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NickLapin · 01-27-2020, 09:04 AM

Today I found a Sigma Zoom Master in one of my drawers. It's an 35-70mm 2.8-4 A lens.

After trying it out in Manual position on my KP I found out the the apenture didn't work at all.

So by loosening the four scews I was clear that there is no connection between the lever of the apenture ring and the lever inside the lens connected to the blades. Any one here who can tell me how the two levers are connected?

**ProfessorBuzz** · 01-27-2020, 10:10 AM - **1 Like**

Was the lens in A-mode ?

NickLapin · 01-27-2020, 10:17 AM

Yes, it is an A-mode.Holding the lens in the hand, even manually one can't see the apenture blades moving.

**ProfessorBuzz** · 01-27-2020, 10:38 AM

Take the lens out of A-mode, then you should be able to stop it down manually, and you should see it behaves itself.

**pentaxus** · 01-27-2020, 11:16 AM

Or the blades are greasy and stuck open.

NickLapin · 01-27-2020, 11:23 AM

The blades don't move, moving the lever near the bajonet. The don't move by turning the apenture ring from 22 to 2.8. Unscrewing the bajonet unveil the second lever inside the optic, which is attached to the blades. They move freely.

Took the old Program A, switched it to B, and with the open body moving the apenture ring doesn't change a thing.

stevebrot · 01-27-2020, 11:36 AM

Originally posted by ProfessorBuzz

Take the lens out of A-mode, then you should be able to stop it down manually, and you should see it behaves itself.

Even with the ring in the A position, flicking the aperture actuator on the lens rear should open/close the iris.

Stee

**Just1MoreDave** · 01-27-2020, 02:32 PM

My guess is a spring used to connect the mount lever to the second lever - especially if the second lever opens the blades but they don't snap closed. Look for places where the spring might have attached. You might find a replacement spring that works.

I used to have that lens until I dropped it and the rear element fell out.

01-27-2020, 09:04 AM	#1
NickLapin Forum Member Join Date: Jan 2020 Posts: 91	No connection Aperture ring and blades Today I found a Sigma Zoom Master in one of my drawers. It's an 35-70mm 2.8-4 A lens. After trying it out in Manual position on my KP I found out the the apenture didn't work at all. So by loosening the four scews I was clear that there is no connection between the lever of the apenture ring and the lever inside the lens connected to the blades. Any one here who can tell me how the two levers are connected?

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01-27-2020, 10:10 AM - 1 Like	#2
ProfessorBuzz Loyal Site Supporter Join Date: Feb 2018 Posts: 1,903	Was the lens in A-mode ?

01-27-2020, 10:17 AM	#3
NickLapin Forum Member Join Date: Jan 2020 Posts: 91 Original Poster	Yes, it is an A-mode.Holding the lens in the hand, even manually one can't see the apenture blades moving.

01-27-2020, 10:38 AM	#4
ProfessorBuzz Loyal Site Supporter Join Date: Feb 2018 Posts: 1,903	Take the lens out of A-mode, then you should be able to stop it down manually, and you should see it behaves itself.

01-27-2020, 11:16 AM	#5
pentaxus Site Supporter Join Date: Jun 2010 Location: Central Coast, CA Posts: 1,320	Or the blades are greasy and stuck open.

01-27-2020, 11:23 AM	#6
NickLapin Forum Member Join Date: Jan 2020 Posts: 91 Original Poster	The blades don't move, moving the lever near the bajonet. The don't move by turning the apenture ring from 22 to 2.8. Unscrewing the bajonet unveil the second lever inside the optic, which is attached to the blades. They move freely. Took the old Program A, switched it to B, and with the open body moving the apenture ring doesn't change a thing.

01-27-2020, 11:36 AM	#7
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by ProfessorBuzz Take the lens out of A-mode, then you should be able to stop it down manually, and you should see it behaves itself. Even with the ring in the A position, flicking the aperture actuator on the lens rear should open/close the iris. Stee

01-27-2020, 02:32 PM	#8
Just1MoreDave Site Supporter Join Date: Feb 2007 Location: Aurora, CO Photos: Gallery \| Albums Posts: 6,340	My guess is a spring used to connect the mount lever to the second lever - especially if the second lever opens the blades but they don't snap closed. Look for places where the spring might have attached. You might find a replacement spring that works. I used to have that lens until I dropped it and the rear element fell out.

No connection Aperture ring and blades

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