RZ67: Broken Dark Slide Safety Switch Allows Release
Originally posted on Instagram. Notes from the repair bench, kept here as a searchable archive. View the original on Instagram
If your RZ67 will allow shutter release with the dark slide in place, the issue is a broken dark slide safety switch. I have done two of these switch replacements this week and will describe the operation and solution to this issue.
The RZ67 has two safety interlock switches for the dark slide. One for horizontal and one for vertical. The second photo shows the body with the revolving back removed and visible are the two silver switches, one at around 5 o’clock on the circular ring and the other, the vertical, at around 8 o’clock. When either of these switches are pressed in after a dark slide is installed, an inhibit signal is sent to the main board and the shutter can not be released. This is different from the RB67 which uses a purely mechanical shutter release block when a dark slide is in place.
The third photo (video) shows how a broken switch reacts. It has no spring to it and is not bouncy. Since the switch is NO (normally open) this state will allow shutter release regardless of the dark slide being installed or not. Certainly could cause disappointment when you get back blank negatives.
Photo four shows the bottom cover removed and the switch, not really visible at this point, is located under the small circuit board by the moving coil.
The broken switch removed from the camera is shown in the fifth photo. The plastic ages out after 40 years or so and cracks. Mamiya probably did not design these to be working after these many decades. Pro photographers at the time likely would use a camera for 10 years or so and then switch to the newer models which had more functionality.
In this case, a new switch is installed and we are back to normal.
