15.检查前镜桶里面是否有灰，有的话清理一下。清理干净后把前镜桶拧上。好了，大功告成，光圈无法收缩的问题彻底解决。
相关链接：
Servicing a Pentacon 50/1.8
http://gabriel·mp3-tech·org/blog ... =entry080827-180800
Cleaning aperture on Pentacon MC 1.8/50mm
http://forum·mflenses·com/cleani ... -8-50mm-t33418.html
Camera.Maintenance.and.Repair.Book1，2.pdf
http://www·filestube·com/a6630c97319ae93903e9,g/Camera-Maintenance-and-Repair-Book1.html
http://www·praktica-users·com
http://www·praktica-users·com/
Disassembly Guide for Pentacon 135mm f2.8 (Preset) Lens
http://frozenfate·blogspot·com/2 ... pentacon-135mm.html
http://frozenfate·blogspot·com/2 ... tacon-135mm_10.html
How to Strip and Clean a 29mm Pentacon M42 Lens
http://www·wikihow·com/Strip-and-Clean-a-29mm-Pentacon-M42-Lens
原帖链接：（原创）现场直播：一步一步教你维修潘太康（pentacon）镜头
