[Audi 5 cyl]

I can not change aperture in Av mode on the camera any more. I have tried several pentax-a lenses and I can forget about taking properly exposed pictures unless viewfinder aperture value is set to wide open (even though i can change the presented value, but only in the viewfinder). This problem indicates that aperture actuator or "A" contact are surrendering to the dark side.

I know that there have been similar issues reported before, and once even the exactly same problem here: K-x aperture problem - PentaxForums.com, presented by vicentesagerado. But there were no solutions given. I figure that with the time that passed maybe somebody can offer something else.

Because the camera works and meters normally in the M mode, that I use roughly 95% of the time, I will not send it to the repair shop for this small problem, but I would like to know the cause of it. And I do hope that the solution is simple.
Can anybody suggest a solution or give advice before I start warming up the soldering station.

[Adam]

Have you tried cleaning the lens mount?

[Audi 5 cyl]

Well yes, that is one of the first things I tried. Tonight I have taken the camera apart and did not find anything obviously wrong. I've just assembled everything hoping that I might have done something accidentally but the problem persists. I will think it through more thoroughly in the following days.

[Canada_Rockies]

It is not all that uncommon to have an aperture actuation lever bent just enough to not engage. I've never had it happen on my K10D, but I did have it happen on my film KX. I suspect I accidentally hit it while changing a lens.