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820-01949 brain dead

N

Narek

Member
Hi, I'm working on 820-01949 board which has slight coffee spill on it. Affected areas are R7439, some corrosion on caps around 7210 and U7100. R7100/7101 have been eaten away along with their pads. I have cleaned up all corrosion, replaced components, resoldered U7100 and recovered traces.

-Board starts, but doesn't show any image on the screen and there is no chime.
-Caps Lock doesn't light up
-When I put it into DFU mode Apple Configurator detects it but can't revive or restore - after some time of waiting "installing software" just dissapears and shows lock with status "booted"
-thermal camera doesn't show anything heating up
-tested with other battery - the same
-the only activity computer has is clikcing trackpad

Some basic measurements:

PPBUS_G3H - 12,72V
PP0V9_SSD0 - 0,9V
PPVCCQ_ANI_SSD0 - 1,8V
PP2V5_NAND_SSD0 - 2,5V
PP1V8_IO_SSD0 - 1,8V
PPVCCIN_S0_CPU - 0,601V
 

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2informaticos

2informaticos

Administrator
Staff member
With 0.6V on VCORE, machine seems to boot.
It gets stuck for some reason.
You should check the board alone on the desk; just charger and USB tester connected.
Use USB-C hub with PD support; connect charger on it.
PLT_RST_L comes on?

Be aware, R7439 problem could caused an overvoltage and damaged PCH.
 
N

Narek

Member
Board alone takes 20V and is floating around 0.075A.

PLT_RST_L is not comming on, it's flat 0V, it doesn't even spike.
 
N

Narek

Member
No, CPU VCORE now is 0V. As I know this board needs to have good battery connected to boot, right?
 
N

Narek

Member
With battery and charger there is VCORE. There is no VCORE when I connect just charger to board alone on the bench.

EDIT: Actually now I don't get VCORE. Battery and charger connected, board in topcase with everything connectes as before..
 
Last edited:
N

Narek

Member
Yes, I trigger it and anyway VCORE doesn’t show up anymore, though I haven’t done anything to the board..
 
2informaticos

2informaticos

Administrator
Staff member
Corrosion around CPU power supply is very bad.
CPU may be damaged now.
You can try to heat it with quality flux; in case of accumulated crap underneath.

Check all resistors, caps and traces related with CPU power supply.
 
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