There is one way to tell if the remote(s) are turly dead or is it the TV set.
If you have a cell phone with a camera in then try this test.
First you need to see if the camera in the phone will see the infrared light (IR) from a remote, find a working remote from something else,(DVR, second TV set) then enable the camera function on the phone, point the test remote at the phone, see if you can see the remotes IR led blink on the phone.
If this works then try one of the Sharp remotes and do the same test, if you can see the remotes LED blink then it may be the TV set it's self, if not then you need to try a new remote.
One good brand of remotes is the ones from Logitech, they make a very fine remote that is programmed via a web site, you select the type of device by the model and make, you then set it up like you want it to function, once this is done it then configures the remote by a USB cable, when done it will act just like the OEM remote.