820-01521 MacBook Air 2018 turns off while boot

[focus2k]

hi there,
got a spill damage MacBook Air 2018.
USB C IC replaced and cleaned the board.
everything looks fine now.

Macbook is booting and loading rescue data, but then while boot it turns off.
just load around 5% under the apple, fan spins high 1 second and then turns off.
same in target mode.
Hardwaretest runs normal and all fine.
Voltages and Rails are all there...
T2 Chip is recovered in DFU und up to date. SSD was detected before restore t2.

Any ideas?

[MobileXT]

Re: 820-01521 MacBook Air 2018 turns off while boot

check the current sensing resistors resistance, should be around 10ohms I think sorry I don't have the schematic in my hands right now.

[MobileXT]

Re: 820-01521 MacBook Air 2018 turns off while boot

check the current sensing resistors resistance, should be around 10ohms I think sorry I don't have the schematic in my hands right now.

Sorry I take that back is not 10 Ohms should be 1 Ohms R7021 and R7022

[mon2]

Re: 820-01521 MacBook Air 2018 turns off while boot

I think I have the schematic for the 820-01521. What parts of it do you need?

[focus2k]

Re: 820-01521 MacBook Air 2018 turns off while boot

booth resistors are 1.4 Ohms.

did anyone knows what happens in the first 5% of loading... Apple Hardware test is also fine. Maybe a Problem with bridgeOS ?

[focus2k]

Re: 820-01521 MacBook Air 2018 turns off while boot

With question mark folder the Mac stays on all the time

[focus2k]

Re: 820-01521 MacBook Air 2018 turns off while boot

That's all... what happens at this Point of Boot

[mon2]

Re: 820-01521 MacBook Air 2018 turns off while boot

try a PRAM reset - press the attached keys till the system reboots with another chime.

any improvement?

[focus2k]

Re: 820-01521 MacBook Air 2018 turns off while boot

tried many times...no change

[waakye]

Hi focus2k , I know it is a very old post but did you manage to solve this problem as I am experiencing the same.
Thanks in advance