I have seen exactly one Zenith projection TV with the motorized screen; it was at a TV shop in my home town in the 1980s. I never saw the set working; I just remember seeing it on the sales floor and seeing an ad or two for the set online. That set was called the "Space Screen 45" and also had Space Phone, in addition to full remote control.
I'm not surprised that many if not most of these sets had the screen's drive motor disconnected after a year or two; the mechanism that raised and lowered the screen must have been complicated as all get out, so no wonder the drives went bad after such a short period of time. Many people who owned these probably figured it was better just to fix the screen in the up position and unplug the motor when it went bad (if the rest of the television still worked well enough to watch) than to have the drive mechanism repaired.
How good or bad was the picture on these sets, anyway? I just read a post in this thread that said these TVs didn't have the best pictures by any means, the fact that they were Zeniths notwithstanding. Were these sets really that terrible as far as picture quality was concerned? I would think, for the amount of money these sets sold for when they were new, they would have a fairly decent picture out of the box and for some years afterward.
The Space Screen 45 was a novel idea, but from what I just read about it, the picture quality, along with the troublesome mechanism to raise and lower the screen, made these sets an embarrassment to Zenith and an insult to the company's 70+-year reputation for quality as well. I wonder just how much money Zenith lost on warranty repairs on these sets.
I never owned a projection TV in my life, and wouldn't want one today. They are probably much more reliable than they were 30 years ago (the heyday of the Space Screen 45), but they are huge, and I'm sure I would not have the room for one in my small apartment anyway. I don't care for plasma TVs either, due to their problems with burn-in, et al. In my opinion, the best kind of flat-screen TVs are the LCD-LED sets, which use arrays of light-emitting diodes rather than a cold-cathode fluorescent lamp to illuminate the screen. They are light in weight, consume less energy, and I am sure they make much better pictures than many plasma sets today.