good day to all got a '''LG 49LF5400-UB which suddenly jus went black but the sound was still there and i could still use the remote jus couldnt see anything on the screen. so i held a bright light next to the screen to see if there was any image but there was none so i opened it and saw that when i on it the back lights would come on but the screen still remained black with sound. so i ordered a t-con board and replaced the existing one but it did the same thing . do i need to replace the mainboard or powerboard or is there something else thats wrong .id greatly appreciate some help'''