Asus Q502L does not boot up properly

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  • tibimakai
    Badcaps Legend
    • Jan 2012
    • 3680
    • USA

    #61
    Re: Asus Q502L does not boot up properly

    I'm committed to repair it. I will buy what is needed.
    The ferrite bead is already purchased, I just need to replace it.

    Comment

    • caspian
      Badcaps Legend
      • Oct 2015
      • 1589
      • Laptop

      #62
      Re: Asus Q502L does not boot up properly

      you need to do lots of measurements. first, start with Post58 when you will have free time.

      Comment

      • SMDFlea
        Super Moderator
        • Jan 2018
        • 20317
        • UK

        #63
        Re: Asus Q502L does not boot up properly

        Can you also test,with no power to the board PR8108,it should be 10K ohms and PQ8101 pin 4 ohms to gnd
        All donations to badcaps are welcome, click on this link to donate. Thanks to all supporters

        Comment

        • tibimakai
          Badcaps Legend
          • Jan 2012
          • 3680
          • USA

          #64
          Re: Asus Q502L does not boot up properly

          PL8100 is 450 Ohm and PL8101 it keeps changing, but it is around 16 kOhm, to GND.
          PR8108 it measures 9.38 KOhm.
          PQ8101 pin 4 to GND, measures: 134.6 kOhm.

          No problem measuring a lot, this is my hobby, fixing electronics. I have the equipment to do it, as well. Fluke 189, 87V.
          Usually, I repair Onkyo receivers. I used to repair LCD/LED TVs.
          Last edited by tibimakai; 07-21-2018, 02:18 PM.

          Comment

          • caspian
            Badcaps Legend
            • Oct 2015
            • 1589
            • Laptop

            #65
            Re: Asus Q502L does not boot up properly

            without the main battery, plug the AC adapter in but do not turn the laptop on. then, check whether PU8100 gets hot or not. In addition, measure voltage on PL8100 , PL8101 , and pin7 of PU8100. unplug the AC adapter ASAP if PU8100 is getting hot.

            Comment

            • tibimakai
              Badcaps Legend
              • Jan 2012
              • 3680
              • USA

              #66
              Re: Asus Q502L does not boot up properly

              The IC gets hot, when I plug in the AC.
              Before, it used to reboot over and over, with AC. With battery, only started once.
              PL8100 and PL8101 voltages are raising and dropping, since it is rebooting. The 5V(PL8101) does not reach 5V, only 3.9V.
              Last edited by tibimakai; 07-21-2018, 05:50 PM.

              Comment

              • tibimakai
                Badcaps Legend
                • Jan 2012
                • 3680
                • USA

                #67
                Re: Asus Q502L does not boot up properly

                Soon I will measure pin #7.

                Comment

                • caspian
                  Badcaps Legend
                  • Oct 2015
                  • 1589
                  • Laptop

                  #68
                  Re: Asus Q502L does not boot up properly

                  In addition, measure resistance on all pins of PU8100 and report if you find any pin with less than 1000 ohms.

                  Comment

                  • tibimakai
                    Badcaps Legend
                    • Jan 2012
                    • 3680
                    • USA

                    #69
                    Re: Asus Q502L does not boot up properly

                    I'm stopped, because I don't trust my soldering job, on the PWM.
                    I don't have a microscope and I can't be sure if it is soldered correctly.
                    Every time I try re-soldering, I'm getting different results. Now I have lost 3V(0.8V), 5V is only 0.8V, but nothing oscillates.

                    Comment

                    • mcplslg123
                      Badcaps Legend
                      • Jun 2015
                      • 7262
                      • india

                      #70
                      Re: Asus Q502L does not boot up properly

                      Originally posted by tibimakai
                      I'm stopped, because I don't trust my soldering job, on the PWM.
                      I don't have a microscope and I can't be sure if it is soldered correctly.
                      Every time I try re-soldering, I'm getting different results. Now I have lost 3V(0.8V), 5V is only 0.8V, but nothing oscillates.
                      It seems Either 3v or 5v(or both) lines are shorted. Might be 2 pins got connected while soldering or reading voltage.

