Originally posted by Outis Now this same body is having the same problem. Again. I tried cleaning the contacts myself with contact cleaner, which once again didn't help.
You might want to use a different approach. Typically a light buffing with a clean microfiber cloth should be all that is needed. The F--- display is due to lack of continuity across the "A" contact (* on diagram below) to the mount face.
Image lifted from Dimitrov's K-Mount Page. Full discussion of how the mount contacts work may be found
HERE and
HERE.
On lenses lacking an aperture ring, the "A" contact should always have continuity to the mount face. For lenses with an aperture ring, this is only true when the ring is locked at the "A" position.* When you see F--- with a lens having contacts, the first thing to check is the aperture ring position followed by making sure that the lens is properly seated on the mount. If neither work a quick cleaning usually does the trick. I would avoid solvent-based cleaners since there is a risk of the liquid penetrating to places other than where it was applied. Before blaming the body, I would confirm that you get F--- with ALL of your lenses. You can test the "A" contact on the body with voltmeter. With the camera switched on there should be 10mV potential between the center of the "A" contact and mount face.
Steve
* On some lenses the "A" contact is a small pin that raises/lowers depending on ring position. On others the contacts always mate and state is determined by a small switch within the aperture ring mechanism.