MacBook Air A2179 - 820-01958 - Stuck at 5V/0.25A

[datatech85]

Hello !

I hope to find some help with this case.

I've got a Macbook Air A2179 (820-01958) that got an electric shock. First mesurement show 5V / 0.016A.

The first observation was the capacitor C78B7 with burn marks near U7800. There was a short cut on "PP3V3_G3H_PMU_VDDMAIN".

I replaced the capacitor but the short remained. Then I decided to replace U7800 after checking some rails.

The short is gone but now I've got 5V / 0.25A and I find no short on thermal camera.

There is only the T2 Chip that warm up around 40°C.

I don't find any explaination why i can't get the 20V.

Any idea with this case ?

 

[2informaticos]

Check U7800's LDOs; page 63 in schematic.

 

[datatech85]

I checked all LDOs:

LDO0_IN (PP1V1_SLPS2R) = 1,10V
LDO1_IN (PP3V3_G3H) = 3,22V
LDO2_IN (PP1V8_SLPS2R) = 1,79V

LDO_CORE = 1,49V

LDO0 (PP0V8_SLPS2R) = 0,79V
LDO1 (PP3V_G3H) = 3V
LDO2 (PP1V2_AWAKE) = 1,19V
LDO3 (PMU_LDO3_OUT) = 1,79V

LDO_RTC = 1,48V

Are the values normal?

 

[2informaticos]

All correct.
Check if is recognized in mode.