The previous owner said this MacBook was fallen from the table. I don't know if this was the reason of the malfunction. No visible damages.
I'll explain the history of the repair:
Original it started with 20V 900mA current, drops to 700 and ends with 660. CPU became hot. Every important tension was present as it should be.
Reballed CPU, no solution.
Wrote a file with clean ME into EFI chip, no solution. Sometimes while doing further measurements in cold condition I've got a backlight for a few seconds.
At a certain moment, out of the blue, PP1V2_S3_CPUDDR missing. This due a shorted to ground capacitor C1061.
Replaced, got backlight but no Apple logo. Reboots a few secs after backlight came up.
Reprogrammed original file into EFI. Apple logo a few secs after backlight, but laptop still seems to reboot every time.
When board is warm, no more backlight.
Reflowed PMIC and reballed SMC. Temperature rise has no more effect on behavior.
The reason of the restarts is a dropping PM_SYSRST_L line. It becomes low for 1/2sec. At this moment, Apple logo disappears.
What could be the reason for this reset line to become low? Searched days for this behavior. Hopefully someone could give me the long desired clue...
I'll explain the history of the repair:
Original it started with 20V 900mA current, drops to 700 and ends with 660. CPU became hot. Every important tension was present as it should be.
Reballed CPU, no solution.
Wrote a file with clean ME into EFI chip, no solution. Sometimes while doing further measurements in cold condition I've got a backlight for a few seconds.
At a certain moment, out of the blue, PP1V2_S3_CPUDDR missing. This due a shorted to ground capacitor C1061.
Replaced, got backlight but no Apple logo. Reboots a few secs after backlight came up.
Reprogrammed original file into EFI. Apple logo a few secs after backlight, but laptop still seems to reboot every time.
When board is warm, no more backlight.
Reflowed PMIC and reballed SMC. Temperature rise has no more effect on behavior.
The reason of the restarts is a dropping PM_SYSRST_L line. It becomes low for 1/2sec. At this moment, Apple logo disappears.
What could be the reason for this reset line to become low? Searched days for this behavior. Hopefully someone could give me the long desired clue...
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