My Sony XBR-55X900B TV blinks 5 times and does not turn on.

I have a Sony XBR-55X900B. The tv is about 4 years old. At first the tv HDMI connection 1 was not working. Several months later the tv would not turn on and the red light began blinking 8 times over and over. I was told to get a main board and I did so. At this point the TV is now blinking 5 times. Can someone please assist me in diagnosing this issue.