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04-06-2022, 06:39 PM   #1
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Pentax 20-40mm LTD Focus Motor failure

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

04-06-2022, 07:28 PM   #2
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Rare but not unheard of are DC motor failures. A few 16-85's have been reported with failures for example. I'm sad to say you are out of luck I think.
04-06-2022, 09:04 PM   #3
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Is there any where on the forum where I can find a guide to dismantling?

Thanks
04-06-2022, 09:24 PM   #4
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Sorry to hear of this As already suggested, DC motor failure is rare - but it can and does happen occasionally.

At $300, it might be worth getting your lens repaired - especially considering its overall condition. The retail price of a new one is a shade under USD $800, and even with the current discount B&H is selling it for just under $500. It's not a cheap lens...


Last edited by BigMackCam; 04-07-2022 at 12:30 AM.
04-06-2022, 10:51 PM   #5
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I don't know of any tutorial/Guide for disassembling the DA20-40ltd.
It is really bad luck, half a year warranty is too bad, really.

You can't buy the motor in USA or Canada, they don't sell it to private people.
I would get it repaired.
04-07-2022, 12:05 AM   #6
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I had a similar problem with a used DFA 100 macro, a year or so back, although in that case it was the aperture module that failed and was unrepairable. I’d bought the lens at a good price, and it worked well for a year. The local shop couldn’t repair it because of the lens alignment needed on reassembly, so it went to the national distributor for repair. All up, it cost me almost the price of a new lens for purchase and subsequent repair. Like yours, mine was in excellent (apparent) condition, so I decided not to scrap it for parts, and coughed up the repair price. I’m still happy with it. I suspect you will be, too, once the cost fades in your mind and the lens yields its best images.

PS: welcome to Pentax Forums.
04-07-2022, 12:26 AM   #7
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QuoteOriginally posted by RobA_Oz Quote
I had a similar problem with a used DFA 100 macro, a year or so back, although in that case it was the aperture module that failed and was unrepairable. I’d bought the lens at a good price, and it worked well for a year. The local shop couldn’t repair it because of the lens alignment needed on reassembly, so it went to the national distributor for repair. All up, it cost me almost the price of a new lens for purchase and subsequent repair.
Having serviced a number of relatively simple, vintage manual-focus lenses over the years, and a couple of early AF zooms, I'm not surprised at the seemingly-high cost of modern lens repair. Even those older, simpler lenses require considerable time and effort just to service them, never mind any repair work - so I can only imagine the increased complexity and difficulty with modern devices. Once you take into account the time, effort and cost involved in diagnosis, disassembly, component replacement, re-assembly, testing, investment in alignment and testing equipment, and guaranteeing the work against future failure, a few hundred bucks really isn't unreasonable.


Last edited by BigMackCam; 04-07-2022 at 12:33 AM.
04-07-2022, 01:39 AM   #8
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QuoteOriginally posted by RobA_Oz Quote
I had a similar problem with a used DFA 100 macro, a year or so back, although in that case it was the aperture module that failed and was unrepairable.
And the D-FA100macro has no internal motor, is just screwdrive.

So what Mike wrote:

QuoteOriginally posted by BigMackCam Quote
Having serviced a number of relatively simple, vintage manual-focus lenses over the years, and a couple of early AF zooms, I'm not surprised at the seemingly-high cost of modern lens repair. Even those older, simpler lenses require considerable time and effort just to service them, never mind any repair work - so I can only imagine the increased complexity and difficulty with modern devices. Once you take into account the time, effort and cost involved in diagnosis, disassembly, component replacement, re-assembly, testing, investment in alignment and testing equipment, and guaranteeing the work against future failure, a few hundred bucks really isn't unreasonable.
This is absolutly really true.

I once disassembled a Sigma AF HSM Zoom but don't want to do it anymore, too complex and difficult to almost impossible now to get the motor.

