Welcome. I am Mike, an experienced field technician. We are now connected together on this convenient website where I am able to help you.
You can try unplugging the tv POWER cord for 3 full minutes and holding the power button on the tv for 30 seconds, then release, before plugging it back in.
If that does not help then in your own words, describe your level of experience with electronics because at this point the tv needs diagnosis, parts, and service. I can help with that but if you do not have the needed skills and tools then having it repaired by a local shop will end up costing almost as much as a new 50" tv. Just an in home diagnosis is usually at least $100 up front.
I'm sorry for the bad news. I do understand that finding out your tv needs expensive repairs is not pleasant but at least now you can make the most of your situation without high repair costs and long wait times. You saved a lot of time and money by coming here first.
Remember, I will be here with you throughout this entire process. Unless there is something else you can think of, please take a moment to submit at least a 3 star rating at the top of this page before you go. Rating now does not close your question or prevent future replies which are at no additional cost.