50mm/f1.7A aperture ring problem

Does anyone know what is causing this problem: I have a Pentax-A 50mm/f1.7 lens that came with a Super Program body I bought last year. Externally the lens is in excellent condition. However, turning the aperture ring is a difficult job. It sticks, and when I try to turn it, it grinds. Turning it one stop is often impossible and it feels like it is locked into the “A” setting when it is not. I paid £36 to have it repaired, which I now regret, because it improved temporarily but is now worse. Having it repaired again is not something I would consider. I will either put up with it or bin it and buy another.

Hi,
Don't bin it just yet. It isn't too difficult to get into the back of the lens. I am working on a "how to do it" for another forum member and will let you know. It is a bit time consuming though and can be a bit frustrating.

Where did you get it repaired? £36 seems a bit steep I reckon you should be able to get a prime serviced for between £20 and £25.

If you do decide to bin it, I would quite like to practice on it. I've done a few Takumars and a couple of M/Ks but not an A yet. It would be nice to have something to practice on that I wasn't worried about getting back together

Regards
Kim

It sounds like the same problem that I had with my lens of the same type. What had happened was that a metal part which should be riveted to the plastic lens body had become detached due to failure of the plastic material. The debris was fouling the aperture ring causing it to jam intermittently.
I got it professionally fixed last year (for £18, repairer now sadly retired) and all has been well since. However I no longer use it very much, not trusting it now that I know how it was made!. Also it lives on my Super A, which is my least favoured body, but I guess that is for another thread.......

I too had an (early) SMC Pentax-A 50mm f1.7, and the aperture ring became totally unusable. I did open the lens, which is not difficult at all, but the mass of springs, screws and sundry bits and pieces was a total disaster!

I now leave lens repair to the professionals. Having said that, this one lens is the only one that has ever had any sort of problem.

I opened mine too and soon realised what a mistake I had made!. Luckily I was able to put it back together in only two or three hours with the aid of a big illuminated magnifier and lots of extreme bad language.
Definitely a job for the professionals.

I really am going to have to find me a trashed lens and take it apart. This is too good a challenge to miss. I am sure Simon has had a couple of A's apart

Kim

Thanks for your replies. Unfortunately, I took the back off and tried to fix it myself (I wasn’t going to pay again) and lost a microscopic copper-coloured spring. I think it fell inside. When I tried to find it by unscrewing more parts another spring I hadn’t noticed got bent and broke off so it was time to give up. I think I found the problem, though. Screwed into the inside were two metal leaf blades that pressed up against the aperture ring and sprung out when I took the ring off. One stuck out much more than the other, so I unscrewed it and bent it back slightly. Then I lost the spring and broke another so it was all a disaster, but I have another 50mm/1.7A and a 50mm/f2.0A anyway, so I was prepared to take the risk.

Lots of people successfully take lenses apart. Not so many put them back together again. I speak from experience.

G