Mamiya 7 80mm Lens: Filter Ring Replacement and Rangefinder Cam
Originally posted on Instagram. Notes from the repair bench, kept here as a searchable archive. View the original on Instagram
This Mamiya 7 80mm lens arrived with two issues: 1.) damaged filter ring 2.) rangefinder calibration off.
While I can normally straighten damaged filter rings, this one was beyond salvation. At some point, part of the ring had been cut out where the impact damage had been as seen in the first photo. While this would allow filters to be installed, it was quite unattractive. Solution was straightforward: replace the front filter ring. Photo two shows my technique for removing the screws holding on the front assembly on these lenses. A few very light taps (yes, I hold onto the screwdriver) will form the screw to the driver tip and also loosen up the threads from any sealer. Otherwise these particular screws are very easy to damage. Photo three shows the lens with a new filter ring assembly.
In checking the rangefinder cam on the lens, it showed as being out by +0.04mm as seen in photo four. Although this is out of specs (specs are (+0.015mm) - (-0.00mm), it is not out by a lot but coupled with the body rangefinder also being out by about the same, error was +0.08mm which is noticeable in the rangefinder. Photo five shows the lens in a much happier state.
Looking at the lens before I started adjustments, I noticed that the adjusting screw had some sealer on it and it was not factory sealer (photo six). In almost every case, when I encounter this, the lens is not calibrated properly because if you don’t have the correct fixture, calibrating to .01mm or so is very difficult.
