Risoluzione dei problemi del MacBook Air che non si accende

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 MacBook Air A1466 (Mid-2013) won’t turn on the 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.

Risoluzione dei problemi del MacBook Air che non si accende

Phenomenon

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

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

Disassembling

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

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).

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

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

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.

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.

Locate the inductor withdrawing and bitmap and confirm the circuit diagram of L7095.

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

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.

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. The resistance value of R7095 is 200KΩ, R7096 160KΩ. Which is normal.

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

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

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

Phase 2

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

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

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.

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 the target board. Clean the logic board after cooling.

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.

Phase 3

Measure the voltage value of logic board again. The 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.

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

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.

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.

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

Test

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

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

We can finish the MacBook Air won’t turn on repairing work by getting the MacBook full assembled. And do you want to MacBook air ram upgrade, you can read this post.

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

Tools Used, for more repair tools please go to shop.rewa.tech per ottenere.