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09-17-2016, 07:52 AM   #16
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QuoteOriginally posted by Not a Number Quote
Could you take a photo of the lens mount on the bellows from the front, e.g. looking into the bellows. Perhaps someone had modified the mount to open the aperture. Why one would do this I don't know. Unless they wanted to use lens without aperture rings. You can stop down by unlocking the lens and turning it in the mount.
This is the solution, as explained in the manual (thanks for the link). Mine is just Bellows K, not Auto Bellows, so I guess that's the difference.

Thanks!

09-17-2016, 07:57 PM   #17
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Well something's not right. From what I'm reading from the manual the iris should close down as you turn the ring. Either the mount on the bellows has been modified or there is a problem with the lever on the lens. Does the diaphragm stay open on all your K=mount lenses?
09-18-2016, 11:32 AM   #18
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QuoteOriginally posted by Not a Number Quote
Well something's not right. From what I'm reading from the manual the iris should close down as you turn the ring. Either the mount on the bellows has been modified or there is a problem with the lever on the lens. Does the diaphragm stay open on all your K=mount lenses?
Yes. I mounted the bellows to an empty MX, with the bellows retracted completely. I mounted 2 different lenses, and looked through the front of the lens as I moved the aperture ring. No change - wide open all the way.

Still looking through the front of the lens, I tripped the shutter at 1/2 sec. I couldn't see the blades stop down even then.

Edit: all 3 lenses I've tried work normally when mounted to various camera bodies.
09-18-2016, 03:28 PM   #19
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With the Bellows Unit K there is no mechanical linkage in mount to control aperture which eliminates a problem there.

My best guess would be that the bellows have had the lens mounting ring removed at some time & been incorrectly reinstalled. On the attached image the area adjacent to the yellow arrow is the area of mount that will effectively hold the aperture open on lens when mounting. Look for any irregularities in this area. My best guess without seeing image of your bellows lens mount would be that the spring steel mount washer (red arrow) which is behind the front mount plate has been reinstalled in the incorrect position bending the tab out into the path of the aperture lever on the lens.

Second option which is highly unlikely on all 3 lenses, but will mention to cover all bases. The lever on the lens mount which holds the lens aperture open may be bent out a fraction. This rides just inside the bellows front standard adjacent to the yellow arrow. It normally has minimal clearance from the front standard & as such would not require much of a bend to rub against it. The best way to check this would be to mount a lens on the bellows ( at minimum extension) while looking through the camera standard opening.

Third option which is once again unlikely but worth a mention. The aperture lever of lens rubbing against the actual bellows due to damage to bellows or a slightly bent aperture lever. This will rub on the actual bellows in area of blue arrow. Damage to the actual bellows in this area is highly unlikely as it is behind the front standard flange.

As there is nothing native to the design of Bellows Unit K which will cause the issues you are experiencing, so you are definitely looking for a irregularity from some sort of damage.

Attached Images
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PENTAX K200D  Photo 

Last edited by Tool_Horder; 09-18-2016 at 04:13 PM. Reason: Added 3rd option.
09-18-2016, 04:23 PM   #20
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@Tool_Horder...After reading this, I examined the areas you had indicated. I don't know that I have the expertise to know if it's correct or not.

So, I loosened the screws that attach the mounting ring. I didn't remove it, just loosened the screws and wiggled it a bit, then retightened.

I mounted a lens, and found that the diaphragm opened and closed just as it should. Mounted another lens to double-check, and it worked fine as well.

Maybe, as you suggested, it had been removed at some point, and the mechanism was in a bind or something. I don't know.

In any case, it seems to be working now.

Thanks for the help!
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