Film      Camera Repair

Introduction


The Mamiya RB67 was introduced in the 1970's.  Many of these cameras need new light seals.

If your Mamiya RB67 has light leaks, it's going to be the seals in the film holder or the revolving back.  There are other foam seals or bumpers inside the camera, but we won't deal with those here. 

So let's get to it.


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Revolving Back


You could remove the film holder from the rest of the camera first, by simply disengaging both the "Lock" switches:




Actually, though, I think it's better to remove the whole revolving-back assembly, with the film holder, as one unit.  Otherwise the revolving back plate doesn't seem to detach as easily.

So, look for a chrome-plated lever on the underside of the camera.  In the picture it's to the upper-right of the Lock switch.




Pull the lever outward, and the whole revolving back assembly should pull away from the camera.  This is what the camera should look like now:






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Don't Forget This


Next you're going to be removing the film back from the revolving-back plate.  However, at some point you might need to put the camera back together before you finish re-light-sealing it.  So here's a bit of knowledge that will save you some frustration.

There is a small metal tab.  See photo:




Press that tab in with something, and hold it there.




That moves another tab which was holding the Lock mechanism in place.  Now you can slide the Lock mechanism out of the way. 




You'll have to do this for the other Lock switch, too.  Without this, you might waste a lot of time trying to figure out why the film back just won't seem to go back on there.  In fact, every time I take this camera apart, I seem to forget this.  So now I can refer to this article.



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Film Back Disassembly


Look for the chrome-plated tab that holds the film cover shut.  It's not all that obvious here, but it's near about two-o'clock in the photo:




Pull that tab out, and you can open the film-back cover. 




The whole thing lifts apart easily now. 



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Light Seal Priority


Some people say you can get by without replacing all the light seals. 

At least be sure to replace the light seals along the film-cover hinge:




The main one is a flat strip that's about two-tenths of an inch wide, and about 2.8" long.  If you use a light seal kit, there should be one already in there.

This is one reason why I use an acrylic glue for DIY light seals.  If you mess one up, you can remove it and try again.  The kits are self-adhesive, but it's possible to re-position a piece if you place it crooked or something.

The light seal kit, when you can get it, contains all of the seals.  So you might as well install the rest while you have the camera apart.   A couple of them are sort of tricky, but I'd rather replace them now than waste a roll of film later.






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Light Seal Kit


If you can find a light seal kit ready-made, then great.  Another alternative is to make your own seals from a sheet of the material;  try this link to order some.

Just know that the complete RB67 kit is rather complicated.  You might have no idea what goes where.  Start by getting yourself a set of precision calipers (I like SAE dial calipers, but you might prefer metric).  Measure the widths of each strip and match them up to actual ones on the camera. 

If you want to make your own seals, you'll still need to make precision measurements. 

I would also suggest, if you're going to do much camera repair work, that you buy quality dial calipers.  Working on cameras and other precision mechanical goods requires an entirely different set of tools than my usual arc-welded hack repairs



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Cleaning & Replacing the Seals


Don't use acetone, MEK, or lacquer thinner for this.  These have a tendency to dissolve plastics.

91% isopropyl is what I've been using to remove old light seals.  Another possibility is mineral spirits or VM&P naphtha, though I haven't tried these on the Mamiya. 

A reader recommends using a wooden orange stick to remove the old light-seal material.  This seems like a great idea;  sure a lot better than the toothpicks I was sometimes using, which keep breaking.

From here, it's basically the same procedure as any other film camera

The Glue:  If you get a self-adhesive light seal kit, no glue is necessary.  For everything else, I've been using Loctite Crafter's Indoor-Safe Adhesive (now called Loctite Stik'n Seal).  Also try this link.  Get the Indoor adhesive, not the Outdoor.  I was calling this a PVA-based glue, but it's acrylic.  There are a lot of applications where this type of non-toxic, non-solvent-based glue isn't that great, but it seems to work well for light seals. 

Don't glue anything until you're sure the light seals will fit.  And when you do glue them, you probably won't need to glue the entire length.  Just dab the glue here and there, in case you need to re-do the installation.  Let it dry for a couple days before putting everything back together.



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Conclusion


In this article we looked at how to disassemble the Mamiya RB67 film holder and revolving back.

If you don't have a light seal kit, most (all?) of these seals can be made by cutting strips out of a wide foam brush, the kind you can usually pick up for a dollar or so.  Better yet, get specialized light seal foam, either 1.5 or 2mm thickness.  (Also try this link).  Just be careful;  mind the danger when cutting the material (Disclaimer.) 



         

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