I have an old FA that I picked up for almost nothing. Seems to work fine and meter just fine but the metering display is out (works but is not responsive; see below).
I have looked at the camera and noticed there are two mechanisms that couple aperture setting on the lens to the body; one inside the lens mount (a robust metal lever with very short travel that changes when you change aperture), and one around the outside (a rotating plastic ring with a square tab that is pushed by a ridge on the lens when you change aperture).
The inside one is fine. The outside one does not travel correctly. The lens only pushes the ring in one direction; and it does not return when you turn the lens ring back the other direction. I'm guessing there is supposed to be a spring inside the mount somewhere which normally makes the ring return to the starting position, and that spring is missing. If I move this ring to make sure it presses against the ridge on the lens, it seems to display correctly, so I guess it impacts the display (shutter speeds change when I change aperture regardless of whether this little plastic ring moves).
My specific questions are:
1. It seems the outer ring only impacts the metering display inside the viewfinder, and that the inner mechanism is what actually controls the metering logic and exposure. Am I correct in this? I will happily just use the camera in aperture priority mode, if so. (Seems weird though; why would nikon use two different aperture sensing mechanisms, one for metering and one for meter display?)
2. Is there a way to replace the spring so that this will function properly.