DA* AF problem - diagnostic opinions welcome

P. J. Alling webstertwentysix at gmail.com
Mon Oct 26 23:49:15 EDT 2009

Stan Halpin wrote:
> The lens in question: DA* 300/4.
> Basic symptom - it does not autofocus on my K20.
> Expanded description - sometimes it works when first turned on, but 
> then refuses to work when woken up after a Sleep period.
> "Doesn't work" = nothing happens. It is not mis-focusing, it is rather 
> doing nothing - no response to shutter depression or AF button.
> Expanded description of "doesn't work" = not only will it not 
> autofocus, but I cannot manually focus either. Focus rings turns but 
> nothing changes.
> I tried another DA* lens (50-135) and it works flawlessly.
> OK, simple issue, right? Lens needs repair.
> So, when it isn't working,  I switch the lens, on the lens barrel, to 
> MF. I still cannot focus!
> So, I also switch the AF/MF switch on the body to MF, and then I 
> regain (manual) control.
> All pretty definitive so far, it seems that it must be a lens problem, 
> and off to Pentax with it.
> But when I use the same lens on a second K20, no problem. It works as 
> it is supposed to.
> Dirty contacts on the lens and/or first body? I cleaned those; no 
> change in the lens (mis)behavior.
> Any suggestions as to what is going on?
Sounds like gremlins, I suggest DDT.

> stan

More information about the PDML mailing list