Nikon EM/FG/FM/FE lightmeter repair to fix jumpy needle problem.

I recently acquired a Nikon EM. Small, light, beautifull and contains the only automation I ever use: aperture priority. The problem with these cameras is that the lightmeter is often defective.

The symptoms start with a jumpy needle: the lightmeter needle in the viewfinder jumps up and down whenever the aperture ring is turned. Before taking a shot you need to wiggle the aperture ring a bit to ensure that the exposure will be correct.

The repair for this was very easy: first, you unscrew the 4 screws that hold the lens mount. Next you remove the 3 screws that retain the plastic front plate. Be carefull when you remove the top, since this snaps under the top of the camera. You don't want to break any plastics. Next you remove the lens mount, the metal ring and the plastic ring. At the top part you can see the variable resistor that implements the diaphragm sensor. It is a white plastic plate coated with 2 metal strips. The ring that sits around the lens mount contains a tiny gold plated contact at the back which drags over the 2 metal strips. The problem with the light meter is that the metal coating on the plastic has oxidized. To remedy this, take a cotton bud, dip it in alcohol and clean the metal coating. I did this 3 times until the cotton but stayed more or less white. Don't use too much alcohol. It's a solvent and you don't want to get any of it in the camera or on any contacts.

In reassembling the camera you need to pay attention to 1 thing: the diafragm ring is meant to be spring-loaded. The first time I reassembled this camera the metering ring didn't return to it's starting position when I turned the diaphragm. There is a small white gear (behind the red circle in my image) that is connected to a spring. This gear engages in the diaphragm sensor ring. If the spring is unwound when remounting the camera, it will not be able to do it's job.

To wind the spring before assembly, you insert a small jewelers' screw driver from the top in the screw that sits in the center of the spring (again, indicated by the red circle). You wind the spring all the way and then, whilst holding the screwdriver, replace the ring over the camera in the counterclockwise most position when looking at the front of the camera. Now the diaphragm ring will return to the resting position without trouble.

This lightmeter repair takes about 15 minutes in total and can probably be performed on any Nikon SLR with the needle lightmeter system: Nikom EM, FG, FM,FE and maybe also the Nikon FA (is has an LCD meter instead of a needle, but I think it still retained the same diaphragm sensor).