Sometimes having a repair manual still is not enough information to fix a VCR. You'll likely need parts and some experience with repair. The service manuals may only help you in finding out what's wrong -- not in fixing the problem. In fact, sometimes a DIY job will just risk breaking the unit even more, as VCR internals can be quite delicate, brittle or flimsy!
Where are you located? If in the USA, then considered sending it to a reliable repair shop. All of our equipment is serviced by Jots Electronics
in the Dallas, Texas metro. I'd say the average total cost (repair, cleaning, shipping) of the AG-1980P units is about $300. But these are pro decks, and very much worth it. If this is equipment used for a business, just invest in the pro repair work.