To unlock your set requires two steps: the first is to get past the lock screen.To do that, press the QV( or previous channel?) and 9 buttons at the same time when you are asked to enter your lock code.
Now that you're past the lock screen, find the menu that covers locking and unlocking. QV/9 (previous channel/9) is a one-time bypass; if you turn the set off, it'll be locked again when you turn it on, so you first need to LOCK it again, with a pass code you can remember (try 1,1,1,1). Once you lock it, you can exit from all the menus, then try to change inputs. It'll ask for a pass code, which you now know!
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