There is a real good video on youtube that will show you how to repair the CD.

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

Updated this old answer due to somebody having some issues with the original answer.