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04-07-2022, 07:01 PM   #16
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QuoteOriginally posted by Kelvunlee Quote
I have another question. How do I properly diagnose a broken DC motor? Is there a way for me to use a multi meter to check the electrical contacts? I don't think there was a point when I thought the motor was "failing", it just stopped working all of a sudden.

Is there a way to "warm up" the DC motor like they do with the SDM motors?

Thanks
SDM motors (the older ones, anyway) are piezo-electric, and rely on friction to operate. I presume that “warming-up” means manually operating the focus ring to help unstick them. I used to partially disassemble my DA*16-50 to unstick the drive with a screwdriver, until I got fed up and changed it to in-body drive (you don’t have that option with the DA20-40).There’s some evident misunderstanding about SDM and similar drives, even here.

04-07-2022, 09:53 PM   #17
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QuoteOriginally posted by Kelvunlee Quote
I have another question. How do I properly diagnose a broken DC motor? Is there a way for me to use a multi meter to check the electrical contacts? I don't think there was a point when I thought the motor was "failing", it just stopped working all of a sudden.

Is there a way to "warm up" the DC motor like they do with the SDM motors?
You'd need data of the DC-motor.
The "warming up*" (using a hairdryer or similar) only worked with some of the original SDM lenses made by Pentax.
The newer lenses which have that name as well like the DA18-270 SDM are made by Tamron and use their PZD motor (and


Differences are explained here:
The 5 Lens Autofocus Drive Types Explained - Articles and Tips | PentaxForums.com

*warming up can be misleading because some use that word just for

a)"trying to use the lens several times until it works again, this method does sometimes work
b) opening the lens and moving the motor with a screwdriver which indeed won't do wonders at all
c) method b) but applying some thin oil which in some cases works
04-07-2022, 10:24 PM   #18
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QuoteOriginally posted by photogem Quote
You'd need data of the DC-motor.
How do I get data from the DC motor?

Thanks
04-07-2022, 11:41 PM   #19
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QuoteOriginally posted by Kelvunlee Quote
How do I get data from the DC motor?
by measuring a healthy one, Ricoh must likely won't give it to you.

Could well be that the DA (-L)18-50DC lenses have the same motor
Size of the lens would match.

So buying of of those to check could be a solution.

04-08-2022, 06:48 AM   #20
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QuoteOriginally posted by Kelvunlee Quote
Hello everyone, long time lurker on Pentax forums.

Today, when I grabbed my 20-40mm Limited after not having used in in a few weeks, I found out that the autofocus motor has stopped working. I tried it on 3 bodies, (K10D, K3, K1), but nothing. I bought the Lens from KEH 196 days ago, 16 days past warranty period. I called KEH and they basically told me I was out of luck and repairs from them would cost $300 USD (nearly the price of the lens).

Has any one else had the same issue with the DC motor AF systems? I have barely used the lens, and physically, it looks like new...

I have tried cleaning all the contacts, but no luck.

The lens acts like a MF lens, aperture still works.

Anyone on the forums have a solution?

Thanks
Sorry to hear about your lens. If you're going to look for another lens, right now B&H has the 20-40 $300 off at $496. A bit more than the cost of the repair, but maybe worth it.
04-08-2022, 11:01 AM   #21
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Be wary of sending Pentax gear to KEH for repair. It has been reported in the recent past that Ricoh will no longer sell them parts. If the repair requires parts most likely KEH will not be able to fix the gear. And you'll be out shipping costs. It's also been reported on rare occasion that the gear will come back in worse shape then when sent in.
04-08-2022, 05:02 PM   #22
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QuoteOriginally posted by photogem Quote
You'd need data of the DC-motor.
The "warming up*" (using a hairdryer or similar) only worked with some of the original SDM lenses made by Pentax.
The newer lenses which have that name as well like the DA18-270 SDM are made by Tamron and use their PZD motor (and


Differences are explained here:
The 5 Lens Autofocus Drive Types Explained - Articles and Tips | PentaxForums.com

*warming up can be misleading because some use that word just for

a)"trying to use the lens several times until it works again, this method does sometimes work
b) opening the lens and moving the motor with a screwdriver which indeed won't do wonders at all
c) method b) but applying some thin oil which in some cases works
I don’t know what you mean by that, but it always worked for me, although it was a pain having to do it, and it didn’t last for long if you weren’t using the lens continually.

04-08-2022, 08:24 PM   #23
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QuoteOriginally posted by RobA_Oz Quote
QuoteOriginally posted by photogem Quote
b) opening the lens and moving the motor with a screwdriver which indeed won't do wonders at all
I don’t know what you mean by that, but it always worked for me, although it was a pain having to do it, and it didn’t last for long if you weren’t using the lens continually.
Then imo this is only a temporary solution, i.e. not a wonder.
A wonder for me would be if the problem is solved. If you apply some resin-free thin oil which won't get harder over the time and which won't attack metals then it works better and longer. But again just a temporary solution. The motor itself is the problem.
But this thread is about the DC-Motor, no idea if those methods apply as well.

Last edited by photogem; 05-20-2022 at 10:08 PM.
05-20-2022, 10:01 PM - 2 Likes   #24
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I wanted to give everyone an update. I just got the lens back from Henry's Camera, which helped me ship it to Ricoh Pentax in Ontario. They replaced the focus assembly which cost $287 Cad tax included.
05-20-2022, 10:10 PM   #25
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The repaircosts are much cheaper than a used DA20-40ltd and with a new focus assembly better than a used one (as you know).
Enjoy a great lens!
05-20-2022, 10:51 PM   #26
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QuoteOriginally posted by Kelvunlee Quote
I wanted to give everyone an update. I just got the lens back from Henry's Camera, which helped me ship it to Ricoh Pentax in Ontario. They replaced the focus assembly which cost $287 Cad tax included.
Excellent news. At that price, the repair was definitely worth it. Enjoy!
05-21-2022, 02:34 AM - 1 Like   #27
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The main reason why I prefer repearing rather than getting a new lens is that you already "know" your copy, tested it billion times. You have to go through this all over again with new one.
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