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Lens identification and repair hints, please
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PostPosted: Mon Jun 06, 2011 1:03 pm    Post subject: Lens identification and repair hints, please Reply with quote

Hello everyone!

Just registered to MFlenses to learn more and (probably much later) give something back.
So, first post, first set of questions:
I recently bought this M42 lens below for next to nothing. I searched the net for info but didn't find anything, at least not in languages I understand. I suppose it's a branding of some lower quality model but not sure. Any idea what exacxtly an Auto Universar is?

The 6 aperture blades weren't moving freely so I ventured into the unknown and unscrewed the back element, mount, and aperture ring in order to understand the mechanics and clean the blades. The movement improved but gradually became stuck again and again. I cleaned them several times. The last time I did that, I noticed that that the entire aperture "array" (lacking the correct term) rotates before it opens or closes which means it won't open or close all the way.
I took it apart as far as dared but when I got to a very thin washer just on top of the part with those tiny springs that move the aperture, I chickened out...
Anyone with a hint on what might have happened and/or how to fix it?

While the aperture worked, I managed to get some pictures, and I think the lens isn't optically useless at all, so I'm keen on getting more info that might help.

Thanks in advance!
Andreas









Last edited by nightfly on Mon Jun 06, 2011 1:05 pm; edited 1 time in total


PostPosted: Mon Jun 06, 2011 1:04 pm    Post subject: Re: Lens identification and repair hints, please Reply with quote

nightfly wrote:
Hello everyone!

Just registered to MFlenses to learn more and (probably much later) give something back.
So, first post, first set of questions:
I recently bought this M42 lens below for next to nothing. I searched the net for info but didn't find anything, at least not in languages I understand. I suppose it's a branding of some lower quality model but not sure. Any idea what exacxtly an Auto Universar is?

The 6 aperture blades weren't moving freely so I ventured into the unknown and unscrewed the back element, mount, and aperture ring in order to understand the mechanics and clean the blades. The movement improved but gradually became stuck again and again. I cleaned them several times. The last time I did that, I noticed that that the entire aperture "array" (lacking the correct term) rotates before it opens or closes which means it won't open or close all the way.
I took it apart as far as dared but when I got to a very thin washer just on top of the part with those tiny springs that move the aperture, I chickened out...
Anyone with a hint on what might have happened and/or how to fix it?

While the aperture worked, I managed to get some pictures, and I think the lens isn't optically useless at all, so I'm keen on getting more info that might help.

Thanks in advance!
Andreas









Welcome!


PostPosted: Mon Jun 06, 2011 7:31 pm    Post subject: Reply with quote

This lens appear under zillions of names. Mostly in black but also in white aluminium. I have one in white. I consider it quite good.
Don't know the producer but from the same series a 135 mm exist for shure and maybe a 35 and 28 also.


PostPosted: Fri Jul 08, 2011 12:31 am    Post subject: Reply with quote

I'm guessing(!) --- the diaphragm assembly rotates because its retaining screws are loose. I'd open the lens from front end: remove name ring with friction tool of correct size, remove front element, probably held in place by a retaining ring, to expose diaphragm assembly retaining screws which are probably loose.


PostPosted: Fri Jul 08, 2011 6:36 am    Post subject: Reply with quote

Mhhm, though I have a UNIVERSAR 1 : 4.5 f = 3 0 0 m m 6 7 that looks pretty similar (it is grey metal and the aperture indicator is a red triangle though), ID is not so easy. All these 2.8/135 and 3.5/200 (e.g. chinon) look pretty similar. It does have the same little-squares on the focusing grip though. DOF figure looks same too, but additional red R on the left

As for the aperture, cannot help, mine came with a stuck M42 aperture pin, great for digital


PostPosted: Fri Jul 08, 2011 11:48 am    Post subject: Reply with quote

Welcome! Nice to see you here!


PostPosted: Sun Jul 10, 2011 7:14 am    Post subject: Reply with quote

Since you cleaned only from back you left the dirt on other side not to mention parts you don't see. Mostly trying to clean blades from one side the grease travels on other. Besides when using different solvents even more grease is released that was unimportant before thus situation might get even worse.

