Mamiya RB67 Backs

fresnel10 · Dec 27, 2015

Hi all-

I have a Mamiya RB67 Pro S that I bought from KEH, along with the Pro S backs. Unfortunately, I have had my 4th back seemingly go bad on me, and this has been since I bought the camera in October. All of them develop some sort of issue with advancing. I'm starting to wonder...can the body make something go bad with the backs? I'd really appreciate any help!

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Theo Sulphate · Dec 27, 2015

What exactly is happening and when does it happen? At the beginning? Mid-roll?

There are interlocks between the body and back.

fresnel10 · Dec 27, 2015

Well, a couple things. They've pretty much all happened mid-roll. A couple of the backs failed to retract the little red thing in the counter window all the way, and a couple others had the advance lever get to its full extension and just stick there. Not even the small switch in the center top can get it to release.

I will say, KEH was great about the replacements. But now one of the replacements (with an EX grade) has the stuck advance lever.

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StephenT · Dec 27, 2015

Does that happen when it is off the camera body? You can test them off the body by using the backing paper from a roll. You have to manually hold down the lever that is pushed in when the door is closed, and use a paper clip to depress the tiny little doodad that is depressed when the shutter is fired (on the upper right hand side when looking at the film holder from the body side). Sounds harder than it is!

fresnel10 · Dec 27, 2015

The advance lever does not move from the position it's stuck in regardless of whether or not it's on the body. The backs that had the red window problem were returned.

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David T T · Dec 27, 2015

Never heard of this issue before. Giving the thread a bump for the OP...and for me cause I'm curious.

fresnel10 · Dec 27, 2015

Unfortunately, that's the most common response I have gotten. From everything I've seen and read about the RBs, they're pretty rock solid.

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Theo Sulphate · Dec 27, 2015

Odd that this would happen with four backs, although there are actually two different problems you're seeing. I can't imagine what the body could be doing to cause that. I'm assuming you're loading it correctly.

I am thinking that somehow you got four bad backs, even though it sounds unlikely.

MattKing · Dec 28, 2015

I assume you are referring to the film advance levers that are actually on the backs, not the shutter cocking and mirror moving lever on the camera body.

A problem on the body with the double exposure prevention interlock could cause a problem with all backs - I'm just not sure it would cause your problem.

Do you have access to any other bodies to check your backs on them?

paul ron · Dec 28, 2015

4 bad backs, 2 different problems both related to almost the same mechanical system inside the advancing mechanism.

the red flag problems are always related to the signal lever that runs to the ratchet n pawl of the lever. it ties into the counter system. as you advance it sets the counter to the next frame number and takes down the red flag. as it does this, you'll hear a pop sound that opens a gap to lock the lever from double exposure.

second problem, stuck advance lever. the ratchet n pawl can get locked up because of either a faulty signal arm or a counter problem or a cracked lever mount.

how are they all related? the user. i find alot of first time users are pretty rough on advance levers on the RBs. they advance as if this were a 35mm quick shooter alowing the lever to snap back on each advance. that cracks the cast ratchet n pawl mount, breaks the tiny hair springs of the pawl and signal arm. there is a small rubber damper on n the lever internal stop but I'm sure that completely rotted off years ago... thus the delicate condition most backs are in these days.

im also sure none of those backs have been serviced in the past 10 years regardless of their appearance n behavior. they tend to sit in converted pros closets n basements of relatives.

i can of course be wrong without opening the top plate for an autopsy to see exactly whats going on in there. but i have seen this happen on several cameras over the years.

these cameras are built like russian tanks and can take a real beating but to an extent of normal abuse. regular service is a must on heavy machinery but at the cost of service, its cheaper to replace these days.

id be very curious to find out what the problem n fix is for these backs.

you can take the top plate off fairly easy if you are a handy fella? no special tools are needed other than a good set of screwdrivers and steady nerves.

fresnel10 · Dec 28, 2015

Paul-

I do tend to be a rather methodical advancer, though I can't guarantee I didn't let it snap back once or twice.

If it's nothing too complicated, I might be willing to give it a look. Is there somewhere that you know of that some visuals to accompany that kind of work? I usually do better with some sort of visual guide so I know what the heck I'm looking at.

Kirks518 · Dec 28, 2015

this might help - (there was a url link here which no longer exists)

Or you can learn as you go.

