See the latest quick interview by the PF with a Pentax repair technician at Photokina:-
http://www.pentaxforums.com/news/jens-petersen-on-pentax-sdm-failure.html
Whilst I am rather sceptical to what are told, even if all of them true, the following questions have quickly come to my mind:-
1. Why it takes so long, i.e., for more than five years, for Pentax to cure this problem? It is worth noting that the two DA* lenses were first launched back to 2007!
2. If it is just a design problem for all those reported failure of the SDM, aka Sudden Death / Suddenly Died Motor or Saddam as creatively named by some users before ;->), which is yet "prone to failure from the get-go due to their design", WILL Pentax Ricoh make a product recall and fix the earlier production lenses prior to 2012 which have that latent design defect, *for Free*?
3. I could never agree that the DC motor is of the same design of a conventional rotary electric motor (DC or AC), they are different! To learn more, just read my previous technical article about the working principle of the DC motor and its related patent.
Well, as an UK chartered electrical/electronic engineer myself, I don't believe in "technicians" when they are talking about designs. Note that I am not saying anything bad about technicians but their knowhows are mostly limited to hands-on things, but not about designs and more in-depth engineering principles, frankly.
Indeed, see the reply comments to that PF article, Pentax users are actually raising similar questions as mine! :-)
Last Related:-
Improved DIY SDM Repair Method!