I have a saturn and mine would turn on to the main screen, but would not spin the disc. I noticed if the door was pushed down just a little bit more, it would then spin the cd. I took the saturn apart and just ajusted the arm for opening the lid. it worked fine after that. It has been a few years since I have done it, so I really don't remember the details, but there may be a tutorial somewhere if you google it.
There are apparently some fuses on the CD that can burn out and will cause you CD drive to fail. There is a real good video on youtube that will show you how to repair the CD. http://www.youtube.com/watch?v=v_2uJfWBf...!
Of course make sure that all cables are connected and in good working order. You could try to replace your cd drive for your sega by getting a console that has a working drive. Just checked on ebay.com and there are a few that are inexpensive. Keep those great consoles going:) good luck