Diamond Cutting Stylii

[mossboss]

Hey All
It just occured to me that the RCA videodisc player had a diamond pick up stylus installed it The first DVD players 12" ones
Now these old dears are sold in the US for almost nothing as no one wants them any longer
I am not sure what the reproducing stylus looks like but I would not be surprised if it is very close to the shape we use today for cutting records It runs linear across the disc at play back just like a cutter rather than elliptical like a record player
So Physically it should be the same shape like the original cutting stylus which may be a bit finer than we use today as it cut at about 2000 odd LPI
never the less it is a triangular shape so it should not present any issues
Who is going to get one of those junk it and have a look at this closer?
I am quite a long way away so I cannot oblige
It may be a low cost option for US residents
Bancho?
Cheers

[andybee]

nice idea, bossi!
If have a ordered a few discs from RCA one year ago.
(rocky, pink panther and some star track)
very nice made!
very close to the optical laserdisc system.
the idea with the stylus is great!
I always want a working player, but because of NTSC system,
I never bought one....
I really like to see microscope pics of the stylus!

[cymbalism]

i did a little searching into it as i'm trying to find a decent way to get an affordable diamond cutting tip but from what i've found online via schematics and old machines, it's basically the same concept as a playback stylus housed in a plastic shell. also it wouldnt work because it's not faceted properly for cutting - only playback otherwise it would just shred the rca discs. nice thought though - there's got to be something out there to make this easier for guys like us

[cd4cutter]

The playback styli used in the RCA CED videodisc players are NOTHING like those required for audio disc recording or playback. They are extremely tiny by comparison. The CED records turned at 450rpm and were recorded at about 9,000 lpi and the styli are appropriately small. Yes, Virginia, this is more dense than the spirals on optical discs like CDs and DVDs. When people think "hi-tech" they think "optical". But the mechanical CED stylus-in-groove disc was smaller in dimensions than any optical disc. The signal elements in the CED disc are smaller than the wavelengths of the light used in CDs. The CED disc could NOT be mastered with a laser cutter because the light beam is TOO BIG to differentiate the tiny signal elements! You want to talk about intricate, hi-tech mastering systems, THIS was the ultimate hi-tech mastering. The lathes required air bearings on the platter spindles with mirror polishing of the mating surfaces to eliminate the possibility of wobble of even the tiniest amount. The original CED discs were mastered with electron beam recorders. Later, mechanical cutters were developed which could resolve these tiny elements. In fact, RCA had to go to optical interferometry techniques to adapt a laser scanner to be able to read CED discs as part of the quality control system.

The CED playback stylus looks much like the hull of a flat-bottomed boat. It glides over the top of the signal elements in the groove with the trailing edge being flat and positioned perpendicular to the plane of the record. This trailing edge is plated with metal to make it electrically conductive. This edge, in the proximity of the bottom of the record groove forms a very tiny capacitor, the capacitance of which varies with the depth of each signal element. This rapidly changing capacitance as the record spins under the stylus is what transmits the data off the record, thus the name "CED" or "Capacitance Electronic Disc". Again, the size and shape of this stylus is completely incompatible with cutting analog audio record grooves.

[cuttercollector]

The playback styli used in the RCA CED videodisc players are NOTHING like those required for audio disc recording or playback. They are extremely tiny by comparison. The CED records turned at 450rpm and were recorded at about 9,000 lpi and the styli are appropriately small. Yes, Virginia, this is more dense than the spirals on optical discs like CDs and DVDs. When people think "hi-tech" they think "optical". But the mechanical CED stylus-in-groove disc was smaller in dimensions than any optical disc. The signal elements in the CED disc are smaller than the wavelengths of the light used in CDs. The CED disc could NOT be mastered with a laser cutter because the light beam is TOO BIG to differentiate the tiny signal elements! You want to talk about intricate, hi-tech mastering systems, THIS was the ultimate hi-tech mastering. The lathes required air bearings on the platter spindles with mirror polishing of the mating surfaces to eliminate the possibility of wobble of even the tiniest amount. The original CED discs were mastered with electron beam recorders. Later, mechanical cutters were developed which could resolve these tiny elements. In fact, RCA had to go to optical interferometry techniques to adapt a laser scanner to be able to read CED discs as part of the quality control system.

The CED playback stylus looks much like the hull of a flat-bottomed boat. It glides over the top of the signal elements in the groove with the trailing edge being flat and positioned perpendicular to the plane of the record. This trailing edge is plated with metal to make it electrically conductive. This edge, in the proximity of the bottom of the record groove forms a very tiny capacitor, the capacitance of which varies with the depth of each signal element. This rapidly changing capacitance as the record spins under the stylus is what transmits the data off the record, thus the name "CED" or "Capacitance Electronic Disc". Again, the size and shape of this stylus is completely incompatible with cutting analog audio record grooves.

So it WAS mechanical modulation!
I was told it could not possibly be for video even in an FM capacitance system. I had thought the stylus rode an unmodulated groove and the variable capacitance was from the distance to a variable height substrate under the plastic groove. Or is that what you meant by the copper part that was cut then plated and reproduced somehow? Was it inside or was the inner plate flat and the thickness of the plastic providing vertical mechanical modulation of the capacitance?

