RZ67: Mirror Cocking Failures from Worn Wind Shaft Parts
Originally posted on Instagram. Notes from the repair bench, kept here as a searchable archive. View the original on Instagram
First, let me say that I like the RZ67. This post is not bashing it. Just some technical info:
The majority of issues that I see with the RZ relates to the mirror cocking mechanism. The symptom is that the mirror will not release ( you will hear a small click but the mirror does not move). This is caused by either: 1.) winding shaft lever 2) wind shaft or 3) wind crankshaft lever. If these parts get only slight wear, the mirror will not cock and the camera will not release.
Photo one shows the wind side cover removed and the pick is pointing to the winding shaft lever on the end of the wind shaft. Photo two shows the shutter speed dial side removed and the pick is pointing to the other end of the wind shaft and this is where the large gear cocks the mirror. Photo three illustrates the wind shaft, winding shaft lever and the plate with the winding crankshaft and external cocking lever attached.
Wear on any of these parts will grind things to a halt and prevent mirror release. And it does not take much wear at all. Just preventing the wind mechanism from cocking 1mm is enough to cause a problem.
Mamiya recognized this and made multiple changes to the parts:
1.) changed chemical treatment to the wind shaft in January 1987
2.) changed material of the crankshaft from stainless steel to cemented steel in May 1987
3.) ultimately changed the crankshaft from being held onto the cocking hub with a pin to attaching by being keyed to the shaft. (photo four shows both styles, the older type using a pin which often would wear and cause problems on the left)
4.) providing a service part that was cut with a negative tolerance so as to provide addition movement of the shaft.
The only way to fix this issue is to have all the revised parts on hand, something that is not really possible any longer.
If you have an RZ, treat it kindly as many repairs are not possible. Also, if purchasing an RZ, models made from May 1987 onward would be my choice. But, even the RZII has these issues so there is still a risk with the newer version.
