Tak 50 1.4 8 element - blades lag

kevinh · 05-07-2013, 09:15 AM

Hi all. I am looking for some help.
I start with the lens at f16. I open two clicks then close one. And repeat this pattern all the way through the scale. Following this pattern, f11 for example, is one size when your opening to it, but bigger when you are closing down to it from one click larger. Closing from two clicks larger will return it to the right size. When you move all the way up or down the aperture scale everything moves as expected. There is no oil on the blades.

I have the elements removed and have access to the top and bottom of the aperture blades, but would rather not go into this aperture mechanism any deeper. When pushing the aperture rod the is some intermittent resistance, but if it is because of dirt, it is hidden. Any ideas how to free/clean this up intact? I might be willing to break the aperture blade mechanism down if I could see how it is done. Thanks.

aoeu · 05-07-2013, 10:01 AM

Originally posted by kevinh

Hi all. I am looking for some help.
I start with the lens at f16. I open two clicks then close one. And repeat this pattern all the way through the scale. Following this pattern, f11 for example, is one size when your opening to it, but bigger when you are closing down to it from one click larger. Closing from two clicks larger will return it to the right size. When you move all the way up or down the aperture scale everything moves as expected. There is no oil on the blades.

I have the elements removed and have access to the top and bottom of the aperture blades, but would rather not go into this aperture mechanism any deeper. When pushing the aperture rod the is some intermittent resistance, but if it is because of dirt, it is hidden. Any ideas how to free/clean this up intact? I might be willing to break the aperture blade mechanism down if I could see how it is done. Thanks.

I just pulled mine out to play with it a bit and have noticed that if the A-M selector isn't all the way to M that I can get a similar behavior.

vladimiroltean · 05-07-2013, 01:47 PM

Is this the same as your issue?
https://www.pentaxforums.com/forums/maintenance-repair-articles/193521-broken...p-repairs.html

05-07-2013, 09:15 AM	#1
kevinh Inactive Account Join Date: Feb 2013 Posts: 61	Tak 50 1.4 8 element - blades lag Hi all. I am looking for some help. I start with the lens at f16. I open two clicks then close one. And repeat this pattern all the way through the scale. Following this pattern, f11 for example, is one size when your opening to it, but bigger when you are closing down to it from one click larger. Closing from two clicks larger will return it to the right size. When you move all the way up or down the aperture scale everything moves as expected. There is no oil on the blades. I have the elements removed and have access to the top and bottom of the aperture blades, but would rather not go into this aperture mechanism any deeper. When pushing the aperture rod the is some intermittent resistance, but if it is because of dirt, it is hidden. Any ideas how to free/clean this up intact? I might be willing to break the aperture blade mechanism down if I could see how it is done. Thanks.

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05-07-2013, 10:01 AM	#2
aoeu Veteran Member Join Date: Sep 2010 Location: Oregon Posts: 496	Originally posted by kevinh Hi all. I am looking for some help. I start with the lens at f16. I open two clicks then close one. And repeat this pattern all the way through the scale. Following this pattern, f11 for example, is one size when your opening to it, but bigger when you are closing down to it from one click larger. Closing from two clicks larger will return it to the right size. When you move all the way up or down the aperture scale everything moves as expected. There is no oil on the blades. I have the elements removed and have access to the top and bottom of the aperture blades, but would rather not go into this aperture mechanism any deeper. When pushing the aperture rod the is some intermittent resistance, but if it is because of dirt, it is hidden. Any ideas how to free/clean this up intact? I might be willing to break the aperture blade mechanism down if I could see how it is done. Thanks. I just pulled mine out to play with it a bit and have noticed that if the A-M selector isn't all the way to M that I can get a similar behavior.

05-07-2013, 01:47 PM	#3
vladimiroltean Veteran Member Join Date: Dec 2010 Location: Bucharest, Romania Photos: Gallery Posts: 1,465	Is this the same as your issue? https://www.pentaxforums.com/forums/maintenance-repair-articles/193521-broken...p-repairs.html