Recently we noticed some complaints about MacBook air black screen issue during system boot.
Instead of a traditional blue screen, the MacBook air is booting to a completely black screen with the initial “chime” sound.
And keyboard backlights are also on.
Which means the MacBook is on, well supplied by power and runs normally, and you just can’t see that it is.
Our previous post How To Fix MacBook Pro Won’t Turn On explained some kind of power-related issue that prevented the MacBook from turning on as expected.
Different from that, however, this time the MacBook is well turned on and booted to a completely dark screen due to some display issue.
The situation may be rare, but we take it a good opportunity to share the potential logic board solutions for MacBook No Display Repair.
If you have different opinions or solutions, please leave a comment below.
MacBook No Display Repair
Disassembling
Power button power up.
The MacBook is booted to a completely dark screen.
Yet keyboard backlights are on, which indicates that the MacBook is on with no screen display.
Disassemble the MacBook.
Disconnect flex cables and remove screws.
Then detach the logic board and remove the SSD and WiFi modules.
Diagnosing
Run a cosmetic inspection—whether there are mildew, component missing or burnout on the logic board. No particular damage.
The test grounding resistance value of fuse F7700 with diode mode and the value proves to be normal.
Then connect AC adapter and test voltage value of fuse F7700, the displayed value is 8.58V—normal value.
Test grounding resistance value of logic board display port pins with diode mode.
All display normal value.
A test grounding resistance value of backlight resistors with diode mode. All display normal value.
Connect AC adapter and test voltage values of display chip U7701 and nearby components. BKL_SCL displays abnormal voltage value (3.3V under normal circumstances).
Roll out the maintenance bitmap and locate BKL_SCL.
Confirm the corresponding resistor as R7753.
Then roll out the circuit diagram.
Analyzing the circuit network, we find that SCL is connected to pin D3 of U7701 via resistor R7753.
Then we can infer that U7701 might broke down.
Repairing
Remove the sealing adhesive around display chip U7701.
Take down display chip U7701 with the help of some BGA paste flux.
Use a soldering iron to flat the bonding pad and then clean the bonding pad with PCB Cleaner.
Apply some BGA paste flux to the bonding pad and align the new display chip with a hot air gun.
Cool down the logic board with the ion fan.
Connect AC adapter and test voltage values of display chip U7701 and nearby components.
All display normal value.
Testing
Insert the SSD and WiFi modules and assemble the MacBook.
Power button power up, the screen displays normally. The fault has been cleared.
For more details on MacBook no display repair guide, please go to REWA YouTube channel.
