You need to look at the connector 1 for LCD, it may be damaged or dirty. Try turning phone off, reopen and clean the connectors. Make sure that the pins that connect to the flex aren't damaged and that all the pins are soldered to the motherboard. Any damage may mean that you will need to replace that connector..an extremely tricky job most of us don't have the tools for. Have a look online to see if there is anyone near you who offers this kind of repair/search ebay/google or pop in to your local phone repair shop. You can buy the connector fairly cheaply and ask an electrical/computer repair shop if they are able to do it.