820-02536 (A2681) - Stuck at 5V

[HeyWatchOutDude]

Hi,

I have a MacBook Air M2 (13” / 820-02536 / A2681) that is stuck at 5V.

It had water damage in the following areas:

• F5200 was blown and has been replaced.
• R8450 (pin 1 / PPBUS_AON): the pad was missing. After restoring the pad, PPBUS_AON could not be measured there for some reason, so I ran a wire from F5200 (pin 2 / PPBUS_AON) to R8450 (pin 1). PPBUS_AON can now be measured there and at RD531/XWD530 (pin 1).
  
  
  
  
• PPVBAT_AON_CONN was shorted to ground; the short has been removed and now measures 1.106 in diode mode.

Notes:

• PPBUS_AON is not stable. When F5200 is removed, PPVBAT_AON_CHGR_REG is stable.
• U5200 has already been replaced, with the same behavior.

What should I check next?

 

[2informaticos]

Both R8450/1 have correct ohm value?
Check U8450 output voltage also.

 

[HeyWatchOutDude]

R8450 = 887kOhm
R8451 = 453kOhm
PBUS_DIV = 3.6-4V (not stable)
PBUS_DIV_SNS = 3.5-3.7V (not stable)
PP3V8_AON = 3.5-3.7V (not stable)

 

[2informaticos]

Possibly more liquid damage on secondary power rails, or other sensors.

What about M/SPMU LDOs?
Compare diode mode readings with good board.

Did you test with charged battery?

 

[HeyWatchOutDude]

With battery connected I just get an apple logo (without progress bar).

It jumps up to 20V.

Already tried to get it into DFU, doesnt work. (even with FORCE method)

 

[2informaticos]

Stuck on apple logo, or goes black/off?

 

[HeyWatchOutDude]

I only get 20V when I press hard on the battery connector.

I will replace it and try again.

Note: Multiple layer damage on that spot, had to remove multiple layers to get rid of the dead short on PPVBAT_AON_CONN