Blu Life Play X, Service Manual

Page: 18 / 27

18 / 27
2.2.4.1 Analysis of the Keyboard Fault
This board includes 3 side-buttons. All the keyboard circuits use the scanning method to detect
except the power button, volume up and down. The scanning signal will be triggered when a
button is pressed,, then the corresponding row and column will be detected, the function of the
key can be identified according to the software definition.
a. The cell phone can power on
，
but all the keys are invalid.
In general, this situation is caused by some key short-circuit, the equivalent of a long
pressing this button.
At this point ,you should analyze the following first
：
⑴
Check peripheral TVS of the button to see if they are short-circuit.
⑵
Then ,check the connector to see whether it is short-circuit when it is welded.
b. Failure of a single button
This situation needs to check whether the beneath of the DOME key is dirty. If the
problem is still existed, you have to check whether the circuit is open.
c. Failure of a few buttons
This situation is usually caused by a short-circuit row or column. Checking the
interface circuit to see if it has open weld phenomena and detect the disconnected
phenomena of the resistance.
2.2.4.2 Analysis of the Display Module Circle
Display module use the 4.7"IPS LCD, which including 4 pairs MIPI differential bus mode. All of
commend and data go through the MIPI differential bus mode except the reset signal.