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04-22-2016, 02:47 PM   #1
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Stuck aperture ring

I have an as asahi Pentax m 1:1.4 50 mm lens and the aperture ring is stuck. When I put the lens on the body it opens to 1.4 and stays there. Can I get the lens repaired or do it myself.. I have taken off the silver plate but am stumped after that.

---------- Post added 04-22-16 at 02:49 PM ----------

The aperture ring on my old asahi 50 mm 1.4 is seized. Suggestions please.

04-22-2016, 02:50 PM   #2
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Is the ring physically stuck, or does the aperture just not close down when you turn the aperture ring? If it's the latter, then everything is normal- the aperture only gets stopped down when you take a picture.

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04-23-2016, 09:10 AM   #3
Mjh
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stuck

The ring refuses to budge. It is like it is welded.
04-23-2016, 11:49 AM   #4
osv
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i would google the disassembly for this lens, for example


04-23-2016, 02:00 PM   #5
Mjh
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stuck a ring

thanks for the video Do you know what the tool he used is called
04-23-2016, 04:06 PM   #6
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You probable got the ball bearing which is responsible for the clicking sound jammed in between the aperture ring and the body. Try a small amount of w-40 on a q-t tip and dab it on so it gets in between the aperture ring and the body. after it loosens up take apart and put the ball back in its indent. good luck
04-23-2016, 09:20 PM   #7
mee
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QuoteOriginally posted by niceshot Quote
You probable got the ball bearing which is responsible for the clicking sound jammed in between the aperture ring and the body.

That's my guess too. I wouldn't try to force the aperture ring, you could do damage to the ring. Rather, it needs disassembly and the bearing reseated if this is the issue.

BE CAREFUL when opening the lens as that ball bearing is both tiny and quick to jump out and get lost.

Take this with a modicum of salt, but I'd disassemble on a cloth towel just to ensure the bearing doesn't roll away on you. That is, even if it isn't the bearing that is the issue.

On an aside, does anyone know the specific size of the bearings used in these old M series lenses for the aperture ring?
04-24-2016, 03:15 AM   #8
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I don't recall the ball size, but Micro Tools carries several sizes. I got a small number of each from them a few years ago, which lets me trial fit to get the correct one when needed.

04-24-2016, 04:32 AM   #9
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QuoteOriginally posted by Mjh Quote
thanks for the video Do you know what the tool he used is called
Spanner wrench

One example : https://www.amazon.ca/Spanner-Wrench-Camera-Opening-Stainless/dp/B00NUPYDP0/...s=lens+spanner
04-24-2016, 07:37 AM   #10
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He doesn't need to take the lens elements apart to fix this problem, in fact it is a wast of time for him to do that unless the elements are filthy.
04-24-2016, 09:12 AM   #11
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Yes, since the aperture opens when he mounts the lens the diaphragm works freely, so no reason to open the optical head, just the body where the control ring is located. If the diaphragm were frozen from oil glueing the blades together it would take more disassembly.
04-24-2016, 11:45 AM   #12
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https://www.pentaxforums.com/forums/114-maintenance-repair-articles/88051-pentax-50
04-25-2016, 11:32 AM   #13
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that's coming up as a dead link... it looks like you can remove the screws in back, pull off the chrome mount, and gain access to the aperture ring, watch out for the ball bearing, as others have posted: M50 1.4

if you start doing this with any regularity, you'll want the spanner wrench and proper screwdrivers.
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