My 42" hd Sanyo flat

Chances are your backlight inverter circuit has failed, repaired one a few months back with the same problem. To verify this, take the tv in a dark room. plug it in and take a bright\ flash light and shine it on the screen. turn the set on, you should see either the screen saver or video from your source. If this is the case, your inverter is at fault. Depending on your model, your backlight inverter is built onto your power supply board so you will have to replace the power supply/inverter board. Not hard to do, you can do it yourself with care.