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I fixed the board by taking a U7701 from a donor board and using that.
I can think of two reasons for my previous replacements not working;
1. bad soldering
2. bad IC's.
I think my soldering was fine; checked all sides under the microscope and could see no dodgy stuff. Also, my three...
update: I measured continuity from all 6 LED_RETURN resistors to the corresponding balls on U7701. Had to fix the board upright and use a very small probe point, but I got what I wanted to know.
Backlight stopped working. I replaced U7701 (again) and it worked, but again with the same dark...
Resistors are all measuring as 0-2 Ohms, connections from resistors to J8300 are fine.
I've replaced J8300; still have the same problem.
You mentioned I have bad voltage on two lines; which ones? I dont know what normal readings are for these rails and have no comparison (except older pro's...
This board came in with only slight corrosion on U7701 and no backlight. I replaced U7701 and got backlight back, but not completely. On the left half of the screen only half of the leds are on, resulting in a row of dark spots. I tried different screens first, but they show the same pattern...
PPBUS is 8.6V
battery LED is on
PP3V3_S5, PP3V3_S5_EN and P5VS4_PHASE are all constantly jumping around, cant get a proper measurement but they're certainly not ok.
CPUvcore is at 0V and not cycling.
Should I pack this thing back up or is there anything to check out?
Update on this one: the firmware update fixed the problem. Had to do it a couple of times and got an error about the thunderbolt cable, but it worked in the end. Laptop is booting and functioning fine now.