Other uses for old TVs

I started this thread to see if anyone else has used old televisions for other interesting projects, other than wine cabinets, that they would like to admit to on this site.

I was finishing high school in the late 60's when I recaped my first set. It was an Admiral with a 19 inch round metal tube. Shortly thereafter, I decided to play around with the idea of using it to display audio signals. After much experimenting I ended up with something I called my Psychoscope. The Psychoscope was a box that contained audio amplifiers that could drive the deflection yoke of the TV with audio signals. One channel was fed to the vertical, and the other channel was phase-shifted with a resonant tank tuned to bass frequencies common to most rock and pop recordings, and fed to the horizontal. The vertical and horizontal amplifiers were push-pull 6L6 transformer-coupled designs, and coupled to the yoke using the 16-ohm secondaries. Since the yoke was an inductive load and fed with what was more or less a voltage source, the low frequencies resulted in the most deflection on the CRT.

The display on the TV using the audio as the deflection in this way resulted in a toy that was a real blast. I even sold a bunch of these in the early 70's. With rock music, you would get pulsing circles and cardioids that would explode and spin around to the music. For classical music, you could switch out the phase shifter and get exploding squiggly patterns. I also added several internal oscillators to the Psychoscope that could be used to apply video signals and additional deflection signals that could be mixed with the audio. With the video, you could get exploding star-burst patterns or dashed lines. The oscillator-audio mix produced other patterns that were too weird to describe. Because all of the light output from the CRT that is normally spread out over the whole screen via the raster pattern was now concentrated into thin lines, these lines were extremely bright and vivid. With only one exception, I made all of these using B&W sets. The lines were so vivid, though, in a dark room most people would start seeing colors after a short time. Actually, the color on occasion was real; as if the high-intensity beam was allowed to shrink to a small dot it would quickly burn the phosphor with an orange flash. On the color one I made, I designed auto-brightness circuits to prevent this from happening.

Magnetic deflection TVs of this era needed the deflection yoke for energy storage for the flyback pulse that was used to provide high voltage for the CRT. Because I was using the yoke for audio deflection, I mounted a second deflection yoke somewhere in the TV cabinet so that the inductance from the winding could be used in the flyback-based high-voltage circuit. On many of the sets that I converted for use with the Psychoscope, I included means to switch back and forth between Psychoscope use and TV use.

I might even be able to dig up the schematic for the Psychoscope if anyone is interested in seeing it posted.