The Capacitance Electronic Disc (C.E.D) Format

Not to be confused as it so often is, with laser discs. C.E.D is an analogue video disc playback system developed by RCA, in which video and audio could be played back on a TV set using a special needle and high-density groove system similar to phonograph records.

Conceived back in 1964, the C.E.D. system was widely seen as a technological success which was able to increase the density of a long-playing record by two orders of magnitude.

Despite this achievement, the C.E.D. system fell victim to poor planning, conflicts within RCA and technical difficulties that slowed development and stalled production of the system for 17 years until 1981!! By this time it had already been made obsolete by the laser videodisc  called LaserVision and LaserDisc as well as Betamax and VHS video cassette formats.

Sales for the system were nowhere near projected estimates. In the spring of 1984, RCA announced it was discontinuing player production, but continuing the production of videodiscs until 1986, losing an estimated $600 million in the process.

RCA had initially intended to release the SKT425 CED player with their high end Dimensia system in late 1984, but cancelled CED player production prior to the Dimensia system’s release.

The format was commonly known as “videodisc”and as mentioned at the start of this article lead to much confusion with the contemporary LaserDisc format. LaserDiscs are read optically with a laser beam, whereas C.E.D. discs are read physically with a stylus (similar to a conventional gramophone record). The two systems are mutually incompatible.

Hitachi VIP201P

The capacitance electronic disc (C.E.D.) was an early audio video medium aimed at home use. C.E.D. was developed and primarily sold by RCA. C.E.D. used a grooved carbon doped PVC disc similar to a phonograph record. Carbon was added to give the discs a conductive surface. C.E.Ds are read by a needle with an electrode. The needle physically contacts the disc riding in the groove, but unlike the phonograph needle, the needle in the C.E.D. player uses conductance to read the peaks and valleys in the groove below. This is necessary due to the extremely high density of C.E.Ds.

C.E.Ds have a density two orders of magnitude greater than a  phonograph LP. The audio and video on a C.E.D. is all analog, but 77 bits of digital auxiliary information that includes frame number is stored on the disc to prevent debris from causing a groove to replay repeatedly (Prentiss, 27). The discs could be damaged by handling, so they were stored in caddies that are inserted into the player and removed leaving the disc in the player. C.E.Ds were sold as SelectaVision Videodisc or simply Videodisc. The C.E.D. was introduced to the U.S. market in 1981.

My VIP201P turned it has more problems than just a non power up fault, though it may be related but without a circuit diagram at the moment I cannot be sure, I need to study whats what. Firstly there is a broken micro-switch (function unknown at present) at the rear of the unit. Also the brass post that holds the cog that drives the linear tracking head, has sheared from the bottom plate. I think some of this damage was done in transit. Rubber belts have perished as well.

After looking at how the unit should mechanically operate, I’ve deduced the Micro-switch is related to power. When the CED cartridge is inserted its guide tray pushes on a bar, this bar is sprung and the caddy pushes the bar onto the micro-switch. This in turn powers the machine up and actuates the loading sequence, the motor lowering the tray and spinning up the platter ready for reading and the linear arm positioning.

I wonder if I can find a suitable micro-switch anywhere?

The brass rod for the linear tracking arm drive wheel; I’m wondering if this could tapped and screwed from beneath. Not sure about tapping as its a tiny bar, would need micro-taps and that would be a prohibitive cost as I don’t have tooling to do it. There must be a solution, perhaps superglue would suffice but doubt it.

I’m tempted to attack my home built Thyristor tester, that has two Burgess micro-switches that look identical, it would at least allow me to function test the player. Linear arm removed so as to see how or even if the tracking cog can be repaired.

I found the solution to the sheered off post for the Linear arm drive transfer cog. The original post was attached to the base-plate via the brass post having a peg passing through and then hammered over in a rivet type fashion. I know this to be so by looking at how other cog posts are attached on the player.

My solution was to drill a hole down into the post centre using a dremel tool-kit. Then using a screw which is of harder material than the brass, let it self tap a thread.

It seems to have worked!  I have manually rotated the wheel and it transfers the drive to the linear arm.

I need to find a couple of belts in my stock as the platter loading belt is perished and loose to the point it does not transfer drive when manually operated. Also the linear arm tracking motor belt has long since gone having turned to goo leaving its mess behind in the motor pulley.

I’ve temporarily robbed a micro-switch from my Thyristor tester and have installed it into the Hitachi. I’ve also now reinstalled the Linear arm and tested the worm action, it tracks. Now I just need to go hunting in my belt draw to see if I have anything suitable. If I can find a couple matching the platter belt will be easier as I have the original slack one as a guide. The linear are drive belt will be a tad tricky as its gone. I will have to measure and deduct 10%, I believe that’s the rule of thumb to follow.

Success!

Plugged in, inserted the caddy, the machine powered up, it lowered the tray onto the platter which span up to speed. The linear arm twitched and there was a lot of clattering. I’m not sure but I think this was due to me having removed the stylus cartridge, I did this as a safety precaution and I’m sure I saw a youtube video where someone explained a similar occurrence. I wil now put the stylus in and see if the arm locates into position.

Trust me it is spinning in this photo.

I now have the linear arm loading, skipping when FF or scan fast is selected. Eject works and return to landing for the arm. Time to hook up to a telly.

TV tested and very pleased to report it works.

The only problem I need to sort out is the linear arm worm drive loading post I repaired, its sitting a little higher now and catches on the edge of the linear arm as it docks and undocks. Occasionally this results in the arm stalling, a little filing down on the top should resolve that. All in all very pleased and it looks like my reward for the effort is the Stylus being a good one, Phew!!!

To recount what was needed in order to get this working.

1. The micro-switch which operates the power on of the player, the disc loading sequence and linear arm positioning, was broken. This was replaced with a donor from my Thyristor tester.
2. Next the linear arm worm drive; the post had sheered off from its base plate. The brass post was drilled and self tapped with a steel screw. This now needs minor adjustment as the post is a little high and catches on the arm when docking and undocking.
3. Tray loading belt perished and replaced.
4. Tray worm drive plastic post that the bar locks into was broken, temporarily taped down to hold in position. This will be drilled and split pinned.
5. Linear arm motor belt perished, new belt fitted.

Solution to the platter worm drive bar not locking. I found an edge clip in my cabinet spares box, this tightly fitted over the lock block but was a tad too high so the bar could still jump out. This was overcome by cutting a rubber block which when tightly wedged in filling the gap, ensures the worm drive bar stays firmly in position.

To cap this little repair project off I won 40 brand new sealed, never opened C.E.D. movies. A wide range of material from sci-fi, horror, drama, comedy, classics, animation and music. An instant collection, hours of entertainment ahead. Can’t believe my luck that it contains my all time favourite 50’s sci-fi movie “Forbidden Planet”.

It makes one almost miss the format wars of yesteryear and constant innovation. Now we’re just left with no ownership and streaming services of which I avoid like the plague. Happy to live in my bubble with obsolete formats and CRT, I neither need nor desire HD or downloadable content.