Mamiya 645 80mm f/2.8: Oily Diaphragm and Loose Focus
Originally posted on Instagram. Notes from the repair bench, kept here as a searchable archive. View the original on Instagram
This 80mm f/2.8 lens for the Mamiya 645 wins the prize for most oil on lens diaphragms this week. Also, the focus was very loose and uneven.
For the lens diaphragm, standard removal of blades and cleaning of oil residue from them and the surrounding mechanism.
For the focus issue, disassembly of the lens focus helix to remove old lubrication and re-lubricate. In this case, there was almost no grease on the helical threads. Just oil. Perhaps this lens was in a hot environment for some time and the grease all melted? In any case, oil removed, new lubrication added to the threads and all is well.
Just a note about oily diaphragm blades: In the days when the manufacturers had service centers to fix film cameras, many chose to just replace the diaphragm blade assemblies rather than clean them. Less costly than paying the technicians time to disassemble and clean. That’s why I have quantities of new diaphragm assemblies ready to drop into a lens!
