DA 55-300mm will not focus on K70 body with any settings

My 18-135 works perfectly, but the DA 55-300 will not focus with any settings, i have tried multiple combinations and a factory reset. The in lens motor works constantly but will not focus at any length in auto or manual. when the camera is set to manual the lens continues to flicker between manual and af.a or af.s. the manual focus ring has no effect. This is a used lens which worked perfectly on the camera in the shop. all other lenses work on my camera. it does not work with either view finder. am i missing something?

Can you tell us which version of the lens it is. There have been several versions. The latest one (PLM version) has the focus motor in the lens, previous versions were focused by a motor in the camera body.

Steve

I have the PLM version. I have updated to the latest firmware and that didn't make any difference.
it is the motor in the lens that twitches constantly but wont focus. switching the camera to MF doesnt stop it

It may be worth cleaning the contacts on both the lens and body.

Do you have another body you can test the lens on?

I dont have another camera, no. this is the only lens not working correctly, and I have cleaned the contacts already. I suspect it is beyond repair. just taken it out in bright light and it was shifting wildly between iso 200 and 1600, f4 and f6 and shutter for 1/20 to 1/400, it doesnt seem to know how much light its getting. and the one shot i managed to get it to take was almost completely dark at iso 800 and 1/60. its also constantly switching for af.s to MF on the display

While it's on the body, see if adding a bit of CW/CCW torque causes the shutter speed/ISO to stabilise.

sadly not

It sounds like a cpu issue.

Can you return it? Or is there a warranty?

How about taking it back to the shop to try it on another body there? Even if it's out of warranty they might help you out. Or maybe you can find another Pentaxian close by who's willing to provide another camera to try it on?

If you haven't had it very long, haven't used it heavily and haven't dropped it or done anything else that might damage it internally, then I would go back to the shop with camera and lens and say 'look what's happening'. You don't say whether you are in the UK or not, but consumer law in the UK does provide some protection for used goods (although not as much as for new).

Unfortunately, the behaviour of the lens sounds suspiciously like a known problem with the Pentax Q 06 lens - different camera system but a retractable lens like the 55-300mm PLM. Someone stripped down a failed 06 and found that the cause of the problem was a broken ribbon cable that flexes to allow the lens to open and retract. The lens suddenly does strange things and never works properly again. It happened to mine... .

Steve

looks like I'm sending it back! thanks for all the suggestion, hopefully the replacement will work

This may be of no use whatsoever, but I Googled your problem and came across this

"This specific lens features a collapsible retraction mechanism to save space.Action: Ensure the lens barrel is fully locked into position at the 55mm mark. If the retraction button or locking mechanism fails, the electronics may behave erratically.Check Manual Focus / ResetAction: Take the lens off the camera and attempt to turn the focus ring manually. If the ring feels physically stuck or continues to grind/twitch when not attached to the body, an internal gear or the PLM motor may have stripped or broken"

This info may be about as much use as a chocolate teapot, on the other hand.....

Michael