Aperture lever does not "spring."

**gump** · 05-06-2021, 05:38 AM

A short "drop" with my 17-50 sigma yesterday resulted in exposure problems. After a lens change to determine it was not a problem with the KP, I took a look at the sigma and the aperture lever (I have no idea if this is the correct term) moves and the blades do their thing but the lever does not snap back. I have never had a lens apart but it leads me to think there is a spring that is either broken or detached. does this sound reasonable? Is there a quick simple DIY fix or should I send it to someone who knows what they are doing? The lens has proven to be very good, I got it used for a bit over $200. Any suggests on repair shops and cost?

**c.a.m** · 05-06-2021, 05:55 AM - **1 Like**

Sorry to hear of your accident. Always a heart-stopping moment.

I've worked on a variety of lenses. Offhand, I'd agree with your diagnosis -- the aperture return spring probably has been dislodged from its pin(s).

I'm not familiar with the Sigma lens, and I assume it's the 17-50 f/2.8 autofocus.

The job to reattach the spring could be fairly complicated -- it depends on where the spring is located and attached. It would require removing the lens mount and working in a fairly tight space at the back of the lens. The mount screws probably have JIS heads (Japan Industrial Standard), which require a special screwdriver of the proper size (not Phillips). Care is needed to remove and replace the electrical contact pins along the lens mount, which can be fiddly. Depending on where the spring is located, further disassembly might be required, including removing a small printed circuit board. Finally, mini needle nose pliers and possibly a scratch awl or spring tool would be used to reattach the spring.

The job would be considerably more complicated if both ends of the spring have become detached and it's fallen into the guts of the lens.

I'd also be concerned whether the drop caused any other problems such as an optical misalignment or fractured plastic parts.

- Craig

**c.a.m** · 05-06-2021, 06:11 AM

Originally posted by gump

Any suggests on repair shops and cost?

@gump, I've edited my post to indicate that the job might be more complicated than I first thought.

**gump** · 05-06-2021, 06:20 AM

Originally posted by c.a.m

@gump, I've edited my post to indicate that the job might be more complicated than I first thought.

Aside from investing in tools and my very questionable ability at "fine" work I am leaning toward finding someone who knows what they are doing. Shooting at a fixed aperture and a general exam does not suggest further damage but who knows what may hide within. I appreciate your response.

MikeMcE · 05-06-2021, 06:32 AM - **1 Like**

Most aperture control ring springs are easy to rehook, as it’s on the inside of the flange. Remove the flange screws, carefully tilting the flange so you don’t tear the ribbon wire. Now it should be obvious. If everything is hooked up the control ring might be bent causing a bind.

This is easy for me, but I’ve repaired cameras and optics for years. Proper tools are a must.

Hang up and DRIVE!

05-06-2021, 05:38 AM	#1
gump Site Supporter Join Date: Apr 2018 Location: Canton, Ohio Posts: 1,016	Aperture lever does not "spring." A short "drop" with my 17-50 sigma yesterday resulted in exposure problems. After a lens change to determine it was not a problem with the KP, I took a look at the sigma and the aperture lever (I have no idea if this is the correct term) moves and the blades do their thing but the lever does not snap back. I have never had a lens apart but it leads me to think there is a spring that is either broken or detached. does this sound reasonable? Is there a quick simple DIY fix or should I send it to someone who knows what they are doing? The lens has proven to be very good, I got it used for a bit over $200. Any suggests on repair shops and cost?

05-06-2021, 05:55 AM - 1 Like	#2
c.a.m Site Supporter Join Date: Jan 2013 Location: Ottawa, Canada Photos: Gallery \| Albums Posts: 4,189	Sorry to hear of your accident. Always a heart-stopping moment. I've worked on a variety of lenses. Offhand, I'd agree with your diagnosis -- the aperture return spring probably has been dislodged from its pin(s). I'm not familiar with the Sigma lens, and I assume it's the 17-50 f/2.8 autofocus. The job to reattach the spring could be fairly complicated -- it depends on where the spring is located and attached. It would require removing the lens mount and working in a fairly tight space at the back of the lens. The mount screws probably have JIS heads (Japan Industrial Standard), which require a special screwdriver of the proper size (not Phillips). Care is needed to remove and replace the electrical contact pins along the lens mount, which can be fiddly. Depending on where the spring is located, further disassembly might be required, including removing a small printed circuit board. Finally, mini needle nose pliers and possibly a scratch awl or spring tool would be used to reattach the spring. The job would be considerably more complicated if both ends of the spring have become detached and it's fallen into the guts of the lens. I'd also be concerned whether the drop caused any other problems such as an optical misalignment or fractured plastic parts. - Craig Last edited by c.a.m; 05-06-2021 at 06:13 AM. Reason: Looked at some online disassembly jobs

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05-06-2021, 06:11 AM	#3
c.a.m Site Supporter Join Date: Jan 2013 Location: Ottawa, Canada Photos: Gallery \| Albums Posts: 4,189	Originally posted by gump Any suggests on repair shops and cost? @gump, I've edited my post to indicate that the job might be more complicated than I first thought.

05-06-2021, 06:20 AM	#4
gump Site Supporter Join Date: Apr 2018 Location: Canton, Ohio Posts: 1,016 Original Poster	Originally posted by c.a.m @gump, I've edited my post to indicate that the job might be more complicated than I first thought. Aside from investing in tools and my very questionable ability at "fine" work I am leaning toward finding someone who knows what they are doing. Shooting at a fixed aperture and a general exam does not suggest further damage but who knows what may hide within. I appreciate your response.

05-06-2021, 06:32 AM - 1 Like	#5
MikeMcE Pentaxian Join Date: Jun 2020 Photos: Albums Posts: 1,093	Most aperture control ring springs are easy to rehook, as it’s on the inside of the flange. Remove the flange screws, carefully tilting the flange so you don’t tear the ribbon wire. Now it should be obvious. If everything is hooked up the control ring might be bent causing a bind. This is easy for me, but I’ve repaired cameras and optics for years. Proper tools are a must. Hang up and DRIVE!