Mamiya RB67 Pro S Mirror Stuck

DannyC71 · Oct 20, 2025

Starting a new thread to continue on from my Pentax post.

A quick recap. I got rid of the Pentax 67 because it looked like the electronics were fried, and went fully mechanical with an RB67 Pro S. The mirror is stuck halfway up. I am able to push it down to get the lens off, but it won’t stay down. I can’t fire the shutter and the cocking lever is forward with very little play. I have downloaded the service manual and know how to get to the mechanism on the left side of the camera, just wondering if anyone has any easy suggestions before I head down this rabbit hole.

mshchem · Oct 20, 2025

I have a (newer 1990's) motor Hasselblad, this was happening. I put a couple drops of Kodak movie film cleaner, solvent, on the gears. Works fine now. Didn’t open it up. Applied it from outside, very sparingly.

MattKing · Oct 20, 2025

Make sure the Mirror lock-up setting on the lens/shutter isn't engaged.
Are you sure the shutter in the lens is cocked?
The various interlocks are important!

flavio81 · Oct 21, 2025

DannyC71 said:
A quick recap. I got rid of the Pentax 67 because it looked like the electronics were fried

Camera technician here.
The Pentax 67 electronics can't get fried. They are as reliable as it gets. The Pentax 6x7 electronics are very reliable, the Pentax 67 take the reliability to Arnold Schwarzenegger/Terminator levels. IT DOES NOT FAIL, period. Unless vandalism, of course.

The mechanicals require periodic CLA and the electric contacts need to be clean if you want the camera to work. So not a good idea to blame the electronics.

All this, plus your problem with the RB67, sound like you have no camera technician or you have a pretty bad camera technician.

DannyC71 said:
I have downloaded the service manual and know how to get to the mechanism on the left side of the camera

Ah, so you want to repair it yourself.

Camera repair is not something you can easily do it the DIY way.

Good luck. One word of advice: don't mess the timing on the gears that move the cocking pins on the lens mount, or you'll have a really really hard time making everything work fine again.

DannyC71 · Oct 25, 2025

So I tried all the potential combinations of components being on and off and lens settings and nothing changes, so fairly certain something is jammed in the camera body. The only other thing I’ve noticed is that the leaf shutter in the lens was maybe halfway closed, and it would open up when I took the lens off (had to push the mirror down to get the lens off). so I put the lens back on and was just doing things like moving the aperture ring, shutter speed ring, and after moving the depth of field preview a couple times the shutter would close back down halfway. And it’s definitely the leaf shutter blades and not the aperture blades.

reddesert · Oct 25, 2025

It is not clear what state either the camera or the lens is in. It does sound like the camera is jammed, but also putting the lens on and off in an indeterminate state may screw things up further. You can test the lens separately from the camera. You cock it by moving the cocking pins on the rear counter-clockwise to the green dot position. This should open the shutter. You then fire it by depressing the small silver pin on the rear at top, and moving the cocking pins clockwise. This should close the shutter, then as the pins reach the end of travel, the lens should stop down, open the shutter for the selected time, and close again.

What the camera body does to the lens, is rotate the ring that rotates those cocking pins back and forth. So if that is stuck in some intermediate state, the results are unpredictable and repeated attaching/forcing it may make things worse.

DannyC71 · Oct 25, 2025

reddesert said:
It is not clear what state either the camera or the lens is in. It does sound like the camera is jammed, but also putting the lens on and off in an indeterminate state may screw things up further. You can test the lens separately from the camera. You cock it by moving the cocking pins on the rear counter-clockwise to the green dot position. This should open the shutter. You then fire it by depressing the small silver pin on the rear at top, and moving the cocking pins clockwise. This should close the shutter, then as the pins reach the end of travel, the lens should stop down, open the shutter for the selected time, and close again.

What the camera body does to the lens, is rotate the ring that rotates those cocking pins back and forth. So if that is stuck in some intermediate state, the results are unpredictable and repeated attaching/forcing it may make things worse.

Thanks. Tried that and the lens appears to be functioning normally. As much as I like to tinker with old cameras I think this one may be out of my depth. I may just return it and look for a body that functions.

DannyC71 · Oct 27, 2025

Out with the old, in with the new (to me). New body on the way from Used Photo Pro instead of a Japanese proxy site. Can’t return the old one, so let me know if anyone is looking for a project.

Mamiya RB67 Pro S Mirror Stuck

Moderator

Privacy & Transparency

Privacy & Transparency