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A2681 - 820-02536 Air M2 5V 35mA

J

jadao

Member
This board came in liquid damage near the daughter board and slightly on the logicboard.

Cleaned everything, checked for shorts and plugged in usbc charger, I see only 5V 35mA. Don't know where to start with this board.

I took this measurements but it doesn't give me any clue and have no other reference board.

PPBUS_AON 12.3V

PP3V8_AON 0.4V(0.309 DIODE MODE)

PP5V_S2 0V (0.230 DIODE MODE)

PP3V3_S2 0V (0.371 DIODE MODE)

PP3V3_AON 0V (0.365 DIODE MODE)
 
J

jadao

Member
Pin 8 : PPBUS_AON 12.3V
Pin 7 : PP5V_AON 4.99V
Pin 5 : P3V8AON_PVCC 4.99V
Pin 12: P3V8AON_PWR_EN_R 4.46V measured at the zero ohm R5710 on both sides 4.46V
 
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J

jadao

Member
I replaced U5700 501CR17 with U5700 501CR0B coming from A2337 board and i have exactly same results. 5V 35mA with same values on pins 8, 7, 5 and 12
I had doubts for the chip but schematics shows same pinout...
 
2informaticos

2informaticos

Administrator
Staff member
Not sure if are directly compatible.

Check all surrounding resistors and traces; also the capacitors.
 
J

jadao

Member
I ended up puting back the original chip U5700.
I checked also all surrounding components near u5700 and evrything is in spec. Liquid was more near speakeramp UR700 and UR730.

Something may probably help, I injected 5V at PP5V_S2 rail (it is not shorted) and plugged the usbc charger, surprisingly the meter is going to 20V 0,455A and the board is booting but bootlooping, I can even see the apple logo with the progress bar, it doesn't stuck but just doesn't have time to finish and it bootloops.

Same if I hold power button I will see loading options message then it will bootloop.
I plugged the battery in just in case but it didn't help it's bootlooping even with the battery only.

When I shut off external 5V power supply, board stays at 20V bootlooping to 5V and coming back to 20V a couple of cycles and then it comes back to 5V 35mA constant until the next time I provide external 5V to PP5V_S2.

Any hope or hint to check further or I am just bypassing a mountain of conditions...

Thanks!
 
J

jadao

Member
As soon as I get 20V on usbc-meter with providing at the same time external 5V to PP5V_S2 I will get 3V8_AON.

usbc meter cycles as follow: 5v->20V-> 0v and repeat 5v->20V-> 0v it stays long enough at 20V to be able to see progress bar going to 25% and then it cycles again.

When I shut off external 5V, PP5V_S2 (5V) 3V8_AON remains on the board both during 3-4 cycles (usbc meter 5v->20V-> 0v) and then it comes back to usbc meter 5V 35mA with no more 3V8_AON (0V) and no more PP5V_S2 (0V).

I don't know if it's random or particular power sequence I am messgin with because I just tried now, and after shutting off external 5V, board stay on for 15 minutes at 20V I had a screen with exclamation mark and the famous support.apple.com/mac/restore I think it's normal to shut off after a while when you do nothing at this screen (restore page). But after that it comes back to 5V 0.35A and I am not able to reproduce that.
Tried also dfu to see what happens but it doesn't work.
 
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2informaticos

2informaticos

Administrator
Staff member
No need to repeat DFU, if already got the mac/restore message.
You should try now internet recovery.

BTW, this machine has USB boot enabled by default; check what happens.
 
J

jadao

Member
Unfortunately I wasn't able to reproduce the same situation, can't load options to go with internet recovery, machine keeps constantly rebooting even with 3V8_AON..
Thanks for the usb boot trick didn't know that on this recent machine but the machine doesn't pick up external usb drive...neither usb mouse or keyboard.
I will stop on this one, M2 may got hit by liquid near speakeramp circuitry...
Thanks for your support always learning
 
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