no video display on old as well as replacement lcd screen

My phone, LG Venice AKA LG Optimus Showtime LG86C LG730, was very quickly submerged. I have dried it out with rice and the alcohol. I have looked everywhere for signs of corrosion with nothing anywhere. The phone works perfectly, except i get no lcd power. I have replaced the screen and still darkness. The menu buttons work, the speaker works and touch works and it will even make phone calls.

I need to figure out how to troubleshoot the out put from the motherboard to the video on the lcd. Anyone?