Mechanical Television (3)This section goes into quite a bit of detail on how I built my rotating disc television. Please note that I'm not responsible if you do or copy anything I describe and something goes wrong!
The early method used to control the speed of the motor was to put a rheostat in series with it. This technique can still be used but making the disk run at precisely the right speed is difficult. I suspect the method may have worked better than expected because once the disk was very close to the right speed incidental coupling between the radio driving the neon light source and the motor supply (such as common ground connections) may have helped lock the motor to the correct speed. The modern method is to monitor the speed of the disc and use an electronic circuit to adjust it to match the signal to be displayed. More on this later.