Poor Image Quality
If the in-game visuals have deteriorated, appear scrambled or flicker, your NES might be dirty. Unplug all controllers as well as the power adapter, and clean the surface of the NES as well as all ports (including the big game port at the top) with a damp rag. Be careful not to bend any pins inside the ports.
Game Screen Goes Blank
If the NES power light is on but the screen turns solid white or black when you start a game, you might have a dirty or damaged game cart. Pull the cart out of the game cart and wipe it down with a soft cloth to remove dust. You also can use a small electronics vacuum to pull out any remaining particulates.
Power Light Doesn't Come On/Flickers
If the power light on the NES does not come on or flickers on and off, you might have a problem with the power adapter and will need to replace it. The NES takes a 9-volt adapter with a 120-volt input, so finding a replacement should be fairly easy.