HP DM1 netbook without 5v voltage

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  • JulioChuts
    Member
    • Nov 2022
    • 15
    • Brasil

    #1

    HP DM1 netbook without 5v voltage

    Hello, folks from badcaps. I'm coming here to ask for help because I'm facing a tough issue on my workbench.

    I received this HP DM1 netbook at my station, and it's not turning on, even though the charger light is on.

    After analyzing the circuit, I noticed that there was no 5V voltage. I started measuring the PWM, and eventually, I decided to replace it. I changed the PWM about 3 times, but still no luck. I also checked for shorts and even replaced the MOSFETs, but nothing worked.

    Could anyone lend me a hand? I'm feeling quite lost, to be honest.

    I'll leave some pictures and the circuit diagram here for anyone who wants to take a shot at it.

    The IC responsible for generating these 5V is PU8. I have 5V at LDO5, but when I check PL508, it's showing zero, and the LL1 output is also zero.

    MOD Edit: Schematic moved to new thread -> https://www.badcaps.net/forum/showthread.php?t=121299
    .
    Attached Files
    Last edited by SMDFlea; 07-17-2023, 06:58 AM.
  • mon2
    Badcaps Legend
    • Dec 2019
    • 14030
    • Canada

    #2
    Re: HP DM1 netbook without 5v voltage

    Remove all power. Meter in resistance mode.

    What is the exact resistance to ground at PL508?

    Comment

    • JulioChuts
      Member
      • Nov 2022
      • 15
      • Brasil

      #3
      Re: HP DM1 netbook without 5v voltage

      It's reading about 35.31 ohms, it's not exactly a short circuit.

      What I find strange is that when I apply voltage, the current goes up to 100 amps on the asymmetric power supply, and it starts to heat up. I've already replaced it about 3 times, as I mentioned before.
      Attached Files

      Comment

      • janocko
        Member
        • Nov 2015
        • 19
        • indonesia

        #4
        Re: HP DM1 netbook without 5v voltage

        You can check voltage PU8 at pin1 or entrip1, its to enable 5v alw. then compare with entrip2 (this is to enable 3v alw)

        Comment

        • JulioChuts
          Member
          • Nov 2022
          • 15
          • Brasil

          #5
          Re: (Good news) HP DM1 netbook without 5v voltage

          Hello everyone, just wanted to share the results with you.

          I want to thank "janocko" for the tip to check entrip1; indeed, it was without the enable voltage. After studying the schematic a bit, I realized that to generate this voltage, it required a signal from the PCH. Initially, I thought I might have to do reballing, but upon examining the PU8 datasheet, I found out that if I cut the trace connecting to the PCH, it was possible to activate the 5V voltage. So, that's what I did, and it started generating the 5V voltage. However, it still wouldn't power on, and I began to suspect that some voltage from the PCH was indeed necessary.

          Then, I noticed something amusing: the power button was lacking the 3V required to turn on the system. Testing the continuity, I saw that the trace was broken. With a gentle scraping of the trace and connecting my alligator clip to the ground, I touched that trace, and the notebook turned on. After that, I connected the screen to see if it generated an image, and it worked!

          It took a little effort, but it worked. Thank you so much EVERYONE for your help! :grupo:
          Attached Files

          Comment

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