Asus Q502L does not boot up properly

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  • tibimakai
    Badcaps Legend
    • Jan 2012
    • 3680
    • USA

    #41
    Re: Asus Q502L does not boot up properly

    Pretty cool this boardview software.
    It looks like, it is 0603 size, 120V/2A ferrite bead.

    Comment

    • tibimakai
      Badcaps Legend
      • Jan 2012
      • 3680
      • USA

      #42
      Re: Asus Q502L does not boot up properly

      PL8100 and PL8101 are oscillating.

      Comment

      • SMDFlea
        Super Moderator
        • Jan 2018
        • 20302
        • UK

        #43
        Re: Asus Q502L does not boot up properly

        PL8100 pin 1 goes to pin 8 of PU8100 . PL8101 goes to (amongst other parts) PU8100 pin 18,so they both have that in common, and pin 12 of PU8100 is connected to AC_BAT_SYS ,pin 1 L4510 the inductor ! . Heres a datasheet for PU8100 https://cdn.badcaps-static.com/pdfs/...bc7e0fa746.pdf
        Last edited by SMDFlea; 07-09-2018, 02:24 PM.
        All donations to badcaps are welcome, click on this link to donate. Thanks to all supporters

        Comment

        • tibimakai
          Badcaps Legend
          • Jan 2012
          • 3680
          • USA

          #44
          Re: Asus Q502L does not boot up properly

          The display is not connected, though. I work only on the motherboard, everything else is disconnected, except for the little board that contains the power on switch and a separate board, that has the LEDs on it.

          Comment

          • SMDFlea
            Super Moderator
            • Jan 2018
            • 20302
            • UK

            #45
            Re: Asus Q502L does not boot up properly

            You said 2 of the LVDS pins were bent,they could have been shorted and thats why L4510 got damaged, and it could have damaged PU8100. Check PU8100 voltage , pins 3,8,13,18
            All donations to badcaps are welcome, click on this link to donate. Thanks to all supporters

            Comment

            • tibimakai
              Badcaps Legend
              • Jan 2012
              • 3680
              • USA

              #46
              Re: Asus Q502L does not boot up properly

              I have forgot that the battery it was still plugged in, and when I have removed the connector, I have seen a spark coming from the L4510.
              This is not the initial fault. This did not change anything. The laptop, it was doing the same thing, before as well.
              What I don't understand, why after the BIOS re-flash, the laptop is not doing what did before?
              It used to spin up the fan(RPM was changing up and down, than settled at high RPM, the power LED it was on, charging LED it was on, when it was plugged in, now it is different).
              I will take those measurements, later on.

              Comment

              • SMDFlea
                Super Moderator
                • Jan 2018
                • 20302
                • UK

                #47
                Re: Asus Q502L does not boot up properly

                "RPM was changing up and down, than settled at high RPM" That can be the ME area of the bios. The new bios from @cacla has clean ME firmware . Don`t connect the LVDS cable until you replace L4510 and find out why PL8100,PL8101 are oscillating.
                All donations to badcaps are welcome, click on this link to donate. Thanks to all supporters

                Comment

                • tibimakai
                  Badcaps Legend
                  • Jan 2012
                  • 3680
                  • USA

                  #48
                  Re: Asus Q502L does not boot up properly

                  Sounds good.

                  Comment

                  • tibimakai
                    Badcaps Legend
                    • Jan 2012
                    • 3680
                    • USA

                    #49
                    Re: Asus Q502L does not boot up properly

                    OK, I'm back.
                    Pin #3= 3 - 3.3V
                    Pin #8= 0.19V - 3.3V
                    Pin #13= 3.4V - 5V
                    Pin #18= 0.06V - 3.5V - 5V (stops at each voltage)
                    Later, I will investigate more, because I have felt something pretty hot in that area.

                    Comment

                    • tibimakai
                      Badcaps Legend
                      • Jan 2012
                      • 3680
                      • USA

                      #50
                      Re: Asus Q502L does not boot up properly

                      PU8100 is the one, that gets very hot. Almost burned my finger.
                      I did the alcohol test, and PU8100 was the first part that dissipated first the alcohol.
                      I have measured the other parts around it, and none of them were shorted.
                      I should order a new one, right?

