After I installed new RAM into my 2013 21.5 iMac the LCD started displaying these black bands on the screen. The RAM installation procedure is very difficult because I basically have to take the entire iMac apart. I double checked all the connectors and everything is plugged in. Did I break the LCD while putting the RAM in? Is there something, I should double check? I checked the 2 ribbon LCD monitor cable and they seemed to be plugged in. What am I doing wrong? Please help.