Hawes Electronic Television Archive by James T. Hawes, AA9DT
Did J.L. Baird Invent the Trinitron® Tube?




Speculation About a “One-Gun” Telechrome


Photo: 
        Baird holding 2-color Telechrome tube
Baird holding two-color Telechrome tube (Herbert, p. 26)

Sony Corp., the eventual marketer of the illustrious Trinitron® tube, opened in May 1946. That was about a month before John Logie Baird died.

Several Web sites claim that Baird invented the Sony Trinitron tube. Or that Baird invented its precursor. Why? Because Baird was allegedly working on a single-neck Telechrome tube: A single-neck Telechrome would seem a practical idea. The Telechrome that Baird presented to the press had three or even four necks jutting out in all directions. Each color neck required its own power and signal connections. Obviously, the design required refinement. Pruning a few necks would have helped bring the tube to market. Now comes the leap of faith: “ A one-neck Telechrome,” you say? “Why, Trinitron also had only one neck, and so...

One gun? Sony ads claimed that Trinitron had only one gun. (Actually, this statement was subterfuge, because Trinitron's “one gun” had three cathodes.) Here's where the dreamers drift off again. (A little reader participation is necessary here. Gesticulate wildly, raise your eyebrows and read the next passage aloud in a breathy voice.)

But if one can say that Trinitron had one gun, and if Baird was thinking about a one-gun Telechrome, why then...

Fables. Peter Waddell (1976) carries the torch for such Baird fables. Channeling Baird, Waddell strains credibility with this statement (p. 344)...

One of his [Baird's] assistants, Edward Anderson, states that they had the equivalent of the Sony “Trinitron” tube on the drawing board at that time. Baird's colour equipment vanished after his death. (p. 344)

Equivalent? In what sense? On what drawing board? Whose drawing board? Where is the evidence? This much we know: Sony did manufacture Trinitrons. Millions of them. Yet is there a one-neck or one-gun Telechrome tube anywhere? No. “Baird's color equipment vanished.” How convenient. Whenever Baird fanatics make an outlandish claim, the supporting documents, prototypes and even physics disappear into a conspiracy. But let's consider the merits. Below, we hold these spurious claims up to the light.

Exhibit A: Flaws in the Telechrome Patent

The Telechrome prototype by J.L. Baird and his glassblower Arthur Johnson used a ready-made tube envelope. This envelope came from Hackbridge Hewittic. Normally, such a tube served as a mercury vapor rectifier. Such rectifiers found uses in railroad switching and theatrical lighting applications. For Baird's two-color tube, Johnson mounted two gun necks on the Hewittic envelope. With the Hewittic neck and Johnson's necks then, the two-color tube has three necks.

The Telechrome patent drawing (Baird, 1942) contains several flaws...

The Hewittic neck doesn't appear in the drawing (right). This neck was very important, because it contained the support for the dual mica targets. The Hewittic neck also appeared to carry the anode wire. The anode was probably the metal frame (ring) that one can see in some photos. In these photos, one can spot part of this frame atop the mica targets. In the actual tube, the gun necks were much longer than in the idealized patent drawing. Also, the two mica targets were smaller than in the drawing.

Baird's Telechrome patent (1942) contains another flaw: It never mentions a one-gun or one-neck Telechrome tube.

Art: 
        Telechrome, 2-color version. Click for version with Hewittic neck.
Conceptual technical drawing: Baird Telechrome, 2-color version. (Herbert, p. 26) Click image for our revised drawing with Hewittic neck.

Flaws That Relate to the Trinitron

Missing Pieces. The Telechrome patent (Baird, 1942) fails to include several structures that distinguished the Trinitron tube from other CRTs, including Telechrome. Missing from Telechrome were these structures...

  • The aperture mask.

  • A single target with alternating, vertical stripes of red, green and blue phosphor.

  • An electron gun with three cathodes and a single focusing magnet.

  • A single neck. (Baird might have invented a one-neck gun, but his Telechrome patent doesn't claim this feature.)

  • A bell-shaped envelope with a cylindrical front end.

  • The requirement of a straight neck. (Typically, Baird's Telechrome tubes used at least one slanted neck. In contrast, Trinitron was a straight-neck tube.)

