Mamiya Sektor C (80mm) - Lens became unscrewed ?

Hey everyone - first post here!

Today (after some time being idle on the shelf), I picked up my Mamiya 645pro which is equipped with the Sektor C 80mm lens. When I moved the lens to focus, it just fell apart in two pieces. It doesn't seem broken, but just loose. I wanted to check in with some more experienced photographers as to how to put it back together... here's the situation. Any advice on the reassembly would be greatly appreciated (even if the advice is to take it in somewhere).

Thanks in advance!

- Savannah

Welcome to Photrio!
A lens can separate this way only if it was reassembled incorrectly. Someone worked on this lens and didn't put it back properly.

Thank you! Hmm, good to know, could explain some other very minor issues I have had with it in the past. Do you know if it is possible to then fix this at home?

Yes, usually it's possible to reassemble a lens correctly. It's been years since I've taken apart Mamiya lenses, but I've always found them quite self-explanatory - at least the helix mechanism. The general approach is to start by unscrewing the circular faceplate that surrounds the front element and then disassemble the lens from that side until you reach the problem area (in this case the helix). Then rebuild the right way, examining each step at a time.

I'm sure there are some instructions and perhaps some exploded view drawings online somewhere, but I've never looked into it. I bet some other users may chime in on this, so hold on for further assistance!

Sometimes, the part that stops a lens from turning at a certain point is not very strong. If the lens sat on a shelf for a long time, maybe someone picked it up and turned it too far, too hard, and the lens popped past its stop. I have a lens for a different camera that did exactly that - without any real amount of force.

Putting the lens back together may be a bit tricky because you will need to get the parts aligned correctly. There is probably only one correct location for threading the lens together - you'll need to do it by trial and error, looking at the distance scale on the lens.

You will have to take the back end of the lens apart, also. See:

The things pointed at on the left have to go in the spots indicated on the right. That has to happen after the lens is screwed back together.

Was there no rear element in that lens?

I would recommend taking this to a repair shop as unless you have experience with focus helix reassembly, it can be challenging. And that is when you take it apart properly and mark the positions of the parts. In the case of the 80mm Mamiya lenses, I see this issue often and many times it is caused by dried focus helix grease. The grease gets stiff and when a force is applied to focus, this is the result. Unfortunately you can't just screw it back in, the rear of the lens needs to be removed and also the two focus guides need to come out so that you can reposition the inner lens barrel in the threads in the correct position. And then usually refocus the lens.

what he says^^^^^
It can be tedious and frustrating dealing with something like this.
Take a deep breath and find a new friendly technician.