Just wish to add a couple of small points: This lens started life as the Meyer Oreston, went through several versions. Their mechanical constructions differ from each other, sometimes significantly, so the method for fixing this final "Multi Coated" version would not apply to an earlier version. Over time, the grease applied by many German manufacturers would have failed, and made the lens operation progressively more difficult. The lighter part of the grease distillates and covering the iris mechanism would make its action sticky, but the heavier component would cause even more problems. When I attend to one, I routinely take the focussing helicoid apart, clean off all the old grease and replace with modern grease.

Once I learned what the issue might be from your video, I was able to fix mine without even taking apart the lens. Just focus down to the minimum distance (0.33m) - this creates enough of a gap around the rear element that you can access the stuck lever with a small thin instrument, and clean the inner part of the hinge spring. Of course, on a "more stuck" lens this might not work, but I'd say it's worth a shot in case someone is too afraid (or lazy) to open their lens.

非常有幫助的視頻， 教你如何修復光圈

I just bought a m42 adapter to play with some old lenses from my mom. I was very excited about this f1.8 pentacon, but the aperture was stucked and thank to this video I was able to fix it. Thank you very much

I have the exact opposite problem. I also went about it the wrong way, as you first did. I spent ages tinkering with the auto aperture actuation mechanism at the back, only to realise that the problem is slightly sticking aperture blades. It wouldn't be a problem, but as you know, it's indirectly operated by a spring, and the spring just isn't strong enough to overcome the tiniest resistance. It works fine until I face the lens downwards, then it is jammed fully open until I take it apart again.

Thanks very much indeed for this - I swerved the bit about the blades and took the Mount off first, sure enough the lever was stuck. Thank goodness I didn’t have to take the blades out!

Thanks I lot. I just fixed my aperture ring!

To hopefully save others time, check the auto/manual mechanism first - turns out my issue was a stuck (dried out?) auto mode - I did the entire teardown, wiggled that mechanism a little and it started working haha. Was worth going through it anyway, was fun reassembling the aperture blades. Thanks for a great tutorial :) Saved me a couple hundred dollars!

Very nicely done. You are very delicate as it should be ! Thank you !

Thanks so much, I had exactly this issue, and whilst it may have taken me 3 hours, I fixed it thanks to you!

Thank you for the tutorial! Just fixed mine! Cleaning the sticky blades did it! ✨

Zen and the art of photographic lens repair!

I almost took it apart, but then I checked the pin (0:51) and realized I was on Manual mode ( I have the Pentacon 29mm f2.8), and this helped me out! I got so scared that my lens suddenly broke, but it was just a minor mistake thanks to this guy. Try this before you actually take apart your lens - It may save you a lot of excessive work. :)

Had to make it twice couse the first time did not clean well the blades and stuck again. Just finish to assembly and all good. Made my day again👍

thanks a million mate! Following your video I was able to repair my pentacon!

Thank you! Just fixed the aperture on my lens with help from your video :D

Very helpfull. Just fixed mine following these steps. Thank you!!

Thanks for the video. So possibly it could've been fixed with just taking off the rear of the lens and clean+lube the lever system? I have one that's stuck, but taking off the front and blades isn't something I want to attempt myself. The rear looks manageable though.

Same problem again😭. Thanks i did it twice. Will disable it again👍

ive unstuck aperture blade by just applying isopropanol to the blades with a paint brush then using the level inside the lens to open and closes them a few times, then used a cotton bud to soak up the oil/isopropanol mix on the blades. Did this a few time and aperture blades work fine. I myself just didn't fancy taking the Aperture mechanism apart

You made my day👍👍👍

Merci beaucoup ,c'est super j'ai le même problème je vais pouvoir réparer grâce à vous ,j'adore cet objectif qui est vraiment très bon.Thank you very much

Thanks man, done

Всё чётко и понятно,респект!

This is a scary movie!

Have an earlier version Jena lens the 50/1.8 Pancolar with similarly unmovable aperture. The aperture pin is fully loose in/out however no blade action to speak of. This video will help me get it fixed. Thank you.

It must be a common issue. If memory serves, I've had the exact same problem on at least three Pentacons, a 1.8/50, a 2.8/135 and a 4/200.

Hey, thanks so much for the video. I have an older version of this lens (electric), and for some reason moving the focus ring is also adjusting the aperture blades slightly - any ideas what may be causing that?

I just received a 135/2.8 Pentacon where the aperture blades moved erratically, so that they would sometimes not close, and sometimes they would close partially, so that the true aperture would be bigger than the set aperture. I removed the four screws at the back to expose the arm which pushes the tab the operates the aperture blades (the arm is seen at 9:05 in this clip). I found that the blades operate without any friction, so there is no reason to disassemble them. But the arm moves freely also. So, if everything moves without friction, why does it not work? There is a super tiny screw at the base of the arm which controls the extent of the motion of the arm, and I opened it by 3/4 of a turn, and that seems to have fixed the problem. Essentially, the arm now pushes the tab that operates the blades a little harder.

Я буду пробовать❤

Damn, checked the lever and seems to work perfectly but I can actually tell the blades are oily by looking through the lens from the back. Works fine until I open the aperture to 1.8 and it sort of goes too far and get stuck. So let me get this straight - oily blades are bad?

How to fix Pentacon lens that unscrews and separates after turning focus?

My lever isn't stuck it works fine when I push the button. If I manually operate the blades with the vertical rod they move. Any other suggestions? I read a comment regarding the blades could be too sticky for the strength of the spring? It feels like there's a piece missing...the aperture ring has nothing connecting it it just sits in there.

Hello, I can't remove the branding ring. I've already applied wd-40 but I can't remove it, even with the help of a rubberized cover to apply more force. Any ideas on how to do this?

So if I am able to move diaphragm with the pin then I need to disassemble the front?

Nice and neat repair...liked n subbd...BUT the techno music was TOO irritating ! Better some soft lounge jazz !

you cut through the heart of the lens to fine the problem in the very rear ?

Hi! Please tell me how to screw in the helicoid, I unscrewed it without putting a mark

Whats mean that M/A switch in Pentacon Auto series? I am Lumix user with 2,8/29 lens on - its pointless for me?

Hii. Thank u for this video.This lens a radioactieve?

Hi, I have the very same lens. It works fine but the aperture ring is loosen and doesn't "tick" when rotating. Can I Fix this? Thank you!!