iPhone 7 Plus Dim Screen Issue

Malfunction Phenomenon

For the iPhone 7 Plus dim screen issue, it’s the left side of the screen was dim when we turned on the phone. All other functions worked well.

Trouble Shooting

According to the malfunction phenomenon, this was a backlight issue.

First, we can change another screen to test, the phenomenon was the same, then we can check the backlight circuits by measuring the diode values on the relevant pins of display connector J4502, all the diode values on the relevant pins were normal.

We continued to check the diode values on the small components around the backlight IC, there are two backlight ICs on iPhone 7 plus, U3701, and U4601.

Especially the diode values on the two diodes D3702 and D4602, the normal value should be around 200. After measuring, the diode values were normal.

Then we checked the connection of M2800 by measuring on the A-side of D3702 and Pad 1 of C3718, it showed OL, which means M2800 was broken. 

After we replaced a new M2800, the dim area disappeared, the problem resolved. 

Tips: The combined inductor is easy to break if the temperature is high, so we have to control the heating time and the temperature of the hot air gun, or we can use low-temperature solder paste when we replace it. 

iPhone 7 Motherboard Repair Course