back light flashes on intermmittenly?

i have a sanyo dp42480 that the relay keeps cycling you hear it click every min. or so the back light flashes intrmittenly some times it will stay on long enough to get video and second or two of audio than goes back out. the power supply seems to be good i have my24 volts going to the invertor and all other voltages are there which tells me that the invertor is at fault, the thing that is puzzling me is that when the invertor is failing usally you have audio and video if you put light to screen .can anybody tell me which board is failing