Sigma 28-300 lens has stopped working with Pentax K-r DSLR

This lens has worked perfectly with the camera for several years without bother. I tried using it with a 2x teleconverter (non-electic connections) and the lens simply will now not communicate with the camera any more. I suspect possible linkage problems. Any ideas to try to rectify please?

I might add that the camera works fine with another lens.

Check the lens contacts. The converter might have caused damage.

Have you tried wiping the contacts? and checking the aperture lever? I suppose you don't have another body to check the lens on?

Hope you get to the bottom of this and everything sorts itself out.

I have two identical bodies. I have tried the 28-300 on both and get the same result, ie it doesn't work. I tried switching to live view on each body and got the message "Live view cannot be started". To all intents and purposes the lens seems to be "dead" as far as the bodies are concerned.

I've cleaned the contacts but it makes no difference. The aperture lever is working OK and does not appear to have been displaced at all.

I have a Sigma 10-20, which works OK on both cameras, and as far as I can tell the contacts and aperture lever look identical on both.

Would it be worth wiping the contacts with a cotton bud with WD40 (or switch cleaner) on? I believe that the contacts are spring loaded. Could one have been jammed when you used the teleconverter?

Regards

Michael

Thanks Michael. I have wiped the contacts with switch cleaner on both camera and lens. Some dirt came off but I'm afraid it made no difference.

The contacts on the camera are spring loaded, and all work. Those on the lens are fixed.

I've just noticed that when the 28-300 lens is attached the correct information isn't shown on the screen relative to the selection made on the picture mode dial (is that the correct terminology?) For just about every position it shows "Av aperture priority."

Are there any switches on the lens body?

sounds like a lens problem , had a sigma lens go wrong and it put the camera in a hizzy fit if i selected live view. It was no longer supported so they would not touch it. have had a look at the servicing list and your lens does not appear in it so would suggest a phone call. If they will do it then it could cost around £120 , Just guessing which section it would come under. My 17-70 cost me £92 for new stabilisation module and service. Hope you can get it fixed

There are no switches on the lens body.

I am now thinking that when the lens was connected to the converter and mounted on the camera body, there might easily have been a short circuit between the various contacts which triggered some mishap in the lens' elecronics when the camera was swicthed on. If that is the case then a repair sounds as though it would be quite pricey and maybe not worth it. It would be a shame however to write off the lens.

Does the teleconverter still work with other lenses and is it one with all the electronic contacts on it?
What happens if you try the lens with the camera in manual mode?

The teleconverter has no electrical contacts just a completely smooth metal service, an ideal conductor between contacts unfortunately. It still works with other lenses.

In manual mode exactly the same thing happens, ie nothing works.

What happens if you try the lens again with the converter, which will have to be in manual mode anyhow?

Actually I think the problem might be with the electrical circuit where the lens has disconnected itself at the point. the contacts from the lens mount meet the lens 'proper'. A fairly common fault with some Sigma lenses where the mount contacts are only pressed against the lens contacts. Usually it fails just showing it can't read the lens aperture, but quite why its not showing anything in your lens I've no idea.

It might be worth trying to wiggle the lens mounted on the body to see it it shows an intermittent fault.
Try that in normal SLR mode rather than live view.

The only reason the lens cold have shorted out if there was power in the lens when it failed. The teleconverter without contacts in between would mean there was no power going into the lens from the body to cause damage. . Whether a charged capacitor inside the lens might do that I've no idea, but haven't heard of that happening before.

I don't think that could happen, if it did the same problem would arise when mounting any lens on a camera bayonet mount.