I have an old macbook 13, with a cracked lcd screen and a dead battery that was giving to me. So i decided to open it up and clean it out and replace the screen my self. I took out the ram and hardrive, and then put them back in correctly after I was done. Now my computer just comes on but the screen doesn't, I know the screen wont come if the computer doesnt detect the ram. I know for sure the ram is secure and locked in place because I havent put the l bracket back on. Could you tell me what the problem is or what I did wrong?