The only thing wrong with the SC4 I bought from a gentleman was the cd changer was not working and is too expensive to have fixed.
I read up on the subject and saw a lot of discussion on it (rollers, skipping, etc.) and the concensus was it is a piece of junk and throw it out.
I tinkered with mine and after figuring out how it works got it working just fine.
There is a reset button, a probe that that recognizes the cartridge is inserted and an arm that pushes/extracts the discs.
After cleaning rollers, lubing parts and freeing up extractor arm I pushed the silver button that lowers the cartridge, reset the unit and now it works great!
Though the unit is terribly over engineered in my opinion it is functional and I think some dealers/repairman are making a fortune off some Lex owners though I am sure there are times the units are actually blown.