820-02098 power cycling

[Kyle93]

Which secondary power rails specifically should be checked? I do not know these newer boards as well as the older ones

 

[2informaticos]

Any low voltage power rail.
But start with mentioned LDOs.

 

[Kyle93]

PP3V3_S2 3.2V
PP3V3_AON 3.3V
PP5V_AON_P3V8AON 5V
PP1V8_AON 1.8V
PP1V8_AWAKE 1.8V
PP3V8_AON_SPMU_ISNS 3.8V
PP1V5_AON_VCORE_SPMU 1.5V
PP1V2_AON_SPMU 3.2V
P1VP2_AWAKESW_BLC 0V
PP0V72_S2_VDDLOW 0.72V

Bad U7700 from P1VP2_AWAKESW_BLC 0V????

 

[2informaticos]

Compare ohm resistance to ground with good board.

 

[Kyle93]

They are the same

 

[Kyle93]

L8242 diode mode on good board is 0.024 but 0.057 on bad board

 

[Kyle93]

all voltages are good on U8100 and U7700

 

[Kyle93]

LID sensor disconnected

Tried with lid sensor connected but no change still cannot get into DFU mode

 

[2informaticos]

What said the client about how the problem appeared?

With battery connected, PPBUS_AON drops to 0V in the same rithm of USB input?

 

[Kyle93]

There was minor liquid damage but only in C5210 area. Nothing was even shorted or looked damaged except some very minor corrosion on the board itself not touching any components.

PPBUS_AON drops to 4V during power cycle of USB input. Goes up to 12.33V when first plugged in, drops to 4V then back to 12.33V e.t.c

 

[2informaticos]

Possibly bad CPU...