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Biometar 120 repaired (kind of)
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PostPosted: Fri Apr 01, 2016 8:35 am    Post subject: Biometar 120 repaired (kind of) Reply with quote
edited

Last edited by bernhardas on Wed Apr 06, 2016 6:58 am; edited 1 time in total


PostPosted: Sat Apr 02, 2016 1:32 pm    Post subject: Reply with quote
I also have a CZJ Biometar 120mm. My lens is the leather ring version. Apart from some minor details, I believe the mechanics is equal to the zebra version.

I'm not convinced that the spring you showed is defective. That spring is not critical in my opinion. I am pretty sure that the root problem is migration of oil to the iris diaphragm blades. That happened to my lens, too. Cleaning the oiled diaphragm blades is a palliative. The problem will come back in a few months. To solve the problem definitively, it is necessary to disassemble the diaphragm system, clean it completely, and clean and relubricate the focusing helicoids with a proper low-separation grease like the Lubimax XP.

I had to completely disassemble my Biometar 120mm a few times to find out that there was oil migration from the fine helicoid to the diaphragm blades. It is a very easy lens to work on if you have a certain experience and right information. Nonetheless, there are two or three points that deserve special attention. It is a lens very well built and it should last forever if not abused and is properly maintained. I think I know quite well the guts of the Biometar 120mm. If you are confident that you can maintain the lens yourself, I can provide more specific information.


PostPosted: Sat Apr 02, 2016 2:04 pm    Post subject: Re: Biometar 120 repaired (kind of) Reply with quote
bernhardas wrote:


And as a tip to all Biometar owners: I noticed that the spring is relaxed when the aperture is closed, so it might be beneficial to keep your P6 lenses of similar design stored on maximum aperture.


That tip also applies to most Auto M42 lenses as well. Usually if the spring is weak you won't see any difference in size between the 2 smallest apertures (16 & 22 or 22 & 32).

You stated maximum aperture, presumably meaning maximum numerically, most people call this the smallest aperture Wink
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