820-02100 M1 Pro Liquid damage

[prodigy83]

My reference only: TT10141

Board history: Coffee spill. Most damage was around UP800, U5000, and U9300.
Issue: Not powering up, USB-C meter shows 4.92v, drawing .95 amps.
Work performed: Replaced U5200, Q5820, R5215, R5216, CW194, CW187. I removed and placed back down UP800, U9300, Q5240.
PP3V8_AON_SPMU is at 2.85v
F5200/01 is 7.4v. When I had removed these, USB-C meter reads 5.14v and drawing no amps. PPVBAT_AON_CHGR_REG with both fuses still removed has a stable 12.3v.
When I plug in the computer, the thermal camera shows half of the processor is getting warm, and U8100 is getting hot. I did also reflow U8100.

 

[2informaticos]

Check voltage and diode mode to ground on U8100 and U7700 LDOs.

 

[prodigy83]

The filters are the LDO's?
U8100
PP3V8_AON_MPMU .070
PP1V2_S2 .284
MPMU_BUCK4_LX3 .069
MPMU_BUCK4_LX2 .069
MPMU_BUCK4_LX1 .068
MPMU_BUCK4_LX0 .068
MPMU_BUCK10_LX0 .147
MPMU_BUCK10_LX1 .147
MPMU_BUCK6_LX0 .452
MPMU_BUCK5_LX0 .272
MPMU_BUCK5_LX1 .274
MPMU_BUCK5_LX2 .273
MPMU_BUCK5_LX3 .273
MPMU_BUCK2_LX0 .433
MPMU_BUCK3_LX0 .343
MPMU_BUCK8_LX0 .284
MPMU_BUCK9_LX0 .245
MPMU_BUCK1_LX1 .327
MPMU_BUCK1_LX0 .327
MPMU_BUCK1_LX0 .231
MPMU_BUCK7_LX1 .231
MPMU_BUCK7_LX2 .232
MPMU_BUCK0_LX3 .208
MPMU_BUCK0_LX2 .208
MPMU_BUCK0_LX1 .208
MPMU_BUCK0_LX0 .208

U7700
SPMU_BUCK6_LX0 .217
SPMU_BUCK5_LX0 .066
SPMU_BUCK5_LX1 .066
SPMU_BUCK5_LX2 .066
SPMU_BUCK5_LX3 .066
SPMU_BUCK9_LX0 .446
SPMU_BUCK8_LX0 .259
SPMU_BUCK3_LX0 .259
SPMU_BUCK2_LX0 .325
SPMU_BUCK1_LX1.148
SPMU_BUCK1_LX0.148
SPMU_BUCK0_LX3 .221
SPMU_BUCK0_LX2 .221
SPMU_BUCK0_LX1 .221
SPMU_BUCK0_LX0 .221
SPMU_BUCK10_LX2 .103
SPMU_BUCK10_LX1 .103
SPMU_BUCK10_LX0 .103
SPMU_BUCK4_LX0 .086
SPMU_BUCK4_LX1 .086
SPMU_BUCK4_LX2 .086
SPMU_BUCK4_LX3 .086

 

[2informaticos]

Look better at pages 41 & 37; many VLDOx there...

 

[prodigy83]

Yes, I saw the LDO's at the bottom of page 37 for chip U7700, but when I click on PP1V2_S2_SPMU for example, it goes no where as opposed when I click on PP3V8_AON_SPMU, it highlights all the capacitors around U7700. It doesn't appear openboard.org has this data either when I looked at a few.

U7700
PP3V8_AON_SPMU .070 this is off.
PP1V5_AON_VCORE_SPMU .383

U8100
PP3V8_AON_MPMU .070 is off
PP1V5_AON_VCORE_MPMU .382 No data on openboard.org.

 

[2informaticos]

Did you check the voltage too?

 

[prodigy83]

U7700
PP3V8_AON_SPMU 2.86v
PP1V5_AON_VCORE_SPMU 1.1v

U8100
PP3V8_AON_MPMU .070 2.87v
PP1V5_AON_VCORE_MPMU .382 1.10v

 

[2informaticos]

Seems to have problems on 3V8_AON power rail.

 

[prodigy83]

How do I narrow it down? What are some possibilites? Should I Inject voltage even though it is not shorted to ground?

 

[2informaticos]

You can try voltage injection.
Will need to wait more time and use IR camera.

 

[prodigy83]

Looks like it's the processor.
What is weird is I took up U5700 from the board and plugged the USB-C meter and I saw the voltage go to the regular 5.1v, but when using the IR camera, Q5840 got real hot, so I lifted this too, then Q5820 I noticed was getting quite hot. I put down some alcohol in this area and it was literally bubbling underneath the chip. Tracing the issue came back to P3V8AON_SW3. But injecting about 2.5v in to PP3V8_AON_SPMU, the processor lit up. I had plugged in my USB-C meter several days ago and saw the processor was heating up back then too.
Confirmation it is the processor?

 

[2informaticos]

STOP doing that!
Never ever let the MOSFETs from a buck-converter with Gate floating on air.

 

[prodigy83]

Floating on air?
Looking at Q5840, I see it has 2 gates.

 

[2informaticos]

High side one can get open if its Gate floats on air.
As controller chip is no more soldered on the board, nothing can stop it to burn!

 

[prodigy83]

Oh boy, okay, thanks, I now know. I figured I was safe if the chip is off. Total opposite, thank you for your help and knowledge.