Most likely you have some corrosion damage either on the logic board display connector
[image|2435713]
Or within the displays connection (very difficult to get to)
[image|2435715]
Follow this guide to at least checkout your logic board connection [guide|17045] Follow Steps 1 through 4 to disconnect the battery, then jump down to Step 11. How does the contacts and solder joints look? Post some clear pics if you’ve not sure [guide|21499].