Sharp 14AG1-S TV with no raster

Please guys I need help on a sharp TV am working on,  the problem is that there is no raster but the blue background is there, when  you plug an AV wire the blue background will disappear as if the picture will come but it will come and if you remove the AV the blue background will come back. Please help me out. It is a sharp TV  model No 14AG1-S