Cleaning Mamiya RB lenses with floating elements

[M Carter]

My next RB lens will be a 140 Macro or a 50mm; both of these have floating elements; and like many RB lenses, deals can be seen with "light haze" or "some fungus" - both issues that are often easy cleanups with RB glass, usually pulling the front element and rear group, cleaning, and you're back in business in to time.

What about those floating element lenses though? Do they present any challenges to a non-repair-expert? I'm finding over time that my RB lenses get shutter issues, one by one, and I do know how to clean and properly lube the shutters - just never dealt with the floating element. Paging Paul Ron??

 

[EdSawyer]

I've disassembled the 140 macro for the RZ before, which has the floating element. Also worked on many other RZ lenses. The floating elements usually have a separate small geartrain that adjusts them, sometimes with a plastic gear that can wear. Now that MAC is out of the Mamiya business, not sure where to source replacement parts if necessary. They were great about that. The floating element pieces are not too hard to work on generally. They will be a separate element/group in a mount with a fairly simple helicoid adjustment (limited range). If you are comfortable working on RB lenses in general and swapping out shutters, then the floating element stuff is not really all that tough. Mechanically they are pretty straightforward. There are also service manuals online that show the various parts/assemblies and how they go together.

 

[M Carter]

I've disassembled the 140 macro for the RZ before, which has the floating element. Also worked on many other RZ lenses. The floating elements usually have a separate small geartrain that adjusts them, sometimes with a plastic gear that can wear. Now that MAC is out of the Mamiya business, not sure where to source replacement parts if necessary. They were great about that. The floating element pieces are not too hard to work on generally. They will be a separate element/group in a mount with a fairly simple helicoid adjustment (limited range). If you are comfortable working on RB lenses in general and swapping out shutters, then the floating element stuff is not really all that tough. Mechanically they are pretty straightforward. There are also service manuals online that show the various parts/assemblies and how they go together.

Thanks - and to be clear, it wouldn't be a repair-the-floating-element situation, just getting it out and back in functionally, if I needed to clean past it. Mainly because I see lenses that are good prices but have some fungus or haze. Got a 127 essentially free due to a fungus spot - it was inside the front element and cleaned right out, other than that the lens was in mint condition. I have a project in mind where the 140 Macro would be a great help, but I may find one needing some TLC.

 

[ic-racer]

If you can put one helicoid back together, you can put two together

Maybe this will give you ideas or scare you away.

It can be a pain. In this case I'm repairing a 28mm F2 Zeiss with floating element that had been dropped. The front helicoid threads were very fine. So, by my marks I could assemble it 3 ways. I actually assembled it, and tested it with an in-camera test comparing to an identical 28mm F2 Zeiss. With the floating element helicoid a single thread off, the edges of the frame were very blurry. That was good that it was an obvious change. Re-assemble by trial-and error to the next thread over for the floater got me on the spot. There also were three screws with a dab of paint around the perimeter of the helicoid for the floating element for fine tuning the performance. I left those screws un-touched.

This was an interesting project. I disassembled the damaged lens about 8 years ago and couldn't get it apart, so I bought a new 28mm/F2 Distagon. Then one day I found the box with the damage lens and 'discovered' the front element just unscrews. Though, when it came out I saw it had its own helicoid. I was able to straighten out the bent barrel and re-assemble (per trial and error above). The bent part is a clever coaxial mechanism that holds the filter and keeps the filter from rotating as the lens focuses. The actual front floating element (which did not get bent) rotates as if focuses.
Now I have two of them

Also, after going through all of that to get the front helicoid back in place, I never complain about the MANUAL ring to control the front floating element of my 50mm Rollei 6008 lens!