Kirks518 · Dec 28, 2015

and this may also be good (good to have if nothing else) - http://rb67.helluin.org/files/2010/02/Mamiya-RB67-Pro-S-Repair-Manual.pdf

about 2/3 down is the back disassembly instructions.

paul ron · Dec 28, 2015

there ya go. thanks kirks. its that easy. the manual will show you the signal arm n gap. also check all the screws to be sure they are reasonably tight. the counter take up roller tends to get lose for some odd reason. that causes counter problems because it doesnt think there is film in the back.

email me if you have any questions... always glad to help.

Theo Sulphate · Dec 28, 2015

paul ron said:
... i find alot of first time users are pretty rough on advance levers on the RBs. they advance as if this were a 35mm quick shooter alowing the lever to snap back on each advance. that cracks the cast ratchet n pawl mount, breaks the tiny hair springs of the pawl and signal arm. there is a small rubber damper on n the lever internal stop but I'm sure that completely rotted off years ago... thus the delicate condition most backs are in these days. ...

Some of YouTube videos are responsible for that. Several videos I've seen on RB67 film loading show that type of rapid winding and slapping-back action. I wouldn't dream of doing that.

fresnel10 · Feb 28, 2016

Hi everyone! I was hoping to have made some progress on doing a repair attempt thanks to some of the great material you all posted here (thanks again for that!), but I haven't. However, KEH had a good sale on accessories, and I figured I'd give it one more shot. I'm going to try Theo's advice and be very careful when advancing, because I will say that I have been guilty of that rapid-winding/slapping-back action. It's probably a solution that's just that easy. So, I will still attempt a repair, but also have a functional backup or two...

paul ron · Feb 28, 2016

4 screws, 2 in the top front corners, then 2 more on the underside. peel the leatherete dot on the lever, un do the large brass screw. carefully lift the lever up and put the large screw back to hold the return spring in place.... not to worry if it pops out of placs... easy enough to retension it.

now carefully lift the top off, but keep an eye inside by the lever side front, there is a metal slip in a groove that is responsable for double exposure prevention, it covers that right side hole.

now the top is off, install the lever so you can test the advance mechanisms. put a roll of backing paper in so the back thinks it has film loaded.

fresnel10 · May 20, 2016

So...interesting development. I think the culprit might have been the actual piece that holds the backs on. I ended up getting a whole new RB67 Pro S body, and it has worked as flawlessly as everyone says it should. I think I just needed to get a new body and start over. But, I will be referring to this to maybe salvage some of the backs that I have!

MattKing · May 21, 2016

fresnel10 said:
So...interesting development. I think the culprit might have been the actual piece that holds the backs on. I ended up getting a whole new RB67 Pro S body, and it has worked as flawlessly as everyone says it should. I think I just needed to get a new body and start over. But, I will be referring to this to maybe salvage some of the backs that I have!

By that do you mean the rotating back adapter?

My apologies, as I should have drawn your attention to that earlier, because it certainly can be a source of problems if it needs repair or adjustment.

fresnel10 · May 23, 2016

Yes, the rotating back adapter. I kept thinking of it as part of the body, not the separate part that it is.

flavio81 · May 23, 2016

fresnel10 said:
So...interesting development. I think the culprit might have been the actual piece that holds the backs on. I ended up getting a whole new RB67 Pro S body, and it has worked as flawlessly as everyone says it should. I think I just needed to get a new body and start over. But, I will be referring to this to maybe salvage some of the backs that I have!

It's most probably just a lubrication problem on either the body or the back, no need for a new body...

Those backs, and in particular the advance mechanism are the frailest point of the whole RB67 system so they should be overhauled from time to time.

paul ron · May 23, 2016

have you tried off camera? put in a roll of backing paper n advance.

with the film back off.... fire the body as you observe the chrome tits of the rotating back? see the pins pop up?

if youd like me to look at the backs for you, pm me?

paul ron · May 23, 2016

flavio81 said:
It's most probably just a lubrication problem on either the body or the back, no need for a new body...

Those backs, and in particular the advance mechanism are the frailest point of the whole RB67 system so they should be overhauled from time to time.

you're right but they are still pretty robust as far as build n design. id say these backs have more adjustment room to allow for Long term use.

the bigest problem is usually involving the signal arm and the counter wafer. the mechanisms run dry with the exception of the ratchet pawls n load gears.

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