Nikon FM2n: Fallen ADR Mirror Jamming the Camera
Originally posted on Instagram. Notes from the repair bench, kept here as a searchable archive. View the original on Instagram
This Nikon FM2n came into the shop with a piece of the broken ADR mirror in a bag. The camera owner explained how the camera was jammed and he removed the bottom cover and the mirror fell out. This is not uncommon as the small mirror which squirts the lens aperture information from the lens scale to the viewfinder is glued in place at the top of the prism and when it breaks loose gravity brings it to the bottom of the camera where the winding mechanism will chew it up and eventually lock up the camera in some cases. Photo three shows the location of the mirror at the top front of the prism with the two adjusting screws covered with red sealer. The fourth photo shows the broken mirror and the frame removed from the camera ready to accept a new mirror.
The FM2, introduced in 1982, was soon replaced with the FM2n which had a slightly different shutter and a higher sync speed. From 1982 until around 1989 or so, the shutter blades were made of honeycombed titanium, show in photo five. These blades were very thin at 0.02mm and traveled quickly at 3.3ms and Nikon did have some issues with shutter integrity so five modifications were made to improve the blades. Finally in 1989/1990 Nikon switched to the aluminum flat blades shown in photo six.The biggest issue with these blades was actually caused by users who poked their fingers into the shutter. Once this happened, blade replacement was necessary as the thin blades were irrevocably damaged. Photo seven shows a shutter that came into the shop with finger damage and how someone had attempted to “fix” by pushing the blades back in place. Photo eight shows the same shutter from the other side. Needless to say, new blades needed to be installed.
When commercial clients were using film many years ago, I had a repair account with the local PD crime lab. They had around one hundred of these FM2 bodies in circulation at any given time so every week I was brought a box of repairs. The cameras actually held up well, the biggest issue was impact damage or fingers in the shutter.