Exhibit B: Telechrome Internals

Derivative. Telechrome was a derivative project, not an original project. Pointing out this truth, Baird (1942) named his patent “Improvements in Colour Television.” Herbert (1996) mentions the origin of the Telechrome idea (p. 26): Baird had been using “teapot tubes” in his projection experiments. A teapot tube's angled neck and kettle-ish target globe were the source of the tube's nickname. Baird surmised that he could build a two-color, direct-view version of this tube. (Herbert, 1996, pp. 20 & 26)

Top of actual Telechrome patent, 1942
Patent title proves that Telechrome is a derivative project (Baird, 1942, p. 1).

The trick would be to join two teapots at the target. The resulting tube would have two standard teapot necks, each at an angle to the target. Then assuming a transparent target, Baird might coat one side with one color phosphor. The other side, he would coat with a second color. Suppose that, as in industry practice, he chose cyan and red for the two colors: Then the tube would produce color pictures! He would alternately scan the targets, producing field-sequential images.

Baird's notes on the specifics seem to be missing or imprecise. (No wonder: He was operating from scant funds in a makeshift shop. During the war, he persisted in his efforts despite frequent bombardment by Nazi planes.) From Herbert's description (1996), we might assume that the unknown electrode voltages match those of the original teapot tube (p. 26). Perhaps someone will duplicate a two-color Telechrome using teapot electronics. Then we can find out more about its behavior. Hint: In 1942, the Chicago company Rauland bought the rights to the teapot tube. This company continued to develop the tubes. McVoy (2014) provides photos and a description of the Rauland teapot tube. Rauland literature might still be available. (Erb, 2014)

Exhibit C: What Witnesses Said

Press Coverage. Herbert (1996) describes the Telechrome press conference in August 1944. Kludge though Telechrome was, the two-color behemoth worked. The natural flesh tones impressed some of the reporters. Telechrome must have seemed a respite from reporting terrible news of World War II. No doubt this escapism is a reason why newspaper articles cast Telechrome in mostly favorable light.

Technical account. Burns (2000) mentions an earlier Baird demonstration for technical people. This January 1944 meeting resulted in a more sober impression of Telechrome. Afterward, observers decried the unnatural two-color palette. Continuing, the January report criticized 3D Telechrome as a “stunt.” (pp. 379-380)

Exhibit D: Alleged 3-color Telechrome

No Evidence. We know that Baird built at least one two-color Telechrome tube, because one is on exhibit at the National Media Museum (2014). There's no parallel evidence that Baird built a three-color tube. Indeed, since Baird only promoted the two-color version, maybe the three-color (four-neck) version presented some insurmountable problem. A study of the patent drawing suggests several difficulties...

  • Cabinet Troubles. The three-color necks made Telechrome challenging to mount in a reasonable size cabinet. In comparison to a normal, monochrome CRT, two-color Telechrome (three necks) required extra room before, behind and below the tube target. A cabinet for a three-color Telechrome (four necks) would need all this extra space, too. Plus, the cabinet would be taller than the two-color cabinet, allowing room for the top or green gun. (“11” on the drawing, right.) Sony's Trinitron was another story. Due to its conventional, funnel shaped tube, it didn't have the hulking cabinet problem. To see a Telechrome cabinet simulation, click...

  • Alignment Woes. Telechrome necks caused field alignment problems, particularly in the three-color tube. There, the green field keystoned oppositely to the red and blue fields! Contrast that situation with Trinitron: Due to its striped tube face and single neck, Trinitron didn't have these field alignment problems. (Herbert 24 mentions compensating for keystone distortion in teapot tubes, Telechrome's predecessors.)

  • Pincushion. A tube with a straight rear neck (such as the two-color tube at the National Media Museum) would require even more compensation. The rear straight (red) neck would tend to trace pincushion-shaped pictures. (Trinitron also requires compensation.)

Art: Concept, drawing of 3-color Telechrome tube
Conceptual drawing of 3-color Telechrome tube from patent (Baird, 1942, p. 4).
  • Target insertion would be daunting. During insertion, the targets had to clear the sides of the Hewittic (target support) neck. The front mica target was corrugated and the back target was flat. Somehow the assembler had to temporarily fold or roll these targets. Then in position inside the tube, the targets had to snap back to their original shape. When they snapped back, the targets had to register with one another on the scale of pixels. A later patent suggested methods for target insertion that Arthur Johnson could have tried. (Baird patent 579,482, p. 1) Trinitron manufacturing avoided such insertion problems.

