Hissing noise,sound goes off and and i have to turn t.v off and turn it back on

This is a protection circuit that prevents the tv from coming on (to stop damage of the components) ....you need to check your voltages off the power supply and make sure they all read well (EX: 24v12v5v etc). Also look for popped capacitors that would make the values lower than need be for the tv to power on properly.

The hiss is a popped (blown) capacitor! You need to replace it before you keep trying to power on the tv...you will cause more damage

Please rate if this helps!