I spent a few dollars buying a "TOPAZ" brand 2X "PKA" teleconverter. According to my understanding a PKA mount should have the electrical contacts to signal aperture information and the 'A' setting on the lens.
Huh, not so on this TC, they have put insulators on the front of the TC and a single insulator on the rear which corresponds with the 'A' setting contact. In other words the only concession to 'A' is that if you select 'A' on the lens that is not signalled through to the camera! I cant imagine the insulators on the front of the TC will do anything unless the lens has a way of reading these which I assume would require some electronics in the lens and as far as I know none of mine have.
You get what you pay for I suppose which in this case was not very much!