SDMs DO Require Preventive Maintenance!

Owing to the prolonged infamous failure of the SDMs in various Pentax AF lens models, I only bought my first SDM lens, the DA*55 F1.4, back to 2015, which is a SDM-only lens in KAF3 mount (on screw-drive). After that, I bought also another SDM only lens the DA17-70 and then later a DA*60-250 F4 hybrid-SDM/screw-driven lens (which supports also in 2022.

Here is my proven experiences with those SDM lenses and my tip to prevent them from malfunction before it would be too late, as follows:

I observe that all those lenses did require regular use of the motors. If they were left un-use for a period of time, the AF motors would first become difficult to move. In that case, first of all they were moving rather slowly and with some clicks of odd sound coming out when moving, rather not smoothly. So, more exercise with the lenses could improve thing. After they had (been) moved smoothly, then it would work flawlessly for a couple of months again. This first happened with my DA*55 of which the first SDM  problem appeared after about one year of purchase of the lens. (I bought that lens from the Biccamera in Japan brand new.)

Same thing happened with my DA*60-250 but the symptom exhibited, which was even worse. This lens was bought from the Amazon.jp brand new and was manufactured in 2021 as shown in the document in box, which was supposed to be of the rumoured "newly designed" SDM, but which IMHO has actually been non-existent. Eventually, I needed to bring out my old screw-driven AF Pentax DSLR to turn and smooth out the operation of the SDM, which is rather hilarious indeed. After that, the SDM turnsed flawlessly, i.e. quick and smooth, but only after my prevent maintenance work carried out for about ten minute, and turnings of both the SDM and the screw-drive mechanics were required.

Another observation of mine is that the SDMs would slow down in cold weather when the temperature was cold. Hence, despite the "cold-proof" specification and feature of those AW SDM lenses, those lenses equipped with SDMs are in fact vulnerable to cold weather and to work properly under low temperatures unless they do enough "exercises" from day to day.

So, if you have those evil Pentax SDM lenses, do remember to mark your calendar and carry out periodical PMs before they are to die, which will be too late to save by then. My humble advice and true experience shared.