Mamiya 645 Super/Pro/Pro TL: Mirror Stop Replacement and Calibration
Originally posted on Instagram. Notes from the repair bench, kept here as a searchable archive. View the original on Instagram
This is another post on the Mamiya 645 Super/Pro/Pro TL mirror stop repair. I get these cameras in constantly so need to regularly post this info for new buyers/users of these cameras.
The plastic mirror stop in every Mamiya 645 Super/Pro/Pro TL is in one of two states: broken or about to break (unless it has already been replaced). Some say it is a design “flaw” but in reality, these cameras probably were not designed to last forty years.
Photo two shows how the camera often presents, with the bottom of the stop broken. If you are lucky, the broken parts don’t get sucked into the shutter for further mischief.
Photo three illustrates the parts of the stop assembly: mirror stop (shown here with the typical broken off bottom part), spring and adjustment screw.
Photo four shows the new stop installed right before calibration. Speaking of calibration, the mirror needs to be set for 45 degrees. I use a Mamiya tool, a 45 degree fixture that the body fits onto. Then a star target in the auto-collimator is squirted down onto the mirror and aligned/centered using the mirror stop adjusting screw.
I work through the back of the camera and need to lock open the shutter. New users of this camera may not realize this, but you can lock the shutter open for inspection or for long time exposures without using battery power by putting the shutter dial on “B” and the mode switch on self timer. Then, when you release the shutter, you will not be using electrons to keep it open.
Unrelated to the mirror stop, this camera came in with a 58mm Sunpak UV filter, made in Japan. I do test all filters as I mentioned in a post last week and this filter was tested for plane parallelism and surface finish. As shown in the last photo, this filter was quite terrible. Apart from the 6 minutes of arc error, the finish is quite bad as you can see in the really soft secondary image.
