Solution:Connect A.C. charger via USB cable to the phone and charge the device for approximately 10 minutes. For the phones with un-removable battery, such as P1 (U9200/T9200), press and hold power button for 10 seconds until phone powers down completely then charge for a while and then press the power button to see if it can power on.
Solution:There may be static charge on the surface of the touch screen. Light press the power button once to turn off the screen then press the power button again to light up the screen. The phone will work as normal.
Solution:Smart phones are similar to personal computers and have a complex operating system. Various 3rd party android applications could cause the phone to restart on random occasions. If the phone does not restart frequently, then the restart may be related to a 3rd party application
Solution:There is a proximity sensor near the top of the screen to detect when something is close to the screen, like when you put the phone to your ear (to save the battery and minimize the radiation). This way, the screen will go off by itself so you can¡¯t accidently touch it when on a call. If the screen continues to stay black while in a call even with no object close to the proximity sensor, verify that the sensor is not dirty or ensure you have protective film that it is translucent.