Problem with 120 film back for Mamiya RB67

[Profdaydreamer]

Hi everyone.

I bought my first RB67 about a month ago and I’ve encountered a problem already. My film negatives were all coming back with a straight scratch right through, and after some playing around with the film back, I think I’ve found the issue. One of the rollers on the back has become squeaky and hard to move, unlike the well lubricated roller on the other side. My theory is that the film emulsion side was scratching against the edge of the uncooperative roller. Here’s some photos and a video for reference. Has anyone had to deal with this/ how to fix?? Thanks.

 

[shutterfinger]

Those rollers do not touch the emulsion side of the film. The one on the right may be geared with the wind, been tooo many years since I worked on a RB67. On the shell of the RFH are pin rollers, one either side of the image opening in the holder. They should turn with the force of a 1/4 inch long by 1/8 inch wide down feather just touching it. Look carefully at the pin rollers for a polished edge similar to what you would see if it were rubbed against a file. The wear line may be finer than a hair. If a wear line exists the roller needs to be replaced. If no wear line is present flush the roller ends with Isoproply Alcohol or similar cleaner (I hate lighter fluid) then put a drop of light machine oil (not wd40 or 3in1 oil) on the ends about the size of a straight pin point. Clock oil, TriFlow are good oils for cameras. The pin rollers fit into a bushing at each end and if a bushing is worn the complete roller needs to be replaced.
This repair manual covers the RFH also. https://learncamerarepair.com/downloads/pdf/mamiya-rb67-pro-s-repair-manual.pdf
It does not show the pin rollers.

Check the pressure plate for a burr also.

 

[Profdaydreamer]

Thanks for the response, however I’m not sure if this has to do with the pin rollers. Even if the film is scratched on the non emulsion side, could the scratch still come up on the negatives? The straight line scratch lines up directly with the edge of the guide roller that isn’t rolling.

 

[shutterfinger]

If the scratch is on the non emulsion side there should be a corresponding line on the backing paper. If the roller is not turning when the film is advanced then the roller needs servicing.
The parts catalog https://learncamerarepair.com/downloads/pdf/Mamiya-RB67-Pro-S-Parts-Catalog.pdf shows that roller on pdf page 22 and the pin rollers on pdf page 23.
You should be able to remove, clean, lubricate the take up roller by removing the top and bottom covers.

 

[Donald Qualls]

The pressure plate doesn't touch the film, either, only the backing. The backing turns the frame counter mechanism via the supply side roller (at least on ProS series film holders, probably the same for the Pro and ProSD). The takeup side turn around roller is free wheeling, as far as I can tell (I'm not near my RB67, and don't have any unloaded film holders at this time).

IMO, the only reasonable source of scratching on the emulsion side of the film is the pin rollers. My 220 back has a squeaky roller like you describe -- and despite 35mm film driving both rollers by friction directly on the film base, has not scratched my negatives.

 

[MattKing]

IMO, the only reasonable source of scratching on the emulsion side of the film is the pin rollers.

Or the film gate itself - but that is not part of the back.

 

[Donald Qualls]

Or the film gate itself - but that is not part of the back.

With the film back's pin rollers (and room for the dark slide) between film and the actual gate, I don't think that's likely. A burr on the dark slide seems a much more likely candidate.

 

[shutterfinger]

My film negatives were all coming back with a straight scratch right through

If you are sending your film to a lab for processing suspect the lab to be the cause of the scratch.