MacBook A2485 / 820-02100-11 board / Logic Board Failure

[zeydullak]

Hello,

We have a A2485 MacBook that has logic board failure. Customer says there was not water damage. He said screen went black while he worked. We removed the board. There are 3 USB C ports. When connected it shows 5.26v and 0.22a and restarts. Looks like it detects something and restarts. I think we see when it just shows 20V, it restarts. USB C Meter turns off and on. Can you please advise what elements we should check? We also have working donor board.

Regards,
Zack

 

[2informaticos]

Magsafe port has the same behavior?

 

[zeydullak]

5v and 0a and then it restarts.

 

[2informaticos]

Remove both F5200/1 and check C5250 voltage.

 

[zeydullak]

C5250:1 -> 4.475
C5250:2 -> .013

 

[2informaticos]

Did you really check for voltage on its ground pin???
I don't see the logic...

Confirm if you checked voltage, or diode mode.

 

[zeydullak]

I have checked voltage. should i check diode mode as well?

 

[zeydullak]

Sorry my engineer made a mistake in measuring. Once we removed those to F5200 elements, we have 12.33v on the capacitor C5250. It looks like it has good voltage. Thank you for your patience. Please advise if we put them back or let us know what to test further.

 

[2informaticos]

So the problem comes from PPBUS_AON side.
First, check there in diode mode.

 

[zeydullak]

Hey guys we have spotted a difference between elements on our board and our donor, I have attached a few photos for you to take a look at.

This MacBook was looked at by someone else before reaching us, is it possible they have removed these elements?

Is the difference of elements is related to the amount of SSD chips on the board?

 

[2informaticos]

This model may have 4, 5, or 8 NANDs soldered, depending on the SSD capacity.
Check page 151; SSD Config and BOM.

 

[zeydullak]

These are the diode mode Measurements for the Patient Board.

__With_out_Elements___

CR857/PBUS_AON -> 4.9 with beep

__With_Elements___

CR857/PBUS_AON -> 4.7 with beep


We also Have a Working Donor Board and here are its Measurements

__With_out_Elements___

CR857/PBUS_AON -> 4.6 with beep

__With_Elements___

CR857/PBUS_AON -> 4.7 with beep

 

[2informaticos]

Not sure what means w/ or w/o elements.
Imposible to get 4 ohm to ground on good board.
Disconnect charger and battery and wait 15s before measuring in diode mode, or ohm scale.