Hi everyone. Just a reminder I am not a professional repair technician, fixing Apple electronics is my hobby.
Recently got my hands on MacBook Pro A2289 with interesting behavior. Pristine condition, no water damage, no visual issues whatsoever. It has no image, no CapsLock, no life except the fan is spinning. But it is able to boot into DFU and recognized by another MacBook. I tried to revive and restore the laptop, but the process ends when the MacBook usually should show an Apple logo with a progress bar. I assume the main power lines and T2 are working. It seems like the Intel CPU part is not turning on, CPU does not get hot.
On the USB meter I got 20V/0.2A power draw, no looping. The fan is spinning. No image (I checked with a bright flash light), no sound, no CapsLock activity. Found similar case on repair wiki: https://old.repair.wiki/w/A2289_2020_13%22_MacBook_Pro. PP0v95_S0_CPUVCCIO_REG_R is not present (some millivolts instead of 0.95V). But this one does not match my case: "Check the PVCCIO_EN signal at R8165 - It should be present at 3.3v.". I got 1.8V instead on PVCCIO_EN line. Checked the schematic, PP3V3_S5 is present (3.3V). As far as I understand, the PVCCIO_EN signal is made by U7800.
It is possible that U7800 is bad, but I assume something else (voltage/signal) may be missing, before the PVCCIO_EN is made. So may be U7800 is not the cause of the problem? What for should I look next?
May be there is a power on sequence for A2289 model? Looking forward for your help.
Recently got my hands on MacBook Pro A2289 with interesting behavior. Pristine condition, no water damage, no visual issues whatsoever. It has no image, no CapsLock, no life except the fan is spinning. But it is able to boot into DFU and recognized by another MacBook. I tried to revive and restore the laptop, but the process ends when the MacBook usually should show an Apple logo with a progress bar. I assume the main power lines and T2 are working. It seems like the Intel CPU part is not turning on, CPU does not get hot.
On the USB meter I got 20V/0.2A power draw, no looping. The fan is spinning. No image (I checked with a bright flash light), no sound, no CapsLock activity. Found similar case on repair wiki: https://old.repair.wiki/w/A2289_2020_13%22_MacBook_Pro. PP0v95_S0_CPUVCCIO_REG_R is not present (some millivolts instead of 0.95V). But this one does not match my case: "Check the PVCCIO_EN signal at R8165 - It should be present at 3.3v.". I got 1.8V instead on PVCCIO_EN line. Checked the schematic, PP3V3_S5 is present (3.3V). As far as I understand, the PVCCIO_EN signal is made by U7800.
It is possible that U7800 is bad, but I assume something else (voltage/signal) may be missing, before the PVCCIO_EN is made. So may be U7800 is not the cause of the problem? What for should I look next?
May be there is a power on sequence for A2289 model? Looking forward for your help.
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