Acer 7736z no power on, can't figure it out

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  • Th3_uN1Qu3
    Believe in
    • Jul 2010
    • 6031
    • Romania
    #1

    Acer 7736z no power on, can't figure it out

    Schematic here.

    I have this laptop which does not power on, nothing happens when i press the power button I have 3.3v and 5v standby, i am getting power to the KBC and BIOS, and the power button has 3.3v also. The button is good. I have not found any shorted parts, have checked all main rails.

    What i have noticed is that 3.3v and 5v main do not come up. S5_ENABLE going from KBC to U62 ISL62392 is at 0.39v and goes to 0v when the power button is pressed. I think it should be the other way round and it should go to 3.3v but it does not.

    Things i have tried: Flashing BIOS. Same behavior.
    Forcing enable to 3.3v standby. 3.3v standby drops to 2.2v or something, although i do not have high current (it's under 1mA) and the main power supply still does not power on.
    Replaced U62 with a new one. Same thing.
    Replaced KBC. Still the same.

    Measuring without power, S5_enable is not shorted so i do not understand why it does not go to 3.3v. I've run out of ideas on this one. Any help is welcome.
    Originally posted by PeteS in CA
    Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
    A working TV? How boring!
    Tags: None
    • ktmmotocross
      Boardkiller
      • Feb 2014
      • 3572
      • slovakia
      #2
      Re: Acer 7736z no power on, can't figure it out

      resistors around s5_enable/p.42/ signal have right resistance? diode D13 is ok?

        Comment

        • khaahk
          Badcaps Veteran
          • Dec 2013
          • 748
          • Estonia
          #3
          Re: Acer 7736z no power on, can't figure it out

          The word out there is that U58 gets shorted...

            Comment

            • Th3_uN1Qu3
              Believe in
              • Jul 2010
              • 6031
              • Romania
              #4
              Re: Acer 7736z no power on, can't figure it out

              All mosfets have been tested ok, no shorts. I'll try checking the resistors and diode D13 although i doubt i will find anything interesting.
              Originally posted by PeteS in CA
              Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
              A working TV? How boring!

                Comment

                • atsio
                  Badcaps Veteran
                  • Oct 2013
                  • 819
                  • Greece
                  #5
                  Re: Acer 7736z no power on, can't figure it out

                  Remove L27 and L28, supply current and check if anything draws current and what is getting hot. Main suspect is shorted vga.

                    Comment

                    • Th3_uN1Qu3
                      Believe in
                      • Jul 2010
                      • 6031
                      • Romania
                      #6
                      Re: Acer 7736z no power on, can't figure it out

                      This has onboard video. But i will try that before i put the thing back together and send it back.

                      This is from work (i made the mistake of going back to work) and my boss said the guy who brought it in keeps calling twice every day and he's already pissed off about that, so he'd rather have us give it back still broken, than being bothered continuously by phonecalls. I can understand that. It's happened before at the shop and it's annoying indeed. However, it's funny how this never happened with any of *my* customers.
                      Originally posted by PeteS in CA
                      Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
                      A working TV? How boring!

                        Comment

                        • Th3_uN1Qu3
                          Believe in
                          • Jul 2010
                          • 6031
                          • Romania
                          #7
                          Re: Acer 7736z no power on, can't figure it out

                          Removed coils and applied 3.3 and 5v from PC PSU, nothing getting hot and current consumption is low. I'm not bothering with this one anymore.
                          Originally posted by PeteS in CA
                          Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
                          A working TV? How boring!

                            Comment

                            • whaldsz
                              Badcaps Veteran
                              • Apr 2013
                              • 395
                              • Philippines
                              #8
                              Re: Acer 7736z no power on, can't figure it out

                              How about checking if ECRST# is 3.3v?

                                Comment

                                • zedameo
                                  Member
                                  • Jan 2019
                                  • 14
                                  • algeria
                                  #9
                                  Re: Acer 7736z no power on, can't figure it out

                                  thank you . it was it (U58)

                                    Comment

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