Nintendo DS Unit worked OK. Replaced case. Now on pressing the 'Power' key the green light comes on. A few seconds later the bottom screen flashes and the green light goes off.

1. • 1 Turn off the Nintendo DS, and place it on the charger. Leave the device for 45 minutes to allow it to gain a full charge, and then power it back on. Weak Nintendo ds lite batteries may cause screen flicker.
     
   • 2 Turn off the DS, and remove all game cartridges. Turn the system back on to launch the main menu.
     
   • 3 Click the small sun icon to open the brightness menu. Adjust the brightness level using your stylus. Turn it up to max to improve back lighting.
     
   • 4 Check that the Nintendo DS is open and in the locked position. It must be open to its default position to operate properly.
     

The green light is blinking, no red lights or anything else? The fuse is good as well correct?
Thanks,
Lee

One or both your screens have blown.

Try removing the motherboard from the screens and attach the battery the green light should turn on and stay on.

Now attach the lower screen and turn on. If the screen is ok the screen and green light will flash and then turn off. (if the screen doesn't flash the bottom screen is you're problem and will have to be replaced)

If this happens the problem is then you're top screen which you will have to replace.

yes it is fixable sounds like your fault is with the top screen are the hinges ok has it been dropped.

most green light and screen flashes point to a defective screen or connection on the mother board or sometimes fuses. id start with checking the motherboard connection if its ok check the fuses if all is ok buy a new top screen and replace it.

Check L2 near the power switch on your DS mobo. That part usually get loosen or taken out when you drop your DS. And usually you can recover it when dismantling your DS.

You need to check the top screen ribbon is fully inserted into to place on the board. A green light and flash of the screen within a second means ribbon not connecting right

Easy solution, not so easy to fix yourself. the problem is your upper lcd screen, (yes your upper lcd), once the lcd is damaged, most likly from rolling the ribbon threw the hinge.the system will flash from the bottom screen, this is the start up screen. this i know for i've fix over 100 systems, you can have it fixed on ebay for $45.00, look under repair service nintendo ds lite (texas)

if the bottom screen flashes it's the top lcd screen (yes the top) is broken

umm well dose it just turn off if so there is a ribbon camble with a broken cord in it so you might have 2 replace it sorry but i dont kno wat ribbon cable

there is no power and it will not charge