MacBook 820-279-b

[tyasir]

I have a macbook which dont go on.
available rails are pp3v42, ppbusbus, s5 and s0 but no pp5v_s0. i already replaced q7940 but no result. enable signal is also available diode reading on pp5v_s0 is 0.409. power supply hangs on 0.089 amps. I am new to macbook logicboard repair and any help is much appriciated. it is my learning board so i can experiment on it.

 

[2informaticos]

I assume your board is 820-2879; confirm if I'm wrong.

Do you have all S3 voltages and also 3V at =P5VS0_EN?
In such case, post P5VS0_EN_L and P5VS0_SS level voltage.

 

[tyasir]

Hi there,

Thank you for response, it is indeed the same board. i have checked the voltages, P5VS0_EN_L is 5.02v and P5VS0_SS is 4.95. i also measured other s0 power rails enable they are all present. what i find strange is that R7859 and R7879 supposed to be 100k resistence but it is not. i checked another board same results. R7879 is 22k resistor on the boards.

 

[2informaticos]

"P5VS0_EN_L is 5.02v"
No good; ending _L means signal active low (with 0V)...

"3V at =P5VS0_EN?"
???

When you measure resistor onboard, other components can make the value lower.

 

[tyasir]

Ohhh so p5vso_en_l should be zero?
p5vso_en is indeed 3v.

 

[2informaticos]

Change Q7945...

 

[tyasir]

i am sorry i was wrong, just tested it again no enable signal which ofcourse come from processor I am gonna stop with this board. Thank you for your guidence.