Hi
I have just acquired some extension tubes with all 7 contacts for the KAF mount( marked as pentax on end cap ). I have used these on my GX-10 and K-70 without issue when using any of my DA kit zooms or the DA55-300mm and sigma 17-70mm. All work fine. Unfortunately I also have the so called plastic fantastic DA-50mm and this is where my problem has arisen.
The DA-50 when interfaced with a tube would have a very stiff aperture movement but seemingly only on the shorter tubes. When I looked closely this would show itself before any metal to metal contact of the aperture lever in the lens with that of the tube by slow mating of the tube and lens. It was as if the plastic body of the DA-50 was distorting the frontplate/aperture lever fixing of the tube and causing the tube lever to seize or bind. None of the metal bayonet lenses caused any issues at all.
Unfortunately when testing with the longest tube that had seemed to work ok the problem raised its head again to the extent that the aperture slider in the body of the GX-10 no longer works. The slider will move up and down against its spring by finger movement but does not actuate on shutter or DOF preview. The cog behind the slider can be seen to work rotating each time. I've looked at the k-70 and it works similarly and the cog does not seem to be attached to the slider. Does anyone know if the aperture slider is driven from that cog or by a solenoid that has possibly failed under the stalled/seized aperture. Has anyone had a similar experience with GX-10 or K-10d with a seized lens aperture mechanism, it must happen from time to time. Has anyone repaired such a fault themselves if they have had a problem.
I'm seriously annoyed with myself but more so the plastic bayonet mount which clearly is behaving in a manner that the stiffer( or better toleranced ) metal to metal mountings don't. I feel heart sorry for my GX-10 that was enjoying semi-retirement but still in use and running well turning against the DA-50( I should have just got an A-50 f1.7!)
. I noticed a thread list john pye as a new repair centre but if it's fixable myself I would look into doing so.
Hope you can chime in with any similar experiences and the resolution or not.