Mamiya sekor c 110mm iris not closing

[jakeglaviano]

Hello I have a mamiya sekor c 110mm m645 the iris isn’t closing. I assumed it was some oil in the blades. I took it apart cleaned everything, re lubed when I put it back together right be for I put the mount on I tested the Irish with a small screwdriver and opens and closed it with the mechanism where the mount prong sits. It worked great. When the mount is back on the iris doesn’t close. Some times it’ll snap shut when I reach it being closed down and then will be unresponsive until I get back to a 2.8.
Once I get home I can upload some photos.

 

[koraks]

re lubed

I've never found any lube in a Sekor mechanism.

There's a bit of an awkward lever arrangement in these lenses if memory serves; have you verified it engages properly? I mean the one that links the mount to the actual aperture mechanism.

 

[jakeglaviano]

Yes it’s engaged properly that was my first thought. I have repaired one before and it slipped out and took me a while to find out what was happening. But just now playing with this current lens I noticed the aperture works if the mount is loose. If go to the point of where the head of the screw just meets the mount the aperture acts up again.

I took the entire thing apart again and doing another cleaning probably won’t do anything but worth a shot I guess.

 

[OAPOli]

The coupling works via a curved linkage arm (tab towards the inside to link to the aperture, a pin on the other side to link with the body). Maybe that arm is slightly bent or loose?

 

[jakeglaviano]

hello sorry for the late reply. i got swamped on a job. i checked the arm and it looks fine. any other ideas?

 

[jakeglaviano]

hello as I crossposted this onto Facebook someone asked if I could take out screw by screw and put them in one by one and see if it worked (the thought was maybe the tolerances of the screws were slightly off. I did that and still no luck. I'm at a strange point though. The iris ring is a bit tight now i completely stripped the lens all the way down. to expose the helicoid under the iris's plastic. I cleaned it (it had some dirt inside. i then cleaned and re-lube the focus helicoid and re-assembled the lens. after that, the iris is still acting up but if I focus the lens the iris no budges a little for some reason. all the arms are in the correct place. i took apart again and looked at the back of the mount and did notice the spring was a little oblong i have a 55mm donor lens and took the spring from that seeing that both springs looked to be the same size (by spring I mean the small looped metal that pushes the register pin} still no luck.