it's not under warranty. the 190cs is considered an "obsolete product" because it's not a PPC Mac. the 190 is a 68LC040 version of the PB 5300.
Try resetting your PRAM. When you turn it on, hold down Command (the apple key), Option, P, R all at the same time until you hear the chime a couple of times.
If that doesn't work, it's very likely the display ribbon cable. It'd probably be cheaper at that point to get a newer used 'book. A Wallstreet G3 would be a good buy if you don't plan on running OS X. If you do, then look into the Lombard or Pismo G3, or an iBook 466 or faster.