Sylvania tv/dvd/ht less than a year old will not stay on. When power is turn on screen is black and shows digital TV but will disconnect on its own

Try plugging it into a different socket. That socket could be power surging your TV. Had the same problem, went through 3 TV. Finally had figured it out.

You could also have the older style aluminum inside wiring.

First suggestion from above is a good start. Aldo, you might have a defective receptacle (loose connection) with the plug or behind the receptacle the wiring inside the outlet box.

TV's that have a problem will shut down, and need repair.
Like above, verify you have good power first.