Mamiya RB67 film back - film gets stuck and winder tears it up.

[analoguey]

Hello!

I thought things were going well with the RB, and there wasnt much need of maintenance beyond the odd cleanup. The camera obviously thought otherwise. I had bought a couple of 120 backs from someone on ebay, and they both took their turns in failing. While I thought I had two backup backs(one Pro and a ProS), I only have the single back to plug 120 film in.

I found the problem because it became increasingly difficult to wind the film on the ProS back. I had to use rather large amounts of force to get the film moving to the next exposure. Finally when I had to get the full roll out, I discovered that the last two frames were probably not exposed, and that the film had got stuck.

I wanted to recreate the issue and used paper backing rolled in (and dark slide removed) and tried to see what the issue was. Within a couple of windings, the paper got stuck and finally tore out (See pictures 1 & 2 below)

I then opened it up and had a look at what seemed to be tearing it up, and it looks like one of those pins that hold those two rods have given away. I thought I could prise it back in manually, but that wasnt to happen, and the pin seemed to bob out (see last picture).

The issue, at least on the ProS seems to be a minor one. Given that I have only spent a few months with the RB, I am not sure if my assessment is correct.
Could anyone here help clarify whether these can be fixed, with not too much involvement/expense?

 

[John Koehrer]

In the picture it looks like(to me) like the top roller holders are slightly canted.
Try loosening. you shouldn't have to take them out. the crosspoint screws only at the top and see if the holder can be pivoted toward the rollers.

 

[paul ron]

The rollers are tearing it up n causing the friction?

First, are you loading the film properly?
Check to see if the preasure plate is floating and clean?
Be sure those 2 pins (rollers) are in their holders and just slightly raised.
Also see that the backing is not fouling on the rollers or thier holders.
How is the film passing over the bends... Smoothly?... Clean?
When no film is in the back, is it hard advancing the lever?
Check all surfaces for debre or any signs of wear or roughness.
Check the plastic film gate for any roughness or damage?

Oh... Those 2 rollers turning freely or worn flat n don't move at all?
You can replace them easily enough.
Again... Make sure you are loading the film properly.

 

[analoguey]

In the picture it looks like(to me) like the top roller holders are slightly canted.
Try loosening. you shouldn't have to take them out. the crosspoint screws only at the top and see if the holder can be pivoted toward the rollers.

Hmm, not sure I understand- One of the rollers has come out of its groove -if you mean what's on the left of pic5.
Or did I misunderstand you?

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[analoguey]

The rollers are tearing it up n causing the friction?

First, are you loading the film properly?

Yes. Initial insert till the start lines up n then using the winder.

Check to see if the preasure plate is floating and clean?

Be sure those 2 pins (rollers) are in their holders and just slightly raised.

No, One of them has come out at one side

Also see that the backing is not fouling on the rollers or thier holders.

Hm, I rolled in just the backing and it fouled. Although with the rollers out -
Would I still need to check this?

How is the film passing over the bends... Smoothly?... Clean?
When no film is in the back, is it hard advancing the lever?
Check all surfaces for debre or any signs of wear or roughness.

Smoothly and clean. Also not hard to advance film initially, Got harder to advance film later into the roll. Like at least a few shots in.
Ditto when I rolled just the backing of a used roll (no film) in.

Check the plastic film gate for any roughness or damage?

Which gate do you mean? I'm not sure I understand.

Oh... Those 2 rollers turning freely or worn flat n don't move at all?
You can replace them easily enough.
Again... Make sure you are loading the film properly.

One of them has come out.



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[paul ron]

Try putting the pin back in it's holder... The holder is just a thin metal folded over the end of the pin. Take the holder off and carefully reform the end so it will accept the pin's tip. You can form a nice round hole at the end by using a small nail to hold it as you bend n shape it back to normal.

The film gate is the plastic face of the film back... The rectangle opening is the film gate. See if there is any damage to the edges?

Check the preasure plate... That is the plate that keeps the film flat against the film gate... It is on a spring and should be free floating in n out. Be sure it is clean as well.

RB backs tend to feel a bit more resistance as you advance further into a roll.this is normal but it shouldn't be too tough or tear the backing paper of your film.

Btw if you want to reduce some of the friction on the film path... Use some spray silicon but the type the is dry after it is applied. I spray a bit into a cup n using my finger i apply a very tiny amount to fixed points in the film path.

Oh also be sure the double rails on either side of the preasure plate are clean n smooth.

 

[analoguey]

Try putting the pin back in it's holder... The holder is just a thin metal folded over the end of the pin. Take the holder off and carefully reform the end so it will accept the pin's tip. You can form a nice round hole at the end by using a small nail to hold it as you bend n shape it back to normal.

The film gate is the plastic face of the film back... The rectangle opening is the film gate. See if there is any damage to the edges?

Check the preasure plate... That is the plate that keeps the film flat against the film gate... It is on a spring and should be free floating in n out. Be sure it is clean as well.

RB backs tend to feel a bit more resistance as you advance further into a roll.this is normal but it shouldn't be too tough or tear the backing paper of your film.

Btw if you want to reduce some of the friction on the film path... Use some spray silicon but the type the is dry after it is applied. I spray a bit into a cup n using my finger i apply a very tiny amount to fixed points in the film path.

Oh also be sure the double rails on either side of the preasure plate are clean n smooth.

Thanks Paul for the detailed info.

1. I pushed the pin back in the holder, and then made them align similar to the other side (more or less parellel)
2. Checked the pressure plate as well - I didnt realise it was that until now, but usually used to admire its cleanness.
   Not sure what you mean by free-floating, but there is a spring action and I can feel it, and it doesn't give too easily.
   Double rails are smooth too.
3. Hmm, right. I rolled in the paper again (post step 1 above) and it seemed fine.

After the above steps, I ran through a roll of film as well, it ran through successfully and its now in the tank, I will develop it over the morning tomorrow. fingers crossed!

Is there a way to prevent a repeat from happening?
Also, I seem to have two screws or screw-like things (no threads on them) left over, but nowhere to plug them into. They came out of the roller-holders. Wondering what to do with them.

 

[analoguey]

In the picture it looks like(to me) like the top roller holders are slightly canted.
Try loosening. you shouldn't have to take them out. the crosspoint screws only at the top and see if the holder can be pivoted toward the rollers.

John, I finally understood what you meant after relooking at the rollers and successfully screwed them back in, thanks!