Problem Mamiya 180mm TLR Lens aperture ring stuck/tight

Hi there, i just bougt a 180mm for my C330 and got fraud. The aperture ring is so tight i cant switch from f/4.5 to another aperture. I googled this but didnt find any for this particular lens to fix this problem. I unscrewed the rear optical assembly but i dint know how to access aperture internal assembly to maybe clean this etc... Is the first time i am trying something like this of my own.

I uploaded a picture which Version this lens is and another one with the unscrewed rear optical. (www.flickr.com/photos/152753915@N06/albums/72177720304507820)

Maybe somebody could give me please some advice or a hint.

Thanx in advanced

or i just noticed my Thread is wrong here and need to "pushed" to

Camera Building, Repairs & Modification.... sry​

Thread moved.
@Mamiya_Repair might be able to help with this - hopefully he will see it.

Your best bet is to start by removing the shutter block from the lens board in order to find the real problem. The black ring on the back with two slots looks to be the retaining ring.

From there, you need to determine one of three ways that the aperture can be stuck. One is dirt and such under the back plate. The aperture indicator will be attached to this part. Two is a broken or unseated aperture blade- you might be able to see one of the blades either obviously out of position or bending as you try to move it. Be gentle. Need to break down, clean and hope that the blade(s) have the rivets and such unbroken. Three is a basic dirty old grease mess in the internal aperture mechanism- this means breaking down the shutter to get to this and cleaning it out.

Worth getting the shutter out and running a piece of paper under the rear plate to try to clean it out. A little naphtha, more paper or such inside to wipe it clean, etc.

Oh, fourth way, to check first- mechanical interference between the shutter block and the lens board. Sometimes spacers or levers get put in the wrong place, etc. In this case, the movement issue will clear up once you get the shutter off of the lens board.

If this is your first time, take lots of photos with a digital camera. Every time you remove a piece, do a new series of 4 or more angles. You'll have little idea of what is actually important, so the more angles the better chance you'll have a photo of how it was originally.

Hi Dan,

thanks for your reply and helpful clues! I will certainly take photos of the disassembly, because like you said so i know like things have to be in the original way... Maybe i am lucky and it is just dirt unter the back-plate .

In 95% of the cases with stuck aperture rings on this lens, the issue is oil contamination on the blades that has stuck them closed. If that is the case, the shutter will need to be completely disassembled to clean the blades and surrounding mechanism.

Mamiya_Repair said:

In 95% of the cases with stuck aperture rings on this lens, the issue is oil contamination on the blades that has stuck them closed. If that is the case, the shutter will need to be completely disassembled to clean the blades and surrounding mechanism.

Click to expand...

Ok, the Shutter open and close the blades correctly by all times at f/4.5.

kilgore72 said:

Ok, the Shutter open and close the blades correctly by all times at f/4.5.

Click to expand...

There are two sets of blades, the shutter and the diaphragm blades. The diaphragm blades can be stuck closed with oil while the shutter blades may work.

Mamiya_Repair said:

There are two sets of blades, the shutter and the diaphragm blades. The diaphragm blades can be stuck closed with oil while the shutter blades may work.

Click to expand...

oh, I didnt know that... Good to know!