Hello there Samsung slider phones LCD or screen problem. Always you have seen that samsung phone get problem like some phone doesnt have light in LCD and some times they does not turn on. Samsung slider phones like G 600 , U 600 . J 700, E250 ,D800 and D900.Slider phones always has Ribben ( slidr belt ). And this ribben always connect phone upper part ( screen ) to the mother board.when the ribben (slider belt) got damage then it gives you that problem.it happens when you use your phone roughly or when you dropped your phone on concrete or any different floor.Mostly Samsung phone model U600 , G600 AND J700 has this problem.whenever your phone gets this problem firstly check. And Do not try any flashing or any kind of software tools. it easy to change ribben (slider belt ). Just get ribben belt or some tiny screw driver and some slider opener. this tools are easy to get from any tools shop. then mostly phone has screw. firstly open the battery cover and take it out and see two hole under the battery and when you slide up your phone then you can see two screw just under your phone top keypad just hold the slider for while and open those screw and slide up then see two rubber things are both side on camera. Use any flicker type things and take out that rubber top then you can see two screw just under the screw open those screw then use the slider opener if the opener is tight if slider is loose the do not use opener just take it out so softly and remove the one side of the ribben which you can see connected of mother board just take out ribben and put new one ribben the put all things back as a normal then tight the screws and put battery then turn it on your phone will turn on.some phone like U600 ,j600,has touch panel. this type of model slider belt or ribben always comes with touch panel and its quite difficult and quite expensive to change.Samsung U600 has this problem mostly because they are very thin and then slider belt is as well thin and they get this problem so quickly.