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Mid 2010 Model A1278 / 2.4 or 2.66 GHz Core 2 Duo processor

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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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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?

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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.

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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...

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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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