820-3437-b not turning on sometimes

[BCN_Techs]

Hi,


It 's water damage machine. PPBUS was 8.20 so i checked and there was some shit near smc. Reballed it and now het 8,6V. It started few times loading untill desktop, worked ok but now sometimes it boots, sometimes make fan quarter and not booting, and now doesnt even boot. Checked all s5 lines and seems to be ok. Also changed U7400 because it was badly damaged with some components near around,


Getting ALL_SYS 3.3 V but still not booting. If do smc by pass also booting sometimes other times not booting. Board has it's own life.

ISL625 also ok pins 17/18 3,5 Ohms 27/28 20 ohms


What can i check???

 

[2informaticos]

Do you get voltage on all big coils?
Inspect U1950 for corrosion.
Do you get 3V at both pins 7 & 3?

 

[BCN_Techs]

U1950 Pin 7 S0 good geting 0V and pin 3 0V too. Both are pulsing machine try start. There is no visible corrosion on u1950.


Big coils L7320/10 L7630 L7430 pulsing when fan try to sping


Update. As i said before sometime it is booting and U1950 pins 7 and 3 are 3,4 and coils L7320/10 1.8V and L7630 1.08V and L7430 0.3V

 

[2informaticos]

You should still have corrosion issue.
If nothing visible, try heating CPU with quality flux.
Just to burn accumulated crap underneath.

 

[BCN_Techs]

noway informaticos. ALready tried, reflow CPU with good flux , reballed SMC againg if it have some bad ball, I cant understand why without even touching board sometimes it starts from magsafe and other times just trying to sping the fan

 

[2informaticos]

Try again SMC bypass...

 

[BCN_Techs]

not working now even smc bypass. Tried reballing smc again and now and same result. Will change smc from donor board tomorrow and back with results.