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05-16-2010, 07:35 PM   #1
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K-x/lens failures...Help!!!!

My K-x is acting flaky at the worst possible time--during a week-long graduation ceremonies for my daughter.

In short, it appears that some lenses are not providing aperture information to the camera. I get F--- as if I were using a manual lens. The auto-focus is fine. Aperture can be adjusted manually as per a manual lens, and shutter speed sets accordingly. Flash overexposes at all settings. In two days I have a major indoor event where I want to use flash. All these lenses were fine a day ago. Now, however:

Pentax FA50 works fine
Manual Sears 135/2.8 fine
Sigma 10-20 fine
Sigma 24-70 malfunctions per above
Tamron 70-300 malfunctions per above

One of the round contacts on the lens mount, the third one from the right, appears to be slightly depressed, more so than the rest. Not sure if that has anything to do with the problem.

Finally, I read somewhere that removing the lens from the camera, then working the aperture ring back and forth a half dozen times may clear the contacts, well, that seems to have fixed the two problematic lenses, but of course now I'm worried that the problems will recur.

Any idea what's going on? Thanks in advance

05-16-2010, 07:47 PM   #2
xjx
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QuoteOriginally posted by LouD Quote
One of the round contacts on the lens mount, the third one from the right, appears to be slightly depressed, more so than the rest. Not sure if that has anything to do with the problem.
You have guessed it right. This is the "A" pin. If it doesn't have good contact with the body mount the camera thinks the lens is an old pre-A lens.

It looks like the problem is with the two lenses. Not much you can do without taking apart the lens mount. Also please make sure the aperture ring is firmly set to the "A" position.
05-16-2010, 07:48 PM   #3
Ole
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The third contact you mention is different from the other contacts on many lenses. It moves back and forth when the aperture ring is switched in and out from the "A" setting.

I assume that the two problem lenses have an "A" setting and that it is enganged. The lens contacts could be dirty, or that third lens contact could be faulty on the lenses.
05-16-2010, 08:10 PM   #4
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QuoteOriginally posted by xjx Quote
Also please make sure the aperture ring is firmly set to
the "A" position.
Definitely check that. You might have moved it accidentally while changing lenses and not noticed. With the stress of "worst possible time", it's easy to miss.

05-16-2010, 08:34 PM   #5
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It is entirely possible that I disengaged the A position when changing from the FA 50 to the Tamron. In fact looking back on it, I think that is likely. But when the Tamron wouldnt' work, why would the next lens I tried, the Sigma, have the same problem?
05-16-2010, 08:39 PM   #6
xjx
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QuoteOriginally posted by LouD Quote
It is entirely possible that I disengaged the A position when changing from the FA 50 to the Tamron. In fact looking back on it, I think that is likely. But when the Tamron wouldnt' work, why would the next lens I tried, the Sigma, have the same problem?
The aperture ring of the Sigma lens might have been moved, too.
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