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03-06-2015, 05:37 AM   #1
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Screw drive AF Issues

Ive just had my K5IIs out with a screw drive auto-focus lens, the camera was showing a full battery charge, but wouldn't shift the focus on either of the two lenses I tried, interestingly my K5 wouldn't drive the focus on either lens as well....you could hear the focus motor running but nothing moved on the lenses....
So I put the lenses on my K3 and they both worked fine....
The electronic (SDM/HSM) autofocus on all bodies works fine....
Has me baffled......
Andy ideas?
I'm going to charge the batteries again and have another go.....

Andy

03-06-2015, 06:07 AM   #2
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QuoteOriginally posted by Andy_Bell Quote
Ive just had my K5IIs out with a screw drive auto-focus lens, the camera was showing a full battery charge, but wouldn't shift the focus on either of the two lenses I tried, interestingly my K5 wouldn't drive the focus on either lens as well....you could hear the focus motor running but nothing moved on the lenses....
So I put the lenses on my K3 and they both worked fine....
The electronic (SDM/HSM) autofocus on all bodies works fine....
Has me baffled......
Andy ideas?
I'm going to charge the batteries again and have another go.....

Andy
forgive me if this sounds like a stupid reply, it is not meant to be...are your k5s set to manual focus?
03-06-2015, 06:07 AM   #3
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No I checked that I only ever use AF anyway....
03-06-2015, 06:17 AM   #4
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which type of lenses?

03-06-2015, 06:28 AM   #5
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Pentax FA* 400 f5.6 & Sigma APO 100-300 f/4 EX DG
03-06-2015, 09:28 AM   #6
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AF on lens set to AF (push/pull focus ring)?


Steve
03-06-2015, 10:21 AM   #7
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No mate,
Just checked again & the lens drive is recessed, I suppose that is because most of my lenses are SDM or HSM & there is no locating hole for the drive shaft so the spring looses its tension therefore won't engage in the screw drive lens' oriface,
Looks like a trip to Pentax is in order for the two K5 bodies

Last edited by Andy_Bell; 03-06-2015 at 12:28 PM.
03-06-2015, 10:59 AM   #8
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QuoteOriginally posted by Andy_Bell Quote
Just checked again & the lens drive is recessed, I suppoes that is because most of my lenses are SDM or HSM & there is no locating hole for the drive shaft so the spring looses its tension therefore won't engage in the screw drive lens' oriface,
Hmmmm...possibly! That is fairly alarming to tell you the truth.


Steve

03-09-2015, 11:15 AM - 1 Like   #9
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Having the same fault on two cameras is a disaster. I looked at my K5, and the mechanism is the same as all the autofocus cameras including the film cameras. The spring which keeps the drive dog out is linked to the lens removal button as well as the autofocus lever/slider. Try switching to autofocus without a lens and press the lens lock button several times. this might free the drive dog. Hold the camera lens throat downwards to see if the dog drops down. The coil spring can just be seen looking at an oblique angle across the lens throat lined up with the red spot (use a small light source). I don't think the spring is stressed enough to ever break, there is some other fault. If I had this problem, I would get an old, non working autofocus film body to take the lens mount off for practice and possible spares. Also if the lens locking pin is held down by not fitting in the hole in the lens, the drive dog is also depressed.

---------- Post added 03-09-15 at 11:48 AM ----------

Iv'e just noticed another possability, if I fit my 16-50, the bayonet mount allows the lens to rotate just a tiny bit past the point where the locking pin and the hole in the lens mount line up. This depresses the locking pin and with it the af drive dog. Turning the lens back a fraction gives an audible click as the pin springs into place. Manufacturing tolerances would give very slight variations with different body/lens combinations.
03-09-2015, 12:18 PM   #10
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Pentasonic, Brilliant!
I have just checked the 2 K5 bodies and found.....
One body was just, and I mean just, off the continuous AF setting, thus holding the drive pawl back far enough so as not to engage.
The second body I think must have had a bit of grit in there as after a couple of "toggles" with the lens release button everything is fine.
You have just saved me the pain of sending the bodies needlessly for repair!
Thanks
03-09-2015, 03:26 PM   #11
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03-10-2015, 01:54 AM   #12
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Really appreciate your advice, its save me a whole lot of hassle.....
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