Macbook 820-4924 No Boot

[Instafixx]

Machine came in with no boot. Found a few resistors corroded near U7200. Replaced them.
Now I get MagSafe Light.
PPBUS is 12.6V

 

[2informaticos]

3V3_S5/SUS?

 

[Instafixx]

Both 3.3V

 

[2informaticos]

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

 

[Instafixx]

Yes. Drop Pulse is there.

 

[2informaticos]

Now check for pulse at PM_SLP_S4/3_L lines (at same time).

 

[Instafixx]

Both are 0V.
Nothing when triggered.

 

[2informaticos]

This behavior points to PCH.
Check if PM_RSMRST_L is steady high.

 

[Instafixx]

Checked for about 15 seconds. Steady high

 

[2informaticos]

Check PM_DSW_PWRGD, PCH_DSWVRMEN, PM_BATLOW_L and the 4 PCH's RTC signals.

Just in case, test SMC bypass mode.

 

[Instafixx]

PM_DSW_PWRGD is 3.3V
PCH_DSWVRMEN is 3.3V
PM_BATLOW_L is 0V (Diode Mode .532)
RTC_RESET_L is 3.3V
PCH_SRTCRST_L is 3.3V
PPVRTC_G3H is 3.3V

 

[2informaticos]

"Just in case, test SMC bypass mode."
???

Are you testing with original 60/85W Magsafe 2 charger?

 

[Instafixx]

SMC bypass failed.

Don't have original 60W adapter with me.

 

[2informaticos]

This board doesn't start with 45W charger; unless charged battery is connected.

 

[Instafixx]

On DC Power Supply ??

 

[Instafixx]

Found a 85W charger. PM_BATLOW_L is 3.4V

 

[2informaticos]

Still not starting?

 

[Instafixx]

PM_SLP_S4_L is still 0V.
PPDCIN_G3H is 16.7V . Shouldn't it be 18.5V ?

 

[2informaticos]

Stop making wrong assumptions!

Still not pulse at PM_SLP_S4_L triggering SMC_ONOFF_L?
Then you have bad PCH.

Tried again SMC bypass?