EsBee,
I too purchased a used version of this lens and it's a wonderful lens, I think you would be really pleased with it if you did get it repaired. On another note I know you said you didn't pay much and their is no return. Have you stated your case to the person who sold it to you. I recently purchased a lens off ebay which clearly stated no return. I went ahead and contacted the seller and stated my case the seller ended up offering to refund everything except shipping. If you by chance did purchase from ebay you could contact paypal and ask them to help you with your problem. They have helped me more than once to my satisfaction.
Good Luck to you....
Kevin
Originally Posted by EsBee 
Just got a used smc PENTAX-FA 80-320mm f4.5-5.6 in Black but utterly disappointed that its faulty. No chance of return or refund.
No matter what the aperture setting is, including "A", the K20D and *ist DS show the "f" number blank so aperture cannot be controlled from the camera. I took a few shots mounted on the *ist DS and the camera shoots the lens either at f4.5 or f5.6 depending on the focal length. It is as if the aperture ring has no effect. Also, the K20D requests the focal length suggesting the contacts aren't communicating the lens information. However, pictures taken with *ist DS contain correct EXIF information about the lens.
I didn't really pay an arm and a leg for this so its not worth sending it in for repairs. Does anyone know of any tricks or have suggestions as to what might be wrong?
Thanks much.