I have a Hisense model TV202. I do not have the original remote (purchased the floor model). I was using a universal remote to turn the volume down and all of a sudden the tv simply displayed "lock". Nothing I do does anything. I do not have the manual (again, floor model). I called the 800 # for Hisense, but all they want to do is sell me a remote. Is there a way to UN-lock this thing?
I have a hisense TL2020. My son just had a friend sleep over and he told me the next day he pushed something and the T.V. went black. I thought no biggie but then I looked at it and I am having the same issue you have. Mine was also a floor model so not remote. I will keep looking for an answer but if you found/find one I would greatly appreciate you passing it on. Thanks!