Auto Yashinon 5cm f2 strip down - a photo on Flickriver

            This old lens is quite sought after, especially by Fuji digital camera owners. There’s a glowing on-line review by a Fuji user (see Theoria Apophasis) who tested it against 34 other M42 lenses.  He thought it was the best of the lot.

My copy came with some serious problems, which the seller had clearly flagged. A ding in the front thread blocked access to the front element. Fungus starting in the rear elements. And most critically, an aperture stuck wide open – so stuck that the aperture ring wouldn’t turn at all.

For a while I was happy to use the lens wide open (the glass – minus the fungus – is great). However, the lens has a lot more potential, and I decided to undertake major surgery.

Before starting, I spent some time on the internet investigating how to repair the lens. Or more accurately, how to repair a 60 year old M42 lens with a front aperture ring and a rear cocking lever, since I couldn’t find instructions for completely stripping down this specific lens. (There is a video of a partial disassembly, but it doesn't go as far as taking the blades out). 

Simon Hawketts (on his Photo Blog) had repaired a similar type of lens with a cocking lever – an Auto-Takumar 55mm. His write-up and photos were very useful, and gave me confidence the repair could be done relatively easily. In particular, the cocking level wasn't something to worry about! (I was concerned parts might spring out across the room or a tiny ball-bearing might shoot out and disappear – things that have happened to me before with other lenses). 

Someone else had come up with the idea of beating out dents in front threads with a hammer, a chopstick and blu tack under the body – and strange as that sounds, it worked! 

Finally, I watched two excellent videos by Retro Poto House on repairing a Helios 44-2 and a Helios 81M (Nikon mount) - particularly helpful for demonstrating how to access the blades and put them back. 

It didn’t all go according to plan. After opening up the lens, and removing the glass elements, I became convinced that someone had removed the blades. They were nowhere to be seen. And the aperture mechanism was still jammed, regardless of how much pressure I applied to the mechanism. 

I decided to take drastic action and soak the lens body in vinegar (minus the glass and some other pieces) for 24 hours, followed by a clean-up of the inside with pure alcohol. Only after this cleaning could I see leading edges of the blades, and get them to close. They were so jammed into their space and so covered in rust they had disappeared from sight, or at least merged in appearance with the body. 

So here are all the parts of the lens laid out, awaiting for the re-assembly, including the tricky part of putting back the blades....

Taken on: March 13, 2020

Tags:

Yashica Auto Yashinon 5cm f2

M42 lens stripped down

Fuji M42 « less

Sets appears in: • Pentax DA 35mm Macro Limited • Yashica Auto Yashinon 5cm f2 more » • Photos of lenses « less

Groups appears in: • M42 • Pentax Limited Lenses more » • Pentax K-01 • Effected Cameras (and other photographic items) « less

Camera: Pentax K-01, f/8.0, 1/5 sec, 35mm (=52mm), ISO 100 (more info) (hide info)

Camera:	Pentax K-01
Aperture:	f/8.0
Exposure Time:	0.2 sec (1/5)
Focal Length:	35mm (35mm equivalent: 52mm)
ISO:	100
Exposure Bias:	+1 EV
Flash:	Off, Did not fire
Exposure Program:	Aperture-priority AE
Exposure Mode:	Manual
Metering Mode:	Multi-segment
White Balance:	Manual
Sharpness:	Hard
Color Space:	Uncalibrated
Software:	Adobe Photoshop Lightroom Classic 7.4 (Windows)
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