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HP 460 G4 boot loop restart

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    #1

    HP 460 G4 boot loop restart

    Hello,

    I have HP 450 G4 laptop with DA0X83MB6H0 motherboard that is stuck at boot loop restart.
    When powering ON, firste there is a dealy about 10 sec before showing HP logo and then after 15 to 20 sec it restarts itself.

    If I try to enter BIOS (with F10) or Sys diagnostic (F2) there is a message "Entering Setup" or "Entering diagnostic" and after 20 sec restart.
    I have tried with different BIOS dumps, exchange RAM modules remove/short CMOS battery and many more, but it didn't change behavior.

    Keyboard is working since it detects function keys. If I place another RAM module, after first power ON I can see a message "Amount of RAM changed", and that stays for about 20 sec and new restart.

    So basically, it is stuck at boot loop before it is possible to enter BIOS settings.

    There is a problem on the board, but don't know from where to start. Did you have any similar experience?

    Thank you
    Last edited by Askic; 02-08-2021, 02:57 AM.
    Tags: None
    #2
    Re: HP 460 G4 boot loop restart

    Originally posted by Askic View Post
    Hello,

    I have HP 450 G4 laptop with DA0X83MB6H0 motherboard that is stuck at boot loop restart.
    When powering ON, firste there is a dealy about 10 sec before showing HP logo and then after 15 to 20 sec it restarts itself.

    If I try to enter BIOS (with F10) or Sys diagnostic (F2) there is a message "Entering Setup" or "Entering diagnostic" and after 20 sec restart.
    I have tried with different BIOS dumps, exchange RAM modules remove/short CMOS battery and many more, but it didn't change behavior.

    Keyboard is working since it detects function keys. If I place another RAM module, after first power ON I can see a message "Amount of RAM changed", and that stays for about 20 sec and new restart.

    So basically, it is stuck at boot loop before it is possible to enter BIOS settings.

    There is a problem on the bopard, but don't know from where to start. Did you have any similar experience?

    Thank you
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    Comment

      #3
      Re: HP 460 G4 boot loop restart

      I'm almost certain this is not a bios issue. I have the same board which works and I even solder its BIOS chip but it behaves the same. I even swap the BIOS chips. The issue is something with the motherboard.

      For example when measuring resistance against the ground on PL22 it is 4 ohms, while the same resistance on the correct one is about 11 ohms.
      Interesting, I cannot measure any voltage on this coil on both boards, but one board works fine.

      The only difference I could find so far it this resistance, but it is expected to be low, since it is CPU area.
      Attached Files

      Comment

        #4
        Re: HP 460 G4 boot loop restart

        Try replacing PC262/276/279

        Comment

          #5
          Re: HP 460 G4 boot loop restart

          Originally posted by mcplslg123 View Post
          Try replacing PC262/276/279
          Those are big electrolytic caps. Do you suspect that their resistance has changed?
          What DC voltage on this PL22/ caps is to be expected, 0.9V??
          Last edited by Askic; 02-08-2021, 11:58 AM.

          Comment

            #6
            Re: HP 460 G4 boot loop restart

            Here is that part of the power supply in which I cannot measure any voltage. I can measure VIN to be 19.5V. Without power, resistance between Drain and Source of PQ10 low side MOSFET. I have taken it out and between pins there is still 4 ohms and PQ10 is good.

            I would normally expect to measure here around 1 V, but there is nothing there. I must say, that this is probably not the issue because I have picture on the screen and HP logo for about 20 sec.
            Attached Files

            Comment

              #7
              Re: HP 460 G4 boot loop restart

              You know you can't just swap SPI ROM between boards because ME region is paired with the PCH right?
              OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

              Comment

                #8
                Re: HP 460 G4 boot loop restart

                Originally posted by piernov View Post
                You know you can't just swap SPI ROM between boards because ME region is paired with the PCH right?
                yes and I wrote in the first post that I have tried different BIOS dumps. I even used cleaned BIOS dumps from one forum. However, I’m really not sure why behaviour is like that to restart laptop after 20 sec. When different ME region laptop usually works very slow, but not restart after the same time period. It detects function key F10 and there is a message Entering Setup... and after that new restart.

                Do you think that problem is likely related to BIOS/SPI ROM issue than hardware? I must admit I have never had this behaviour.
                I know these are typical symptoms of mismatch Between ME region in BIOS software and PCH:
                1. If ME Region Get Corrupted In Most Cases The System Will Start At Least, But Not Total Dead.
                2. Fan Spinning At 100% Full Speed.
                3. Random Shutdow at Regular Interval ( Say 1min, 30min, even 1 Hours…).
                4. When Facing Problem With Reboot Seems ME Region May Corrupted.
                5. Corrupted ME Region May Cause Hanging Problem.
                6. Somtimes Corrupted ME Region May Cause Spalsh Screen.
                7. Corrupted ME Region May Cause Slow Down System Performence.


                So there is a reboot/shutdown at regular intervals, but in all cases so far, I could at least enter setup or no start computer at all.
                Last edited by Askic; 02-08-2021, 02:46 PM.

                Comment

                  #9
                  Re: HP 460 G4 boot loop restart

                  I was referring to:
                  When powering ON, firste there is a dealy about 10 sec before showing HP logo
                  and
                  I even swap the BIOS chips.
                  OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

                  Comment

                    #10
                    Re: HP 460 G4 boot loop restart

                    Originally posted by Askic View Post
                    Those are big electrolytic caps. Do you suspect that their resistance has changed?
                    What DC voltage on this PL22/ caps is to be expected, 0.9V??
                    Yes , 0.9V seems ok to me. Electrolyte caps loose their capacitance over time-thats why try replacing them.
                    Last edited by mcplslg123; 02-08-2021, 11:00 PM.

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