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ITiPhone 8 Plus turns on with black screen. What will you start with?
For screen issues, the most common solution is to replace with a new display assembly to see whether it’s a screen problem or a board issue.
As for black screen issues, we can also start with the boot current.
Run boot current measurement first.
If the boot current is normal, then we can confirm that the phone is turning on with no display.
As for display issues, find the display connector at the very beginning.
Related post: Samsung Galaxy S6 edge+ Turns On With Black Screen
Sounds quite simple? Well, follow our repair guide and you can figure it out by yourself.
Problem
Press power button to power on. There is no response from the phone.
Disassemble the phone and disconnect the battery.
Connect the battery connector with DC Power Supply and press power button to power on.
Current reading on the ammeter is normal.
Which indicates that the phone is turning on, yet with black screen.
Diagnosis
Since J5700 is the LCD/touchscreen connector of the logic board, we need to run diode mode measurement of J5700 first.
The measured value of Pin 39 and Pin 45 on J5700 is 0. Judging by this, the fault is related to relevant circuit of the two pins.
Refer to Refox – the maintenance drawing and we can see that the two circuits are parts of the screen backlight circuit.
Now we need to run further measurement of the two circuits. We can start with R5730 and R5733.
The two are Zero Ohm “resistors” that usually act as protective roles on the circuit.
R5730 and R5733 are located under the shielding cover.
For better operating, we have to tear off the shielding paste and remove shielding bracket with Cutting Nipper first.
Attach the logic board to PCB Holder and run diode mode measurement of R5733 and R5730.
The measured value of Pin 1 on R5733 is normal and there is no measured value of Pin 2 on R5733, which is abnormal.
The measured value of Pin 1 on R5730 is normal and there is no measured value of Pin 2 on R5730, which is also abnormal.
Judging by this, R5733 and R5730 have been damaged and we need to replace with new resistors.
Tips
As R5733 and R5730 are Zero Ohm “resistors”, we can simply replace with new resistors or replace with ferrite bead inductors.
Troubleshooting
Detach R5733 and R5730 from the board with Hot Air Gun.
Apply some BGA Paste Flux to the bonding pad. Then apply mid-temperature solder to the bonding pad with Soldering Iron. Once done, clean the bonding pad with PCB Cleaner.
Then apply some BGA Paste Flux to the bonding pad and align the two inductors to the right place. Solder with Hot Air Gun.
Once finished, wait for the logic board to cool for 5 minutes. And then clean thoroughly with PCB Cleaner.
Reassemble And Test
Get the logic board mounted first. Then run diode mode measurement of Pin 39 and Pin 45 on J5700.
The measured value is normal this time. Continue to buckle the display assembly and connect the battery. Press power button to power on.
The phone turns on with normal display. Run function test. All going well.
Tools & Parts Needed
- Motherboard Repair PCB Holder
- Hot Air Gun Rework Station
- Integrated Mobile Phone Repair Platform
- DC Power Supply
- iPhone Disassembling Tool Kits
You can also visit REWA YouTube Channel to check our video and learn how to fix iPhone 8 plus black screen issue.
