Rangefinder adjustment

Soviet camera manufacturers strove to keep their cameras as easy to service as possible, in conclave with the Soviet mentality of manufacturing for endurance. (All the more ironic that most Soviet cameras are so delicate.) One of the ways they achieved that aim was by making their rangefinders childishly easy to adjust. Horizontally, that is. Vertical misalignments are more, eh, permanent in nature.

Generic Zorki (and early FED?)

This applies to all rangefinder Zorki's except the 5, 6, and 10 when KMZ got cocky and broke with Leica paradigm. It probably also applies to some of the earlier FEDs, although I haven't tested that because I don't own any.

1. Mount a known correct lens and set it to infinity.
2. Next to the large rectangular viewfinder window is a small screw with a big head: unscrew it with a suited screwdriver.
3. Now exposed is an internal screw. Work it with a small screwdriver while monitoring the results of your action in the viewfinder. Make sure the lens is still at infinity, and calibrate on some very far object.
4. Put the covering screw back on – done!

FED-5/5V/5S

I figured this out myself... heh!

1. Mount a known correct lens and set it to infinity.
2. Slide the name plate to the left. There's a spring on the right, so don't worry about bending it. The plate should pop out.
3. Be careful to not lose the spring! It's a small bent strip of metal that will fly all over the place if you don't watch it. Ideally, keep the camera tilted during the adjustment so it doesn't fall out.

4. Now exposed is an obvious hole in the front, through which you can see an inner setting screw. Work it with a small enough screwdriver while looking through the viewfinder to monitor your progress. Making sure the lens is still set to infinity, calibrate on some very distant object.

5. Snap the name plate back in – done!

Jay Javier has a pretty good overview of rangefinder adjustment.