Here's the story. For years I've had a 2010 macbook pro mc374ll/a (We'll call this LaptopA) and it's served me well. One day I manufactured a new charger for it myself and it ruined the computer. How? I was not so sure. So six months after it had become sterile I went and bought a second working mc374ll/a (We'll call this laptopB) so that I could diagnose my own. The first step was getting new chargers and new batteries for both. After I installed the batteries LaptopB was working perfectly where as LaptopA seemed functional, but was suffering from a black screen. Eventually after a bit of experimenting I found the problem wit LaptopA. It was simply a faulty LCD Connector Cable. I was very excited because this was only a $3.00 fix and I was going to be able to sell LaptopB for more than I had bought it for once reassembled. Unfortunately it seemed that some force had other plans for me. Ok... I had taken the LCD cable from LaptopB and hooked it up to LaptopA. I tested LaptopA while: 1. The LCD display was free but plugged in to both ports of the logic board and resting on a towel. 2. The wifi hardware and webcam were not plugged in. 3. All of the rest of the computer was assembled, in its casing and resting while overturned (keyboard facing down) on a towel. It worked. It powered on just fine like it was bran new. When I reassembled it... It did not charge or power on. I could not figure out why. So... I began to reassemble LaptopB. I took the LCD wire out from LaptopA and put it back into LaptopB and tested it in a disassembled state just as I did with LaptopA. It also worked liked normal. So I began to reassemble LaptopB and guess what? Once I was finished... It did not charge or power on. Now I am in deep here and have TWO dead laptops. Does anyone know what might of happened here? And how does one properly reset the SMC? Although I do not think that will be my solution.