Press the Menu button on the remote
Go to System
Select Reset & Admin
Select Reset TV to Factory Defaults
Enter the parental control PIN if prompted
Confirm the reset
Wait for the TV to restart and complete the reset
If you do not have the remote, press and hold the Input and Volume Down buttons on the TV for 10 to 15 seconds
Release the buttons when the TV resets or restarts
If that does not work, unplug the TV, then hold the Power button on the TV for 10 seconds
Plug the TV back in and try the reset again