You can try unplugging the TV from the wall for an hour and plugging it back in. If that doesn't help try
They sell replacement boards and are very helpful.
If you don't feel you can open the TV and work on it yourself a repair tech is your next step.
3 ways to reset Sharp LCD TVs and enter SERVICE MENU, unplug tv hold buttons input and vol.- and while holding buttons plug in tv power till tv boots up K popup should appear then press together ch- and vol- to enter service menu, or also try press menu 9,9,9,2,2,2.