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MacBook is not booting, no chime, just the fan spins on full speed

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

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一个新的屏幕或电池就在一个套件之内。

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Android 维修工具包

一个新的屏幕或电池就在一个套件之内。

现在开始购物

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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.

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i did change the u7600 and the mosfets but still the same result. Little bit confusing is that the voltage increased sligthly to 0.18v on PPVCORE. do you have another idea?

完成的

Do you know how u7400 works? I just got 0.2V on the Gates of the Mosfets on the two ugate from the u7400. Seems pretty low.

VRON is 3.38V i think this is to enable the chip.

完成的

You can look for ISL9504 online, but it's an old IC, not sure you can find any details about it. Here you can find some basic info: https://www.intel.com/content/dam/www/pu...

完成的

its running now will need to test it if it will last. i just rework the hole area around the u7400. and it seem that it was a bad soldering connection i guess... i will see. thank you for your help

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Niklas Jakob 将永远感激不已
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