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08-08-2012, 11:49 AM   #1
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DA*60-250 Sticky aperture blades?

Well, if it's not one thing it's another...

Seems like the aperture blades on my 60-250 are sticking wide open now and then. It's quite occasional and when it happens I have to unmount the lens and jiggle the lever until the blades are freed. Once freed they become operational and snappy again.

Anyone else with that problem or am I alone?

Looks like I'll have to send it in to Pentax Canada at the end of the summer to have it fixed...

Pat

08-08-2012, 04:01 PM   #2
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Shoot! Too bad. I hope they don't take too long.
08-08-2012, 04:04 PM   #3
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I'm waiting until the end of summer (after my vacation) as I expect I'm going to lose the lens 4-8 weeks...

Looks like I'll bring my DA55-300 as a backup on my vacation... the sticky problem happened 2-3 times over the summer and all of a sudden today it started happening a lot.

Oh well... I guess it was to be expected.

Pat
08-08-2012, 04:16 PM   #4
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Sounds like it might be a problem with the aperture lever at the mount rather than the actual aperture/blades mechanism. I've had that happen to lenses before -- it becomes a bit bent or misaligned and gets stuck -- remember the body is holding it open all the time it is mounted. Usually fixable just with a slight tweak to the lever. See if you can get it to get stuck when it is off the body just by pushing the lever a bit firmly (maybe slightly outward or inward). If so, you can probably figure out where and why it is catching.

08-08-2012, 04:34 PM   #5
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VonBaloney ... I thought thay might be the problem. I examined the lever and it's straight as an arrow (compared it to the lever on my 16-50) and it doesn't rub or bind at all when I operate it by hand.

Of course being a long zoom, and since the rear element moves (and brings the aperture mechanism with it), the lever "extends" inside the lens so there is plenty of room for mechanical failure in there...

Pat

ps: Love the username by the way!
08-08-2012, 04:53 PM   #6
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Well, looks like I've narrowed it down...

When I extend the lens, it seems to bind (just barely) around 135mm... aperture works fine up to then. When I retract it back, it binds a tiny bit again around 135mm and then the aperture mechanism remains stuck wide open. So it would seem that as I suspected the culprit is probably in the linkage between the lever and the aperture mechanism.

What an annoyance finding this out 5 days before my summer vacations...

Pat
08-08-2012, 05:01 PM   #7
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QuoteOriginally posted by ve2vfd Quote
VonBaloney ... I thought thay might be the problem. I examined the lever and it's straight as an arrow (compared it to the lever on my 16-50) and it doesn't rub or bind at all when I operate it by hand.

Of course being a long zoom, and since the rear element moves (and brings the aperture mechanism with it), the lever "extends" inside the lens so there is plenty of room for mechanical failure in there...
I've had them get stuck with no apparent bendiness, but would get stuck anyway. One of them I had to take the mount ring off and play with the mechanism a bit and then it worked fine -- in that case it wasn't the lever itself but the thing that the lever moves. I have a theory that this can happen when there are big temperature swings (most likely when the lens is mounted the entire time) -- those parts expand and contract and even bend more then you might think when it gets really hot or cold and then back to more moderate temps -- I don't know how else an internal metal part could just bend, even slightly -- they just aren't under that much pressure, but nevertheless I've seen them become visibly bent at times and screw up the aperture so the stops weren't right anymore or get stuck like you are saying. It has happened a couple of times to me and seemed to coincide with temperature changes, albeit with older and cheaper lenses than the 60-250...
08-13-2012, 03:47 AM   #8
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I have the same problem with a 55-300 DA WR. The aperture lever, when pressed firmly open, sticks in the open position. Overall, the blade and switch movement appears to be fluid, but when i push it firmly, it gets stuck. This translates in overexposure at close aperture when taking pics, since the aperture seems not to properly work when the lens is attached to the camera (kr). Infact when I remove the lens, the aperture is ALWAYS stuck in open position. Is there a simple way to fix it or it's matter for Pentax service?

08-13-2012, 05:36 AM   #9
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QuoteOriginally posted by Ares982 Quote
I have the same problem with a 55-300 DA WR. The aperture lever, when pressed firmly open, sticks in the open position. Overall, the blade and switch movement appears to be fluid, but when i push it firmly, it gets stuck. This translates in overexposure at close aperture when taking pics, since the aperture seems not to properly work when the lens is attached to the camera (kr). Infact when I remove the lens, the aperture is ALWAYS stuck in open position. Is there a simple way to fix it or it's matter for Pentax service?
That's exactly how mine was, but it was a non-AF lens (but with A contacts). I fixed it in about 10 minutes with a bit of tinkering. But I had to take the mount off. So off to service if you're worried about messing it up or voiding your warranty, but if you are not under warranty you might give it a go. I disclaim all responsibility when you lose the little springs and ball bearing...
08-13-2012, 06:35 PM   #10
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I checked mine again and can replicate the problem by extending the zoom past a certain point... it's definitely the linkage between the lever and aperture iris which is forward in this lens. As the lens is still under warranty it'll send it to Pentax Canada in 2 weeks.

Pat
08-14-2012, 01:03 AM   #11
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I think I will send it to Pentax too... It's new and under full warranty and I am a bit scared by the tought of springs and balls bouncing around the house..........
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