Originally posted by kiafrika I have a K-x with the standard 18-55, and the 50-200 which comes with the kit. I have been given an old TC and wondered if I could use it. It is a Vivitar MC tele Converter 2x PK-A/R-PK .
RioRico gave you the long version. Here is a shorter one:
1) There is no problem mixing film and digital components as such. With a few rare exceptions they will work fine.
2) In order for the TC / DA 18-55 combination to work properly in Av mode by controlling the aperture you need a TC with the electrical pins to pass through the signals. If your TC has these then it will work if not then no it will not work as I think you want. As RioRico notes it CAN work, but not (I think) as you want. If you post a picture of your TC we can tell you if it has the pins, although they are easy to spot.
If you want to use a TC and have the aperture controlled get a TC with the pins, they are on ebay all the time for next to nothing.