Mamiya RB67 strange shutter problem

Hi,

I recently bought a mamiya RB 67 with a mamiya - sekor c 127mm (1:3,8) lens. Upon arrival I read the manual and am fairely certain that I am not the source of the problem: Both, lens and body work fine on their own.

The lens requires some force to cock the shutter as well as to fire it, but it closes and then opens again for exposure.

Mirror and light baffle both flip up instantly within the body.

But as soon as I attach the lens to the body, (yes, both body and lens are cocked) things get weird: when firering, the shutter of the lens closes (rather slowly), but stays closed. The mirror slowly swings up, takes over a second to reach the top. The light baffle stays down, but I am able to force it up by gently pushing it with my fingers. I dont think any light hits the film. And I tried both, mirror up mode and 'normal' mode on the lens, no difference.

When I seperate lens and body, both work just as fine as before.

I am very confused.

 

(dear reader,) do you have any idea on how to fix this or what I might be doing wrong?

The comment that the lens requires some force to cock the shutter is worth exploring. If the body and lens each work correctly when disassembled, they should work when assembled. Cock and fire the body 10 times, without the lens. Do the same with the lens, without the body. Observe very closely. Listen for small ticks or clicks. Watch for slow or delayed movements.

 

Are you conducting tests with a revolving adapter and film back attached?

 

Is the body a Pro, Pro S or Pro SD?

I tried both, with film back and without, but am now only testing the body-lens-configuration (to eliminate variables).

The text on the body only says 'Professional', so its a Pro, right?

 

I'll try the 10 times in just a moment

I was not able to notice any odd behaviour, no delayed movement or strange sounds. With the body, its one simultaineous 'clanck' sound of the mirror and light baffle flipping. With the lens, the initial closing is barely audible while the sound of the spring is easy to pick up.

 

To be more precise about the force the lens requires: I can activate the shutter with my pinky (and I am not stronger than your avarage person), but it just seems a little to resistant. Similar to how tripods used for videography limit the speed, at which you can turn the head (if this is any help to you)

Professional bodies are older than Pro S and Pro SD, so one must always keep in mind that older bodies can malfunction. The Sekor C lens is from the middle generation, between the "non-C" and newer KL lenses. I would put more effort on diagnosing the body at this point, vs. the lens.

 

Can you explain again, what exactly is happening when the camera malfunctions? Try the lens, not connected to the body, through all shutter speeds. Does anything change in its function? Try different shutter speed settings, when you have the camera and lens attached. Need more information on the malfunction description.

 

Try all of the tests with the revolving adapter removed. There is a malfunction that is accentuated when the revolving adapter is attached, which relates to the coupling arms that extend from the top corners of the body, to communicate to the film back, through holes in the revolving adapter.

To describe the problem in greater detail:

In theory, (as far as I understand this machine) when I press the shutter button, the shutter within the lens shut close. Then, the mirror should swing up out of the way of the light, followed by the light baffle. (at some point in here the little metal bits should extend to communicate with the film back) Now, the shutter of the lens should open for the expposure time and close afterwards.

If I attach the lens to the body, the shutter closes far slower than without the body. The mirror takes about a second to reach the top. The light baffle takes over 10 seconds (faster, if the camera points down) to slowly reach horizontal position.

But now a new discovery: (I smell progress) I was able to observe the coupling arms extend (over the time of ~2-3 seconds) followed by the shutter firering (after ~10 more seconds) for the 1/2 second exposure time I dialed in. Maybe this is a new development, maybe I was too impatient when I first realized the cameras malfunction.

Sadly, I was not able to recreate this progress apart from the 2 times it worked. The system now returned to being stuck on the 'light baffle slowly moving up - step'

 

I will investigate this further

I got the same phenomenon again:

about 3-6 seconds after I pressed the shutter, the coupling arms extended (and retracted).

Then, once I wiggle the bayonet ring, the shutter fires. I just found out, it does not have to be the bayonet ring, a strong wiggle on any other part of the lens seems to be enough.

It seems like the connection between the lens and body is not perfect. Or its a spring inside the body which just needs this tiny amount of help (wiggle) to fire the shutter.

One side note that might be related: the lens does not seem to sit perfectly straight on the body. Maybe its just me, maybe it really is a fraction of a degree off. Not sure.

It does take some back and forth to get it on and off the body.

Photos will help.

 

The lens should fit perfectly tight and perpendicular to the body. No looseness or misalignment at all. Wiggling should have no effect. Pointing the camera up or down should have no effect.

The lens fits snugly once the bayonet ring is tightened. I just had some trouble attaching it to the body, but maybe thats because I'm used to the M42 screw mount?

I don't think this possible (if existent, its tiny) misalignment would come across with a photo, I can't even see it myself (its more of a 'this feel a little off' rather than 'this looks off')

 

I am now at the point where the shutter (sometimes) fires, but only after ~15 seconds (still, better delayed than no shot at all, right?)

The guy who sold it told me the camera sat in a box for years, so maybe it just needed some warm up?

I have got a strange result for you: I tested all the different shutter speeds (top row) 3 times (below, in seconds).

