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02-18-2014, 12:31 AM   #1
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Join Date: Feb 2014
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Lens motor failure

How can I tell if the motor in my Pentax 300mm prime is malfunctioning? The accuracy of the auto focus system does not seem to be what it was and a couple of times recently I have had to "wake up" the lens before the auto focus system would work. I have had the lens for over a year now and it quickly became my favorite when I purchased it new. I use this lens ALOT for shooting birds and, though I also shoot with a K7 and 200D and now a K3, have had to send my K5 in for repair. The K5 had well over 105,000 shutter actuations.

Have I worn out the lens motor? When using all of my cameras and lenses, I replace my cameras' batteries as soon as the cameras indicate less than a full battery charge. This seems to keep the focusing quicker and more accurate. However, the problems I have been experiencing with the 300mm lens is not affected by replacing batteris.

If the lens should need the motor replaced, does anyone now what an estimate of the cost would be in US dollars?

02-18-2014, 01:09 AM   #2

Join Date: Jan 2012
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If I recall correctly, you sometimes get an extended warranty when buying with certain credit cards. Try looking that up. Otherwise as far as I remember, the motor costs ~$250-350 to replace. But maybe they'll charge less, since this case shouts 'defect'.
02-18-2014, 05:31 AM   #3
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I just recently had my DA* 50-135 repaired by CRIS. They replaced the SDM motor and the PCB, cleaned and adjusted the lens and return shipped it to me for $208.00. They didn't estimate it until they had the lens in thier shop. They also had to wait for parts from Pentax, but overall it took just a bit more than a month. I'm very happy with thier service. (they repaired an AF360FGZ for me previously).
02-18-2014, 05:59 AM   #4
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Sounds like the SDM is going out. Best thing to do is fill out the online form at the criscam site and send it in. They will evaluate the problem and give you a quote before performing any work. They are the authorized service center for Pentax.


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