Bottom should look like this. Four screws and lever is at left. The lever should be spring loaded and return to small aperture upon release. Start by loosening screws and see if the lever frees up. If not you can remove them all and check the lever. Mine was binding to the the side of the lens mount. Pay attention to the screw at photo right. If over tight it can make the opposing lever bind. Very little tolerance in spacing for that lever.
Since it can’t get to open aperture for focusing and viewfinder brightness, this can make focusing malfunction also. First thing to do is check to make sure the spring will close the aperture.
Last edited by Pentax Syntax; 08-05-2018 at 01:39 PM.