No picture or sound

what brand and model no#
how many times does it blink ? does it blink (led's) at all?
if led comes on and no picture you have a power issue

if your tv does not display menu when you turn it on or does nothing
your tv is not powering up the panel, it must be theres a problem internal circuts or internal boards,

your tv needs a repair service center they will know what to exchange or repair..

hope this helps
happy holidays