Aperture mechanism on Ibsor shutter - difficult to turn, pins popping out

blee1996 · Feb 8, 2025

Hi,

I try to perform CLA on this Ibsor shutter, from a Voigtlander Avus camera with Anastigmat Skopar lens. The shutter itself is all done and all speed are good now, but the aperture is a bit strange.

It is clean and dry, without any trace of oil or grease. But it is very difficult to turn from f/5.6 and beyond. If I use some force, it can indeed change the aperture to smaller, but soon some pins might pop out of the groove, and difficult to get back into the groove. I open the entire thing very carefully, and I don't see anything wrong with the assembly. Do you happen to have any experience with this? thanks! I attach three photos of the aperture assembly. The oily cotton swabs are not from the aperture.

P.S. the Ibsor shutter is probably the most user friendly to disassemble. 4 screws from the back, then the entire aperture unit comes out. Three shutter blades marked with different dots, very easy to recognize the proper order. And the rest of the speed retard mechanism is simple. And it is suitable for flushing with lighter fluid, since neither the aperture nor shutter blades will be there to mess up.

bernard_L · Feb 9, 2025

I have no experience with this shutter. Just a few suggestions from a bystander.

Wear/corrosion/abrasion in the grooves where the pins slide; perform a visual inspection with a strong magnifier and oblique angle of view, and visual inspection of the sliding pins...
Residual dirt; no offense meant, see 2nd picture, but maybe it's purely visual...
Try some dry PTFE lubricant

Steve906 · Feb 9, 2025

I did one of these a few months ago and had a similar problem.
One of the pins had come out of a leaf and the whole thing was jammed up.
I made another pin and riveted back onto the leaf. On assembly it was - as you say not right going to smaller apertures. I assumed it was a previous repairer had used the wrong leaves and that had lead to the damage and improper operation. I modified the slots in the plate with a small round Swiss file (see picture), checked the apertures (all seemed close enough) and left at that.
Definitely no lubricant.
I assume leaves are the correct way round (Can't remember if it is even possible to do them wrong ).
I'm not sure but I seem to recall the leaves on this are some sort of plastic!, could have been another iris I was doing at the time but be careful with cleaners, acetone can melt those ones!
Steve.

Dan Daniel · Feb 9, 2025

It was with shutter blades, but I had a shutter that would work five times, then go all weird, then work fine, very erratic. Found a small crack in one blade at the back hole. Almost impossible to see, but moving the blades in the mechanism without the cover finally showed me the way the crack would sometimes grab an adjacent blade and slide under it or such.

So look closely along all edges for any burrs or cracks. Look closely around holes and rivets. Maybe wipe each blade down with a dry cotton swab to see if any fibers get pulled away by a burr.

OAPOli · Feb 9, 2025

I would measure the diameter of the pins to check that they are all the same. Then test each of the slots to see if one might have a slight taper.

dxqcanada · Feb 9, 2025

I worked on cleaning aperture blades once and after I put them back in it would not open fully ... then I realized I put the blades in wrong side down.

blee1996 · Feb 9, 2025

Thank you all! I will clean everything and put back and see how it goes.

Kino · Feb 10, 2025

Polish blades with Brasso or Flitz metal polish.

Watch Chris Sherlock's Retina Repair videos on Youtube for tips on this method.

Steve906 · Feb 10, 2025

Any polish will remove the blacking from most types of blades leaving them shiny, not what you want. The polish would then need cleaning off anyhow. Pre clean with naphtha / WD then finish with Acetone on metal blades or alcohol on others, always try a tiny spot first.
@blee1996 have a look at the pins as the blades move if they touch the ends of the slots like mine did this may well be the problem (poor original design?) I thought mine had maybe been replaced but yours look identical.
Steve.

blee1996 · Feb 10, 2025

@Steve906 I fully agree with you that the original design was poor. There was no oil or grease in any of the aperture blades or mechanism. In the end, I enlarged the slot a bit like what you did in the previous post, and now it is much easier to adjust aperture down to f/16. Very seldomly one pin will still pop out temporarily, but it will go back when the aperture is opened. So I will leave it at that.

Steve906 · Feb 10, 2025

blee1996 said:
@Steve906 I fully agree with you that the original design was poor. There was no oil or grease in any of the aperture blades or mechanism. In the end, I enlarged the slot a bit like what you did in the previous post, and now it is much easier to adjust aperture down to f/16. Very seldomly one pin will still pop out temporarily, but it will go back when the aperture is opened. So I will leave it at that.

Great, glad you got it sorted.
I don't know what others must have done when these were new, presumably just put up with using it open most of the time?!!
Steve.

Kino · Feb 10, 2025

Steve906 said:
Any polish will remove the blacking from most types of blades leaving them shiny, not what you want.

Clearly not true, as is evidenced by Sherlock's videos and my experience, but that's not to say it might on these blades.

Testing would be in order.

Steve906 · Feb 11, 2025

Kino said:
Clearly not true, as is evidenced by Sherlock's videos and my experience, but that's not to say it might on these blades.

Testing would be in order.

I don't know who Sherlock is but I have cleaned many thousands of iris leaves and never have or will use a polish - no need - and certainly not on any vintage lenses of the age of the OP's .

Kino · Feb 11, 2025

Steve906 said:
I don't know who Sherlock is but I have cleaned many thousands of iris leaves and never have or will use a polish - no need - and certainly not on any vintage lenses of the age of the OP's .

Broaden your horizons:

Chris Sherlock

Mostly stuff related to the Kodak Retina series of 35mm cameras, especially repair. You can find my website here....https://retinarescue.com

www.youtube.com

Aperture mechanism on Ibsor shutter - difficult to turn, pins popping out

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