OK or not ?
      Thank you for your reply.
      All voltages measure good except to those I mentioned.
      In the uploaded file you can see the comments and measurements done.
      Attached Files

      Comment

        #4
        Re: Dell Laptop Inspiron 13 5379 shuts down at start up

        Good work on the comments and measurements , what is the resistance to GND on 3D3V_S0 5V_S0 line ? check all coils resistance to GND example PL5001 ect
        Last edited by Techtiger; 10-21-2020, 03:17 AM.

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          #5
          Re: Dell Laptop Inspiron 13 5379 shuts down at start up

          Thank you for the compliments. Why I didn't bother to measure the impedance to GND is because 3D3V_S0 and 5V_S0 and other measured lines are up and precise for 5 seconds and if there is a short on them they would shut down within 1 or 2 sec.
          However VCC_CORE , +VCCGT and +VCCSA measure about 3 Ohms to GND.
          My question would be...Why does VCC_SENSE connected to pin 47 from PU4601 (NCP81218) measures 3.5R to GND, while if I compare it with the other 2 sense lines (VCCGT_SENSE and VCCSA_SENSE, which measure about 2.1K with diode test. I'm not familiar with this laptop but shouldn't the fan be spinning ?
          What else can be the problem, that prevents PU4601 (1x2x1 PWM NCP81218) from driving the power fets.
          Last edited by tttleaders; 10-22-2020, 02:08 AM.

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