Turns on but has black

Make sure that the console has its A/V cables plugged into the back of the console and the television, if it is and xbox 360, make sure the switch at the end of the base is turned to the right tv type.
There also may be a problem with your A/V cable which can be solved by buying a new cable they are cheap and won't set u back much. Let me know if this helps. :-)

If it is an modded wii throw it in the garbage else repair it.
im not kidding.