TV backlight is like a strobe light (flashing randomly)

I have a Vizio television that a friend gave to me (model # M470VSE) with a backlight that will not stay at one brightness. It will switch between bright and dim sometimes it will keep switching like a strobe light. I have turned off the the ambient light sensor along with any other sort of auto backlight control. It wasn't but up until recently. This made me finally take the back off looking for any swollen capacitors to replace. After doing some searching I have found none to be swollen. So now I am stuck do I need to start replacing boards?