LCD screen black when powering on

I just completed an ssd installation in my mid-2011 21.5'' iMac. When it powers on I get "the tone" however my LCD screen remains black. I opened up the back and checked the diagnostic LEDs: lights 1, 2, and 3 are lit and steady, however the fourth does not light up. I looked up what this means and took the LCD screen back off, replugged all the connections but it remained as before. Additionally, a few seconds (~10) after turning on the fans turn on and go to max. I'm not sure if that's related in any way or if that's just something else.

The installation of the ssd was prolonged after I had serious trouble getting the logic board back in. As it stands it's all "in place" but it's not perfect. I don't think I damaged or otherwise messed up the logic board, but I was a little rough with it, and spent a lot of time (man)handling it.

Anyway I'm not really sure what to do about it. 3/4 LED lights on makes me think I didn't accidentally break my logic board or something horrible, but I can't think of what could be causing the LCD screen of all things to be malfunctioning. I'm going to be taking it to a repair shop, so whatever I can tell them to guide them the better.