conurus

ManWearPants · Joined: 18 Feb 2010 Posts: 51

I am wondering what other types of motors are the N85 and N400 using since it is not being mentioned they are using ultrasonic motors.

Extract:
"Vario-Sonnar 17-35, Vario-Sonnar 24-85, Vario-Sonnar 70-300 and Planar 50/1.4 are equipped with ultrasonic motors "

conurus · Posted: Thu Jan 12, 2012 3:11 am Post subject:

I have never taken apart an N85 or an N400 completely to see what is inside, but judging from the sound of its autofocus action, I guess that they employ ordinary DC brushed motors.

ManWearPants · Joined: 18 Feb 2010 Posts: 51

conurus · Posted: Sat Jan 14, 2012 6:34 pm Post subject:

It may still be very hard to find the exact replacement for the DC motors. Also, no one outside of Contax knows how to replace them yet, as far as I know of.

Judging from the empirical data we have collected over the years

http://conurus.com/forum/reliability-rating-of-n-series-lenses-t667.html

The ultrasonic group (17-35, 24-85, 50/1.4 and 70-300) has a consistently higher failure rate than the DC brushed motor group (85/1.4, 100/2.8, 70-200, 400/4).

The exception is the DC brushed motor 28-80, which arguably has a design issue with a weak part which is prone to break. No worries, we know exactly how to repair that and we have parts. (But we won't be able to perform repairs for the other 8 Contax N lenses after 2015 because we lack the necessary parts.)

These lenses are around 10 years in age, so the failure rates aren't all that bad, in an absolute sense (except for the 28-80 IMO which gets into the 2-digit territory).

AF failures account for the majority of the failures we have seen but there are occasionally other issues. For the purposes of evaluating long term reliability I think we can focus on AF.