820-3437-B No PPVCC_S0_CPU

[machelper]

Hello Everybody

I'm working on 820-3437-B. Machine came my desk doesn't turn on and not fan spining, when i check board too little corrosion around r7520 . after cleaned fan turns on but not chine and nothing screen. When checked voltage

PPVCC_S0_CPU = 0 v
CPU_VR_EN = 0.99 v
ALL_SYS_PWRGD = 3.3 v
PPVRTC_G3H = 3.3 V

other 8v,5v and 3.3v is ok.

Replaced SPI,U7501,u7200 nothing changed

Where can i start to check
Thanks

 

[Glenn]

Have you tried pram reset? I had the same problem on a a1502 when I replaced keyboard on it

 

[Repairable]

no chime = no brain, no brain is no cpu vcore



whats power on these?

PPBUS_S5_HS_COMPUTING_ISNS
PP5V_S0

 

[larossmann]

cpu_vr_en seems low. corrosion is stuck somewhere.