hi after reading about this problem i thought i may help.
hopefully you have not scrapped the television.
A tv with these symtoms, i would begin by replacing the av board ie the audio video board.
remove the back off the tv and look where the main connections for hdmi or scart connections plug in and look for the serial number on the board and look for a replacement board.this is a good place to start.
this issue also can come under a power supply fault in which case i would number two replace the power supply.
where the power lead plugs in.
be aware though there are very high voltages behind a tv so i wouldnt recomend trying unless you know what your doing.