As I have a Logic LCD flat panel TV and there is sound but no picture and I have checked the inputs but it still doesn't work can anyone suggest how to fix this?

With an LCD flat panel TV or monitor, the most common problem is that the back light went dead. It can be either the fluorescent tube or the invertor, which is the high voltage power supply that drives the tube. It could also be the semiconductor that is the switch in the invertor that turns it on and off.

You almost certainly are between a rock and a hard place. If you have to come here to ask this question (and no offense is intended or implied), you probably won't be able to do anything to repair the unit yourself. What you can do is call around to some local shops and describe the problem and see what kind of repair costs you might incur having it repaired.