Maxxum xt-si/ sigma af wont work?

I just recently bought a package that included a beercan, a 50mm and a Sigma 400mm AF. the minolta lenses work on the Xtsi but the sigma will not. I put the sigma on a 7000 I have and it works fine on it. Whats up?

Some older Sigma lenses need to be re-chipped for AF to work with newer camera's. Contact Sigma.

what a great info, thanks.
Great little topic.
And Nice work--thank you for sharing- for me this makes perfect sense though.
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