820-2936 starts only in smc bypass mode

[jadao]

This board had water damage on bottom side, but no corrosion. Doesn?t start (no fan spin) even if I am in S0 state.
In SMC bypass fan does spin but no chime.
I get green/orange light, ppbus is 12,56v.
ISL was a little bit greenish, but seems to work good, with battery and charger.

I checked the traces and resistors for pins 17-18 and 27-28, continuity until the chip is good and resistance is 3ohms and 21ohms.

PPDCIN sensor was hit by water checked the resistors and they are good, don?t know if the sensor itself can prevent the board from starting.

Looks like an smc or sensor issue.
How to troubleshoot sensors without running ASD? One by one?

I did a slight reflow on smc just in the case if water got there but no change.

ultrasonic the board also with no change.


thanks!

 

[2informaticos]

First check AVREF_SMC voltage.
If good, check then VP0R and VD0R sensors output.

 

[jadao]

Hi 2informaticos!

AVREF_SMC signal is 3.3V

2.1 v at VP0R output
Witch looks good according to the voltage divider

2.77v at VD0R output
Witch also looks good according to the voltage divider

Thanks

 

[jadao]

Pff this one was a bitch, I was about to put back the logicboard for no fix and discovered PP5V_S3 present at L7260 but missing at U7300! Run a wire and the board is back to life.

What a luck after 2 hours + ultrasonic

Thanks for everything