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ASUS ROG G751JM - self start and no VCORE and VGPU

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    ASUS ROG G751JM - self start and no VCORE and VGPU

    Hello.
    Today i have something special.

    Have this ASUS ROG G751JM that self start and no VCORE and VGPU

    attached readings and repair manual shows that PM_PWROK signals is missing
    later i make tabe from readings

    have anybody complete schematic for it?

    What can be wrong when it self start?
    Attached Files
    Last edited by ktmmotocross; 03-15-2019, 01:54 PM.

    #2
    Re: ASUS ROG G751JM - self start and no VCORE and VGPU

    from this table of measured voltages looks like it all started from missing 1.05VS_PWRGD signal. so tomorrow i start from it
    Attached Files

    Comment


      #3
      Re: ASUS ROG G751JM - self start and no VCORE and VGPU

      No schematics for newer Asus. Last one available is UX31A2 AFAIK.
      You're missing ALL_SYS_PWRGD so there's at least one S0 rail missing before VCore.

      You measure 0V on +1.05VS_PWRGD so the issue is probably there. With the boardview check the voltage on output, input and enable signal of the +1.05VS regulator. Then mesure the resistance to ground on output of the regulator.
      OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

      Comment


        #4
        Re: ASUS ROG G751JM - self start and no VCORE and VGPU

        have u guys anybody boardview for JM version? i have JY and it is completely differnet

        Comment


          #5
          Re: ASUS ROG G751JM - self start and no VCORE and VGPU

          find almost everything on sulalaptop

          Comment


            #6
            Re: ASUS ROG G751JM - self start and no VCORE and VGPU

            i have readings from U8200 and i have VIN and EN. but this TON looks like low to me. what do u thing after this reading?
            resistance on 1.05V line is 76ohm
            Attached Files
            Last edited by ktmmotocross; 03-16-2019, 06:48 AM.

            Comment


              #7
              Re: ASUS ROG G751JM - self start and no VCORE and VGPU

              I think TON is supposed to be somewhat low.
              The regulator got input voltage and enable signal, but doesn't start switching at all. It is probably bad.
              Do a visual inspection of the circuit around it to make sure the resistors aren't missing/damaged.
              OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

              Comment


                #8
                Re: ASUS ROG G751JM - self start and no VCORE and VGPU

                Originally posted by piernov View Post
                I think TON is supposed to be somewhat low.
                The regulator got input voltage and enable signal, but doesn't start switching at all. It is probably bad.
                Do a visual inspection of the circuit around it to make sure the resistors aren't missing/damaged.
                no missing or damged components find. try to find replacement for it

                Comment


                  #9
                  Re: ASUS ROG G751JM - self start and no VCORE and VGPU

                  no luck, dont have it on any board

                  anybody know intechange for RT8248A ?

                  Comment


                    #10
                    Re: ASUS ROG G751JM - self start and no VCORE and VGPU

                    Check resistence to the ground on JP2603 and JP2604?

                    Comment


                      #11
                      Re: ASUS ROG G751JM - self start and no VCORE and VGPU

                      96ohm

                      Comment


                        #12
                        Re: ASUS ROG G751JM - self start and no VCORE and VGPU

                        replaced that ic but no luck. still the same.

                        i noticed that on PJP8201 and PJP8202 which is rail for 1.05V is resistance 96ohm, but when i attach charger it goes to 0ohm. try to isolate short, but when i desolder both PJP i get 0ohm on both side of it

                        Comment


                          #13
                          Re: ASUS ROG G751JM - self start and no VCORE and VGPU

                          Check jumpers PJ8203 ,PJ8202 and resistors PR8255 ,PR8256 and others in that area .
                          Last edited by SMDFlea; 04-13-2019, 07:33 AM.
                          All donations to badcaps are welcome, click on this link to donate. Thanks to all supporters

                          Comment


                            #14
                            Re: ASUS ROG G751JM - self start and no VCORE and VGPU

                            do u have a schematic?

                            Comment


                              #15
                              Re: ASUS ROG G751JM - self start and no VCORE and VGPU

                              No, just boardview. PJ8203 and PJ8202 are interlayer,if you trace where they go you can see why you get 0ohm on both sides of PJP8201 and PJP8202
                              Last edited by SMDFlea; 04-14-2019, 03:43 AM.
                              All donations to badcaps are welcome, click on this link to donate. Thanks to all supporters

                              Comment


                                #16
                                Re: ASUS ROG G751JM - self start and no VCORE and VGPU

                                i get 0 ohm only with power so there must be some switched power rail from 1.05 that is shorted. but im confused that when i remove both PJ still both side is shorted

                                Comment


                                  #17
                                  Re: ASUS ROG G751JM - self start and no VCORE and VGPU

                                  What boardview software are you using ?
                                  All donations to badcaps are welcome, click on this link to donate. Thanks to all supporters

                                  Comment


                                    #18
                                    Re: ASUS ROG G751JM - self start and no VCORE and VGPU

                                    Originally posted by ktmmotocross View Post
                                    i get 0 ohm only with power so there must be some switched power rail from 1.05 that is shorted. but im confused that when i remove both PJ still both side is shorted
                                    I think the short is around PR8255 and PR8256. You can see how PJP8201 and PJP8202 are connected,what pins 1 and 2 have in common.
                                    Attached Files
                                    All donations to badcaps are welcome, click on this link to donate. Thanks to all supporters

                                    Comment


                                      #19
                                      Re: ASUS ROG G751JM - self start and no VCORE and VGPU

                                      You should not measure resistance with power applied. It will cause false readings.
                                      OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

                                      Comment


                                        #20
                                        Re: ASUS ROG G751JM - self start and no VCORE and VGPU

                                        Originally posted by piernov View Post
                                        You should not measure resistance with power applied. It will cause false readings.
                                        but without it i dont see problem. have enabled signal, vcc voltage, but no output with new chip

                                        Comment

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