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10-20-2015, 07:12 AM   #1
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Help with a crippled M50 1.8

Hey guys, i get this lens (pentax-m 50mm 1.7) for $10 but it seems like the old owner have cuted the aperture lever and the viewfinder darkens when i close the aperture. I realy want to fix it but i can't get the part, Have someone any ideas how could i fix it? (some DIY fix)

Thaks in advance and sorry about my bad english.


Last edited by PabloFP; 10-20-2015 at 07:52 AM.
10-20-2015, 07:20 AM   #2
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perhaps a couple of pictures of what's missing/wrong from the lens?
10-20-2015, 07:21 AM   #3
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i dont know of any SMC Pentax-M 50mm F1.8 there is a F1.7 or F1.4 or there is a K 55mm F1.8
10-20-2015, 07:29 AM   #4
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sorry, it's the 1.7, and i forgot the pictures too , well i'll have to take a pic with my cam, the ones from the cellphone are crap. i'll upload another in a minute

edit:






Last edited by PabloFP; 10-20-2015 at 07:51 AM.
10-20-2015, 07:57 AM   #5
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it looks like the aperture lever has been removed or shortened.
maybe look for a donor lens?
10-20-2015, 08:07 AM   #6
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Yes, it has been shortened. I was looking for a broken lens but so far i got no luck. I'm also looking for a DIY fix, perhaps i can glue something to little piece of the lever that still remain in the lens, but i don't know if it's viable
10-20-2015, 08:11 AM   #7
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That is a non-reversible way of getting rid of the aperture lever and thus making it like a m42 lens in M position. You can still use this lens with stop down metering method, thus you can use Av mode in the camera. There is nothing wrong with that, and besides, you don't want to stop down too much anyway, as it becomes harder to focus.
10-20-2015, 10:02 AM   #8
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The thing is that i've purchased the lens to use it in the me super and it would be nice that the lens was fully functional with that camera.

10-20-2015, 10:12 AM   #9
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Sell it to a Canon user and get another one.
10-20-2015, 10:46 AM   #10
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And as it was $10 dollars...
Sell it for $20 as it is already customized to fit
10-20-2015, 11:18 AM   #11
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The lever is a stamped piece, riveted on to a larger assembly. I think you could try a couple of methods to fix it. If you take off the lens mount (5 screws) the lens probably looks like the lens on the left.



The easier fix is to try to glue a lever on to the stub. The replacement lever needs to engage the camera's aperture arm in the same place, so you may have to bend either the old lever or new extension or both to get that location correct. The lever doesn't take that much force to move so it doesn't need a super strong repair, like riveting or welding.

A second option is to remove the stub and put on a whole new lever, maybe with rivets or small screws. In that case you need to slide the aperture ring off, being careful because there is a spring-loaded bearing trapped between ring and lens body right where the orange diamond is on the distance scale. The bearing is in this photo on the lower left.



Then you can remove the screws hidden under the aperture ring, to slide off the rear of the lens body. You're removing the part with the distance scale and white button. It looks like this:



You can see the other side of the rivets holding the lever on. You need that forked piece also. Probably there is room for some small screws to replace the rivets.

The cheap M50/2 lenses use a different construction unless they are really early Made in Japan models. You may not be able to use any parts from the later version except the aperture lever, redrilling some holes. A later M50/2 looks like the lens on the left here, with the aperture mechanism in the center. There is no fork.

10-20-2015, 11:53 AM   #12
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I would glue or solder a piece of brass on. Silver solder would be my preference. A high strength resin like JB Weld might do. The aperture stop-down lever thwacking against the lever will probably cause most cyanoacrylate glues to fail. Besides these have a habit of out gassing for a very long time after application.
10-20-2015, 06:17 PM   #13
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I agree with Not a Number. A piece of brass bent and epoxied on with JB Weld would be my fix if I had to DYI.
10-20-2015, 11:40 PM   #14
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+1 for soldering!
10-21-2015, 02:51 PM   #15
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i'll try what not a number've said, i'll post later. Thanks
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