                      Comment

                      • SMDFlea
                        Super Moderator
                        • Jan 2018
                        • 20317
                        • UK

                        #71
                        Re: Asus Q502L does not boot up properly

                        Soldering these small qfn chips without a microscope is very difficult,its 50/50 . USB microscopes are quite good,and cheap,the andonstar ones are ok.Its a good idea to find a few scrap boards and practice on those first,and theres lots of youtube videos

                        https://www.youtube.com/watch?v=mr1UVPsExiE

                        https://www.youtube.com/watch?v=c_Qt5CtUlqY
                        All donations to badcaps are welcome, click on this link to donate. Thanks to all supporters

                        Comment

                        • tibimakai
                          Badcaps Legend
                          • Jan 2012
                          • 3680
                          • USA

                          #72
                          Re: Asus Q502L does not boot up properly

                          I have a cheap Celestron microscope, but unfortunately I can use only to inspect with it. It doesn't have a proper stand.
                          The biggest problem now is, that I have ripped off, pin #9 trace. I will give it a try, with a thin wire, but ods don't look good, to be a successful repair.

                          Comment

                          • tibimakai
                            Badcaps Legend
                            • Jan 2012
                            • 3680
                            • USA

                            #73
                            Re: Asus Q502L does not boot up properly

                            I have managed to solder the IC back. Definitely, I have a shorted on the 5V rail.
                            I have measured all the FETs around the IC, and only only one shows short PQ8103, but after I have removed it, it measures good and short is still there.

                            Comment

                            • SMDFlea
                              Super Moderator
                              • Jan 2018
                              • 20317
                              • UK

                              #74
                              Re: Asus Q502L does not boot up properly

                              With PQ8103 removed which pin measures short.If its pin 4 remove PC8102 and check pin 4 again.If its pin 5 can you desolder the jumper at PJP8101, test if 5V is stable,and also measure without power ohms to gnd .
                              All donations to badcaps are welcome, click on this link to donate. Thanks to all supporters

                              Comment

                              • tibimakai
                                Badcaps Legend
                                • Jan 2012
                                • 3680
                                • USA

                                #75
                                Re: Asus Q502L does not boot up properly

                                I have re-soldered PQ8103, right after removing it.
                                Right now, pin 4 is not shorted. Pin 5 is shorted.
                                Pin 5, shows about 1.3 Ohm. Capacitor is not shorted. It shows 1nF(on PCB w/Fluke 189).
                                It seems like, the IC(TPS1285B) that I have just soldered in, it may be shorted?
                                Attached Files
                                Last edited by tibimakai; 08-06-2018, 09:41 PM.

                                Comment

                                • tibimakai
                                  Badcaps Legend
                                  • Jan 2012
                                  • 3680
                                  • USA

                                  #76
                                  Re: Asus Q502L does not boot up properly

                                  OK, I have managed to solder in, the PU8100 and I have low resistance on these three pins.
                                  Pin #14: 2.34 Ohm (+5V SUSO)
                                  Pin #15: 1.94 Ohm (P_5VSUS_DL_30)
                                  Pin #18: 2.32 Ohm (P_5VSUS_LX_30)

                                  Comment

                                  • SMDFlea
                                    Super Moderator
                                    • Jan 2018
                                    • 20317
                                    • UK

                                    #77
                                    Re: Asus Q502L does not boot up properly

                                    desolder the jumper at PJP8101, test if 5V is stable
                                    All donations to badcaps are welcome, click on this link to donate. Thanks to all supporters

                                    Comment

                                    • tibimakai
                                      Badcaps Legend
                                      • Jan 2012
                                      • 3680
                                      • USA

                                      #78
                                      Re: Asus Q502L does not boot up properly

                                      One one side, I measure 19.5V and on the other, only 3.55V.

                                      Comment

                                      • tibimakai
                                        Badcaps Legend
                                        • Jan 2012
                                        • 3680
                                        • USA

                                        #79
                                        Re: Asus Q502L does not boot up properly

                                        Where should I measure the 5V, at the coil?

                                        Comment

                                        • tibimakai
                                          Badcaps Legend
                                          • Jan 2012
                                          • 3680
                                          • USA

                                          #80
                                          Re: Asus Q502L does not boot up properly

                                          OK, I have de-soldered PJP8101 and at the 5V coil, I'm getting 0.055V. At 3V coil, I'm getting 0.017V.
                                          I have also noticed, that at Pin #3(PU8100) I have 2 Ohm, at capacitor PC8103).
                                          At 5V coil, I measure 76 Ohm.
                                          PU8100, is still getting very hot very fast. Should I order another one?

                                          Comment

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