I bought a MBP 2013 Retina A1398 that doesn't work when an LCD is plugged in. The external HDMI port works fine and so does the computer, so I believe its not a graphics card issue. The LCD works fine on another laptop, so I know its not an LCD issue. I read this: https://www.ifixit.com/Answers/View...nd+type+is+the+same+for+a+Mid-2012+Retina+15" and get a reading of 0 ohm across Fuse F9700, so this would mean its good right? I shined a bright light behind the apple during boot up and can not see anything. Im not sure what fuses i need to test or how to tell if they are bad. Does anyone have experience with diagnosing this issue?