Originally posted by ravenorxs 1) Go into some detail of what causes the SDM failure? Is it random? Being unlucky? Are there things to do to prevent it?
Seems that mostly older zoom SDM lenses are problematic. Pentax claimed that the SDM issue has been fixed, so buying a new lens shouldn't cause problems. I think lenses like the DA* 55mm also had very few problems
Originally posted by ravenorxs 2) If a lens is out of warranty will Pentax still accept the lens for repair? How much will it usually cost?
Pentax has repair centres. Warranty and such depends on local laws. You can also send it in if its out of warranty, but it will cost you. Not sure how much, depends on the problem. Sometimes the lens might have to get sent to Japan, so it might take a while.
Originally posted by ravenorxs 3) I've seen 1 or 2 posts on the internet about DIY fixes that seem to work. Lens might not be fully new (i.e some weird noises) but still regains focusing ability. How reliable is this? Is it worth it to try and fix it myself if something happaned?
There is a way to turn some SDM lenses in screw-drive, so the camera motor moves it instead of the SDM. This means the SDM's failure is bypassed. Not sure if it works with all lenses, and I think you need an older camera body to deactivate the SDM. I think someone offered to do it for people, if they send in the lens.
The DA* 50-135mm is a great lens in terms of IQ. For SDM failures, please look at threads specifically about that lens. I think the lens with most SDM failures was the 16-50mm, but even this was supposedly fixed in new batches (a year or two ago)
And probably people with hands-on experience will also post soon