Apple Macbook Pro A2442 / Board # 820-02098-A / Milk Spilled

[zeydullak]

Hi Guys,

We have a A2442 Macbook Pro that has milk damage on it. We removed the board, washed it and cleaned it using DI water, took pictures before washing process no to forget corroded locations. The board stays at 5V 0.11amps. There is a definitely a short on the PCB, maybe multiple of them. I need advise on how to proceed and identify the issues. Please advise what to check. Thank you.

regards,
Zack

 

[2informaticos]

What about PPBUS_AON and 3V8_AON?

 

[zeydullak]

My mistake. Here are the correct readings:

PPBUS_AON - 12.29vdc
3V8_AON - 3.8 vdc

 

[2informaticos]

Remove F5200/1 and check C5250 voltage.

 

[zeydullak]

We have 12.30vdc on C5250.

Previous reading are
PPBUS_AON - 12.29vdc
3V8_AON - 3.8 vdc

I think all good here. What to check next?

 

[2informaticos]

Which other voltages get on the MLB?

 

[zeydullak]

See other element measurements:
LF800 --> 0.985 mvdc
LN420/421/430 missing voltage
LN480/LC260 missing voltage
L5840 --> 3.8 VDC
L5820 --> 3.8 VDC
L5800 --> 3.8 VDC
L9420 --> missing voltage
C9211:1 --> 12.30 VDC
LP800 --> 40 mVDC
L9420/L9500 --> missing voltage
L5230 --> 1.2VDC
CR854:1 --> 12.30 VDC
CR805 --> 12.30 VDC
C5894:1 --> 3.8 VDC
C9220 --> 12.30 VDC
C5207 --> 5.2 VDC
C9205:1 --> missing voltage
CP802/803 --> 12 VDC

 

[2informaticos]

I was thinking about 3V3/5V_S2, U8100 and U7700 LDOs...

 

[zeydullak]

U7700
PP1V2_S2 --> missing power
PP3V3_S2 --> missing power
PP1V8_S2 --> missing power
PP5V_S2_MAIN --> missing
PP3V3_AON --> this power line is fluctuating on Siglent Multimeter. So it shows 3.3 goes to 2.6 and goes to zero and loops.

 

[zeydullak]

PPVIN_P3V8AON_ISNS --> missing power

 

[2informaticos]

You should check U8100 first; is the Main PMU...

 

[zeydullak]

See other element measurements:
U8100

VIN_LDOS:
PP3V8_AON_MPMU_ISNS --> 3.8 VDC

VLDOS:
PP3V3_S2 - missing power
PP1V8_S2SW_CLVR_VDDC1_LDO - missing power
PP3V3_AON - this power line is fluctuating on Siglent Multimeter. So it shows 3.3 goes to 2.6 and loops
PP1V8_AON -- 1.8 VDC
PP1V2_AON -- 1.2 VDC

 

[2informaticos]

Check diode mode to ground on the lines with missing voltage.
Compare readings with good board.

 

[zeydullak]

Why PP3V3_AON this line is comes and goes back?

 

[2informaticos]

Many secondary voltages (including M/SPMU LDOs) derive from 3V8_AON.
An overcurrent detected on any of them, can cause such behavior.

 

[zeydullak]

What is the most easy way to detect it? I have a working board, thermal camera, I can do voltage injection. Please advise best option?

Should I do diode to ground on all test points and compare where we have voltage drop?

 

[2informaticos]

Having good board for comparison, check in diode mode.