I would think that this is due to a poor connection to your top screen. The issues are either that the connection is loose that holds the top screen ribbon cable to the board or that the ribbon cable to the top screen is damaged and will require replacing. The only other thing I can think of are the potentiometers that control the screen voltage. Open up the battery cover (philips head) and right next to SL1 are two holes with 'screw' like things in them, these control voltage to the screens. I'm not sure which one is for the top screen, should be the furthest to the right. Grab a thin philips head screwdriver and turn the 'screw' inside there slowly, your screen might fuzz out like crazy, then turn it in the other direction. Hope that this will help you getting your DS back to work. Good Luck