820-3115 No CPU Vcore

[nik1981]

I have an 820-3115 liquid damage around SMC. Originally no magsafe light. Removed and reballed SMC, now I get magsafe and fan spin with the fan at full speed after 5 seconds.
CPU has a little heat in it after a min or so.

ALL_SYS_PWRGD = 3.29v
PPVCORE_S0_CPU = 0.00v

I'm stuck with this one, please help

 

[nik1981]

also PPBUS_S5_HS_COMPUTING_ISNS is 12.45v

 

[2informaticos]

Check R7402/03.

 

[nik1981]

R7402 = 149k
R7403 = 181k

So they seem fine

 

[2informaticos]

Post U7400 voltages; pins 1, 19, 29, 46, 47, 48.

 

[nik1981]

Pin 1 = 12.22v
Pin 19 = 5.06v
Pin 29 = 5.06v
Pin 46 = 5.06v
Pin 47 = 3.33v
Pin 48 = 12.26

 

[2informaticos]

I bet for some resistors or traces affected for corrosion.
Check all SPI Bus Series Termination resistors and their traces.

 

[nik1981]

All SPI Bus series termination resistors test as schematic. Traces look good, not sure what to check next.

I have PP3v3_SUS

 

[2informaticos]

Check all resistors and traces around SMC; on opposite board side too.

 

[nik1981]

I've checked all resistors around the SMC including the other side. Took ages but it seems they are all okay. Is there any way to narrow it down?

 

[2informaticos]

Try known good BIOS file, clean ME...

 

[nik1981]

Can I take another bios chip off of the same board EMC 2554 to check that?

 

[2informaticos]

Should serve for test, even if no clean ME...