Yeah, I did the same thing at first, because I thought the tv that came with it was broke. Turns out there is a little rocker switch at the base of the screen I didn't see.
Anyway, I put a 22" Vizio in there and it worked, and folded down too. But it felt heavier and I wasn't sure if it was going to be ok or not. This year, we haven't even been watching tv, so I haven't thought about it again.