Monthly Archives: June 2016

Do You Have A Blank Screen When Calling Someone?

When you’re about to ring someone, the screen suddenly turns black before the phone screen gets close to the ear,  you try to push the power button, but it doesn’t even work. The screen can’t be lighted up until the phone conversation is over, this is caused by cellphone’s poor sensor.

black screen

The reason for this symptom is the LCD Screen and front frame has not been pressed by professional equipment in a constant temperature.

If the front housing adhesive used for the screen assembly is not original, its adhesive performance and material quality are not as good as the original. When we go to a Phone Repair Store for a new screen, the shop owner usually assembles the lcd assembly and front housing together at room temperature with his own hands, which directly leads the whole screen’s force point not balanced, nor completed through machines in dwell time(dwell time condition: use pressing equipment in clean room, pressure:0.4 Mpa, temperature:45℃ ). In this case, LCD Screen assembly will be gradually separated from frame which result in poor sensor finally. So there is no surprising that blank screen happens for a phone call.

So why the LCD separation can lead to poor sensor?

First, we need to figure out how the sensor works, as follows:

The sensor is composed of two components: One is to send the infrared ray out, the other is to detect and receive the infrared ray. As the ear is close enough to the phone, the ear can make the infrared ray reflected on the receiving component, so the loop is formed, this signal shows the phone is off, and once the ear leaves the phone which the loop is not formed, the screen can be lighted up again.  working mode

When the glass cover and sensor are not clung to closely, the infrared ray will be reflected by the light-receiving body through the glass cover between two sensor holes, that’s how the wrong loop formed and bad sensor emerges.

poor sensor

Then how to solve this problem?

If bad sensor happens, all you need to do is to put one foam on the glass cover which is between two sensor holes, making it impossible for emitted infrared to produce the reflection through the glass lens between sensor holes. That’s how poor sensor issue solved. That’s to say, it’s only with sensor holes emitting the infrared that is close to the ear, the light-receiving body can be

Operation Guidance

1.Take a piece of foam approximately  1.00*3.00*0.5mm in size.

2. Place the foam attached to glass cover in the middle of two sensor holes (Note: Glue the foam with plastic tweezer to avoid scratching the glass cover and paint loss.)


sensor test