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    Asus A15HC shorted CPU voltage

    Hello everyone!!

    Problem with laptop Pegatron A15HE, has an Asus A15HC motherboard.
    Found boardview only, no schematic.

    First problem was a short on U8000(ISL95831) pin 38(PHASEG) TO GND.
    So i remove it and check Q8011 for any other short between GND or phase to ugate
    and found it ok. So i replace ISL95831 with a new one. Now after power on, ISL95831
    pin 38(PHASEG) and pin39(UGATEG) get shorted between them(not in relation to gnd), change it again and same thing happens AFTER the first power on. When i change it, measurements between pin 38 and pin 39, pin 38 to gnd, and pin 39 to gnd(with CPU removed) are ok. Short begins with the first power on. All other voltages from ISL95831
    are ok. Any ideas? Faulty CPU?

    Attach boardview and program for viewing it.
    Thanks
    Attached Files

    #2
    Re: Asus A15HC shorted CPU voltage

    hi
    when you change CPU Power IC it is better to change all 4 Mosfets too.
    At the same Time.

    Comment


      #3
      Re: Asus A15HC shorted CPU voltage

      Hello mielta, thanks for reply. Next think i'll do.

      Just measured again pin 38 and pin 39, now have 930 ohm resistance between them..strange..if power it up again, will be shorted if i measured again.

      Btw i measured resistance to GND of all pins with CPU removed..
      Low resistance at pins 4,5,6,10,19,45 is that ok?
      Attached Files

      Comment


        #4
        Re: Asus A15HC shorted CPU voltage

        The best way to determine if that sort of resistance is good or bad is to have a 20000 counts multimeter for better acuracy (but a 6000 will also do) and check a working board then note the results so you know what to expect next time. Or, maybe advice from someone who already found out the correct values.

        Comment


          #5
          Re: Asus A15HC shorted CPU voltage

          Hello VladG

          Check resistance of these pins on a working motherboard, different IC(ISL95836) ,different pin assigment but the same pin usage, and all are low resistance, so its normal..

          Any other ideas, anyone?
          Last edited by Nightwalker; 01-07-2018, 07:25 PM. Reason: typo

          Comment


            #6
            Re: Asus A15HC shorted CPU voltage

            Hello again

            Just receive and replace the three mosfets(Q8011,Q8012,Q8013) and also replace again U8000(ISL95831). Problem is the same, power it on, pwr led turns on for 2-3 seconds, turn off for 2-3 seconds and power on again for another loop. Nothing on lcd. After power removal pin 38 and pin 39 measured shorted and after a minute measured again and have 930 Ohm resistance.

            Any ideas before quit on this?

            Comment


              #7
              Re: Asus A15HC shorted CPU voltage

              fan spin or not ?

              Comment


                #8
                Re: Asus A15HC shorted CPU voltage

                It is shorted because probably of discharge circuitry. That is Normal. Check all your coils for resistance relative to ground.

                Comment


                  #9
                  Re: Asus A15HC shorted CPU voltage

                  @dellxps15
                  Fan is not spinning

                  @atsio
                  With CPU the 1st reading and without the 2nd
                  L8802 11 MOHM N22580991 10 MOHM
                  L8200 90 OHM 1.5VO 288 OHM
                  L8201 23 OHM 1.05VO 27 OHM
                  L8701 8 OHM VGA_CORE 8 OHM
                  L8004 9 OHM VGFX_CORE 1.1 MOHM
                  L8001 10 OHM VCORE 1.7 MOHM
                  L8002 10 OHM VCORE 1.7 MOHM
                  L8100 3 KOHM 3VO 3 KOHM
                  L8101 15 KOHM 5VO 15 KOHM

                  The only missing voltage is VGFX_CORE(the root of the problem, was shorted when laptop came, has a short on U8000(ISL95831) at pin 38(PHASEG) TO GND.

                  Thanks again

                  Comment


                    #10
                    Re: Asus A15HC shorted CPU voltage

                    5vs and 3vs voltages also present ? vs not the always...

                    Comment


                      #11
                      Re: Asus A15HC shorted CPU voltage

                      Yes, both voltages are present after power on!

                      Comment


                        #12
                        Re: Asus A15HC shorted CPU voltage

                        Which short? You write that L8004 is 9 Ohm, that is normal. What is the current drawn before shutting down?

                        Comment


                          #13
                          Re: Asus A15HC shorted CPU voltage

                          Was a short before changing the U8000(ISL95831) at first time i found the fault. Has zero ohms with and without CPU. But after U8000 replacement, was not shorted again ever since. I mean now its ok, 9 ohm with cpu, 1.1 Mohm without. Current goes to 1.17A and before shut off draw 1.15A

                          Comment


                            #14
                            Re: Asus A15HC shorted CPU voltage

                            Hello again

                            I also attach voltages of each pin when power is on(before shutting off and on loop)

                            Why pin 1 and pin 48 has low voltage, comparing with pin 12 and pin 13?
                            Maybe the reason for no VR2 output?
                            Attached Files

                            Comment


                              #15
                              Re: Asus A15HC shorted CPU voltage

                              Try another cpu and reprogram bios. Phase 1&2 output ok, pgood high, everything should be good with it.
                              Also PCH might be bad.
                              Attached Files

                              Comment


                                #16
                                Re: Asus A15HC shorted CPU voltage

                                Hello again

                                One year past and decide to start troubleshooting it again, finally the problem was from bad bios, i had test that before, read bios and verify commands was success, at hex editor was looking ok so i move on to this, but now after i reprogram it, as khaahk suggest, system is up and running
                                Thanks everyone for help, problem solved!!

                                Comment


                                  #17
                                  Re: Asus A15HC shorted CPU voltage

                                  Originally posted by Nightwalker View Post
                                  Hello again

                                  One year past and decide to start troubleshooting it again, finally the problem was from bad bios, i had test that before, read bios and verify commands was success, at hex editor was looking ok so i move on to this, but now after i reprogram it, as khaahk suggest, system is up and running
                                  Thanks everyone for help, problem solved!!
                                  Same problem with Asus X45A Rev.2.0 board, no GFX_CORE present. But i immediatelly flash the bios and the problem solved!!!

                                  Comment


                                    #18
                                    Re: Asus A15HC shorted CPU voltage

                                    Dear Nightwalker and kodox,
                                    Do your mainboards have graphics chip?

                                    Comment


                                      #19
                                      Re: Asus A15HC shorted CPU voltage

                                      Hello both of you! Another problem appears after windows 7 installation completes. Cannot see Nvidia GT520M in device manager, like it dosent exist. Flash another Bios for Casper with filename "CASPER A15HE(A15HC REV 2.1)nvida gpu MAIN" but problem is the same, no Nvidia device id. With Intel gpu drivers, i have a little distortion on screen, so troubleshooting is still in progress with this..any ideas?

                                      Comment


                                        #20
                                        Re: Asus A15HC shorted CPU voltage

                                        Does the GPU get warm without its heatsink?
                                        A photo of the screen distortion would help. Use another CPU to see whether the distortion gets removed.

                                        Comment

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