"No Lens Attached" Sony Alpha with a Sigma Minolta Lens

[chmodx]

Hi,

I have a Sony Alpha A200 with numerous lenses(Sony, Minolta, Sigma, etc.). All work fine.

I'm attached a Sigma 28-70mm 2.8 EX lens, yes, it's AF. When I attempt to take a picture, it acts like no lens is attached:
--AF does not kick in at all
--Error message pops up saying "No Lens Attached, Shutter Locked"

I've read around on the internet, before anyone chimes in, it's not the Shutter/AF priority problem. It's contact with the camera body that appears to be the issue. My question is, anyone else had this problem with Sigma? It's my only lens that's doing this so the body is not the problem.

What kind of price am I looking at to be rechipped?

[Dr. Harout]

Try to clean the contacts and tighten up the screws at the back of the lens.

[David Kilpatrick]

I am not aware of any 28-70mm EX f2.8 lenses being old enough to need rechipping. Dirty contacts or, as suggested, a loose mount may be the issue.

David

[chmodx]

I've figured out how to reproduce the problem. When I zoom all the way out to 28mm, the lens cuts off, I think it has something to do with the interior glass moving forward and being just enough to 'nudge' it off the contacts. As soon as I zoom in just a little, it powers back on.

Anyhow, the seller agreed to a refund. I'm getting my money back and looking into the Tamron 28-75mm now. Too bad there's no real deals on it anywhere.