Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
4 Likes  #1
Kiron/Vivitar 28mm f2 (24mm f2) sticky iris fix
Posted By: marcusBMG, 08-21-2019, 12:43 PM

This is not a full write up. Having just gone through freeing up the iris on my kiron 28mm I decided it would be handy to have the info in one place.
There are already several threads etc around to refer to:

Kiron Kino Precision 28mm f2.0 aperture issue - PentaxForums.com - 3 page thread from 2009, resurrected a few times by posters seeking more info, useful pics and discussion.

Kiron 2/28mm disassemble - mflenses thread discussing some of the problems, specifically stuck optical groups.

CLA Kiron 28 f/2 part #1/4 | Boas, antes de mais, CLA signif? | Flickr - flickr pics and full disassembly write up by Paolo Gomes with English translation (scroll down).

It's clear that there are variations in the structure of these kino optical 28mm f2's. I think mine is a later Kiron (serial 60103134), PKA mount. Pic 1 below shows the main parts:
  1. Mount and baffle
  2. rear optical block
  3. front optical block and cover/nameplate.
  4. Focus/distance scale ring.
  5. helicoid and iris assembly, mount side, front side pic 3. Note the PKA contact sits in the recess in the alloy perimeter at 10-after.
The job in essence is straightforward, an easy diy: remove the mount and rear group , remove the front group (both optical blocks just unscrew, no lens spanner required), iris is now exposed from both sides and can be cleaned. In practice it can be problematic. My first mistake was to try to unscrew the front block without realising that it is more likely that the front cover/nameplate is in fact going to unscrew. This is what happened but because I hadn't loosened the locking grub screw GS (see pic 4) the thread got a bit chewed up. Next (normally - in order to get better grip of the front optical block) the focus/distance scale ring can be removed, that's just 3 JIS screws. Note that the position of this ring on the helicoid sets the infinity focus stop, so it's a good idea to reach in with a long pointy something and make scratches to mark its position. It's not difficult to reset the infinity focus stop after though. Next the front optical block. This seems to be regularly sticky. On my lens it turned out that there were 2 access holes for thread locker solvent (pic 5), a dribble of acetone left for a few minutes in these and at the joint, and a strap wrench, did the trick.

I next removed the mount, this comes off as a unit with the baffle, note that the click ball bearing is under the next ring which I didn't need to remove. Note the PKA contact however is loose. There was no "bronze ring" referred to in the other threads on mine. The mount does need to be removed in order to get a grip on the rear group to unscrew it. Once again judicious use of thread locker solvent was key, I used a pair of pipe wrench grips with the rubber strap of the strap wrench providing cushioning.
I used coleman fuel and some iso-hexane contact cleaner spray to clean the iris, small brush, tissue. There is a tab T to manipulate the iris see pic 2. Iris must be totally snappy, no hint of hesitation.
Re-assembly is simple reversal of previous. The one ticklish bit was replacing the mount - the PKA contact kept jamming. Set the lens aperture on "A" and the contact in its elevated position in line with a gap in the mount rim. Manually move the mechanical aperture indicator (opposite the aperture lever) so that a wee tab engages in a wee slot and the mount lies flat before replacing any screws..

Attached Images
         


Last edited by marcusBMG; 08-22-2019 at 03:42 AM.
Views: 755
08-21-2019, 03:48 PM   #2
Site Supporter
Site Supporter
ramseybuckeye's Avatar

Join Date: Apr 2009
Location: Elida, Ohio
Photos: Gallery | Albums
Posts: 10,070
Nice article on a great lens. I had one, sold it, and regret it. Hopefully your article will help people save some of these lenses.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
28mm, aperture, block, contact, f2, front, iris, kiron, mount, pic, sticky iris, thread, vivitar
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
For Sale - Sold: SOLD Vivitar Series 1 70-210mm F2.8-4 Version 3 Komine *STICKY IRIS* steamloco76 Sold Items 2 05-05-2019 05:51 AM
Kiron 28mm F2 MC or SMC K Pentax 28mm F3.5 ? chapolin Pentax SLR Lens Discussion 69 02-06-2019 12:15 AM
Vivitar (komine) 70-210mm, PK-A mount, sticky iris repair. marcusBMG Maintenance and Repair Articles 4 05-23-2016 06:29 AM
The Kiron 24mm f2 and 28mm f2. Yay or nay? ChristianRock Pentax SLR Lens Discussion 22 04-11-2016 05:41 AM
Is the Vivitar 24mm f2 PKA as good as the Vivitar 28mm f2 PKA (Close-focus by Komine) Pepe Guitarra Pentax SLR Lens Discussion 13 03-25-2016 06:50 AM



All times are GMT -7. The time now is 05:47 AM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top