  • Target shape. Telechrome used flat, and not bow-shaped targets. The electron beam could focus sharply in the middle of the target. Yet the beam would lose focus and become elongated as it moved from the center. To correct for this problem, a compensating signal would be necessary. With its bowed target, Trinitron didn't have this problem.

  • Brightness Issues. The green target was brightest at a 45° vertical angle. The blue target was brightest at the opposite 45° vertical angle. Both targets were dimmer than the front (red) target. Compensating by reducing the amplitude of the red signal would dim the picture. With its single target face, Trinitron didn't have this problem.

  • Position sensitivity. Viewers had to watch from a position level with the center of the screen. What if the viewer were too low in relation to the internal screen? Then the brightest image would likely be blue. If the viewer were too high, then the brightest image would likely be green. (See the illustration at right.) On the other hand, Trinitron color wasn't position sensitive.

Art: Problems with 
         viewing alleged '3-color Telechrome' from above or below center of CRT.

Position sensitivity: Viewing angle affects apparent color brightness.

  • Image focal point. As with Cinecolor film (Hart, 1998), Telechrome had more than one focal plane. The viewer's eyes would try in vain to sharply focus both the front and back images. (Let alone images on the serrated target!) But sharply focusing images on different planes was impossible. The attempt could only lead to eye fatigue. Trinitron presented all colors on one target, and didn't have this problem.

  • Transparent targets. Telechrome's targets had to be transparent, or the viewer couldn't see all colors at once. Yet during a show, the transparency might make images seem ghostly. Worsening the situation, the tube exterior had no opaque dag coating. As a result, ambient light could intrude into the tube and mar the already insubstantial image. (Example: Light from other tubes on the chassis.) Avoiding these difficulties, Trinitron had a dag coat on the tube envelope. Trinitron's aluminized screen produced solid, bright pictures. Since Telechrome's screens had to remain transparent, aluminizing them for extra brightness likely wasn't an option. (The aluminized layer is opaque.) Perhaps aluminizing the rear (red) Telechrome screen would have been helpful. But then, rear viewing would have been impossible. Aluminization of the other screens would have been impractical, as it would have blocked them.

Was Telechrome a Trinitron tube?

How might they differ? Many differences are obvious. Baird's preferred Telechrome was a two-color picture tube. Trinitron was a three-color tube. The Telechrome of Baird's preferred implementation was a tube with two targets. It scanned one color target from left to right. The tube scanned the other color target backwards, from right to left. In contrast, the Trinitron, like the delta-gun tube, had only one target. Trinitron scanned its target only from right to left. (Trinitron scanning took place on the back of the target. For the viewer, the scanning action was actually left to right.) Perhaps most damning for Telechrome, it was never more than what Brian Winston (1998) called a “partial prototype.” On the other hand, Trinitron was a mass-produced tube in TV sets that consumers widely accepted on a worldwide basis.

Let's examine the statement that Telechrome equals Trinitron...

  • What relationship did Baird have with Sony? None.

  • Is there evidence that Baird ever built a single-neck tube? No.

  • Is the number of necks the only characteristic that made a Sony Trinitron? No.

  • Was a Telechrome set a simultaneous-color set, like the Trinitron? No.

  • Did Telechrome use an aperture grille, as in Trinitron? No.

Debunked

Conclusion: Not so good for the Baird true believers. Plain and simple: Pseudoscience just beguiled you. Telechrome wasn't a Trinitron tube by any stretch. Telechrome wasn't a precursor to Trinitron in any meaningful way. Telechrome was in fact an evolutionary dead end. What it teaches about Trinitron is this: Posthumous inventions remain impossible, even for John Logie Baird.

Aren't there any similarities between the tubes? There are very few. Please examine the tables below.

Telechrome vs. Trinitron, Part 1

Tube Aperture Grille No. of targets Color Mode No. of Colors Front contour, tube Color emitter Deflection Flicker
Trinitron Yes 1 Simultaneous 3 Slightly cylindrical Vertical stripes on back of screen Electromagnetic Low
Telechrome No Typ. 2 (or 3) Field-sequential Typ. 2 (or 3) Extremely spherical (bulbous) Solid planes of color on mica targets deep inside tube Electromagnetic (probably) High