[now would be a great time to insert an excuse for my handwriting, but I did not expect to get results as interesting as these]

The delay between me pressing the shutter button and it firering is always somewhere between 7 and 16 seconds, except for the first 2 tries with 1/250 sec exposure (only fired when i wiggled the camera)

Something mechanical is significantly wrong with the camera. I suspect the body, but hard to say. Can you post a video of the situation?

its you

After hours of tinkering around with googledrive and youtube I finally managed to get the videos to upload (I think google does not like my vpn).

Once the upload is complete, I will post a link to the folder. If you want any other viewing angles, just tell me what you want to see.

Mamiya RB67 - Google Drive

(I made the shadows a little brighter. This has damaged image quality, but should improve visibility of the light baffle and such)

Just going by your videos, I'm pretty sure what you have here is a defective camera and/or lens that needs professional servicing. Unless you got it for a very low price, I'd recommend returning it to the seller (if possible) and shopping around for another in better condition.

 

I've experienced similar issues with a later RB67 Pro-S and several Hasselblads. While the execution differs, the overall body-lens mechanical interaction works the same as you described for both systems (shutter button press, leaf shutter closes, mirror and baffles fly up, leaf shutter opens and closes for exposure). When working properly, all this happens instantly.

 

But when there's a problem needing significant repair, one or more parts of the firing sequence drag or hang like your videos demonstrate. Very often it will seem the pieces work "OK" when separated, but not when assembled: this almost always indicates old dried gummy lubrication and/or worn springs in firing release mechanism of the lens, body, or both (they seem OK separated because it takes much less force to drive the pins/gears when body and lens aren't joined together).

 

It is possible only one of the items causes the problem, but you would need to borrow another lens or body to check against your own (swap lenses and bodies to see if the problem still occurs, and with which piece). But honestly, I would tend to think this whole kit likely needs an overhaul that may not be worth the expense (unless you live in a country where it is so hard to find a good RB67 that repairing a worn one is justifiable). The seller told you it had been sitting unused for years: lack of use is deadly to a non-electronic leaf shutter SLR like Mamiya or Hasselblad. Your RB67 is the first version, made 1970 thru 1974: these very old RB67s tend to be in worse "as found" condition than the later Pro-S (made from 1974 thru 1990).

 

I'm near-certain you have sticky gummy lube in the lens mechanism that is a little too much for the old, worn body springs to push against, creating the very slow cycle time sen in your videos. That, or you are correct that the lens was maybe dropped or banged at some point and no longer sits perfectly straight in the mount (if off by even a tiny bit, the lens drive pins can drag against the body slots). Throw in the potential issue Wilmarco Imaging raised (back pins dragging in worn or dirty revolving adapter tracks), and things get even more complicated. This RB67 needs to be serviced, or returned to the seller: whichever makes more sense in your circumstances.

Edited January 22, 2019 by orsetto

Agree with orsetto. Body is severely compromised. Needs to be replaced or a thorough clean and lube.

Alright, thank you for your help. Returning the camera is not really an option because shipping and import fees account for almost half of the price.

I'll take a look around town for someone able to repair it, or I have to find out how to disassemble it myelf.

Anyway, I'm glad you (two) helped me through this mystery

Hello again,

I think I fixed it. Not perfect, but at least in somewhat working order.

I disassembled the lens until all but the shutter and apeture were left (very scary moment). I did not know how to lubricate the inner workings of the lens, so I decided it was working good enough.

I tried to disassemble the sides of the body multiple times, but could not find all the hidden screws. But today I looked at the bottom of the camera and decided to start the disassembling process there. Turns out, all the important mechanism is hidden there (at least the parts I needed). In the end, I just tightened this spring (marked in orange)

It seems to be responsible for firering the shutter, flipping the mirror and so on.

The camera does not fire instantly, but within 1-2 seconds. I might be able to tighten this spring a little more, but I am happy with this result so far. Maybe this 1-2 sec delay is caused by old lube, i'll tinker around with it after the first roll of film is done.

It now fires every time, compared to only firering upside down or after a bit of wiggeling.

Well done.

Hey Giovanni,

I somehow hope that you get a mail notification, since this is a rather old thread.

 

I now got the exact problem you had and also wanted to tighten the spring, but how exactly did you do that ?

Or did you find a better solution afterwards ?

 

Really hope you read this !

Cheerio

(For anyone who does not speak German like Karstenente)

My method was the following:

Disassemble the camera bottom using these 4 screws:

 

(take lens and back off, turn camera 90° counterclockwise. Roll a D20 dice. Anything below 15, you may proceed)

 

Loosen the screw on this axle, but do not remove it. It holds the spring in place.

 

Take a small screwdriver, get it between the screw and the latch in the spring. Slowly move the latch around the axle. You probably need a second scredriver or a pair of tweezers once you reach underneath the axle. I dont know if this image helps:

It took me a couple of tries. But fear not, if you slip (and the spring turns back) it will probably catch the screw. You will loose your progress, but wont make anything worse than it was before.

As I sad, it did not fix my problem completely. My camera still has a delay of 1-2 seconds. Probably old lube, as orsetto said.

But hey, better than nothing!

 

Hope I can help future wanderers who stumble into this rabbit hole.

Cheers