820-3787 no fan spin, no S4 state

[ajdoc]

Liquid damaged battery PCB and liquid damage around U7100.
There was no light at all, replaced U7100 and got light on charger.

U7100 resistance:
17/18 - 3.6 Ohm
27/28 - 38.4 Ohm (is too high)

PPBUS_G3H was at 4V
R7122 had 40 Ohm - replaced and U7100 between 27 and 28 is correct at 20 Ohms buts still PPBUS_G3H stuck at 4V.
Replaced U7100 again and got 12.58V on PPBUS_G3H but still no fan spin.

PPVIN_S5_HS_COMPUTING_ISNS - 12.6V
PPVIN_S5_HS_GPU_ISNS - 12.6V
PPVIN_S5_HS_OTHER3V3_ISNS - 12.58V
PPVIN_S5_HS_OTHER5V_ISNS - 12.58
PP3V42_G3H - 3.41V
PPVRTC_G3H - 3.31V

PP5V_S5 - 5.0V
PP5V_S4 - 0V

PP3V3_S5 - 3.32V
PP3V3_S4 - 0.15V
PP3V3_SUS - 3.32V
PP3V3_S3 - 0.46V
PP3V3_S0 - 0V

P5VS4_EN - 0.08V
P5VS4_PGOOD - 0V

S4_PWR_EN - 0V

U1950 area looks clean.
CPUVR_PGOOD - 0.5V
ALL_SYS_PWRGD - 0V
PP3V42_G3H_PCHPWRGD 3.40V

And I am lost...

 

[2informaticos]

PM_BATLOW_L is correct?
Are you using original 85W Magsafe 2 charger?
Try connecting known good battery.

 

[ajdoc]

PM_BATLOW_L - 3.31V
Got genuine 85W Magsafe 2 charger.
tried with two kwon good batteries and same issue.

 

[2informaticos]

Trigger SMC_ONOFF_L and check for drop pulse at PM_PWRBTN_L (at same time).

 

[ajdoc]

When located PM_PWRBTN_L on the board then I saw Q2120 looks not too good.

Replaced Q2120 and got fan spin, no chime, nothing on display, caps lock LED off and after a few seconds single sound BEEP.

 

[2informaticos]

Try the board alone on the desk.
Use USB activity tester only.

Inspect the board for more corrosion, close to SMC, PCH and CPU.