Second N80 arrived today. This one was also $20. I thought I had paid $20 for a spare door and battery cover for a while as the camera was totally unresponsive, only showing ERR. It would not even focus, I spun the focus ring on the lens wondering if the motor just had a dead spot, nope. Tried resetting, only got ERR and no reset. after messing with it for about 20 minutes I was resigned to having lost on this gamble.
So, I took the lens off, but forgot to turn off the camera first. When I did the shutter fired 3 or 4 times in a row. I fired the shutter a few more times and it worked. Put the lens back on, the focus motor is working now! Tried resetting and was able to reset all modes! fired the camera about a dozen more times to loosen things up a bit, put a roll of film in it and gave it to my 10 y.o. son to go give it a work out. I'll know how that went in a bit.
Moral to the story, never give up on an N80! LOL.