Telechrome vs. Trinitron, Part 2

Tube Guns Target color method Cathodes per Gun Interlace Colors per Field Market Worthy World Standard Adaptable to Other World Standards?
Trinitron 1 One cylindrical target with vertical color stripes: R-G-B-B-G-R, etc. 3 2:1 3 Extremely popular. Widely produced NTSC/PAL/SECAM Yes
Telechrome 2 (or 3) Multiple flat targets, each with solid color coat 1 3:1 (each screen)1 1 Never produced. Prototypes only. Industry reject.2 Proprietary Yes, but only with increased flicker.3

Notes

  1. Total: 6 scans for 2-color version. For 6 scans, frame rate is only 50/6, or 8.3 Hz. Possibly more scans and even lower frame rate for 3-color version. In large areas of color, flicker would be unbearable. As means of coping with problem, Baird proposed line-sequential scanning. (Baird Patent 562,334, p. 1) According to Burns (2000), Baird probably didn't pursue line-sequential television. (See pp. 376-377.)
  2. No evidence of practical tube. 1-gun (or 1-neck) tube has never turned up. No museum has one.
  3. To work on 3-color world standards, 2-color version requires color-translation circuits.

Some Incidental Differences

Necks. Trinitron tubes had relatively short necks. In contrast, Telechrome tubes had long necks. On multi-neck Telechrome tubes, each color neck had a separate filament, cathode and grid or grids (control, screen and focus).

Envelopes: Bulbous vs. Cylindrical. There were differences in the tube envelopes. The front of the Telechrome tube was bulbous and it projected outward. This projection of the front (or rear) glass functioned as a crude lens. The lens distorted the image from the interior screen. To correct such 'fishbowl' distortion, a later Baird patent suggested flatter viewing surfaces. (Baird patent 562,433, p. 1) On the other hand, Trinitron painted pictures on the back of its screen. Although the screen profile was cylindrical, distortion was minimal.

Envelopes: Dag. Unlike Trinitron, Telechrome didn't have an exterior coating of aquadag (dag.) Since dag is opaque, it would impede the view into the Telechrome CRT. In photos, one can see the targets from several angles. A dag coating would obscure most of these views. Another difference was the anode connection. The Trinitron anode connected through a standard cap in the side of the tube bell. Apparently, the Telechrome anode connected through the Hewittic neck.

Degausser. The Trinitron set included an automatic tube degausser. At set startup, this degausser demagnetized the aperture mask. Telechrome didn't use Sony's aperture mask or anything like it. Possibly the metal supports for the mica targets could become magnetized. (These supports likely served as an anode, because mica isn't a conductor.) That Baird would include an automatic demagnetizer in his experimental design is unlikely.

The Verdict

There were More Differences than similarities between Telechrome and Trinitron. As the tables above prove, there were several key differences between Telechrome and Trinitron. One simply can't arrive at a Trinitron tube by referring to the Telechrome tube or the Baird Telechrome patent (1942). The number of targets differed, as did the neck angle and envelope shape. Unlike Trinitron, Telechrome didn't have an aperture mask. Trinitron sets scanned the colors simultaneously. Telechrome sets scanned the colors field-sequentially.

Disrespect. Baird revisionists that proclaim a connection between Telechrome and Trinitron flagrantly ignore and disrepect the true inventors: Susumu Yoshida, Akio Ohgoshi, Senri Miyaoka and other engineers under Sony president Masaru Ibuka. (Sony, 2014)

Vanished? What about Waddell's statement that “Baird's colour equipment vanished after his death”? Now that doesn't sound like such a mystery anymore. Baird or his associates must have realized that there was no practical use for Telechrome. Outside of a publicity stunt, that is. Fact: Neither Baird nor anyone else ever sold a Telechrome set. It was unmarketable. Then the only way to claim a footnote in color TV history books became clear: Eliminate evidence. And the Telechrome, while it wouldn't fit into a practical TV cabinet, slid nicely into the dustbin. Then the time was right to start improvising whoppers.

The real reason why some people compare Telechrome to the Trinitron is this: The Trinitron was a fabulously popular, successful, widely produced tube. It was highly profitable for Sony and for companies who licensed the tube. Telechrome, on the other hand, was a commercial failure. No one ever produced the tube. In fact, no company even expressed an interest in licensing the Baird Telechrome patents. (Brown, 107) Telechrome's sole purpose was to generate publicity for Baird. Only in this sense did Telechrome succeed. Baird enjoyed his fleeting moment of fame. Today, Baird shills want to parlay this one moment into some form of historic entitlement. But history isn't a matter of entitlement. Instead, history depends on what happened, and public acceptance of what happened. Technical historian Brian Winston (1998) explains this point most eloquently in exquisite detail (pp. 1-15).

