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MacBook Air Won’t Turn On Troubleshooting
Dec 7th, 2017

MacBook Air won’t turn on repair can be seen as one comprehensive fault case with high
difficulty. And MacBook Air won’t turn on issue caused by cockroaches? Have you ever
come across? Today we will introduce a series of diagnostic and repair techniques
regarding to MacBook Air A1466 (Mid-2013) won’t turn on issue. The solution covers
both fault diagnosis by measurement of voltage, current and resistance, and the replacing
of resistor, inductor and IC. Surely you will get surprised.

 MacBook Air Won't Turn On Troubleshooting

MacBook Air Won’t Turn On Troubleshooting

Phenomenon 

Plug in AC adapter, the power light won’t turn on.

MacBook Air Won't Turn On Troubleshooting

The DC Power Supply also displays abnormal standby current. Normal current should be 0.8A.

MacBook Air Won't Turn On Troubleshooting

Disassembling

Disassemble the Mac and Remove the lower case. Traces of cockroaches all around (which caused corrosion).

MacBook Air Won't Turn On Troubleshooting

Disconnect the battery and Remove the SSD module. Confirm the number of logic board, 820-3437-B. Detach the logic board. Active cockroaches can also be seen on the logic board (which caused corrosion).

MacBook Air Won't Turn On Troubleshooting

Warm tips: clean the logic board thoroughly after completion of repairing

Detach IO Board as well and then attach it to the logic board.

MacBook Air Won't Turn On Troubleshooting

Diagnosing And Repairing

Phase 1

Get the Multimeter Prepared at resistance mode. Measure the resistance value of logic board power supply inductors. The value is normal.

MacBook Air Won't Turn On Troubleshooting

Switch to voltage mode. Plug in AC adapter and measure the voltage value of standby circuit inductor. The voltage value is way lower than normal.

MacBook Air Won't Turn On Troubleshooting

Locate the inductor with drawing and bitmap and confirm the circuit diagram of L7095.

MacBook Air Won't Turn On Troubleshooting

MacBook Air Won't Turn On Troubleshooting

Measure the voltage value of IC working condition. The working condition is normal.

MacBook Air Won't Turn On Troubleshooting

Switch to resistance mode and measure the feedback resistance value of IC. The output working condition of inductors should be Vout=1.25V*(1+Ra/Rb). The resistance value is way larger than normal.

MacBook Air Won't Turn On Troubleshooting

So we need to replace with new resistors.

Detach new resistors from the spare plate and solder them to the target board. Then measure the resistance value of resistors replaced. Resistance value of R7095 is 200KΩ, R7096 160KΩ. Which is normal.

MacBook Air Won't Turn On Troubleshooting

Plug in AC adapter. The power light turns on this time.

MacBook Air Won't Turn On Troubleshooting

Measure the voltage value of inductor L7095, 3.41V. Normal voltage value.

MacBook Air Won't Turn On Troubleshooting

Check the current of DC Power Supply. The current is abnormal. Which indicates that the MacBook still can not be powered up.

MacBook Air Won't Turn On Troubleshooting

Phase 2

Measure the voltage value of power supply inductor. The voltage value is erratic.

MacBook Air Won't Turn On Troubleshooting

Locate the inductor with drawing and bitmap and confirm the power supply circuit of L7560.

MacBook Air Won't Turn On Troubleshooting

MacBook Air Won't Turn On Troubleshooting

Measure the voltage value of IC working condition. Pin 23, 8.55V. Pin 29, 4.97V. Pin 22, 3.28V. Pin 21, 3.3V. Pin12, 3.3V. The voltage value of pin 13 and pin 26 is erratic.

MacBook Air Won't Turn On Troubleshooting

We have a suspicion that the power supply IC broke down. So we need to replace with a new power supply IC.

Detach a new power supply IC from the spare plate and solder the power supply IC to target board. Clean the logic board after cooling.

MacBook Air Won't Turn On Troubleshooting

Plug in AC adapter and check the current. The current is just the same as before (with the original power supply IC). The fault hasn’t been cleared.

MacBook Air Won't Turn On Troubleshooting

Phase 3

Measure the voltage value of logic board again. Voltage value of Pin 26 is erratic. So we need to confirm the power supply circuit of pin 26. Roll out the maintenance drawing and bitmap and Locate R7564.

MacBook Air Won't Turn On Troubleshooting

Disconnect AC adapter and switch to resistance mode. The measured resistance value of R7564 is 1MΩ. Which is abnormal.

MacBook Air Won't Turn On Troubleshooting

So we need to replace with a new resistor.

Detach a new resistor from the spare plate and solder it to the target board. Clean the logic board after cooling.

MacBook Air Won't Turn On Troubleshooting

Measure the resistance value of R7564 again. The measured resistance value of R7564 is 0.5MΩ. Which is normal. Plug in AC adapter and check the current. Normal current this time.

MacBook Air Won't Turn On Troubleshooting

Measure the voltage value of resistor R7564. Normal voltage value.

Testing

Get the logic board mounted and turn on the MacBook. The MacBook powered up with normal display.

MacBook Air Won't Turn On Troubleshooting

Assemble the MacBook and test. The fault has been cleared.

MacBook Air Won't Turn On Troubleshooting

We can finish the MacBook Air won’t turn on repairing work by getting the MacBook full assembled.

MacBook Air Won't Turn On Troubleshooting

For more details on MacBook Air won’t turn on troubleshooting, please go to REWA YouTube channel.

Tools Used

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