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MacBook Air A1466 - No chime, no picture, fan spinning

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    #1

    MacBook Air A1466 - No chime, no picture, fan spinning

    Hello!
    I just got and MacBook Air A1466 EMC 2925 (820-00165-A) but it doesn't chime with not light on keyboard and black screen, just the fan spinning.
    I noticed something weird with the fan:
    - When the charger is connected, he powers up on his own (one time fan spining for 5 seconds, stops, then solid normal fan spining until I force the shutdown).
    - When I try to run the Mac on battery, he is just power cycling (fan spinning for 10-15 seconds and then stop before restarting again and so on).
    I already tried to refalshed the BIOS: nothing changed.

    Here are some measurements but I think everything is good here:

    PPBUS_G3H = 8.6v
    PP3V3_S5 = 3.359v
    PP5V_S5 = 5.13v
    PP3V3_SUS = 3.359v

    PCH_INTRUDER_L = 3.361v
    RTC_RESET_L = 3.353v
    PCH_SRTCRST_L = 3.353v
    PCH_INTVRMEN = 3.241v
    PCH_DSWVRMEN = 3.241v
    S5_PWRGD = 3.406v
    PM_DSW_PWRGD = 3.442v
    PM_BATLOW_L = 3.36v
    PM_RSMRST_L = 3.308v
    PM_PWRBTN_L = 1.017v
    SMC_ONOFF_L = 3.423v

    PP3V3_S4 = 3.356v
    PP5V_S4RS3 = 5.14v
    PP3V3_S3 = 3.36v
    PP1V8_S3 = 1.108v
    PP1V2_S3 = 1.213v
    PP5V_S3_RTUSB_A_F = 5.14v

    PP5V_S0 = 5.12v
    PP3V3_S0 = 3.358v
    PP1V05_S0 = 1v
    PP1V5_S0 = 1.522v

    P5VS4RS3_PGOOD = 3.357v
    P1V8S3_PGOOD = 3.355v
    DDRREG_PGOOD = 3.357v
    P1V05S0_PGOOD = 3.356v
    ALL_SYS_PWRGD = 3.355v

    CPU_VCCST_PWRGD = 1.032v
    CPU_VR_EN = 1.063v

    PPVCC_S0_CPU = 1.82v
    PP0V6_S0_DDRVTT = 0.610v

    CPU_VR_READY = 1.061v
    PM_S0_PGOOD = 3.442v
    PM_PCH_PWROK = 3.443v
    CPU_VIDALERT_L = 1.061v
    CPU_VIDSCLK = 1.061v
    CPU_VIDSOUT = 1.061v

    SMC_DELAYED_PWRGD = 3.439v
    PM_PCH_SYS_PWROK = 3.442v
    LPC_PWRDWN_L = 3.36v
    PLT_RESET_L = 3.36v
    PLT_RST_BUF_L = 1.038v

    EDP_PANEL_PWR = 0v

    SMC_LSOC_RST_L = 8.6v
    SMC_MANUAL_RST_L = 2.682v
    SMC_RESET_L = 3.4v
    PM_SYSRST_L = 3.308v
    CHGR_RST_L = 3.402v

    SMC_CPU_VSENSE = 1.818v
    SMC_P1V05S0_VSENSE = 1.066v
    PP1V05_SUS = 1.073v

    I don't have any ideas on what to check next...
    Any ideas?

    Ps: Sorry in advance if my english is bad (I am trying to get better at it)
    Tags: None
    #2
    Re: MacBook Air A1466 - No chime, no picture, fan spinning

    Originally posted by j.bisous View Post
    PLT_RST_BUF_L = 1.038v
    Something wrong here. Remove R2088 then R2072 and see if it comes back up to 3.3V.
    OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

    Comment

      #3
      Re: MacBook Air A1466 - No chime, no picture, fan spinning

      Originally posted by piernov View Post
      Something wrong here. Remove R2088 then R2072 and see if it comes back up to 3.3V.
      Thanks for fast reply.

      I checked again of PLT_RST_BUF_L's value. I put wrong value here sorry. I have 3.3V.

      Comment

        #4
        Re: MacBook Air A1466 - No chime, no picture, fan spinning

        Anyone have a solution? I also tried to put USB key, but no activity sign so far...

        Comment

          #5
          Re: MacBook Air A1466 - No chime, no picture, fan spinning

          Have you tried disconnecting the keyboard/trackpad (at motherboard), the screen connector, and the bridge cable to the LIO board to see if anything changes? Basically, anything that is not required to see power on the board. Make sure the battery is disconnected when pulling connectors.

          Comment

            #6
            Re: MacBook Air A1466 - No chime, no picture, fan spinning

            I tried to remove everything which was not required: still have the same issue...

            Comment

              #7
              Re: MacBook Air A1466 - No chime, no picture, fan spinning

              I believe it is unusual for the fan to start briefly, stop, then start again. I'm trying to remember if I have seen this before and the issue was the SMC. Is this a non-working board that you purchased or is it a complete MacBook Air? Another thing to look for is corrosion from liquid damage. Check your power rail chips to see if you are getting the enable signal and work back from there.

              Comment

                #8
                Re: MacBook Air A1466 - No chime, no picture, fan spinning

                I have a similar problem with the same board (820-00165-A). Charging works (LED is orange and becomes green when charge is complete).

