You have to use your remote to get into service mode. Press sleep timer button, then quickly press video status and display at the same time, this will give you the service mode menu on the screen. Click on 2.DEF. The setting number will be at bottom of screen, D15 is horizontal size, D03 is horiz position. I have a av27f485, your menu may be similar. Do you notice any picture distortion center and right 1/4 of screen when camera pans left or right, or vertical up/down?? I found the service manual at www.fileshare.eshop.bg/index.php?