I seen your other post that said this happened after the phone had been dropped. A white screen usually means that the LCD in the display assembly has either been damaged or its connection to the logic board may have come loose. The LCD is the part of the display that is responsible for displaying the image on the screen. So you may want to disassemble the phone enough to be able to check its connections to the logic board. If the LCD connection is properly seated to the logic board then the LCD was definitely damaged during the drop and will need to be replaced. If there are any cracks in the screen I would suggest replacing the whole display assembly. Hope this information is useful for you.