Black screen I have a portable tv was playing fine then turned on and the screen was dark with a line in the center

Hi,

Sounds like a vertical problem if the center line is left to right. Chances are that it's the Vertical IC. If giving the TV a light tap at the sides causes a momentary opening, then it is a cold solder condition on the same IC.

Both of course would require opening the TV and performing the necessary repair. You should be familiar with components and electronic circuitry as well as soldering.  Should you be not that comfortable, perhaps your best bet is to seek the services of a qualified TV technician.

Good luck and kind regards.