RB67 50mm Lens: Lockup from Damaged Rear Shutter Housing
Originally posted on Instagram. Notes from the repair bench, kept here as a searchable archive. View the original on Instagram
A Mamiya 50mm RB67 lens came into the shop and the complaint was that the lens was causing the camera to lock up. While this is often an issue with dried lubrication, this one was different. Checking the shutter, I found that there was a difference of almost 0.15mm on the rear shutter housing as seen in the first two photos and the cocking mechanism was being squeezed tight and would barely move.
Oddly enough, I did not see signs of an impact to the shutter which is what you usually find when things are this far out of spec (I can accept it being out by 0.04mm or so and still work OK). I also tried to put a gauge in between the housing and the collar and as you can see in photos three and four, it was a no-go on one side telling me that the rear housing was damaged. I finally had a use for my so-called “feeler” gauge after 30 years as I have not had a vehicle with ignition points in about that length of time.
The solution in this case is to replace the complete shutter casing and a bit of work is involved in that process. In this case, I did not proceed with the repair due to cost. The last photo shows the new old stock replacement part from 1973 with a price of $52. While this might seem like a lot of money in 1972 dollars, keep in mind that these lenses had a new replacement cost of around $1500 or so back then so spending $500 to repair them might be cost effective.
