Alpine 6 disc in car dvd changer?

discs load wont play ive had it in for repair they changed the lazer and it wasnt the fault so they say it could be something on the pcb and as they dont have the equiptment needed cant repair this and say it needs to goto alpine thing is i heard tonight it could be the cartridge itself or a microswitch any ideas especially from alpine repair guys or car stereo repairers thanks to all who reply