Originally posted by Yoda boy I have read differing opinions about the use of SDM in DA* lenses. My experience with both DA* 16-50 and DA* 60-250 is that both have had their SDM motors replaced twice within 3 years. The first issues happened within the warranty period of 2 years ( I live in Canada ).
One comment that I have read about is that the capacitor needs to be charged but I had a lens meltdown in the middle of a far away trip where I had been using this lens extensively for days when it suddenly would not operate, even in manual mode. In all 4 instances, the authorized repair facility advised that the SDM had malfunctioned. In the last repairs to each, a new version of the SDM was installed. Replacement costs were around $300 each time.
What recent experiences have others had?
I now have added new D FA lenses: the 100 WR, the 70-200 and the 150-450 and find the last particularly wonderful. I am using these on a K3. Like many, I suspect, I have switched to the DFA designation in anticipation of sometime adding a K1 to the mix.
It used to be that when you mentioned SDM problems, the forum members would say something like "sorry but it was inevitable" and you would have to get it fixed. Now there are a number of deniers who say that is ancient history. I don't have any special knowledge of the issue except that like you, I used to own an SDM lens. In my case it was a 17-70. It was fixed the first time on warranty (also in Canada) and then in less than a year it was fixed on my tab. I was not impressed. I sold it on this site with full disclosure and the buyer got a great deal. I have no idea how it worked after that because I didn't use it after the second fix. The repair place had it cleaned up so nicely that it was like a new lens and that is how I preferred to sell it.
At a recent camera show I met with the Pentax rep who said that there were a lot of problems but the new SDMs are not affected (likely this is because they are from Tamron but he didn't say that). Personally I will never buy an SDM lens unless the price is so good that I just can't lose. I don't understand why Pentax would use the SDM on any lens going forward unless it is from Tamron and a completely different system. The DC motor is so superior in speed and durability that if there is need of updating a lens, it should be a natural choice. I have the 18-135 (a nice travel lens) and it has gone through minus 30C weather, ocean sprays, deserts, humidity, and whatever else I can throw at it and never missed a beat. If the glass was as good as the motor it would be their best zoom.
BTY I did noticed that with my old 17-70 it did seem sluggish if not used for a while. I had forgotten about that because It's been a while and one just doesn't have those sorts of issues with screw drive primes or DC motors.