The DS top screen has two components, which are the LCD display, and the backlight. If the LCD display has gone bad but the backlight still works and the connecter is seated properly, the DS will still power on and the lower screen will be normal, and the top screen will light, but it won’t display anything.
You didn’t mention if your DS is the original DS or the DS Lite. Replacement top screens for the DS Lite are cheap on eBay, but installing the screen is a bit complex. The screen for the original DS is a different part and they are more expensive and hard to find.
I’ve never worked on an original DS, so I can only tell you about installing the top screen on a DS Lite.
First, the DS Lite has to be just about completely disassembled. You have to completely remove the top and bottom cases, pull out the microphone and wi-fi cables, and release the connecter for the top screen, which is located on the main board in the lower case. You’ll need the tri-wing screwdriver. You can
leave the bottom screen/touch screen assembly attached to the main board, but be careful not to pull or tear the flex cables. Check YouTube for videos on disassembling the DS Lite.
Here’s the deal breaker for most people: The speakers are soldered to the flex cable of the top screen. I’ve never seen a replacement sold with speakers. You’ll have to unsolder your speaker wires from the old screen cable and reconnect them to the new one. If you can’t solder, you could take the screens to a local tv/electronics repair shop and pay to have it done.
I got this information for you from http://wiinewz.com/forums/nds-general-discussion/72805-ds-top-screen-white-blank.html
this appears to be a common problem
I hope this helps