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    Asus Prime Z270-A shuts down

    Hi all,

    I started looking into motherboards repair after watching lots of videos on dicky96's channel. Thanks for your work!

    I have this Asus Prime Z270-A motherboard with the following symptoms: motherboard will turn on, then it executes its own tests, passes CPU and DRAM and then shuts down by itself. It is doing it no matter if memory module(s) are inserted or not. I checked for shorts, but I could not find any. I checked VCORE = 0.9V, but it shuts down itself very quick so really impossible to check for other voltages.

    I was reading on the web that this symptom might has something to do with a corrupted firmware. So I desoldered the flash chip 25Q128A and I tried to read it with CH341A programmer. But I can't read it, the chip does not return any ID (I cannot test my 1.8V adapter, I am not sure if it is working correctly or not; although I tested the programmer with another 3.3V chip and I get good results). Thus I assume it is faulty, I will try to order a new one.

    Also once the motherboard shuts down, I cannot power on again using the regular power button. I have to shut down the power supply from the button, then turn on power supply and then turn on motherboard from power button.

    If there are people more experienced with such symptoms, I would like to confirm the following:

    1. Should I assume that all voltages are there if the motherboard reaches its own tests, as it passes CPU_LED and DRAM_LED tests? (I have the repair guide for Z270-A but without boardview it is rather difficult to identify for signals).

    2. A faulty flash chip would shut down the motherboard? Or could be some other issues with the board.

    Thanks!

    #2
    Re: Asus Prime Z270-A shuts down

    Sounds like it's activating thermal shutdown or it shorts the PSU.
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      #3
      Re: Asus Prime Z270-A shuts down

      Ok, I did further tests. As I mentioned I removed the flash chip and now when powering the board, CPU fan spins a bit, then turns off and then turns again on and ... then no more shutdown.

      First I checked for any sign of shorts on USB connectors but there are none. Further from the power supply connector, I checked +12V, +3.3V and +5V and all are fine.

      Then I was able to measure some voltages: VCORE = 0.936 V. There are two other coils on the upper part of CPU and these have 1.097 V (not sure what are these for).

      I got some instructions (from another website) how to measure DDR4 voltages. And these are showing as follows:
      VDD - 76 = 1.209 V
      VTT - 77 = 0.597 V
      VREF - 145 = 0.604 V
      VDDSPD - 284 = 3.393 V
      VPP - 288 = 2.501 V

      I tested PCH chip, in one of the corner there is 3.3V (after removing the heat sink). I did not keep it long without heat sink, the chip becomes warm, not hot. The heat sink has a kind of rubber for heat transfer, this looks fine without wear.

      Also the CPU get warm, not hot. Thus I assume everything should be fine from CPU side, this gets supplied with the required voltages.

      Let me know if you have any other ideas.
      Attached Files

      Comment


        #4
        Re: Asus Prime Z270-A shuts down

        You'd better find the drawing of the motherboard.
        Find then signal named shutdown#
        It often controls then Temperature
        Remove the triode of this control signal

        Comment


          #5
          Re: Asus Prime Z270-A shuts down

          This should help you. It's not the same, but should be very similar.



          Check if you have a TPM header, if yes get a boot code debug card like TL611PRO on Ali, look for the last bootcode which is displayed before restart. This might narrow down the search.
          Sometimes there is only a place for the pinheader for TMP module, then you need to McGuyver a pin header there (deisolating the pads, drilling & soldering necessary).
          You may put the boot code card also into a PCIe x 1 slot, but it not always work there.

          Attached Files
          Last edited by DynaxSC; 05-14-2022, 10:28 AM.

          Comment


            #6
            Re: Asus Prime Z270-A shuts down

            as you had said, it shut down when it is doing ram checking. you should be checking on DRAM slots for missing voltages....or signal. If i am you, i clean up the ram slot first...

            also i check pcie x1 slot at a13 whether there is a 3.3v reset signal. this signal will only appear when all critical voltage appear.

            a damaged program in bios will shut down the system.

            Comment


              #7
              Re: Asus Prime Z270-A shuts down

              pin a11 should be the reset signal. I realise in your case, there could be 3 possible things happening.
              1) one of the chips when power up shorted.
              2) bios corrupted.
              3) PCH issue causing shutdown.

              Comment


                #8
                Re: Asus Prime Z270-A shuts down

                Try to boot only with one DRAM module, in all 4 slots one after the another.
                Try another RAM stick brand, sometimes some RAM's are not 100% compatible.
                If you manage to boot try to increase RAM Voltages, this might help if rams not fully supported.

                Comment


                  #9
                  Re: Asus Prime Z270-A shuts down

                  Hi all,

                  Thanks for your reply, I worked more on the board and here are my latest findings.

                  It seems that around the flash chip W25Q128A I am missing some resistors, the missing resistor pads are square and shows a bit of solder compared to others that are showing round and flat. These are shown F1R16 and F1R15 in the attached schematics which is coming from a Asus Prime Z390-A R1.02 board. These resistors are also showing with the same ID in the attached boardview Asus STRIX Z270E GAMING R1.02A.

                  I ordered some 0402 resistors for the moment, I am waiting for them to arrive. Once I have them I will try to install them.

                  I do not have a debug card, I ordered once from Aliexpress but it never arrived.

                  I will keep you posted when I have more news.
                  Attached Files

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