Mamiya 7II: Replacing a Broken Double Exposure Switch
Originally posted on Instagram. Notes from the repair bench, kept here as a searchable archive. View the original on Instagram
A common issue that I see is a broken Double Exposure slide switch on the Mamiya 7II. The camera presents as either in photo two with it totally missing or in photo three with a crack. Either case is caused by the plastic deteriorating and cracking or crumbling. The fourth photo shows what this looks like from the back once the top cover is removed.
Photo five shows all the parts that make up the Double Exposure assembly and the problem is that if the inner parts fall off into the camera, there can be some danger of them getting into the winding mechanism as they are located right next to the wind gears.
The client of this black Mamiya 7II provided me with a brand new part which I installed. While that will fix the lever, the issue of aging plastics is still here even with a brand new part as it will be at least 12-25 years old. When I installed this new part I could see a tiny crack developing in the threads!
Also, around year 2000 Mamiya changed from a 1.7mm threaded machine screw to a 1.7mm self tapping screw. Photo six shows the subtle difference in the screws, the self tapping screw with more aggresive theads is shown on the left. So, when switching these parts, you do have to make sure that you have the correct screw for the new part. Final photo shows this completed repair.
