Dead AF on DFA* 1.4

Started Jan 4, 2019 | Discussions
Adam007 Contributing Member • Posts: 614
Dead AF on DFA* 1.4
1

Hi, All:

While traveling with the normally stellar 50 1.4 and my K-1, the autofocus has suddenly failed.  When I mount the lens, I get the manual SR focal length input screen, which quickly disappears (this is new).  Then, the display screen reads “MF” regardless of the AF/MF switch positions on the lens and body.  I’ve tried my other lenses; AF Is fine.  Wiped off the 50’s contacts; no dice.  This seems extremely odd for a Les that’s just a couple months old.  Any thoughts?  Hoping to use it for portrait sessions on the trip, and a little bummed.

Thanks for any insight!

Adam

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phoenix15
phoenix15 Regular Member • Posts: 358
Re: Dead AF on DFA* 1.4

Adam007 wrote:

Hi, All:

While traveling with the normally stellar 50 1.4 and my K-1, the autofocus has suddenly failed. When I mount the lens, I get the manual SR focal length input screen, which quickly disappears (this is new). Then, the display screen reads “MF” regardless of the AF/MF switch positions on the lens and body. I’ve tried my other lenses; AF Is fine. Wiped off the 50’s contacts; no dice. This seems extremely odd for a Les that’s just a couple months old. Any thoughts? Hoping to use it for portrait sessions on the trip, and a little bummed.

Thanks for any insight!

Adam

Oh no, this is the first time ever I heard such problem. Do you still have warranty with you right ? You probably can contact Pentax distributor for repair or replacement. 
Sorry to hear that.

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-Canon and Pentax-

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Alex Sarbu Forum Pro • Posts: 11,647
Re: Dead AF on DFA* 1.4

Adam007 wrote:

Hi, All:

While traveling with the normally stellar 50 1.4 and my K-1, the autofocus has suddenly failed. When I mount the lens, I get the manual SR focal length input screen, which quickly disappears (this is new). Then, the display screen reads “MF” regardless of the AF/MF switch positions on the lens and body. I’ve tried my other lenses; AF Is fine. Wiped off the 50’s contacts; no dice. This seems extremely odd for a Les that’s just a couple months old. Any thoughts? Hoping to use it for portrait sessions on the trip, and a little bummed.

I'm sorry to hear about that.

This looks like a communication, or electronic issue. If you can, try the lens on another camera just to confirm.

But only a trip to the service can fix it.

Alex

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zakaria
zakaria Veteran Member • Posts: 5,195
Re: Dead AF on DFA* 1.4
4

Sorry for that.

It seems The curse of failure to haunt this lenses like the formers.

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pentaxian .

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Alex Sarbu Forum Pro • Posts: 11,647
Re: Dead AF on DFA* 1.4
5

zakaria wrote:

Sorry for that.

It seems The curse of failure to haunt this lenses like the formers.

Let's not exaggerate - no product has a zero failure rate, at any cost.

Alex

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karlk79 Junior Member • Posts: 30
Re: Dead AF on DFA* 1.4

Try taking the battery out of the camera and turning it on and off a handful of times. Leave the battery out and let it sit for a few hours.

You could take note of your settings and do a reset of your camera.

This would ensure its most likely the lens and not the camera.

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Labe
MOD Labe Forum Pro • Posts: 11,388
Re: Dead AF on DFA* 1.4

Sounds like SDM failure. Both my 16-50 and 50-135 did the same.

Just send it for repair when you get back.

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Alex Sarbu Forum Pro • Posts: 11,647
Re: Dead AF on DFA* 1.4
7

Labe wrote:

Sounds like SDM failure. Both my 16-50 and 50-135 did the same.

I disagree - the SDM failure is characterized by the lens not being able to focus, but otherwise working fine. The AF motor itself is vastly different from these micromotors - it's a ring type motor.

The SR select focal length screen, the lens appearing as MF points toward lens-camera communication issues.

Just send it for repair when you get back.

Alex

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Roland Karlsson Forum Pro • Posts: 28,994
Re: Dead AF on DFA* 1.4

Sorry to hear. It is always very annoying when things fail when you are out travelling with them.

Too much that can go wrong with modern complicated things. It is a wonder that they are working at all.

It is a bliss to use old manual focus lenses without any electronics at all. Until you get oil on your aperture blades, at least. But then you can go even further back to the days of manual aperture preset.

Anyhow - send it in - it will be fixed. And the risk for it happening again is almost zero.

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MightyMike Forum Pro • Posts: 40,595
Re: Dead AF on DFA* 1.4
2

Sounds like a communication problem, you might consider checking of the screws on the mount plate are tight, if that does nothing for you it will have to be serviced

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OP Adam007 Contributing Member • Posts: 614
Re: Dead AF on DFA* 1.4

Thanks, Everyone.

