As a new year gift from me, I write this article! ;-)
A very smart SDM user at the Chinese Xitek forum has discovered a DIY method for revive a "dead" SDM which is certified death by Pentax, see his post with clear illustration and concise instructions:-
http://forum.xitek.com/showthread.php?threadid=821417
(in Chinese, Google-translated English Page Here)
(Above: The mount side of the DA*50-135/2.8 SDM is dismantled and showing the SDM micro-motor and the female AF screw-driver.)
Update: I hoped the Google translation did work but it seems not to be. So, I human translate and summarise the repair steps as below:-
1. Dismantle the back side of the lens including the mount, showing the SDM, SDM PCB, with a flat/flexible cable connecting between the two (indicated with the Large Circle in the above diagram);
2. You can also see the traditional screw driver (female side) for DA* lenses, i.e., the small circle;
3. At the centre of the SDM micro-motor, there is a cross-type screw, which is actually directly linked to the rotator of the motor. The problem and evil is just here, as it could be, that is, the motor got stuck. Just use the screw-driver to turn the rotator to and fro and then back for several cycles. In fact, when the rotator screw is turned, one can see that the focusing scale of the lens is also being moved/driven;
4. After enough massage to the rotator/SDM motor, carefully reassemble the lens and try out if the lens is revived! Yes, you did it! :-D
Shortly, this repair method has yet been verified by another SDM user at the Xitek. His officially "certified death" SDM DA* lens, "which was needed to be sent overseas for repair", is also revived! What a miracle! Unbelievable?!
http://forum.xitek.com/showthread.php?threadid=822390
(in Chinese, Google-translated English Page Here)
The above author also shares how to carefully dismantle the lens mount and put back all the components after the repair. Btw, I guess I am more experienced in dismantling those K-mount lenses than average Pentaxians. My advice is to do thing with these key principles/tips in mind:-
1. Do the job on a big table with a large white paper (say, an A3 one);
2. Do the job under a bright white light source, preferably also with a bright torch for illumination on particular part and inside the lens for more detailed inspection when needed;
3. Use a high quality cross-type screwdriver with matching size, with magnetised tip;
4. Pick away only components and parts that are necessary to be removed for the repair job. Special care must be taken for not accidentally touching any of them which might cause dropping and loss (as they are NOT fixed now!). This would also minimise the tasks of resuming the lens, thus minimise the risk indeed (as long as great care is taken for not moving the loose parts, in particular those electronic contact pins with springs of the KAF mount);
5. Be prepared to have a small flat tip forceps, which is useful to pick up and put back small components when they are removed out of place or mis-aligned. As for the electronic contact, a toothpick is also useful for proper alignment before the metal mount could be put back and re-installed;
6. For dismantling a particular lens for the first time, do remember for not to be too hurry. Inspect carefully for which component/part should be dismantled first and which is needed and is not. Use another digital camera to take shots to record the status in each step before dismantling anything and hence recording also the steps and order, which is useful for reversing the steps after finishing the repair, for the re-instatement of the lens (by re-installing all the dismantled components step-by-step, in a reverse order).
Nevertheless, by following the above thread, there is yet another SDM user reported that his DA*16-50 lens had the SDM stuck so stubbornly that the method doesn't work at all! :-o :-(
Anyway, the above "big discovery" is surely a gospel for all Pentax SDM users and especially to those who are panic with their death SDM lenses which may just have the SDM micro-motor stuck but the most local Pentax repair agents just know to "send back to overseas" for service, for which the quoted costs are usually very dear, as this has been repeatedly reported and told, the above second Xitek post included.
As a Final Disclaimer and Reminder: IF you are to do any surgery or repair job yourself, DO IT AT YOUR OWN RISK! And you are the one who bears the sole responsibility and any consequences thereafter for what you have done!!
All Related:-
http://www.google.com/search?q=sdm+issues&btnG=Find&domains=ricehigh.blogspot.com&sitesearch=ricehigh.blogspot.com
Read Also:-
(Hardware) Exposure Adjustment of Pentax Lenses
Compatibility List of Pentax Full Frame AF Lenses on Canon 5D Body