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10-15-2009, 04:41 PM   #1
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A-50mm 1:1.7 focus ring off kilter, HELP!

So I've had this lens for only a few weeks, and my dumb ass grabs my camera, don't notice the strap hooked around the end of a table, catches and falls a few feet, landing square on the lens. So, the focus ring is a little off kilter and won't turn. Can anyone point me to an online schematic of this lens? Or give me a run down of how to take it apart without ruining it? My buddy things there is just a stuck ball bearing I have to unlodge, but who knows. Thanks in advance for any help. Here are some pictures:





10-16-2009, 03:41 PM   #2
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Ok, so the only thing I've found is this:

http://grantharg.tripod.com/CameraRepair/M50mmfixa.htm

I've read through it a few times, seems like a long bit of work. Anyone have any similar experience? I'll probably start taking it apart this weekend, was hoping I could find another DIY mr fix it with a similar story to assuage my fears. :P
10-16-2009, 04:27 PM   #3
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It's pretty straight forward. To take off the focusing ring, you don't even need to do anything from the lens mount side. Just start work from the front. Find something to hold and turn the flat ring between the front glass and the filter thread anti clock wise until it comes off, then you'd see the screws hidden there. From then on, you'd figure it out

Good luck.
10-16-2009, 11:47 PM   #4
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Frank's got the right idea, but the wrong method.

Should be able to pop off the "label" ring - the bit with the serial number and "SMC PENTAX-A" on it - to get at the focusing ring. Rather easy to do, if lever something thin under it. It's made from plastic, so be careful, it's easily snapped. This gives access to the focus ring's screws on the A f1.7 50mm. (On the M and K series, yes, it was under the the retaining ring - the ring that's inside the filter ring, which is where I think you've made a mistake, Frank.)

I don't know if this simplified construction or repair of the f1.7 A lens, or if it was simply a matter of being able to see the lens's label even when you've got a filter on it.

I'm betting the focus ring got dented and is jammed against the lens barrel, judging from the pictures.

10-17-2009, 06:13 PM   #5
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Thanks. I've tried to pry off the ring, but its just not budging. The plastic will chip a bit, bend, but won't budge. Not sure what to do besides sell it for parts. Yhar.
10-18-2009, 10:00 AM   #6
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Ryan, I've taken one of these apart before to fix with the same issue.

I will say this: If you can't get at it from the front, you'll need to be brave to take off the rear mount since it's hard to reassemble.

Once the rear screws from the mount are removed, carefully remove it. Then, you will have to remove the aperture ring. BE CAREFUL as there is a tiny, tiny ball bearing that might go flying (it makes the ring "click" into position). Also mind the little pin for the A lockout.

After that, keep removing screws inside and the lens group will come out. I bet the outer focus helicoid shifted. It's silver and sits inside the lens barrel. Chances are, it will need to be pushed back against its stops after the screws holding it are loosened.

Do that, then tighten the screws on the helicoid. Reinstall the lens group. Now the fun starts. I don't know how the factory did it, but you have to manuver the A pin AND aperture ball bearing into place at the same time, without bending the metal tabs holding the A pin in place, otherwise the lens won't lock in A mode.

If you can put those back in (unfortunately, I don't have any tips besides trying the A pin first, then slide the aperture ring over the already-installed ball bearing and hoping it doesn't go flying), then reassemble the rest of the lens. Oh...the aperture lever and aperture communication lever should be self-explanatory once you're in there. The aperture lever just comes out.

I don't have any pics, and I will advise you that it's difficult to reassemble. It can be done with patience and a good work space.
10-18-2009, 10:48 AM   #7
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A small bit of grease will hold that tiny steel ball (that makes the ring "click" into position) while you reassemble the lens.
GP
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