Macbook Air 820-3437 ONE sec fan spin after repair


One of my coworkers has a Macbook air with liquid spill on Q7630 shorting PPBUS to PP1V05_S0.
The PPBUS line dropped from 8V to 2.9V since the shorted line pulled a lot of amperage.
He has managed to replace Q7630 Mosfet with an new one but now the board behaves as follows:

- As soon he connects the charger, he gets a green light (then it turns orange) and he expects the fan turns on-off-on-off-on-off-on but after the fan turns for a sec nothing happens further.
I would say it is a quarter fan spin but it stays on for too long.
In this one second he measured all the S0 Rails one by one and all of them are present.
He tried to boot with SMC bypass method but he get the same behavior expect the fan spun at 100%

Furthermore the board managed to boot once completely and he could use the OS normally... but after reboot he had the same behavior as before!

So this is what I know at the moment. I will take a look on the board by myself after the weekend.
I told him first to check the current sense lines ....
Have you any other ideas where to look at?



Staff member
This could be anything and will be a nightmare. Did he replace U7600 after replacing Q7630? Shorted Q7630 can kill U7600.


If it booted once the chances are high there is some corrosion somewhere else. Does ALL_SYS_PWRGD come high? If yes then check corrosion in U1950 area, pin 8 is famous for being gone.