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As audioguru stated...... try this: in a room with no lights on, in the dark, power on the set and take note if you observe a dim glow from the LCD panel. If you can see a faint glow (or obvious glowing dark gray screen) the backlight lamps and the inverter circuitry are likely working OK. You may have a problem in the video processing section instead. If the LCD panel is dark black (as when it's powered off) then I'd suspect the lamp inverter board first, and then the lamp(s) secondly. Most lamps seem to outlast the inverter circuitry, hence why that would be suspect #1. Some inverter boards have a fuse on them that could have opened for one of more number of reasons.