White Screen Issue

hey all, im new to this forum, i have a applemac macbook white late 2007 core 2 duo 2.0 ghz model, n recently when i power it up i get a startup chime and the screen seems to stay white i have tryed numerous attempt to fix it such as changing the screen, ram, reset the smc, still no change according to what i have read up this could be a logic board issue does anybody have any ideas? many thanks, Sean