I have a HP desktop monitor with a LG screen, model # LM200WD1 (TL) (D1). The display is dimming on most of the screen except the upper right but I can still see the entire desktop. It does not flicker or change brightness during use but it is to dim to work with. I was wondering if it was simply the 2 backlight assemblies that need to be replaced or does this symptom require further troubleshooting/parts?