                      Comment

                      • SMDFlea
                        Super Moderator
                        • Jan 2018
                        • 20302
                        • UK

                        #51
                        Re: Asus Q502L does not boot up properly

                        Yes, order a new one .TPS51285BRUKR . also the ferrite bead. 0603 ,120 Ohms ,2A
                        Last edited by SMDFlea; 07-11-2018, 11:22 AM.
                        All donations to badcaps are welcome, click on this link to donate. Thanks to all supporters

                        Comment

                        • tibimakai
                          Badcaps Legend
                          • Jan 2012
                          • 3680
                          • USA

                          #52
                          Re: Asus Q502L does not boot up properly

                          Placed the order already. Thanks

                          Comment

                          • santytk
                            New Member
                            • May 2016
                            • 2
                            • peru

                            #53
                            Re: Asus Q502L does not boot up properly

                            Originally posted by smdflea
                            are you using a clip to read the bios,or have you desoldered it. Is your tl866 software up to date, and what part number is the bios .
                            prueba esto
                            Attached Files

                            Comment

                            • tibimakai
                              Badcaps Legend
                              • Jan 2012
                              • 3680
                              • USA

                              #54
                              Re: Asus Q502L does not boot up properly

                              Thanks for that.
                              The BIOS chip, it was removed and programmed with TL866A.
                              I have tried 209 and 206, with no difference.
                              I have voltage issues, the PWM IC is bad.
                              Right now, I'm fighting with this IC. I can't solder it to the board properly.
                              My smallest solder tip, is 1.2MM and won't reach into the corner, where the pins are.
                              Hot air station solders it, but I see some pins, that are still not soldered.
                              I have ordered a new tip from Digikey. I will try with that as well, when arrives.
                              Last edited by tibimakai; 07-16-2018, 12:04 PM.

                              Comment

                              • tibimakai
                                Badcaps Legend
                                • Jan 2012
                                • 3680
                                • USA

                                #55
                                Re: Asus Q502L does not boot up properly

                                OK, I have soldered in the new IC, but still the same oscillating 3V & 5V. IC still gets hot. 19V is stable.
                                LEDs are not turning on anymore, either.
                                PC8106 shows 0.31 Ohm.

                                Comment

                                • tibimakai
                                  Badcaps Legend
                                  • Jan 2012
                                  • 3680
                                  • USA

                                  #56
                                  Re: Asus Q502L does not boot up properly

                                  Anybody?

                                  Comment

                                  • caspian
                                    Badcaps Legend
                                    • Oct 2015
                                    • 1589
                                    • Laptop

                                    #57
                                    Re: Asus Q502L does not boot up properly

                                    Do not turn the laptop on in this situation, until the circuit gets fixed, to avoid PU8100 being burned.
                                    how did the fan behave the last time you turned the laptop on?
                                    how much resistance is on PL8100 and PL8101 relative to ground?

                                    turn the laptop on for a second and measure voltage on pin7 of PU8100 to see whether it goes high or not.
                                    Last edited by caspian; 07-20-2018, 11:22 AM.

                                    Comment

                                    • tibimakai
                                      Badcaps Legend
                                      • Jan 2012
                                      • 3680
                                      • USA

                                      #58
                                      Re: Asus Q502L does not boot up properly

                                      Initially, I have started with BIOS reflash.
                                      By replacing the BIOS, the behaviour of the laptop has changed.
                                      It used to turn on, with POWER LED on, if I have plugged in the charger, the CHARGING LED was on and the fan was spinning slow than fast, than slow and than fast again a couple of times. It would turn off and start all over again.
                                      It's like it was trying to start a couple of times, that it was shutting off.
                                      After the BIOS reflash, it seems dead.
                                      The POWER LED it was blinking, instead of the fan spinning. Like what the fan used to do, now the LED was doing it. Fan not spinning anymore.
                                      I have tried different BIOS and now it is all dead. PWM IC very hot, 3V and 5V coils are warm, capacitors next to them as well.
                                      1.8V is not present, initially it was present.
                                      As I mentioned before, in the beginning I have removed the LCD connector and one of the ferrite beads sparked(cracked) L4510. I have forgot, that the battery it was still connected.
                                      I'm not sure, how much affected the laptop. I may have caused more problems, than thought initially. Though the laptop, it was acting the same way as before. Like nothing happened.
                                      I will take those measurements later on.
                                      Thank you for trying to help. I appreciate it a lot.

                                      Comment

                                      • tibimakai
                                        Badcaps Legend
                                        • Jan 2012
                                        • 3680
                                        • USA

                                        #59
                                        Re: Asus Q502L does not boot up properly

                                        You may be wondering, why did I mess with the BIOS. I'm a beginner in laptop repair.
                                        I have measured some voltages and it seemed like, a lot of voltages were present(1V, 1.5V, 1.8V, 3V, 5V, 19V), so I assumed, that it could be a bad BIOS.

                                        Comment

                                        • caspian
                                          Badcaps Legend
                                          • Oct 2015
                                          • 1589
                                          • Laptop

                                          #60
                                          Re: Asus Q502L does not boot up properly

                                          since there are multiple problems in this laptop, it takes time to fix. however, I think the probability of a successful repair is high if you have some required ICs.

                                          Comment

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