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03-10-2017, 08:17 AM   #1
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DA*300 focus locking

Apologies for cross posting, I just really need help here...

DA*300 focus locked up on me yesterday.

Using it on my K-3ii paired with the HD1.4xTC.


The SDM has been audible lately (faint squealing noise), but has never done this:
Focus completely locked up at infinity. Turned the camera off and back on, held the AF button while turning the focus ring and it finally snapped back.
This sounds like SDM failure at first, but when it was locked I couldn't even manually focus the lens. The focus ring would turn, but the lens was stuck at infinity.

When the AF motor did engage, it started as screwdrive. Then after a few seconds of racking, it switched back to SDM.
I got home and cleaned the contacts on the TC as well as the lens.
I took off the TC and the lens worked fine again; put the TC back on and everything is fine.

I shot for another hour at home and had no issues.


Why did the lens lock focus? Is this beyond an SDM issue or is this standard with SDM failure?
I couldn't manually focus when it locked up and it was stick at infinity.

Also, why would the screwdrive engage? I thought that had to be programmed into the lens?


Anyone with advice or experience similar, please assist!


I considered replacing with the DFA 150-450, but now I'm reading about zoom locking issues with that lens...


I just want a wildlife lens that's silent, sharp and weather sealed!

I hate having this feeling that my gear will fail at any moment... Especially being an enthusiast. I can't justify replacing gear all the time!

03-10-2017, 08:39 AM   #2
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The switch between the screw-drive to Sdm was a problem with my Da 50-135mm, in my experience that's a sign of sdm failure. On the da 50-135mm the SDM needed "warming-up" before use, turning the manual focus ring back (quick-shift) and forth while pressing the AF button till the af kicked in.
03-10-2017, 10:01 AM   #3
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QuoteOriginally posted by Stavri Quote
The switch between the screw-drive to Sdm was a problem with my Da 50-135mm, in my experience that's a sign of sdm failure. On the da 50-135mm the SDM needed "warming-up" before use, turning the manual focus ring back (quick-shift) and forth while pressing the AF button till the af kicked in.
But, when you turn the manual focus ring back and forth, it would actually engage the focus mechanism manually?
I was doing that but the focus meter window was locked at infinity still until the screwdrive kicked on...

So, even if I turned off AF altogether and decided to just use manual focus, the lens would be stuck.


This doesn't sound like normal SDM failure behavior.
Unless somehow the "confused" af motor pushed the focus mechanism past infinity causing it to get stuck? Is that even possible?

---------- Post added 03-10-17 at 12:06 PM ----------

QuoteOriginally posted by Michaelina2 Quote
Thanks for the tip on how to solve the problem... Must feel good to know you saved yourself and (perhaps) others $2500.

Enjoy the season & cheers... M
Unfortunately I think this goes beyond cleaning the contacts..
I'll cross my fingers though and hope for the best!
Though, the physical locking of my focus tells me otherwise.
03-10-2017, 10:21 AM   #4
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QuoteOriginally posted by UserAccessDenied Quote
Apologies for cross posting, I just really need help here...

Using it on my K-3ii paired with the HD1.4xTC.


The SDM has been audible lately (faint squealing noise), but has never done this:

The focus lock it's peculiar to say the least, I know some zooms tend to have this issue, it's the first time i read/hear about it on a prime. However the squealing/ grinding noise i'm familiar with, both early signs which led to sdm failure on my Da* 50-135 and Da* 16-50.

03-10-2017, 11:47 AM   #5
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Just found this thread on DP:
SDM fiction and fact: Pentax SLR Talk Forum: Digital Photography Review

This pertains to the 50-135, but sounds like it matches what's going on with my DA*300...

"both MF and AF(motor) were on the same gear chain without any clutch mechanism so when MF is used the motor free wheels.

The screw drive is decoupled with a clutch mechanism and does not rotate for inmotor of Manual focusing."

...
"It seems to me that most symptoms reported can be attributed to this adjustment screw.

1 No Focus lock = motor can overcome the friction for large movements but unable to micro adjust so no lock
2 Focus Jammed = screw has drifted right and locked up.
3 SDM failure = lock/stiffness has caused motor/electronics to fail."
03-10-2017, 12:21 PM   #6
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It looks to the the quick shift gear has some problem.
Or do you have a film AF camera, or camera earlier than K10D? Does something happen when lens is on screw drive AF? If same occurs, very like the quick shift gear gets stuck.
03-10-2017, 12:58 PM   #7
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QuoteOriginally posted by grahame Quote
It looks to the the quick shift gear has some problem.
Or do you have a film AF camera, or camera earlier than K10D? Does something happen when lens is on screw drive AF? If same occurs, very like the quick shift gear gets stuck.
Unfortunately I do not own another camera... What's the preferred camera body for testing?
*ist D ?

03-10-2017, 04:19 PM   #8
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Any old camera does not support SDM is fine. even old AF film cameras. check craigslist and you might find someone selling these for $10.
06-09-2017, 07:33 AM   #9
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QuoteOriginally posted by UserAccessDenied Quote
Apologies for cross posting, I just really need help here...

DA*300 focus locked up on me yesterday.

Using it on my K-3ii paired with the HD1.4xTC.


The SDM has been audible lately (faint squealing noise), but has never done this:
Focus completely locked up at infinity. Turned the camera off and back on, held the AF button while turning the focus ring and it finally snapped back.
This sounds like SDM failure at first, but when it was locked I couldn't even manually focus the lens. The focus ring would turn, but the lens was stuck at infinity.

When the AF motor did engage, it started as screwdrive. Then after a few seconds of racking, it switched back to SDM.
I got home and cleaned the contacts on the TC as well as the lens.
I took off the TC and the lens worked fine again; put the TC back on and everything is fine.

I shot for another hour at home and had no issues.


Why did the lens lock focus? Is this beyond an SDM issue or is this standard with SDM failure?
I couldn't manually focus when it locked up and it was stick at infinity.

Also, why would the screwdrive engage? I thought that had to be programmed into the lens?


Anyone with advice or experience similar, please assist!


I considered replacing with the DFA 150-450, but now I'm reading about zoom locking issues with that lens...


I just want a wildlife lens that's silent, sharp and weather sealed!

I hate having this feeling that my gear will fail at any moment... Especially being an enthusiast. I can't justify replacing gear all the time!
Hi
I have same stuffs and same behaviour. I had to send back 300 mm twice a year for service. With the K3 II and the 300mm (SMC DA* 300 F4 ED IF SDM)time to time, I lost indication on the screen, it could be the root cause, this issue do not rise up with my K3 and K30. I do suspect something wrong with the K3 II and this ( nice ) lens.

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