This is my first post on here so please bear with me and my newbie ways.

I have a Sigma AF 75-200mm f2.8-3.5 lens with a Minolta/Sony mount, Serial number 2024767, that not work with my Sony a55 camera. The lens works fine when used with the later models of 35m Minolta STL cameras. Although it mounts to my Sony, it does not communicate with the electronic internals of the camera. I get the No lens attached message when I try to use it.

I have read on some of the on-line forums that there are electronic adapters for this lens that will essentially "re-chip" it to work with digital Sony cameras. This lens is quite fast as it has a maximum aperture of f2.8-3.5 and a minimum aperture of f22, with a constant aperture of f2.8 between 75 -135 mm and f3.5 thereafter to 200mm focal length. Some folks rate it as a best buy and I guess it is if it works on their alphas. If I can get it working it will fit the low light niche in my equipment as I really can't afford a modern f2.8 zoom in this focal length range.

It sure is a beauty with its all metal construction and looks nearly brand new. However, I think that I can dispel the "rumor" about these lenses with serial numbers beginning with 200XXXX working on the Sony digital camera bodies. I have an a100 and a55 that don't even seem to be making any electrical contact with this lens. In my research I have found folks reporting serial numbers beginning in 100XXXX working on these cameras. There seems to be some Sony alpha models that these Sigma lenses will work on and some that they will not, and a disparity among this same model Sigma lens, regardless of the serial number, that will work. Results seem to be all over the place. It is a nice looking lens and I hope that I can make it more than an expensive paper weight.

Can anybody explain the physics of what is going on with this lens and the apparent disparities of whether it will work on alpha bodies or not? I can't seem to see a pattern here. I am looking into buying the chip sold by James Lao as suggested on another forum. First, I would like to know what the technical problems are that caused my lens not to work on the alphas, because I don't want to drop any more cash on something that may not make it operational. Does any one have any experience with this issue and /or re-chipping this lens? So far, Mr. Lao has not returned my email inquiries. This is what I am looking at:

M42 M42-MAF/SONY alpha Adapter With Focus Confirmation