[SOLVED]820-00165-A Power No Chime No PPVCC_CPU_S0

[BCConnection]

Liquid damaged macbook Air

Wine spill on keyboard

no major areas of damage that I can tell, Most damage I can see was 2 slightly blackened pins on the keyboard connector and some dried wine spots on the board.

Board has only been scrubbed in the small spots where wine was dried. Has not been through UC.

All main rails are there but CPU power is not turning on.

Not too familiar with the power sequence for CPU VCC.

 

[aprendiz]

CPU_VR_EN present????? Voltage on pin 16 and 17 from U7200???

 

[dukefawks]

Also inspect pin 8 of U1950 very closely.

 

[BCConnection]

CPU_VR_EN is 0v

 

[aprendiz]

what about Duke's suggestion??

 

[BCConnection]

Pin 16 is 5v and pin 17 are 8.4v

Looking now at the other area

 

[BCConnection]

Checked all resistors on the page that are directly tied to U1950 all within spec. U1950 Pin 3 output 3.378V

 

[BCConnection]

R1963 output is 3.377V

 

[BCConnection]

Got VCC CPU now. U1930 had wine under it bridging pads. CPU is now 1.78V. Testing boot now

 

[BCConnection]

Computer boots now. No backlight but I think its just the diode on the boost circuit is bad.

Thank you guys so much. I now know how the circuit works a little more.

 

[dukefawks]

Diode never goes bad. Probably dead LP8550 or feedback trace.

 

[BCConnection]

You were correct Duke. Feedback had no continuity. Ran a jumper all is good.