SLR not working

The lens you are talking about has either:
1)a faulty diaphragm mechanism ( lens stays closed at f 22 or f 16 when you attach it to the camera instead of opening fully as it should ) . or
2) the lens is fine but the diaphragm coupling mechanism inside mirror box ( on the left hand side if viewed from the front ) is not engaging the lens properly so that your lens stays fully closed ( F 22 /16 ) : because diaphragm stays fully closed image in viewfinder appears v. dark.
Solution ? have a camera technician take a look but my guess is that the diaphragm needs cleaning and it should not cost you more than $ 80 bucks.

Hi, this may help

http://www.pentaxforums.com/forums/pentax-dslr-discussion/24160-help-reset-diaphragm-release.html

If you could send me - or post those pictures you have of the mechanism that would be great.

I also have the link for the service manual for the samsung version of the k10 - it shows how to open it up. Let me know if you want that?