This old a set could have heat issues. I've lost count of how many things I've used CANNED AIR (see google for those all capital words) to clear the vents.
Continued use can reduce what life is left in this one.
Past the user serviceable area with CANNED AIR, we go inside with all the danger signs about death or worse (your choice) to clean heatsinks and possibly replace heat sink compounds.
I have a 2008 47lg50
On any Input after watching tv for an hr and half pic goes to black but sounds continue to play if I shut the tv of and turn it back on in 5 minutes it works again for an hr and half just looking to see if its worth fixing it any help on what it could be???