Virtual Science Museum

CED Player

The RCA Capacitance Electronic Disc system was launched in 1981 and was only around for about five years. It pre-dates Laser Disc by several years. It uses a diamond stylus to play a grooved 12" conductive disc. The signal is read as variations in capacitance between the stylus and the disc. There are 375 grooves per millimeter compared to a maximum of 14 per millimeter on a long play record. The system is so sensitive to finger prints and dust that the discs are contained in caddies.

To load a disc, the caddy is inserted into the front of the player and then withdrawn again. The disc remains in the machine and the caddy comes out empty.

With a good disc, the picture quality is comparable with VHS tape. Not surprisingly, tracking problems are common. To alleviate this, the system automatically advances the stylus if the same revolution of grove gets played more than once. This often occurs on a number of revolutions in succession, with rather bizarre results.

The PAL system can hold 75 minutes of program material on each side of the disc. When the player gets to the end of side one, the screen goes black disconcertingly. To play side two, the disc has to be turned over manually. This is done by inserting the caddy and withdrawing it again. The caddy then comes out with the disc in it. The caddy is then turned over, inserted into the machine and withdrawn again. The disc is then in the machine the other way up and side two starts playing.

This is a Hitachi VIP201P CED player. It has stereo sound and infra-red remote control. This is the same machine as above, with the top cover removed. A film has been loaded and the edge of the disc can be seen at the front of the machine, just under the main printed circuit board (PCB). The white part is the inside of the caddy, which remains in the player with the disc. On the left hand side is a motorized 'gantry' which runs the length of the machine, from front to back. It is driven by a motor and belt at the back of the machine which moves it to the right as the disc is played.

Here, the main PCB has been raised while the machine is playing. Note that the gantry has moved across to the disc. The stylus is located in the front part of the gantry with the signal amplifier mounted directly behind it. The motor which drives the gantry can be seen in the rear left hand corner.

When a disc is loaded, switches tell the machine when the caddy has been withdrawn fully. A motor then lowers the transport so that the disc engages with the spindle motor. Another switch tells the machine when the transport is fully lowered. The gantry then moves across to the disc and stops when an infra-red beam is broken by an arm on the gantry. The stylus is then lowered onto the disc.

The part of the caddy which remains in the player is shaped on the leading edge, to identify which side is playing. When side two is loaded, a switch is pressed. This lights an indicator on the front of the machine.

The play time indicator is simply a light emitting diode (LED) mounted on the gantry. The LED is viewed through a window. As the film is played, the gantry traverses the disc, and the LED moves across the window.

This is the stylus cartridge. It fits in the front section of the gantry. The overall length of the cartridge is 95mm. The actual stylus is on the right hand side.

This is a close-up of the stylus. The area shown in this picture is 11mm wide. The ribbon loop, which is probably beryllium copper, connects the stylus to the signal amplifier. The amplifier is mounted on the gantry, close to the stylus to minimize stray capacitance and electrical noise.

Coils mounted either side of the stylus control the gantry motor so that the stylus does not get pulled too far to one side. There are also coils which raise and lower the stylus and control the tracking force.

Much more information is available at CED Magic.