74LVC1G99 Logic Gate IC for MacBook Retina 12 A1534 (2015-2017)

On a MacBook Retina 12, a single tiny logic gate can sit in the chain of signals that lets the board power on. If it's damaged, the machine may stay dead even though the power rails ahead of it are fine, which makes it worth checking during a no-power diagnosis.

This is the 74LVC1G99, a configurable logic gate in an 8-pin QFN package, listed for the MacBook Retina 12 A1534 from Early 2015, Early 2016 and Mid 2017.

Signs that point to the gate

• The output signal is missing while its inputs and supply are present.

• Corrosion around the chip after liquid damage.

• A short on its supply pin traced to the chip.

Working on it

The package is very small, so use magnification, fresh flux and low airflow, and protect neighboring parts. Check the pins under the microscope for bridges before power is applied.

Measure the inputs and output again once fitted. If the output now follows the inputs as the schematic shows, the signal chain should continue as designed and the board can move on to the next stage of power-on.