A1278 2012 820-3315 fan spins, no chime

[VinceLx]

Hello,
This board was water damaged.
- green light ok, fan spins (after a while fan spins high even with trackpad connected)
- no chime, no display, no USB activity with a mouse

PPBUS_G3H=12.3V
SMC_RESET_L=3.44V

SMC_PM_G2_EN=3.48V
PM_SLP_S5_L=3.31V
PM_SLP_S4_L=3.31V
PM_SLP_S3_L=3.3V
So it is running

ALL_SYS_PWRGD=3.31V
CPUIMVP_PGOOD=0V

R7402 and R7403 OK

What should I check next? Are the processor or U7400 dead?

 

[VinceLx]

Any idea on this?

 

[2informaticos]

Board cannot boot without VCORE.

R7974 is good?
Did you try known good BIOS?

 

[VinceLx]

Indeed R7974 is good, and I see 3.3V on both sides.
I flashed a known good BIOS, no luck this time...
So, next step is replacing U7000?

 

[2informaticos]

12.3V on PPBUS_G3H and missing VCORE should not be related.
You can fix PPBUS_G3H first, but this doesn't assure you that machine will start working after that.
If SMC is the culprit, then could be the reason...

 

[VinceLx]

I replaced U7000, exactly same behaviour: PPBUS_G3H=12.3V, and signals on SMBUS_SMC_5_G3_SCL and SMBUS_SMC_5_G3_SDA identical as before.
So I guess next step is SMC replacement, but this is not my level... so I have a donor board