[mossboss]

Hey CD4
Thank you for the insight Marvelous It was an idea that just "occured" Pitty
You worked for RCA in that area? you seem to be well versed on the subject
Cheers

[cd4cutter]

Moss - Yes, I worked at the Indianapolis pressing plant and engineering department of RCA Records from 1973 to when we turned the lights out on the press floor at the end of 1987. The SelectaVision CED cutting and disc manufacturing technology was a spinoff (pun intended) of the RCA Records Division, using our personnel at first. The player design group was started under the RCA Consumer Electronics Division, also headquartered in Indy. Later, these two areas were broken out and put into their own corporate SelectaVision division, ALSO in Indianapolis. None of today's youngsters know what a BIG RCA town Indy was just a few decades ago. Even those living in Indy! There is NOTHING left of its footprint now. Even the RCA Dome has recently been trashed.

As an (rather lengthy) aside, this is what irritates me a lot about the internet. Every Gen-Yer out there thinks that EVERYTHING they need to know is in Wikipedia or somewhere easily googled on the internet. But the fact is that anything REALLY old - you know, the stuff they used to document in BOOKS (anybody know what those are?) is still in the books and NOT on the internet. That's what libraries are for. But just as sadly, there is little or nothing about fairly recent historical data on the internet either, say stuff from 1990 and earlier. The people who are populating and contributing to the internet databases only write about the stuff that they know about, meaning stuff than Gen-Yers know about, meaning nothing that their parents have experienced. Google RCA and all you'll get is the canned historical stuff about how RCA bought Victor Talking Machine Co. and set up shop in Camden, NJ. You don't read about how Indianapolis WAS RCA for decades afterward when Camden became just the government contract location. See anything about the vast RCA electron tube manufacturing at Harrison, NJ? Or the RCA semiconductor division? Damn little. Ditto the same complaint about Zenith, GE, Westinghouse and all the other major USA manufacturers who had their heydays in the 1950s thru the 80s before corporate asia sucked all the manufacturing out of this country. Here's the real shame of it: This history will eventually get written about 50 years from now when some self-appointed "expert" decides he knows all about one of these companies and writes the "definitive" history of it. But he'll just be another whippersnapper who never had ANY personal experience with the subject, who will make some ridiculously WRONG assumptions about why this or that happened, and whose writings will be taken as gospel by all future readers. A perfect example is the book "From Tinfoil to Stereo" by Read and Welch which purports to document the history of the phonograph. This book is so full of technological bias and misinformed crap that it needs to be ignored by any future readers. It was written by a couple of self-appointed "experts" who were technological incompetents and who come to a horrid assortment of misguided conclusions based on their limited knowledge and ability. And I'm sure that is now the case with some of the "common knowledge" out there regarding Edison's companies because not enough was written by knowledgeable people who were actually in his employ. Edison's footprint on the technologies of the last 100 years was GARGANTUAN - he had to invent virtually ALL of the home electrification technology (insulated wire, fuses, switches, lamp sockets) as an adjunct to his invention (perfection, actually) of the incandescent lamp. He started the General Electric Company (originally known as the Edison General Electric Co.) as but one of his many commercial efforts. But who knows anything about him these days except for a few of his admirers. And some of them are harboring misconceptions about him based on incorrect biographies written by hacks. The point is, the internet is now the perfect opportunity for fairly recent history to be properly and accurately documented by people who have just recently lived it and who are still living to tell about it. Oh well, enough of that particular rant for now.

Cuttercollector - The CED playback was not a matter of recovering the signal via mechanical stimulation of the stylus. See my other postings about the CED system. The stylus tip was shaped like the hull of a flat-bottomed boat. It was very large compared with the signal elements and it rode on the tops of numerous signal elements at any given time, remaining essentially motionless, as a boat skims across small waves in the water. The modulation contained in the depth and spacing of the signal elements was purely vertical. The change in depth from the top of the signal elements to the bottom of the pit between elements was sensed as a change in capacitance between the record and the metallic trailing edge of the stylus. There was no lamination of the record. It was pressed as one piece just as an analog vinyl record. It was coated with a silicone lubricant to reduce record wear, but there was no insulating layer between the conductive plastic of the record and the stylus. The design was a compromise in conductivity that allowed the record itself to be sufficiently conductive while also being sufficiently insulating to allow this variable capacitance effect to be sensed. The modulation was primarily FM with a carrier frequency of about 9 Megahertz and with a number of subcarriers for the two channels of sound and for some other digital data that was used for indexing and stylus control by the servo systems in the player.

[mossboss]

Hey Cd4
I think that you and I have a somewhat similar views on many subjects ie in you rant It comes with age
I personally have had a few things which where pioneering either as self or otherwise employed Was involved in a start up for a hard disc drive in your part of the world in San Jose in fact in the late 80's as well as being involved as an employee in semiconductor manufacture here in this country One of only two plants Fairchild was the other I was at Anodeon This was back in the days when a 60% yield was considered good around 68-70 I remember buying my first transistor in 1966 an OC 26 at a cost of a weeks wages to experiment with
Yes you are right about Edison Even though he was a tough man he did do an incredible amount of pioneering work with lasting results And Morgan? money man! Tesla? AC man Ex Edison employee The guy at Westinghouse Electic, Niagra hydro The list is a long one indeed But at the end of the day this internet thing does allow a couple of old fuddys to exchange ideas knowledge and be around to perhaps "set the record"
I have an extensive Book library at home mostly on engineering subjects however there would not be enough space left if I was to keep in books what is available on the net It is quite amazing however one needs to be selective Any way your post's are always full of indepth insight and I agree with you on the fact that the record ought to be kept straight Post's like this are also good as the owners of the internet good old Google will keep it in an archive for years to come long after you and I met our maker or have gone on to greener pastures after we stop collecting "moss"
Cheers