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    Asus X421EA no longer starts

    Good morning
    I am encountering a problem on an Asus X421EA card which no longer starts; I checked the voltages, the 5v and 3vd are missing, has anyone encountered this problem, I have been looking for several hours without finding the source of the problem. Thank you!

    #2
    Start with voltage checks at the dcin power adapter connector. Next check the dcin mosfets that should follow this connector.

    Meter in dc volts mode @ 30v or higher.

    Check the voltage to ground of the first dcin mosfet with only the power adapter connected.

    Source (1-2-3) to ground.
    Gate (4) to ground.
    Drain (5-6-7-8) to ground.


    Post each measurement.

    Comment


      #3
      Thank you Monday2
      Could you be more specific about the components to measure?

      Comment


        #4
        PQ8901 pin 1 0v pin 2 0v pin 3 18,9v. PRS 8901 19v. PQ 8902 pin 1 et 2 0v, pin 3 0,223v

        Comment


          #5
          See attached - appears to be similar.

          Click image for larger version

Name:	power_path.png
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          Click image for larger version  Name:	charger.png Views:	0 Size:	139.8 KB ID:	3264265


          Click image for larger version  Name:	DC_in.png Views:	0 Size:	80.6 KB ID:	3264262

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            #6
            PCI8901 PIN 1 19V 0V PIN 2 PCE 8901 19V 0VPIN2

            Comment


              #7
              Remove all power. Meter in resistance mode.

              Measure the resistance across the PQ8901 mosfet:

              source & drain
              source & gate
              gate & drain


              Post each measurement. Checking to see if this DCin mosfet is leaky.

              Comment


                #8
                Thanks, I'll check that and let you know!

                Comment


                  #9
                  PQ8901 : PIN 1 ET 2 0V PIN 3 18,96V

                  Comment


                    #10
                    I will already change QM3056 and see if the current comes out! I will keep you informed, time to order the component! Many thanks

                    Comment


                      #11
                      Good morning
                      I'm still waiting for the components ordered, it's a very long time, thank you for your advice, I'll come back as soon as I receive the component

                      Comment


                        #12
                        Good morning
                        I just replaced PQ8901 without result, I took measurements on the PCR8903 diode there I found 21ohm and 0 which is normal, I removed several components to isolate the problem without result! Do you have any ideas?
                        Thank you for your suggestions.

                        Comment


                          #13
                          Re all the diagram that I found on the forum has points of difference with the broken x421ea r2.0 motherboard, some components are unknown, others do not correspond to the diagram, PC8915 PC8916 etc, do you have this diagram ? thank you

                          Comment


                          #14
                          Good morning
                          Which component makes the 3v, 5v and 3vs?X421EA THK!!

                          Comment


                            #15
                            Originally posted by Pasglop View Post
                            Good morning
                            Which component makes the 3v, 5v and 3vs?X421EA THK!!
                            Look for and post all part numbers for the QFN chips
                            All donations to badcaps are welcome, click on this link to donate. Thanks to all supporters

                            Comment


                              #16

                              Good morning Thank you for your interest in my problem, my problem is that the references on the boardview send me to components without references on the diagram, and sometimes the references are not found from the boardview on the diagram! From my previous question, are there other Asus X421EA diagrams? Thanks again

                              Comment


                                #17
                                I noted the references on the motherboard
                                -ALC3251
                                -9241H W021LF
                                -IT5125VG 128
                                -SV=7K
                                -Y038C 122
                                Thk you

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