DA* 50-135mm - problems with autofocus

Hi All,
I have a second-hand DA* 50-135mm that has developed a problem - most occasions it just cannot find focus, it just hunts in and out.
I've heard this is not an uncommon issue with this lens.
Anyone had similar experience ?

A couple of years ago I sent an MZ-S body to Pentax for repair and the service was very poor, so I'm wary of where I might send this lens for attention.
Anyone able to comment on reliable repair centres for Pentax lenses in the UK ?

Best Regards
D_C_D

Never heard that's a common problem with this lens, it does had some SDM problems where the SDM did not work.
If it catch focus or not has also to do with your camera and what you're focusing on.
The AF sensor needs to have contrast to judge if it's in focus or not.

Without having the camera and testing it, it's hard to say if it's normall or not for the lens (camera).

Hi Stefan, Thanks for your comments. I have a DA* 16-50mm that works fine on the same camera (K10D). So I think this 50-135 might have a problem with the SDM.
It's a shame, the lens is not very old.

Kind regards
Alan
(deck_chair_dave)

From what I have heard most SDM problems are due because of misalignment, Pentax blames the rough shipping handling.

You could send it to Pentax, they replace the SDM for 70 Pounds I believe, someone here had a price list.

I thought SDM issues involved total failure of the motor, not hunting?

D_C_D, can you reveal your source(s) please?

Yeah most of the time but it's strange the 16-50 isn't effected, that's the lens that had most problems with the SDM.

I had a DA* 50-135mm develop this problem after a trip to Pentax Germany for repair for other issues. I found that wiggling the lens on the mount would sometimes effect a temporary cure. I found thet the lens would also hunt on a non SDM body, e.g. *istD or MZ-S. The lens was replaced by SRS.

Pentax have recently outsourced repairs to JP Service Solutions in Newcastle under Lyme. However as I've not used them I cannot advise whether they are likely to be better than the outfit which dealt with your MZ-S.

Hello, Thanks again guys for your comments.

I had come across comments elsewhere on the web that the SDM could fail, and that sometimes the failure was gradual - and I jumped to the conclusion that the hunting was the first sign of a failing motor.

I've just been looking at the lens again.
The SDM seems to be working smoothly and following your comments I tried the lens on my MZ-S and it did not hunt at all, in fact the focus was very quick.

The hunting only seems to occur when I put the 50-135 on my K10D.

I will try and test the lens on another K10D, and then most likely, send the lens to JP Solutions.

Thanks again guys.
Alan (D_C_D)

Try cleaning the contacts. On your MZ-S it will be using the screw drive. I have found that a quick rub with a clean tissue often works wonders.

Johnson's Photopia did a good job on fixing my 50-135 (self inflicted problem) but aren't all that quick, and aren't very communicative unless prodded (e.g., they didn't let me know the lens had arrived until I asked, but replied very quickly when I did).

K.