Ive just bought a second hand 80-200 F2.8 AF-S twist zoom. I think this is the 4th gen version with twist zoom and three rubber AF LOCK buttons around the lens and tripod collar. I know there is a autofocus issue with it but it looks well looked after and was an absolute STEAL!! I'm looking for any help or instructions on how to get the best out of it. I will be mounting it to my Nikon D7200. If it has autofocus failure, will the camera motor not assist with this? There is a small lock switch on the aperture ring which locks it at f22?? What is this for? Do I need to set aperture manually? Will the AF LOCK buttons work if the autofocus is broken? The AF/M switch surround has a small crack around the corner screw which maybe why the AF is broken? Does anyone know if this can be replaced and return the AF to working order? If so, roughly what costs for this and a service?