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The March 2015 update of Apple's 13" MacBook Air features fifth generation Intel Core i5 and i7 processors, resulting in slightly increased performance and battery life.

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5V rails are not working normally when connecting to the I/O board.

Could you give me advice?

My MacBook Air 13 (2015, A1466) has something circuit problem.

The charging lamp is on, when connecting to the power adapter.

But, the computer does not power on and boot.

Then, I am trying to inspect the logic board and fix it.

The situation is below.

PPBUS_GH3 rails: 8.6V

PP3V42_G3H rails: 3.42V

PP5V_S4RS3 rails: 5.1V

PPV5_S0 rails: 5.1V

However, in case LIO Connector "J9500" on the logic board is connecting to the I/O board using I/O board flex cable, 5V rails have a problem.

PPBUS_GH3 rails: 8.6V

PP3V42_G3H rails: 3.42V

PP5V_S4RS3 rails: no 5.1V (The voltage is too low.)

PPV5_S0 rails: no 5.1V ((The voltage is too low.)

Also, the voltage of 1.2V rails and 1V rails are facing with the same situation.

Although I tried to replace both the I/O board and its flex cable with others, the situation does not change.

Answer this question I have this problem too

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Is the fan spinning up?

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The fan is spinning up without the I/O board flex cable connection.

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You likely have a bad cap in the power circuit. Using a thermal camera or simply wetting the logic board area with 90% IPA which the heat will evaporate quickly Vs the other areas (only a few drops is needed)

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Circu will be eternally grateful.
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