iPhone XS Max Flickering Screen - A False Alarm?

Rédigé par : Phryne (et 2 autres contributeurs)

Difficulté

Modérée

Étapes

Temps nécessaire

Introduction

This is an example of an iPhone XS Max abnormal screen display problems caused by a rare mistake-someone soldered the wrong boards together.

Connect an iPhone XS Max display assembly with the motherboard and connect the battery connector with the DC Power Supply.
Get the motherboard powered on with tweezers. We can see that the screen comes with abnormal display and the boot current is larger than normal value. However, the phone can access the activation screen.
Judging by this, the display problem is probably related to the display circuit, the GPU circuit or the third space PCB.

Let’s check the display circuit first. Run diode mode measurement of the display connector J5700. The measured value is normal. So the display problem has nothing to do with the display circuit.
Next, we need to check the GPU circuit.

We need to separate the motherboard before the test. Place the motherboard on the specialized Heating Platform. 3 minutes later, pick up the upper layer with tweezers and then the lower layer.

Connect the iPhone XS Max display assembly with the upper layer and connect the battery connector with the DC Power Supply. Get the upper layer powered on with tweezers. The problem remains the same.
Which indicates that the display problem has nothing to do with the third space PCB.

We need to continue with the GPU circuit.
Attach the upper layer to the PCB Holder. Open REFOX and find the GPU circuit of iPhone XS Max.
Compare the upper layer we are dealing with and the one on the bitmap, we find that the one we are dealing with is an iPhone XS upper layer not an iPhone XS Max upper layer as described. This is obviously a rare case that you will likely never see in real life.

Try to connect an iPhone XS display assembly with the upper layer and connect the battery connector with the DC Power Supply.
Get the upper layer powered on with tweezers. The phone turns on normally with normal display. The phone can access the activation screen and the boot current is also normal this time.
We can confirm now that our client soldered an iPhone XS upper layer onto an iPhone XS Max lower layer and resulted in the abnormal screen display.