Modified Nikon SF-200 slide feeder
On its best day, this device is picky about the condition of slides it's feeding. Some plastic mounts, for instance, will only feed in one orientation without jamming when ejecting. A few jams out of a hundred or so is not too much bother. When I was given the job of scanning several thousand slides from the 1960s whose mounts were bent, worn, and swollen from the high humidity environment they'd been stored in, the jam rate went up to about once every 3 slides.
Without detailing the fiddling I had to go through, it turned out that the pressure in the input feed mechanism was so high that friction was making the slides feed in doubles and triples. I messed about a bit with various methods to lower the spring tension-none worked. I also built a little card stock septum to choke the throat of the mechanism to just one slide wide in the hopes that would stop the problem. What finally worked was to combine the two approaches.
The photograph shows the result. A large spring clip disables the pressure plate completely. The scanner is turned on its side to allow gravity alone to hold the slides in place. A cardboard septum chokes the mechanism to allow only one slide at a time to pass.
All images and text Copyright Dale Austin, 1962-2008