MacBook Air 2337 M1 - 820-02016 - No power , stuck ok 5V after screen replacement and hard reset.

[Megabit]

Hi everyone,


I’ve on hands this strange case:
Customer came to my store to replace a broken LCD. Nothing difficult, common fix.

After installing the brand new LCD and Lid assembly , the Mac power up and booted normally so I did some fast testing.


Then having momentally trackpad disconnected I decided to shut down pressing power button till it shut down.

After that, nothing. Its dead.
I’ve got 5V and 0.050 on USB-C Multimeter.


After yelling and cursing myself, I taken the board out and start measuring some point:

PPBUS_AON : its jumping to 11.6V to 12.1V every second.


PP3V8_AON : is 3.8V steady


PP5V_S2: Absent


PP5VS2_EN: jumping to 0.06 to 0.20V every second , 376 resistance to ground in diode mode.


PPBUS_5VS2_VIN : is cycling as PPBUS_AON


PP3V3_S2 : 3.3V steady


PPV3_S2_LDO: is cycling 2.0V to 3.2


PPV1V25_S2: on SWV011 : 1.25 steady


Testing another identical working board I have in store, I notice that PP5V_S2 is absent too (probably because LCD and other things are not connected)

After this I start looking for shorted lines:

I found 2 :

PP0V805_S1_VDD_FIXED are shorted to GND with 0.00 Resistance.
This line is coming from U7700.


RF_ANT_0 and RF_ANT_1 are shorted to ground… are supposed to be shorted?? :\

Appreciate your help guys.

Customer is pressing me

 

[2informaticos]

First of all, welcome to the forum!

"PP0V805_S1_VDD_FIXED are shorted to GND with 0.00 Resistance"
That may be normal for some board version; check attached screenshot.

Test if board turns on with charger alone.
Also check if is detected in DFU mode.

 

[Megabit]

Thanks for replay.

So that's the reason for the short on that line. Ok thank you.

Anyway, board is already removed from the chassis and plugged only usb-c ports cable.

About DFU, I try to connect the faulty board to an MacBook Pro 2018 running Sonoma, in the upper left usb-c port, but in Apple Configurator the faulty board is not recognized.

In other threads I read that is necessary to jumper FORCE_DFU pins to get DFU correctly. Is it possible?

I'm not really trained with M1 architectures and this is the first time a Mac dead on my hands just shutting it down

How can I proceed to diagnose the issue?

thanks

 

[2informaticos]

For M1 Mac, use the left back port (close to the screen).
DFU Blaster can be used to force it in DFU mode.
External switch method can also help you.

DFU Mode Restore (Macs) - LogiWiki

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