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Konica Hexar 28mm 3.5
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PostPosted: Mon Aug 11, 2014 10:17 pm    Post subject: Konica Hexar 28mm 3.5 Reply with quote
Does anyone have any experience disassembling this lens?
I just picked one up today at a thrift store ($3 with hood!) with a very stiff aperature ring. There is a small dent in the ring. Though the dent is very small, would this be the likely culprit?


PostPosted: Wed Aug 13, 2014 7:48 am    Post subject: Reply with quote
Fwiw, I own a mint Hexar 28, which also has a very stiff aperture ring. Yours isn't necessarily damaged, the aperture seems stiff "by design".


PostPosted: Wed Aug 13, 2014 8:26 am    Post subject: Re: Konica Hexar 28mm 3.5 Reply with quote
lenny wrote:
Does anyone have any experience disassembling this lens?
I just picked one up today at a thrift store ($3 with hood!) with a very stiff aperature ring. There is a small dent in the ring. Though the dent is very small, would this be the likely culprit?


There are very small movement tolerances between an aperture ring and a lens barrel, so if the aperture ring has a dent in it, it is very likely the reason why the ring doesn't operate properly.
No need to disassemble the entire lens. The aperture ring can be lifted off once the lens mounting plate is unscrewed (four screws). Just make sure you have a well-fitting screwdriver. Those screws can be tight and if you damage the heads, you will have to drill the screws out. Also be careful not to loose the tiny spring loaded aperture stop detent ball. I suggest wrapping the entire lens in a clean piece of cloth while lifting the aperture ring. This will prevent the ball from flying away. Once the aperture ring is off, you can use a wooden dowel and a little hammer to straighten out the dent, just as with a filter ring repair. There are many discussions on how to do this on this forum.

@ Sceptic: You may very well also have a tiny dent on your aperture ring. It may not be an obvious one, the ring may be simply out of round. Failing this, you may have some accumulated grime under the aperture ring.


PostPosted: Wed Aug 13, 2014 4:36 pm    Post subject: Reply with quote
Found it! I knew the lens has no physical damage whatsoever and that it had to be something on the inside. Having taken quite a few Konica lenses a part for cleaning (28/3.5, 40/1.8, 50/1.7, 52/1.8, 55/3.5 macro, 85/1.8, 100/2.8, 135/3.2 and 135/3.5, but I digress) I knew that aperture ring stiffness can be caused by a too tightly wound "aperture detent ball spring". My 52/1.8 had the same problem, although not as severe as the Hexar 28, which was fixed by loosening the screws on the opposite side of the little ball (tightening the screws tighten the spring and thus the force required to turn the aperture ring).

The Hexar has no such screws, it has just a hole with a spring in it, with the ball resting on the spring. The spring was far too tight, so I simply replaced with a similar, yet looser spring - problem solved!
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