Mamiya 7 43mm Lens: Bent Filter Ring Binding Diaphragm Ring
Originally posted on Instagram. Notes from the repair bench, kept here as a searchable archive. View the original on Instagram
This Mamiya 7 43mm lens came into the shop with impact damage. The diaphragm ring would not move. After removing the filter ring, the diaphragm ring did move smoothly so this tells me that the filter ring impact damage (not really visible) was enough to bind the diaphragm ring when things were screwed tight.
The second photo shows the two rings and their relationship to each other which is very close, does not take much for them to bind.
The third photo shows the back of the filter ring with the detents for the click stops.
Photo four is of the tools that I used to straighten out the ring which is placed on a metal anvil. In the foreground is a scrap ring and a block of aluminum. In the fifth photo, I have put the scrap ring and the aluminum block on the filter ring. Not shown is my hammering on the aluminum block.
The sixth photo shows the diaphragm ring on the base of an auto-collimator with an optical flat about to be placed on top of it. The image returned from this flat pre-straightening is shown in photo seven and visible in the reticle is that the ring is out of parallelism by 14 minutes. The final photo is after treatment and is about as close as you can get to parallel. The lens is now much happier and working well.
