Chosen Solution
Hey there i have a wierd Macbook. The Macbook starts, fan starts to spins then shuts down and automaticly starts again it takes a few seconds and than goes full speed on the fan. No image no Backlight. I checked all Power Rails = Macbook is in S0 state - all power rails are good except PPVCORE_S0_CPU is only 0.15V I reflowed U7400 and after the reflow WOW it worked. Ran the ASD all fine passed every test. BUT next boot, back to the start same thing again . Then I replaced U7400. WOW it worked. Ran the ASD all fine passed every test. BUT next boot, back to the start same thing again . So i guess there is a bad capacitor or something i heated up and made it get better temporary. Or did i miss something? How do i find the bad cap the easiest way? thank you for your help
There are not tricky poly-tantalum capacitors on PPV core. It might be a bad U7600, I’d try replacing that IC and the four mosfets too.
