geraymartha
New member
i been saving some boards that I'm unable to fix , they all seems to have same problem quarter fin spin , green light ok , 12.6v ok , 3v3_s5 ok , but on 5v_s3 voltage go back and foward , thinking that maybe something is getting the voltage down ahead , i decide to remove the resistor that enable the s0 lines for example on the first board I'm going to ask for help 820-3115 the resistor is R7978 once this resistor is removed , 5v_s3 go back to normal , 5v steady , then i imagine one of the s0 voltages was guilty maybe a transistor whatever , then i isolate them and i when 1 by one , i finally found that problem was coming from =PP1V5_S0_REG , i remove u7770 and the fluctuation stops and all other rails when back to normal , then i imagine , that my problem was somewhere on PP1V5_S0 then i locate all the nets , and remove all possible ic , transistors , and caps 1 by one , and resolding u7770 to see if stuff when back to normal and no as soon as i resolder u7770 voltage start fluctuation again , i also replace u7770 and nothing. no short to ground on the line.
the only one i can't remove and test is u1800.
i have different boards with exact same issue a macbook air board 2012 , a 2015 , and this pro 2012 , I'm stuck i think my approach to this problem is incorrect , thank you for your help.
the only one i can't remove and test is u1800.
i have different boards with exact same issue a macbook air board 2012 , a 2015 , and this pro 2012 , I'm stuck i think my approach to this problem is incorrect , thank you for your help.