[micmrc]

Howdy.

In taking out the rear group of lenses to clean and verify a possible balsam separation, despite taking care of not messing around with any other part (in particular the aperture mechanism), I ended up by rotating the aperture ring, which slightly rose up from its standard position. The problem now is that 1) it wont seat back down where it was; 2) it will not rotate back or forward; 3) it proves impossible also to to extract it from its seat to reset it. Pretty much stuck. I can't figure out what is blocking it, since I can't see hardly any mechanism, except the aperture lever. Could it be the A function button? The ring is stuck on f22 and it does not go forward to lock on the A position. Does anybody happen to have stumbled upon a schematic of the lens or know what to do?

Regards

[Not a Number]

Even though they are vastly different lenses as well as being budget vs premium I suspect the aperture lock and pin mechanism are similar. You may want to review the photos of the Pentax-A SMC 50mm f/1.7 lens in the following thread:

Pentax-A 50mm f1.7 Aperture ring repair - PentaxForums.com

Several possibilities (and perhaps in combination) come to mind::

• The "click-stop" ball bearing and/or spring popped out and are jammed under the ring.
• The "A" button slipped under the leaf springs
• The "A" pin assembly slipped out and jammed under the ring.
• The linkage between the ring and iris mechanism is out of place

I'm afraid there is nothing to it but to use a reasonable amount of force the remove the ring. I suggest you do this in a plastic bag so as not to lose any of the tiny parts like the ball bearing, spring, button and pin assembly.

Otherwise as this is a high value lens you may consider having it professionally serviced.

[micmrc]

Thank you very much. Yes, I know about the tutorial concerning the 50mm f1.7. I am much in debt to that for avoiding troubles. And yes, the list you provided is more or less what I had in mind (I suspect the A button got stuck where it should not). I am grateful for somehow confirming the 'brute force' need. I was concerned there could be some more mechanism inside, attached/connected with the ring. I will await for the inspiration to act. Will try to keep an update here, later.

[Lowell Goudge]

Is it possible that the A button locking mechanism has slipped causing all the issues

[micmrc]

Thank you all for the support on this issue. I left it to settle for a while, waiting for the inspiration to work on it again. As suggested by Lowel Goudge, there must have been a problem with the A button leaf and the two small spring posts that stay underneath it. Upon removing the mount, if the aperture ring can even only slightly pop up from its seat under a twist and the spring post effect, the parts could lose their lining, creating problems. What seemed impossible even with very thin filler gauges and long pins, was resolved by some careful giggling of the ring. I have not yet put it back together. I will take some images and possibly post them and make them available for the repair section, before that. I'd like to acknowledge a debt of gratitude for giving me very valuable leads on how to work it out properly to Brian, which was once part of this forum - still lurking - but that seem to having been put out for some reason he did not mention. He contacted me privately. Cheers.