Dorothy on old RCA 'CED' disc

[NewVista]

Box says this player was for store demonstration unit.
Seems player prefers a TV with slow AFC for steady pic.
No picture in 'Pause' mode for screen photography.

[Phil Nelson]

I restored a Wards (Toshiba) CED player a few months ago. Are you referring to horizontal jitters? My player looked wonderful on the older 27" CRT set that I have on my workshop. When I moved it upstairs and connected it to a new flat screen TV, the picture jiggled horizontally a little, making me wonder if something had gone wrong with it already.

They do make a nice picture when working right.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

[NewVista]

Yes, depends on TV, some H stability shake, needs slower time constant ?

[wa2ise]

RCA dropped about $570 million trying to market that thing. I used to work at the Smirnoff R&D lab where they invented it. It may be the reason GE corporate takeovered RCA, it wasn't pretty...

[Eric H]

Originally Posted by wa2ise

the Smirnoff R&D lab where they invented it.

Well that explains a lot!

[Penthode]

Originally Posted by NewVista

Yes, depends on TV, some H stability shake, needs slower time constant ?

I had never thought about this before. So the spinning video disc has the same sort of timebase errors as video tape when no timebase correction is used?

Bending or jitter requires a "faster" or reduced time constant. Uncorrected timebase errors from VHS tape needs the reduced time constant horizontal AFC low pass filter so that the horizontal oscillator keeps step with the velocity errors.

I found it interesting to find that negative modulation for North American 525 line TV broadcast required a horizontal AFC circuit to help overcome false triggering with noise impulses whereas older British televisions receiving positive modulation 405 line transmissions did not. I suspect this was because the horizontal sync pulse was at the modulation envelope peak for 525 which made it more susceptible to noise? I recall weak British 405 reception on sets with horizontal AFC locked well under the noise.

[old_tv_nut]

Originally Posted by Penthode

I found it interesting to find that negative modulation for North American 525 line TV broadcast required a horizontal AFC circuit to help overcome false triggering with noise impulses whereas older British televisions receiving positive modulation 405 line transmissions did not. I suspect this was because the horizontal sync pulse was at the modulation envelope peak for 525 which made it more susceptible to noise? I recall weak British 405 reception on sets with horizontal AFC locked well under the noise.

Exactly correct - with an envelope detector, impulse noise goes toward max signal. With negative modulation, that means it goes into the sync region. Better NTSC set designs included a noise inverter so that impulses going beyond normal sync level would be inverted and go back toward lower signal level (away from sync, towards white). The time constants in the inverter would be much shorter than those in the sync circuit input filter, so the narrow noise pulse that remained would not affect the sync separator.

[old_tv_nut]

Originally Posted by Penthode

So the spinning video disc has the same sort of timebase errors as video tape when no timebase correction is used?

The disc output is continuous through vertical sync and therefore does not have the sudden offset of H sync timing that is possible with tape - no "flag waving" at the top of the image even with slow AFC, but the smaller random timing variations will be visible.

[wa2ise]

Originally Posted by old_tv_nut

The disc output is continuous through vertical sync

There was a crude attempt to reduce the time base errors in the CED players. There was a feedback mechanism that moved the pickup stylus perpendicular to the direction to the disc's center. They used what was essentially a speaker voice coil as the driver of this stylus mover. This was to counteract errors due to poor disc centering and turntable wow and flutter. But feedback loops reduce but not completely remove such errors, if they tried they could overshoot and go unstable.

Early CED players used a synchronous AC motor fed by the 60Hz powerline, so the disc would rotate at a speed to produce vertical sync at 60Hz. The color subcarrier was recorded on the disc at around 1.53MHz, and the player would upconvert that to the 3.58MHz NTSC standard, using a beat oscillator around 5.11MHz. The above time base errors would also show up as subcarrier frequency errors, so the beat oscillator frequency was FMed to counteract that, to produce a stable NTSC 3.58Mhz subcarrier.

Back in the day, TV sets' horizontal was designed to cope with erratic horizontal sync from VCRs.

DVD players use digital FIFO buffers and frame store memories, and they control the disc spin rate to keep these buffers and memories half full, and thus produce precisely timed video.

[old_tv_nut]

It makes me shake my head, but when you look at formats that succeeded and those that didn't, there is a correlation to whether porn was available or not. The most shocking thing on CED was "Barbarella."

[lnx64]

Originally Posted by old_tv_nut

It makes me shake my head, but when you look at formats that succeeded and those that didn't, there is a correlation to whether porn was available or not. The most shocking thing on CED was "Barbarella."

I have LaserDisc and the only thing I had ran into was anime porn. Yea, not real stuff, just animated. lol

Not that I'm trying to look for either. I'm just going through the boxes of LD's when I'm at the flea market.

[ChrisW6ATV]

Originally Posted by lnx64

I have LaserDisc and the only thing I had ran into was anime porn. Yea, not real stuff, just animated. lol

There were definitely numerous "real" porn Laser Discs available. Image Entertainment, now one of the major home-video distributors, got its start by releasing porn discs. At the time, most Laser Discs were made in Japan, which has laws regarding porn if I remember right (and see my comments about Sony, above), but Image contracted with an American manufacturer (perhaps the only one at the time) to make its discs.

Now, I hope people don't get the wrong idea when I seem to know a lot about porn on video disc formats.

[ChrisW6ATV]

Originally Posted by old_tv_nut

It makes me shake my head, but when you look at formats that succeeded and those that didn't, there is a correlation to whether porn was available or not.

That didn't help the HD DVD format, though. Early on, Sony (that controlled the Blu-ray format) said it would not release porn video on Blu-ray, but porn HD DVDs were available pretty quickly after the debut of both formats.

[Title17]

I swore I'd never mess with CED, then someone had a SJT-100 for sale for $5.

Had to replace some belts in the transport mechanism but it works perfect now. Pretty interesting format that pretty much everyone has long forgotten about.

[Ed in Tx]

Wow! The discs still play! I worked on those in the early '80s when they would come into the shop still in warranty. Usually a new pickup stylus fixed the problem. Had a copy of "Mash" for my test disc. I recall the theory was the silicone lubricant on the disc would eventually dry up and make them unplayable. So much for that! Anyway, pretty cool!