How can I fix My Slide Projector KODAK CAROUSEL S-AV 2030?

I have a very old KodakCarousel S-AV 2030 Slide Projector Has been a good old work-horse.The slide-holder or carriage only partly goes down..gets stuck,hence you can only see half the slide.I took it to Jessops and they sent me a letter back saying it needed no new parts but would cost £148.00p+ VAT.Has anyone any ideas how i can mend this.I thought it may have been a spring .I have been on Kodak Web and got a manual but still no better off.