Well from what i can see the LCD is composite so S-video won't work.
Are you sure the power wires are right?
If so then all you have to do is hook up the composite signal to test.
the wires that have nothing could be nothing its a standard socket so no all pins have to be used.
Also u said a little black box is used im wondering it this box powers but also switchs the video source.
But i don't know if the button for video source is on the LCD or not.
use a composite signal and try it no harm in testing as long as the power wires are right u can put the composite signal on all pins (besides power wires )