Sharp LC42SB48UT 42 reset - Sharp LC42SB48UT 42 in. LCD TV

maintenance reset = crop 20 -01
developer reset = crop 42-01

re place lcd panel that is dead pixel

try to reconnect all connector on cable box and your cable connection on your TV.

Check its antenna orientation.

my initial guess would be the power supply, but a proper diagnosis will need to be done. Check for bulging capacitors on the power supply board. If you notice any, that's most likely your problem.

Back - light problem. Check and replace damaged component/s at its back-light inverter board, or replace this board as card basis. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts. It will be best to replace the inverter board as card basis.
http://electronicshelponline.blogspot.com/
To some model sets; especially LED back-lighted types; the back-light inverter circuit will be part of the main power supply board [SMPS]. In such cases, the power supply board might need replacement. To some models sets, the back-light inverter and SMPS section circuit will be integrated at its main board itself. If so; the main board should be replaced. To some models of sets, all these section circuit will be integrated at its main board. If this is the case, you have to replace the main board.

I would look to see if this unit has a back light and if so it may be your problem--either the actual back light or the voltage source that powers it.

Not likely to be a do it yourself repair.