RB67 65mm Early Lens (1971): Oil on Shutter Blades
Originally posted on Instagram. Notes from the repair bench, kept here as a searchable archive. View the original on Instagram
Servicing a Mamiya RB67 65mm lens. This early example is from 1971 (Type LH61 made from 1970-1972).
For the first five years of production the 65mm had a flash sync socket as part of the shutter housing. The models from the first three years also had the large M/X sync lever next to the socket as seen in photo two.
This shutter had quite a bit of oil residue on the blades as seen in photo four. The only solution to this is a complete disassembly of the shutter to clean oil residue from the blades and the shutter mechanism.
The shutter blades must be clean and operate with very little friction. There are two different blade styles in this shutter and they also must be assembled in the proper sequence. There are certainly several opportunities for assembling these shutters incorrectly. The video shows a test of the blades after cleaning and they are moving with very little force applied. Also, you can notice that the blades don’t quite fully open. This is by design as they open to 25mm for this particular lens design.
After the shutter is assembled, a flash sync test is performed. The video shows this shutter at more than 70% which is within specs.
