Originally posted by netuser Well, it's tested.
I blinded with tape both side of the "sdm" contacts on the teleconverter. Still no SDM and no screw.
(Remmember the teleconverter works fine with tamron 70-200 2.8)
You should just need to cover one of the sides, but hey, no problem to overengineer it
Although I'm wondering if it's something more than "electrical contact" that makes the camera body think it needs to use SDM. Maybe there is a pressure switch too, I don't know, but there shouldn't because the same TC works with your Tamron lens and the TC's contacts are still in contact with the body in this case.
Bear in mind that even if you do get AF working, it might not actually work because the resulting f/8 aperture might not be bright enough for the AF sensor to lock focus. In this case what would happen is that the lens motor would whir back and forth but never achieve focus. But you'll never know unless you get the AF working.
How did you mask the contacts? I assume you used think electrical tape.