The Slide Gate in the Selectron Changer
shown opening in five stages. The
right hand aperture as shown has two
sliding plates that can just be seen.

A Wide Format Selectron Changer
for the TDC Stereo Projector

By Max Hem, Victorian 3D Society

When I heard of the TDC Selectron slide changer many years ago my first thoughts were "bewdy!!" I'll get one and open it out to 7 sprocket (at the time this was the format of my Iloca camera).

On asking around however I was assured it couldn't be done, so I left it at that. Years of fumbling in slide boxes in the dark, dropping slides and getting Competition slides out of order, has however finally driven me to attempt the impossible. So after a lot of brainscraping I can happily say that the impossible just takes a bit longer - here it is:

The main design problem concerns the way in which the projector light is "dowsed" while changing a slide. For ease of viewing it is important that the left and right images are dowsed evenly. In the original Selectron this is done with a shutter mechanism that has separate metal curtains for the left and right apertures. In a wide format stereo mount however there is insufficient space between the left and right apertures for a shutter blade large enough to cover the left aperture. I've come up with a double-plate sliding telescoping design that works very well.

The Selectron Changer with Slide Cassette.
I tried it out for the first time at the 1997 screening of the Southern Cross Exhibition in Melbourne for a record 140 people. It made the show so much easier and smoother to project than a manual changer - leaving one hand free to operate the other controls at all times. Being able to pre-load the slides into cassettes is a real luxury.

The conversion needs some sheet metal thinner than the original sliding shutter blade because there will be two blades in the same groove (0.0012" to 0.0015" will do), and five brass bolts and nuts 15mm long and 2mm diameter to replace the rivets drilled out when dismantling the changer. Tools required are: drills, files, tinsnips, vice, and a lot of patience, skill, and good luck.

See Figure 1 of the parts required for conversion.
See Figure 2 of the parts required for conversion.


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