Hello, I have bought a Samsung 850 512GB SSD for my mother's mid 2010 iMac. I was able to swap the original hard drive with the SSD and install Yosemite on it. It went great, but after a day, the screen went black and I don't hear the welcome music when I power it on. I was wondering what it could be since nothing has changed. I haven't moved it or whatsoever. Swapping back to the original hard drive make the iMac work. Any idea what is going on ?