I have a Sony CDP-C910 CD player that quit playing last night. This unit uses cartridges to put the CD's in, 10 CD's to a cartridge. Each cartridge loads OK however when I try to play a CD the system doesn't try to play it and then reloads another CD, this cycles through until all 10 have tried. Any ideas what is wrong and how to fix it? The unit was built in 1991 however it doesn't have that many hours on it, maybe 200 total.