Insisting, despite facts, that Trinitron somehow emerged from Telechrome is a way of hitching Baird's wagon to the Trinitron star. Like Telechrome, this ploy is hopeless, pathetic and a footpath to failure.


Bibliography

Abramson, Albert. The History of Television, 1942 to 2000. Jefferson, NC: McFarland, 2003.

Baird, John Logie. "Improvements in Colour Television," G.B. patent 562,168, filed July 25, 1942, and issued June 21, 1944. •Re: Original Telechrome patent.

Baird, John Logie. "Improvements in Colour Television Apparatus," G.B. patent 562,334, filed October 10, 1942, and issued June 23, 1944. •Re: Line-sequential patent. Burns (2000) believes that Baird probably didn't pursue this patent. Reason: Implementation would have been arduous: Might not have been possible with technology of time.

Baird, John Logie. "Improvements in or Relating to Screens for Television," G.B. patent 579,482, filed April 8, 1944, and issued August 6, 1946. •Re: Target insertion into Hewittic envelopes.

Baird, John Logie. "Improvements in Cathode Ray Tubes for Television," G.B. patent 562,433, filed July 23, 1943, and issued June 30, 1944. •Re: Compensating for lens distortion from bulbous screen faces of Telechrome tubes.

Brown, Douglas. The Three Dimensions of John Logie Baird. Bedford, UK: Radio Society of Great Britain), 2012, 107. •Re: Rauland rejected Telechrome. Reason: Telechrome tube's viewing screen was internal, instead of on the face of the tube.

Burns, Russell. John Logie Baird, Television Pioneer. London: The Institution of Electrical Engineers, 2000. (This book is part of the IEE History of Technology series.)

Erb, Ernst, HB9RXQ. "History of the radio manufacturer Rauland Corporation; Chicago," n.d., access on June 7, 2014. http://www.radiomuseum.org/dsp_hersteller_detail.cfm?company_id=3219

Hart, Martin. "Cinecolor," 1998, access on March 6, 2018. http://www.widescreenmuseum.com/oldcolor/cinecolor2.htm

Herbert, Ray. Seeing by Wireless: The Story of Baird Television. Sanderson, Surrey, England: Herbert, 1996.

Kamm, Antony and Malcolm Baird. John Logie Baird: A Life. Edinburgh: National Museums of Scotland, 2002, 326.

McVoy, Steve. "Baird/Rauland Projection CRT," n.d., access on June, 7, 2014. http://www.earlytelevision.org/rauland_crt.html

National Media Museum. "Telechrome Tube: Television Receivers," 2014, access on June 16, 2014. http://www.nationalmediamuseum.org.uk/collection/television/televisionreceivers/collectionitem.aspx?id=1962-48

Rauland. "Company History of Rauland," 2014, access on June 7, 2014. http://www.rauland.com/History.cfm

Shiers, George. Early Television: A Bibliographic Guide to 1940. (Garland Reference Library of Social Science) New York: Routledge, 1996.

Sony. "Superior Quality of Trinitron TV Screens Leads to Computer Display Applications," 2014, access on September 30, 2014. http://www.sony.net/SonyInfo/CorporateInfo/History/SonyHistory/2-14.html

Waddell, Peter. "Seeing By Wireless." New Scientist 11 (1976): 342-344.

Wikipedia "Trinitron," 2014, access on September 30, 2014. http://en.wikipedia.org/wiki/Trinitron#Chromatron Wikipedia article with more information on Trinitron development and the developers. Contrasts the Trinitron to the Lawrence Chromatron. Unfortunately there are several broken links.

Winston, Brian. Media Technology and Society: A History: From the Telegraph to the Internet. New York: Routledge, 1998. Won the American Association for History and Computing Prize for the Best Book of 1998.


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Contents

Speculation About a “One-Gun” Telechrome

Exhibit A: Flaws in the Telechrome Patent

Exhibit B: Telechrome Internals

Exhibit C: What Witnesses Said

Exhibit D: Alleged 3-color Telechrome

Was Telechrome a Trinitron tube?

Speculation About “One-Gun” Telechrome

Debunked

Telechrome vs. Trinitron, Part 1

Telechrome vs. Trinitron, Part 2

Notes

Some Incidental Differences

The Verdict

Bibliography



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