It is different with some Pentax SDM lenses, the motor is easy to exchange (but difficult to get the motor!), I never disassembled a Pentax DC lens, so no idea how much time/effort would be involved.
Alignement is crucial, they have the test equipment which I lack, so repair of AF lenses is history, good manual lenses I sent to Görlitz.

Very good manual and A-lenses I sent now to Olbrich, Görlitz. Andrea Schönfelder does such an excellent job for a very reasonable price that I hardly clean/repair lenses myself anymore.


She doesn't do AF lenses, even if screwdrive. I never asked her for the reason but as I had repaired a few myself I can understand it well.
She anyway has a long waitinglist, is wellknown internationally now.
04-07-2022, 05:02 AM   #9
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Thank you everyone.
I bought the lens for around $370 USD + $50 USD shipping to Canada. The repair cost is $320 + Shipping there and back. Financially, I think I'd be better off buying another at a similar price once one goes on sale used. It just sucks that my brand new (to me) lens stopped working after only half a year. I've probably only shot a few hundred photos with it...

I guess I could try selling it at a discounted rate...
04-07-2022, 05:48 AM   #10
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QuoteOriginally posted by Kelvunlee Quote
I bought the lens for around $370 USD + $50 USD shipping to Canada. The repair cost is $320 + Shipping there and back. Financially, I think I'd be better off buying another at a similar price once one goes on sale used.
That was a good price - I presume it was used?

One consideration - if you have it repaired, a recurrence of the same fault - or other problem resulting from the work carried out - would likely be covered by some form of warranty (repairs are usually guaranteed for a period of time). A lens that's been repaired and fully checked by an authorised service centre is almost as good as a new lens, IMHO - internally, at least. If you buy another used lens, there's always the remote possibility you'll eventually experience a problem with that one too, with no warranty to fall back on. Of course, if you buy a new one during a discount event (again, B&H has it for just under USD $500 presently), you get a full warranty.

Having said all that, issues with the DA20-40 seem to be very rare indeed.

Whatever you decide, good luck!

Last edited by BigMackCam; 04-07-2022 at 01:50 PM.
04-07-2022, 11:49 AM   #11
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Sun Camera repairs Pentax products in Canada. Sun Camera Service Ltd. - Home
You'd probably be better off dealing with them for repairs vs cross border shipping, taxes and the higher US dollar.

Also, The Camera Store in Calgary sells this lens for CAD $599 new with 2yrs warranty, which, with shipping, is pretty close to what you paid for yours.
https://thecamerastore.com/collections/slr-lenses/products/pentax-hd-da-20-4...-limited-dc-wr

Last edited by johnyates; 04-07-2022 at 12:00 PM.
04-07-2022, 01:44 PM   #12
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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
That really is tough luck. As others have said, the DC motors used in Pentax lenses rarely fail, especially this lens. The DA 20-40mm Ltd is an exceptionally well-built lens. But anything made by us humans can be flawed. It seems johnyates offers the best advice for your choices here. If you should get a new one, you could either keep the old one for parts in case of accidental damage, or try selling it as is. This lens is designed for exceptionally fine manual-focus handling, which is a plus for those who often prefer to use MF.
04-07-2022, 01:49 PM   #13
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QuoteOriginally posted by johnyates Quote
Also, The Camera Store in Calgary sells this lens for CAD $599 new with 2yrs warranty, which, with shipping, is pretty close to what you paid for yours.
https://thecamerastore.com/collections/slr-lenses/products/pentax-hd-da-20-4...-limited-dc-wr
This is why I'm Hesitant of getting a repair, it may almost cost the same as getting a new one. The local repair shops here in Vancouver don't have a good reputation.

Thank you everyone for you input!!
04-07-2022, 02:03 PM   #14
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QuoteOriginally posted by Kelvunlee Quote
it may almost cost the same as getting a new one.
Or, it may not. Call them and see.
04-07-2022, 05:41 PM   #15
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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
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