                After powering on, fan starts and runs (does not stop). CPU heats up (and also Samsung SSD controller). But no sound, no video, no attempt to read USB flash drive - its LED blinks only briefly (USB initialization?), repeats about every 5 seconds.

                No damage to the board, no other component heats up. There seems to be no activity on the flash CS# pin (at least on analog scope).
                Last edited by Rainbow; 11-08-2021, 03:42 PM.

                Comment

                  #9
                  Re: MacBook Air A1466 - No chime, no picture, fan spinning

                  Originally posted by Rainbow View Post
                  I have a similar problem with the same board (820-00165-A). Charging works (LED is orange and becomes green when charge is complete).

                  After powering on, fan starts and runs (does not stop). CPU heats up (and also Samsung SSD controller). But no sound, no video, no attempt to read USB flash drive - its LED blinks only briefly (USB initialization?), repeats about every 5 seconds.

                  No damage to the board, no other component heats up. There seems to be no activity on the flash CS# pin (at least on analog scope).
                  Have you tried a know good BIOS? and are you trying it on it's own without anything connected to it (trackpad, wifi etc)

                  Also have you tried PRAM, sound might be disabled and finally try using ext monitor.

                  Comment

                    #10
                    Re: MacBook Air A1466 - No chime, no picture, fan spinning

                    I've disconnected everything, no change.
                    PRAM reset does not do anything.
                    Haven't tried another BIOS yet. I'm going to desolder flash and read it repatedly while lowering VCC to find weak bits.

                    Comment

                      #11
                      Re: MacBook Air A1466 - No chime, no picture, fan spinning

                      There are no weak bits. Tried "bin a1466 display NEW.zip" from here https://www.badcaps.net/forum/showthread.php?t=78905
                      There are not many differences compared to my original file so it's probably a correct one. But it does not even power up.

                      Comparing with 820-00165_cleanME_configured.zip on the same page, there is a huge diff. Haven't tried that.

                      Comment

                        #12
                        Re: MacBook Air A1466 - No chime, no picture, fan spinning

                        1) Are you testing without keyboard & without trackpad? If not, do so and check again.

                        2) Remove the SSD and test again. The SSD is not required to test the boot up of the logic board.

                        3) Are the voltages at every coil correct and holding while the logic board is on ?

                        Comment

                          #13
                          Re: MacBook Air A1466 - No chime, no picture, fan spinning

                          Only fan, battery and LCD connected. Powering up by shorting the PCB pads.

                          Flashed back the backup, now it turns on, fan runs (exactly like at the beginning).

                          Comment

                            #14
                            Re: MacBook Air A1466 - No chime, no picture, fan spinning

                            EDP_PANEL_PWR = 0v

                            This is not correct if the display is attached.

                            Check the display connector and cable for possible issues.

                            What is the resistance to ground for this power rail with lcd attached? No power while checking resistance.

                            Comment

                              #15
                              Re: MacBook Air A1466 - No chime, no picture, fan spinning

                              I've tried that BIN again (flash was probably not soldered correctly the first time?). Now it turns on the same way as with the original flash contents. Fan spins up, CPU heats up, fan accelerates to max. speed. And that's all. No power for the LCD.
                              The resistance is over 360Mohm.

                              Maybe the CPU is bad? The resistance between VCore coils and GND is 9 ohms. I know that low resistance is normal for CPUs but how low is OK?
                              Last edited by Rainbow; 11-20-2021, 11:32 AM.

                              Comment

                                #16
                                Re: MacBook Air A1466 - No chime, no picture, fan spinning

                                1) Voltage of PP3V3_S0SW_LCD_UF = Pins 18 & 19 on J8300 ?

                                2) Voltage of PPHV_S0SW_LCDBKLT = Pins 3 & 4 on J8300 ? Confirm same voltage @ D7701, cathode.

                                3) Voltage of PPVIN_S0SW_LCDBKLT = enable voltage for the backlight IC @ U7701?

                                4) Voltage of PPVIN_S0SW_LCDBKLTFET ?

                                5) Voltage of LCDBKLT_EN_DIV_L ?

                                Comment

                                  #17
                                  Re: MacBook Air A1466 - No chime, no picture, fan spinning

                                  1) 0v
                                  2) 0v
                                  3) 0v
                                  4) 7.88v
                                  5) 7.64v

                                  So the backlight is not enabled. Probably because the CPU is not working.
                                  Last edited by Rainbow; 11-20-2021, 03:03 PM.

                                  Comment

                                    #18
                                    Re: MacBook Air A1466 - No chime, no picture, fan spinning

                                    Can you confirm the following voltage rail from the first post? It is too low.

                                    PP1V8_S3 = 1.108v

                                    Comment

                                      #19
                                      Re: MacBook Air A1466 - No chime, no picture, fan spinning

                                      I'm not going to waste any more time on this.

                                      Comment

                                        #20
                                        Re: MacBook Air A1466 - No chime, no picture, fan spinning

                                        can someone help me?i have a macbook air A1466 emmc 3178.it has or had a bios password enabled. its not stolen .a frind buys starage lots at autions and he brings me all eltronics to go thru and fix. . I desolderd the bios chip went thru the steps to erase the password and in the process my cat fell asleep on my keyboard . so got togather and it will charge but no display no chime no fan . so i figured i the cat messed up somthgen because she managed to erase the orig bio bin. i njust need a lil advce where to go from here even if its just how to pull the serail number in bios with the hex so i can confirm.

                                        Comment

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