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10-16-2014, 03:40 PM   #1
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HELP!! 645nii and fa75 Aperture "A" doesn't work

Hi everyone,

Just a few days ago I purchased a "Like New" 645nii. It's really cosmetically perfect. And I purchased from another seller a fa75.

that's a long time Pentax dream come true I used mamiya 7ii and some fuji medium format before. This Pentax 645 system is my first Pentax camera ever!!

However, I'm having some problem here:
when I set the lens aperture to "A", the camera reads it as f32..... no matter what the light condition is, even at the cost of doing 8" exposure, the aperture just sticks to f32. The meter works though, in Aperture Priority mode and Manual mode the meter reads quite correctly. Just that the A Aperture doesn't work... so I lost program and shutter priority mode....

Who should I blame for?? the camera or the lens? the lens has two cracks on the front plastic, but that's far away from the aperture ring...

Has anyone had a similar problem?

Last question, if in the end I can't return it to the seller, where can I send it for a CLA? I'm located in Italy, so all europe is fine~

Many many thanks!!!

10-16-2014, 05:57 PM - 1 Like   #2
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QuoteOriginally posted by CrazyGenius Quote
Hi everyone,

Just a few days ago I purchased a "Like New" 645nii. It's really cosmetically perfect. And I purchased from another seller a fa75.

that's a long time Pentax dream come true I used mamiya 7ii and some fuji medium format before. This Pentax 645 system is my first Pentax camera ever!!

However, I'm having some problem here:
when I set the lens aperture to "A", the camera reads it as f32..... no matter what the light condition is, even at the cost of doing 8" exposure, the aperture just sticks to f32. The meter works though, in Aperture Priority mode and Manual mode the meter reads quite correctly. Just that the A Aperture doesn't work... so I lost program and shutter priority mode....

Who should I blame for?? the camera or the lens? the lens has two cracks on the front plastic, but that's far away from the aperture ring...

Has anyone had a similar problem?

Last question, if in the end I can't return it to the seller, where can I send it for a CLA? I'm located in Italy, so all europe is fine~

Many many thanks!!!
I just got my P645N, checked and mine works in Av mode or Program mode...

it seem in your case it is very difficult to determine which one is at fault - do you have someone also shooting P645 that can borrow you a lens and/or body to test them?
10-16-2014, 11:43 PM - 1 Like   #3
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Dry fire the camera with the lens attached and visually confirm whether the aperture blades are working correctly. As you change the aperture setting you should see the iris changing size. The DOF preview lever will also show the blades stopping down. Also inspect the butt of the lens, flicking the aperture lever to confirm whether the aperture blades stop down properly, and more importantly, whether they spring back open properly.

Finally I would suggest cleaning the electrical contacts on the lens and the mount.
10-17-2014, 12:19 AM   #4
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QuoteOriginally posted by LFLee Quote
I just got my P645N, checked and mine works in Av mode or Program mode...

it seem in your case it is very difficult to determine which one is at fault - do you have someone also shooting P645 that can borrow you a lens and/or body to test them?
Congratulations!
well, I don't know anyone around me shooting p645 so..... thanks for the advice!

---------- Post added 10-17-14 at 09:22 AM ----------

QuoteOriginally posted by revdocjim Quote
Dry fire the camera with the lens attached and visually confirm whether the aperture blades are working correctly. As you change the aperture setting you should see the iris changing size. The DOF preview lever will also show the blades stopping down. Also inspect the butt of the lens, flicking the aperture lever to confirm whether the aperture blades stop down properly, and more importantly, whether they spring back open properly.

Finally I would suggest cleaning the electrical contacts on the lens and the mount.
thanks for the advice!!

the aperture is all working correctly, at any aperture settings, just as you said. however at A position it performs as if it's f32...

I cleaned the electrical contacts but nothing changed...

is there a chance that Pentax mis-printed the A instead of 32???.....

10-17-2014, 12:51 AM   #5
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I have the A75/2.8 and so I can't be sure about the FA version, but on mine the aperture ring shows f/stop values up to f/22 and the next one is the green "A". To set the lens to the "A" mode requires pushing down the silver button next to the "A" and then turning the ring. Once there it is locked in place and cannot be released without pushing the silver button again. Strangely, when pushing the button and turning the aperture ring to "A" there seems to be another distinct click between f/22 and A. But I think it is just an anomaly... I can't get the ring to that position without pushing the silver button but when the ring is in that position it can still be turned either direction without pressing the button. If you turn it toward A it clicks again and locks in place. If you turn it toward f/22 it goes there and then is once again in aperture priority mode. When the aperture ring is set to this "in-between" setting the camera appears to function in auto aperture mode but with a slightly different exposure than when it is fully clicked into the A mode. Anyway, the reason I mention all of this is that I was wondering if your lens wasn't getting fully locked into A mode... although the behavior of my camera when the lens "in-between" is different from the problem you've described.
10-17-2014, 08:07 AM   #6
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ah... I remember this clip, you can remove the film loader and dry fire it and see if the aperture open...just make sure don't touch the shutter curtain (you probably already know)...

hope this helps.
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