820-02020-A Macbook Pro M1 bootlooping/power cycling

[bogosort]

Hello,

I managed to repair a liquid damaged 820-02020 board. There were two shorted capacitors.

However, the laptop is stuck in boot looping. Everything is connected correctly (battery, trackpad...)

I cannot even get to the boot option selection screen by holding the power button.

I cannot get into DFU mode neither.

I managed to get to the login screen once, but I can't get to it anymore.

Video here:
https://streamable.com/2ayubc

Here is a video of the amp meter:
https://streamable.com/k57gd5

PPBUS_AON starts at 12.33v then drops to 12.04v a second after plugging it in

I can also hear a clicking sound when it power cycles (right when shutting off)

Any idea?

Thank you!

 

[2informaticos]

First of all, welcome to the forum!

Which area has been affected by liquid?
Did you try connecting both charger and known good battery (holding some charge)?

 

[bogosort]

Thanks for the welcome!

The two shorted capacitors were CR608 and CR606.

I see signs of liquid damage around UC300, CR605, CR607, CR635, CR637.
I don't remember the other areas since I cleaned it a while ago.

I unfortunately don't have the original charger for this one, I do however have a third party that goes up to 96w and an official charger for an A2442 Macbook Pro 14".

I thought it could be related to the battery since the only time I could get to the login screen was the first time I tried to power on the laptop with the battery connected. Since then, even when disconnecting the battery and reconnecting it, I can't get to it anymore.

I do want to mention, however, that the battery seems to hold a charge and can power on without a charger plugged in (but shows the same behaviour as originally explained)

 

[2informaticos]

Very dangerous if corrosion extended under audio amplifiers (UR600/30).
Many data lines go directly to M1 processor; leakage from PPBUS_AON may destroy it.

Corrosion on UC300 area is also dangerous.
Do you get correct 5V_S2 now?
Also check 3V_S2 voltage.
3V8_AON is stable?

Write directly into reply box, instead of clicking Reply button.
I don't see any reason to quote an entire post, visible few centimeters above.
Please, maintain forum aesthetic...

 

[bogosort]

5V_S2: 5.19V
3V_S2: 3.3V
3V8_AON: 3.8V, stable

When putting red probe on ground, black on L5800 in diode mode, I get a reading of 0.161

 

[2informaticos]

There is something more affeceted by corrosion.
Possibly accumulated crap underneath BGA chips...