There is also possibility you softened the Teflon coating found on many blade types. This also stops the moving and it's really problematic since best solution is to completely remove Teflon. Both sides of blades Smile.

What i suggest you do is to completely remove automatic mechanism in lens and integrate small spring on part that pushes aperture to close down when Auto pin is pressed. I know that is very hard to understand to newbie but it's the only way in most such cases. The procedure overrides smaller blades abnormalities since spring can be stronger. You lose auto function of course but it's unneeded on DSLR anyways.

Send me a photo of rear interior for details.


PostPosted: Sun Jul 10, 2011 2:41 pm    Post subject: Reply with quote

Thank you all for your help!
I've now disassembled the lens completely to get to the aperture array and can see what the problem is. The whole array consists of layered rings with levers and springs in different places. The lever on the bottom ring seems to be missing at least one spring. That missing spring seems to make sure that the aperture opens completely when you choose f3.5 and close it completely when you choose f22.
Since this bottom ring can now move freely, it can have any random position within its range, meaning you get a random opening of the aperture.
I have not yet understood how to fix this. I will post some pictures when I get home from work again next friday.

Edit: For testing purposes, I locked the bottom ring with a removable drop of glue in a position that seemed right. The result was that the aperture closes completely but won't open all the way. Dialling to f3.5, the opening movement stops at what I'd guess to be f4.5.
Next weekend, next try...


PostPosted: Fri Jul 15, 2011 8:06 pm    Post subject: Reply with quote

Right, here are some pictures. The lever in the last (arrows) seems to be the culprit. When opening the aperture, it has to go to its right limit, otherwise it won't open all the way. When stopping down, it has to go to its left limit (actual position), otherwise the blades won't close to the selected value but come to a rest short of that. In other words it has to be locked in the opposite direction relative to the movement transferred from the aperture ring.
Wow.. I hope anybody can understand this...







PostPosted: Sat Jul 16, 2011 7:40 am    Post subject: Reply with quote

It looks complete. If there is any oil or dirt on the blades, it may not move freely. Perhaps the arrowed tab is moved by another part of the lens?


PostPosted: Sat Jul 16, 2011 8:05 am    Post subject: Reply with quote

It's not complete. You are missing small spring (not typical since it's short and only one circle) connecting the part with arrows with right side screw (the one that is not golden color).


PostPosted: Sat Jul 16, 2011 11:33 am    Post subject: Reply with quote

You'll have to connect this two:



PostPosted: Sat Jul 16, 2011 2:42 pm    Post subject: Reply with quote

Yes, that's what I suspected. Thanks a lot!
Now it's just to find a suitable spring. I'll try at the watchmaker's...


PostPosted: Sat Jul 16, 2011 5:44 pm    Post subject: Reply with quote

Or you can make one yourself using harvested parts. I suggest total disassemble of some broken FD mount or Super-8 cam.


PostPosted: Thu Aug 18, 2011 7:28 pm    Post subject: Reply with quote

I found it.
I found the spring I needed in a rather nasty looking Siclass 135/2.8 which has an identical aperture array. The spring looks like an unsymmetrical "figure 8" and is fastened to the silver screw and the lever. (Well, where else, doh..!)

I had a VERY hard time to reassemble the helicoid, and I will have to take it apart again for adjustment. Objects in focus are farther away than indicated on the distance scale. I think that means I have to increase the distance between the the front and back element. Can anybody confirm that (or correct me)?

Btw, does anyone know anything about Siclass lenses? I recently got the 135/2.8 and a 28/2.8 together with a Pentacon auto 50/1.8 and a Praktica LTL3 for next to nothing. Neither of the lenses seems to be worth while but I'd like to know more about the Siclass anyway...


PostPosted: Thu Aug 18, 2011 8:56 pm    Post subject: Reply with quote

The Pentacon is a nice lens, it has great colour rendition and is decently sharp. I like mine a lot.