MacBook Air M2 (820-02536) – Power Cycling Issue

[2informaticos]

Very likely board has been affected by corrosion in time, probably under some BGA chips.

Remove F5200 and check if C5252 voltage is stable.

 

[HeyWatchOutDude]

Without F5200 PPVBAT_AON_CHGR_REG is stable (12.26V)

 

[2informaticos]

So main power supply is discarded; resolder F5200 now.
Any fluctuation/spike on CHGR_A/BMON lines?

 

[HeyWatchOutDude]

No fluctuation/spike visible on CHGR_A/BMON lines.

Note: I measured at RD518 (CHGR_AMON) and RD528 (CHGR_BMON).

Diode values:
CHGR_AMON: 0.584
CHGR_BMON: 0.584

 

[2informaticos]

Check voltage and diode mode to ground on all buck outputs of U8100 and U7700.

Just in case, replace L8430.

 

[HeyWatchOutDude]

U8100:
- MPMU_BSTLQ_LX: 0.326 / 3.8V
- BUCK0_LX0: 0.091 / 0.6 - 1.0V
- BUCK0_LX1: 0.091 / 0.6 - 1.0V
- BUCK0_LX2: 0.091 / 0.6 - 1.0V
- BUCK0_LX3. 0.091 / 0.6 - 1.0V
- BUCK0_LX4: 0.091 / 0.6 - 1.0V
- BUCK1_LX0: 0.006 / 0V
- BUCK1_LX1: 0.006 / 0V
- BUCK1_LX2: 0.006 / 0V
- BUCK1_LX3: 0.006 / 0V
- BUCK1_LX4: 0.006 / 0V
- BUCK2_LX0: 0.052 / 0.7 - 1.2V
- BUCK2_LX1: 0.051 / 0.7 - 1.2V
- BUCK2_LX2: 0.051 / 0.7 - 1.2V
- BUCK2_LX3: 0.053 / 0.7 - 1.2V
- BUCK2_LX4: 0.051 / 0.7 - 1.2V
- BUCK3_LX: 0.250 / 1.8V
- BUCK4_LX0: 0.039 / 0.9 - 1.6V
- BUCK4_LX1: 0.039 / 0.9 - 1.6V
- BUCK4_LX2: 0.039 / 0.9 - 1.6V
- BUCK7_LX0: 0.253 / 1.0 - 1.5V
- BUCK7_LX1: 0.253 / 1.0 - 1.5V
- BUCK9_LX0: 0.255 / 0.6 - 1.1V
- BUCK9_LX1: 0.255 / 0.6 - 1.1V
- BUCK11_LX0: 0.237 / 1.0V
- BUCK11_LX1: 0.237 / 1.0V
- BUCK13_LX: 0.250 / 1.2V

U7700:
- BUCK5_LX0: 0.250 / 0.7 - 1.1V
- BUCK5_LX1: 0.250 / 0.7 - 1.1V
- BUCK6_LX: 0.391 / 2.6V
- BUCK8_LX0: 0.222 / 0.8 - 1.2V
- BUCK8_LX1: 0.222 / 0.8 - 1.2V
- BUCK8_LX2: 0.222 / 0.8 - 1.2V
- BUCK10_LX: 0.108 / 0.5V
- BUCK12_LX: 0.320 / 0.8 - 1.3V
- BUCK14_LX: 0.411 / 1.1 - 1.8V
- SPMU_BSTLQ_LX: 0.324 / 3.8V
- SPMU_AMUX_AY: 0.589 / 0V
- SPMU_AMUX_BY: 0.589 / 0V

Note:
- It initially rises to 1.0 V (for example BUCK0_LX0), then drops to about 0.6 V. I observed this behavior on all BUCK regulators that have more than one listed voltage level.
- L8430 looks fine and voltage is stable (3.8V), so it should be fine?

 

[2informaticos]

Is important voltage on boost side of L8430; which shoudn't be 3.8V...

 

[HeyWatchOutDude]

I have replaced L8430 with a known good one, still "MPMU_BSTLQ_LX" is at 3.8V.

Note:
- Measured both sides of L8430 on both sides 3.8V.

 

[2informaticos]

Check L7700 voltages too.
You can also try replacing it.

 

[HeyWatchOutDude]

Same behavior.

But why is 3.8V wrong I mean the input is 3.8V (PP3V8_AON), shouldn’t be the output the same?

 

[2informaticos]

These coils are for MPMU and SPMU boost converters.

 

[HeyWatchOutDude]

But why are they so low?

 

[2informaticos]

Corresponding boosters of M/SPMU don't start for some reason.
Not sure if these chips expect some commands from CPU, or should start by default.

 

[HeyWatchOutDude]

what should I check next?

Diode values of U8100/U7700 according to https://openboarddata.org/?a=showboardsolutions&bpath=laptops/apple/820-02536 are looking good.

 

[2informaticos]

Diode mode to ground on 3V8_AON power rail?

 

[HeyWatchOutDude]

0.328

 

[2informaticos]

Not too low probably, but compare with good board.
I got weird issues for 0.100-0.160 readings.

 

[HeyWatchOutDude]

Says the same:

OpenBoardData Project

And another logicboard (working) has the same readings, so 3V8 can’t be the issue. (I mean 3.8V is also present)

 

[2informaticos]

May have problems with the NANDs.
You can try to reball/replace.