820-00840 20V 0A in S0 state

[jadao]

This one is a liquid damage board.
PPBUS_G3H is 13,06V, I got 20V and it charges the battery just fine.

Without battery it is stuck with 20V@0A

I am in S0 state and all rails on the power rail page are present except for the cpu:
PPVCCPU_S0G = 0V
PPVCCSA_S0G = 0V
PPVCCGT_S0G = 0V

On U7800
PM_PCHPWROK is missing
PMIC_SHUTDOWN_L is present 3V
Inputs VSA to VSH are all present
Input ENA to ENG are all present
input ENH is missing, R7874 is 0 ohm and PM_PGOOD_CPUVCC is 0V , there is no short and diode mode is 0,479.

On U7100, I confirmed that PM_PGOOD_CPUVCC is 0V
I made sure PP5V_S4 and PPBUS_G3H are present to VIN and VCC
PM_ENCPUVCC (ALL_SYS_PWRGD) is present, 3,3V on both sides of R7148.

Is it reasonnable to blame U7100 who must output PM_PGOOD_CPUVCC, I notice a via pad going to VIN (pin 41) was corroded so probably the chip took a hit, although it is well bonded with sillicone.

Thanks

 

[2informaticos]

You cannot expect a power good signal, before corresponding power rail appears.

U7100 requires more than a simple enable signal.
It is controlled through CPU_VID bus.
So there could be a problem with PCH/CPU, or even BIOS.
iGPU voltage (PPVCCGT_S0G) will not appear until high graphics load is detected, but CPU core voltage (PPVCCCPU_S0G) is of course required.
Many blocks of CPU are already powered with other voltages and communication is necessary between some blocks of CPU and PCH, prior to generate core voltage.

Be aware, liquid sign on the CPU power supply could mean letal damage.
Try known good BIOS, clean ME.

 

[jadao]

I agree that much more signals are involved and required and anything can mess up the proper function of U7100.
I forget to mention that I started with a known working and ME cleaned bios but nothing changed.
I think this one may be a nightmare as it will be difficult to pinpoint a resistor, trace or simply a dead cpu

 

[jadao]

I replaced U7100 and it works now!!
I know it's an exceptional luck, specially that this chip is surrounded with sillicon there was no corrosion under it, but the ppbus_g3h burned via going into the chip leads me to believe it may took a hit... I replaced it out of desperation.
Will check now if it doesn't crashes after couple of minutes