I just received the RCA Selectavision player that I won on eBay, and upon hooking it up, it worked for five minutes perfectly. Then I turned it off, went to the garage to look for something, and when I came back 10 minutes later, I tried playing the disc again (The Dead Zone) and it wouldn’t play it. The screen was black with some tracking, and there was no audio. I opened the maintenance hatch on top and looked in, and I noticed that although the disc was spinning, the metal cartridge containing the stylus (which is supposed to automatically slide down and read the disc) was not moving at all.
Most probable cause is simply gummed-up lube on the mechanism, or a rubber part, such as a belt or roller has broken. Just for sitting in a closet, lube turns to gum, and rubber parts will dry-rot.
The huge trick will be to find parts. RCA stopped production of the major consumable part - the stylus - in 1984 or so, but belts and rollers are hopefully somewhat generic and available from anyone that repairs VCRs.
Uh-oh… Who repairs VCRs any more? Parts are still out there - somewhere. Someone like MCM Electronics might have what you need. They claim to have access to all RCA repair parts, but their site search turns up nothing for CED or Selectavision. They used to have VCR belt and roller kits by the dozens, but now, they’re down to only one. Your best plan might be to try and figure out what’s broken, then call them up and hope the mythical “old guy” answers and remembers these machines when they were new.
If you’re actually buying a Selectravision, you probably already know these websites, but there is a CED discussion board here, and this site has some info on parts.