iPhone 7 Plus Half Backlight/Dim Screen Repair

REWA 11/22/2018

Backlight issues, including no backlight, dim backlight, half backlight, or iPhone won't turn on etc., are commonly seen in iPhone repair for a repairman. Here we will introduce the repair case of iPhone 7 Plus half backlight issue due to pseudo soldering of the display connector and the related backlight circuit. Hope to enlighten you on this subject.


For mobile phone logic board repair, cosmetic inspection always comes to the first. Check the logic board carefully, there is no deformation nor signs of water damage.


iPhone 7 Plus Half Backlight/Dim Screen Repair


Next, let's assemble the phone and test. Get the logic board and display assembly installed. Connect the battery and press power button. The screen lights up and Apple logo appears. We can see with naked eyes that the right side of the screen is darker than the left side. Judging by this, the fault might be related to the backlight circuit.


the fault might be related to the backlight circuit


Take apart the phone and remove the display assembly. Take out the logic board. Run diode mode measurement of backlight relevant pins on the display connector J4502. The measured value of Pin 45 is OL, which is abnormal. A normal value should be around 450.


Take out the logic board


Check with schematics, you will see the voltage outputted from the backlight IC U4601 reaches Pin 45 of J4502 by way of C4602, FL4601 and C4605. So continue to run diode mode measurement of C4602. The measured value is normal. Judging by this, the abnormal value of Pin 45 is probably caused by open-circuited condition of its relevant circuit or malfunction of the display connector J4502. Check J4502 carefully and we find that Pin 45 has been pseudo soldered.


Pin 45 has been pseudo soldered


To further confirm the faulty position, desolder the J4502 from the logic board. To desolder the connector, first stick High-Temperature Tape on components around for protection. Then apply some Paste Flux to J4502 and remove J4502 with 858D Hot Air Gun afterward.


J4502 from the logic board


After the removing of connector, we get access to measure the diode value of Pin 45 on the bonding pad. The measured value is normal.


The measured value is normal.


As of now, we can confirm that the fault is related to J4502. We can fix the problem by replacing with a new display connector. Next, heat with 858D Hot Air Gun. Clean the bonding pad with rosin soaked Solder Wick. And clean with PCB Cleaner afterwards. Apply some Paste Flux to the bonding pad. Get a new display connector in position and solder with 858D Hot Air Gun. Next, secure the four sides with Solder Paste for successful soldering. Once done, clean with PCB Cleaner.


 Once done, clean with PCB Cleaner.


Now we can assemble the phone and test. Get the logic board and display assembly installed. Connect the battery and press power button to power on. The phone turns on normally. The screen is also back to normal. Fault cleared.


 Connect the battery and press power button to power on


Warm tips: get the phone full assembled after confirmation of fault clearance.


Watch the video for more info about the iPhone 7 Plus half backlight/dim screen repair


Tools used in the video. You can also find more great buys on the REWA Online Store.


Communication Maintenance Power Supply 

Digital Soldering Iron Rework Station

Digital Hot Air Rework Station - 861DW

Integrated Mobile Phone Repair Platform

Logic Board Tester for Apple iPhone X

Straight Tweezers BGA Strip Flux Soldering Paste

High Purity Rosin Soldering Flux 


Logic board repair guide:

MacBook Air Won’t Turn On – Logic Board Troubleshooting

Fix iPhone X Keeps Restarting – Logic Board Repair

How to Fix Samsung S7 edge Won’t Turn on – Logic Board Solution

How to Fix iPhone X Won’t Turn on With Logic Board Repair


Want to learn more about the repair? Attend REWA repair training now!  

REWA iPhone Logic Board Repair Training  

MacBook Logic Board Chip Level Repair Training

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REWA is a world leading electronics repair business solutions provider who was founded in 2008 in HongKong. We are committed to delivering one-stop services covering Sourcing Solution, Technical Support Solution as well as Recycle & Resell Solution.

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