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MacBook Air A1465 2014 820-3435B no greenlight missing 5 V rail.

Dear friends, a friend of mine donated me a 2014 MacBook Air A1465 that just stopped working. In Apple's authorized service, the motherboard was condemned (as usual) and then the Macbook was discarded by him. I'm trying to resurrect it and take the opportunity to learn a bit about it.

I measured the primary rails and I got the following results:

ppbus_g3h = 8.55 V

pp3v42_g3h = 3.42 V

ppvrtc_g3h = 3.32 V

PP3V3_S5 = 3.32 V

PM_SLP_S3_L = 0.07 V

PM_SLP_S5_L = 0.00 V

PM_RSMRST_L = 0.04 V

PM_SLP_S4_L = 0.0 V

SMC_ADAPTER_EN = 3.39 V

PP5V_S5 = 5.0 V

PP5V_S4RS3 = pulsating between 0.0 V 5.14 V, it should be 5 V.

PP5V_S0 = also pulsating between 0.0 V 5.14 V.

The 5 V rail is intermittent and as far as I know, it's responsible for powering the CPU and that'd justify the fact that it is not power on. However, PPBUS_G3H and PP3V42_G3H are present and I don't understand why I don't have a green light on the charger.

I am a beginner on this subject and any suggestions would be very welcome.

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Just saw a video of Rossmann. Look for shorts. It is luckily a capacitor that shorts the U7501. These oscilations of 5 v indicate to a short of one of capacitors around this chip. If the chip is dead, you do not get this so called power loop. Hope this will help. I do not know what is the problem exactly but it is 100% related to U7501 that creates these 5V. I am still looking for the solution ;)

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Grigore - Have you tried desoldering and/or replacing the caps? Other than replacing the Q7560 MOSFET which is a common failure.

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Dear friend, I really appreciated your reply. I've hadn't evaluated the possibility of being the neighborhood of U7501, everything was pointed to an SMC issue. Your comment really gives light at the end of the tunnel to this mac. I'll do what you suggested and I'll post the results. Thank you for your help.

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I've ordered a donor logic board on aliexpress. As soon as I get it I will try to give life to my logic board and will be back with an update. But, you can see on the schematics that 5v as well as 3.3 V are created by U7501 from PPBUS_S5_HS_OTHER_ISNS which is 8,6 V The only concernnI have is that you still have a 5V on PP5V_S5. Still, I would strongly recommend to start the research arround the U7501. KEEP IN TOUCH! ;)

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@Grigore Ciobanu have you had any news on your board? I tried to see anything unusual in the u7501 are unsuccessful. now the board shows an intermittent fun spinning and sometimes, out of the blue, a full fun spinning but no chime or boot. however, still no green light.

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You should head over to Louis Rossmann’s YouTube’s where he gets deep into diagnosing logic board issues.

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