No AF (Screw drive Lenses)

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

The only other question is do other screw drive AF lenses work OK on your K-5 models? If so, then I wouldn't let one rogue lens strain the AF motors, I'd send it to be fixed.

Hi John,

No, both of the screw drive lenses I own work fine on the K3, neither will work on either of the K5's
I'll have to borrow the wife's 55-300 DA I think that is a screw drive.....and see if that will work..

Sounds like the screw drive on the 5 is either sheared (say that because you can hear the motor spinning) meaning that the drive signal is being sent, or the drive screw stuck in the retracted position.

In either case that would be on two K5's
but i'll have a look at the drive coupling to see where its sitting..
I can compare it with the K3 which is working....

InFESTation,
You were right
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

Springs don't loose tension when they are held in a compressed state, it's more likely the shaft spline is stuck in the motor gearing.

Might be worth a try using a pair of small long nosed pliers to try and pull the shafts loose before you send them off.

Mcbrian,
I checked what you said and found the drive Pawls to be free,
it really does appear to be a weakening of the springs which push the drive mechanism forwards, they even feel weaker in comparison to the one on the K3 & 1.4x converter

Andy

That's strange that this happened, even stranger that it's happened on 2 K5 bodies, I've never heard of this malfunction before on a Pentax body.

I had a response to my question from the US forum...

Quote:
By Pentasonic49
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.


And my Response......
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

I think that I can post this in the "live & Learn" column......

At least my 2 K5's are not crocked....and I've found something to check and pay more attention to....

Andy

Pleased to hear that you have solved your problem Andy

Good news. When I saw this thread I was surprised, the AF coupler has been bullet proof in all my AF film SLRs (some over 20yrs old) and my K-5, I've never heard of similar problems (two in two cameras seemed a bit strange).

I'm very pleased too!

strange how there were two recessed drive pawls at the same time for different reasons.....I was quite worried, but it will make me look a bit harder next time too....

Andy