I’ve reached out to the seller first, but if I have to send this in under warranty, I’m guessing it goes to Precision, right? For better and for worse, this is my first warranty issue with Pentax.

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James O'Neill Veteran Member • Posts: 5,130
Re: Dead AF on DFA* 1.4
2

Alex Sarbu wrote:

zakaria wrote:

Sorry for that.

It seems The curse of failure to haunt this lenses like the formers.

Let's not exaggerate - no product has a zero failure rate, at any cost.

Alex

And a huge proportion of failures seem to result in a post here.

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James O'Neill Veteran Member • Posts: 5,130
Re: Dead AF on DFA* 1.4

Adam007 wrote:

Hi, All:

While traveling with the normally stellar 50 1.4 and my K-1, the autofocus has suddenly failed. When I mount the lens, I get the manual SR focal length input screen, which quickly disappears (this is new). Then, the display screen reads “MF” regardless of the AF/MF switch positions on the lens and body. I’ve tried my other lenses; AF Is fine. Wiped off the 50’s contacts; no dice. This seems extremely odd for a Les that’s just a couple months old. Any thoughts? Hoping to use it for portrait sessions on the trip, and a little bummed.

Thanks for any insight!

Adam

The bit I've underlined says there is no electronic communication between lens and body. Obvious thing is to make sure all the contacts are clean.  If you've done that, it's just a question of is it the lens or body and send one in for repair.

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OP Adam007 Contributing Member • Posts: 614
Re: Dead AF on DFA* 1.4

Thanks.  I quickly wiped the body contacts, but will clean them more thoroughly when I get a chance and see if that helps.  Again, the body is working with my other lenses, but it’s worth a shot.  Tried removing the battery and waiting. No dice.  Don’t want to reset, as it’s a pain to re-adjust everything, but maybe I’ll try that on the plane!

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Alex Sarbu Forum Pro • Posts: 11,647
Re: Dead AF on DFA* 1.4

MightyMike wrote:

Sounds like a communication problem, you might consider checking of the screws on the mount plate are tight, if that does nothing for you it will have to be serviced

Yeah, lens and camera side.

But don't you need a JIS screwdriver for that? AFAIK using Philips ones can damage the screws.

Alex

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(unknown member) Veteran Member • Posts: 6,680
Re: Dead AF on DFA* 1.4
1

Labe wrote:

Sounds like SDM failure. Both my 16-50 and 50-135 did the same.

Just send it for repair when you get back.

The AF system in this lens is not the same as the failure prone SDM.

Alex Sarbu Forum Pro • Posts: 11,647
Re: Dead AF on DFA* 1.4
1

Wheatfield7 wrote:

Labe wrote:

Sounds like SDM failure. Both my 16-50 and 50-135 did the same.

Just send it for repair when you get back.

The AF system in this lens is not the same as the failure prone SDM.

Indeed. The AF system is definitely not the same - see the image below - and the symptoms are not those of a SDM failure (but of lens-body communication failure). The AF motor is almost certainly fine.

New ring-type SDM vs. the old SDM micromotor

Alex

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DougOB
DougOB Senior Member • Posts: 1,783
Re: Dead AF on DFA* 1.4
1

Adam007 wrote:

Hi, All:

While traveling with the normally stellar 50 1.4 and my K-1, the autofocus has suddenly failed. When I mount the lens, I get the manual SR focal length input screen, which quickly disappears (this is new). Then, the display screen reads “MF” regardless of the AF/MF switch positions on the lens and body. I’ve tried my other lenses; AF Is fine. Wiped off the 50’s contacts; no dice. This seems extremely odd for a Les that’s just a couple months old. Any thoughts? Hoping to use it for portrait sessions on the trip, and a little bummed.

Thanks for any insight!

Adam

When mounted does it act like a K/M lens (M mode only) or an A lenses (M, Av, Tv, P modes)?

Doug

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OP Adam007 Contributing Member • Posts: 614
Re: Dead AF on DFA* 1.4. FIXED
9

So, I tried cleaning the contacts again.  I noticed one of the two gold contacts on the lens was bent in the wrong direction (outward).  I pressed it back into place, and voila!  It looks like this:

Look closely at the contact on the left (just above the screw).

Two things:  I assume this got bent while changing the lens, but I’ve changed lenses a zillion times, and this seems a bit unlucky. Also, I’m a little surprised there is no redundancy here; this contact is sill sticking out a bit from the lens body, and if it gets jostled again, it might not be such a quick fix.

Thanks to everyone, particularly those who insisted this sounded like a lens-body communication problem.  And if anyone has suggestions about that stray contact (I think it’s best to leave well enough alone, but I don’t know), I’d love to hear from you.

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DougOB
DougOB Senior Member • Posts: 1,783
nt - Thumbs up

No text.

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