Talk:Cathode ray tube

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Former good article nominee Cathode ray tube was a good articles nominee, but did not meet the good article criteria at the time. There are suggestions below for improving the article. Once these issues have been addressed, the article can be renominated. Editors may also seek a reassessment of the decision if they believe there was a mistake.
June 12, 2007 Good article nominee Not listed
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Weaponizing old junkyard CRT monitors into harassment weapons[edit]

Weaponizing old junkyard CRT ballast into harassment weapons. I've been hearing strange rumors that a certain group of unethical engineers have been going around and secretly installing the electron guns from out of CRT monitors behind the walls of other people's offices to harass them while working. Is this possible? I realize that CRT's normally have lead glass, etc... but what if they removed it and just used the gun? The office I work in seem to have a strange electronics sound and the feeling of pelted on your skin by something at random times during the day... how would you detect free electrons pinging you from inside a wall? A Geiger counter don't seem to measure electrons below a certain electron Volts level?? What about secondary radiation from electrons striking something outside of a vaccum, etc? — Preceding unsigned comment added by Aloftjunco1 (talkcontribs) 08:35, 15 February 2014 (UTC)

You can rest easy. The electron gun will not function at all once removed from the tube. It requires a vacuum in order to operate at all. Incidentally, can you please note for the future that new entries for talk pages go at the bottom. Alternatively, use the "New Section" tab at the top of the page and it will automagically appear in the right place. DieSwartzPunkt (talk) 17:45, 24 March 2014 (UTC)

Quality[edit]

Can someone PLEASE improve the writing quality? The syntax is dreadful in places, e.g. number disagreement. — Preceding unsigned comment added by 82.68.94.86 (talk) 16:40, 7 February 2014 (UTC)

If it bothers you that much, why not have a go yourself? DieSwartzPunkt (talk) 17:46, 24 March 2014 (UTC)

Diagrams[edit]

Shouldn't the comments on the top two pictures be reversed? The TV screen has a hex grid, the computer screen should have a rectangular one, not the other way around... Right? --89.212.75.6 (talk) 17:05, 28 July 2009 (UTC)

Just found an issue with the picture of the CRT from an old computer monitro. The picture is named 'Fuckin TV'. Someone should probably rename it to something more appropriate. 96.225.77.172 (talk) 20:50, 18 April 2011 (UTC)

Older Comments[edit]

since someones mentioned not messing with a CRT, should it be mentioned that one should short the large capacitors to avoid a shock


I've just added:

These high voltages can persist long after the device containg the CRT has been switched off.

In general, the untrained shouldn't be opening the box in the first place, and providing warnings is better than providing "how-to" details: where do you stop?


To do:


The line "CRT is a triode. More complex CRTs contain greater numbers of electrodes. " was deleted. Primarily, this makes no sense logically, and also, triodes were mentioned later.

Sounds good to me, welcome to Wikipedia. -- Tim Starling 07:47, Jan 5, 2004 (UTC)

CRT illustrations made especially for Wikipedia[edit]

Hi - danish wikipedian here.
For some snazzy illustrations, check out the danish article (language: "Dansk") on the subject: I just rendered some "cut-away" images of various CRTs...

User:Peo on danish Wikipedia

... and now I've moved large versions of those illustrations onto Commons. See:

User:Peo, from danish Wikipedia - again!

How many joules are in the capacitors? lysdexia 22:18, 19 Oct 2004 (UTC)


"...children should even be encouraged to do this so that they may see the immediate and dramatic effect of a magnetic field on moving charged particles, provided they are informed to never do the same with a color tube."

TEACHER: So remember, kids, never put a magnet near your TV or you'll mess up the screen.
JOHNNY (THINKS): Gee, that's great! If I mess up our crappy old TV Dad'll have to get a new one! Lee M 01:59, 2 Dec 2004 (UTC)

---

I wonder if *THAT* is what happened to my crappy old 13" TV? :)

Seriously, the Exploratorium has a color TV and a huge magnet set up for just this sort of playing around.

Meanwhile, [[User::lysdexia]] asks about how many joules are stored. Well, Joules = KV^2 * uF, so lets take a SWAG and call the CRT 0.01 uF. Meanwhile, the charge on the CRT can be 25 to 30 KV on a modern color CRT so we can calculate 6.25 to 9.00 Joules based on our SWAG about the capacitance. Having been on the receiving end of a 17KV discharge from an old B/W CRT (never grab the 1B3GT by the bottom; you might contact the HT pins!), I say that sounds like it's in the right ballpark. The shock wasn't too bad, but I really hurt my elbow when it smashed into the wall behind the TV set.

Atlant

CRT cleaning[edit]

> "(using ordinary household cleaners may damage antiglare protective layer on the screen),"

I disagree with this statement. Firstly, most TV CRTs don't have any antiglare treatment. But even for computer monitor CRTs with good antiglare treatments, ordinary glass cleaners (for U.S. examples, "Windex" or "Glass Plus") definitely don't damage antiglare coatings. It is important to use an oil-free rag, paper towel, or whatever because if you don't, even a little bit of oil will leave a rainbow on the screen and you'll just have to start over again.

There is one good reason not to use liquid cleaners, though, and that's a two-fold risk of electric shock. One aspect of that is that goofy users will use the liquid cleaner a bit too freely and it will run liberally into the guts of the TV, creating a real risk of electrical leakage. A more obscure risk is that you can occasionally provoke quite a static discharge through you; it's no real risk, but it may surprise you.

Atlant 00:46, 21 Dec 2004 (UTC)

The best guide I have to cleaning CRT devices comes from DOS for Dummies (I think):
  • Spray a little window cleaner onto a piece of kitchen roll
  • Wipe
This avoids window cleaner dripping inside the device, and really does work a treat. --h2g2bob 12:00, 26 October 2006 (UTC)

Persistence of the second-anode high voltage[edit]

The article currently states: These voltages can persist long (several days) after the device containing the CRT has been switched off and unplugged. with the phrase several days being a recent addition.

I'm a bit troubled by including an explicit time value. It's way too long for many (most?) color TV receivers and computer monitors because they usually have an actual high-voltage bleed path through the circuits that sense and regulate the 2nd anode voltage. But it's simultaneously way too short for older B/W TV sets that had no discharge path and practically no leakage paths. Thinking back to my youth, I'm pretty sure I've been shocked by sets that were out of service for a long time, and I'm talking about a lot more than several days. (Obviously, based on this posting and my posting above, I spent way too much time playing with loose kilovolts!) You probably should never disconnect the second anode connector from any CRT without taking the time and trouble to explicitly discharge it to ground/earth first.

I think long time without any explicit qualifiers is probably a better statement.

Atlant 16:45, 31 Jan 2005 (UTC)

I know it's been a while, but I can confirm that several days is no exageration. Not all CRT systems are blessed with a bleed path once the supply is switched off. Myself and my colleagues were frequently caught out by one particular monitor design from (IIRC) Silicon Graphics. Not only did it not have a bleed path, but the EHT trippler was in the bottom of the cabinet. Frequently when one of these monitors was picked up by an engineer, it was quickly dropped again as the stored EHT jumped from the trippler to the hand picking up the monitor. 109.153.242.10 (talk) 18:24, 11 January 2012 (UTC)

Faraday???[edit]

My Chemistry textbook states that Michael Faraday was the first to invent a CRT. I just want to know to what extent this can be called incorrect. --GatesPlusPlus 3 J

I think you are confusing a CRT with the use of cathods and anods in liquids.--Trigamma 17:55, 22 January 2007 (UTC)

Shadow Mask[edit]

That picture of a shadow mask close-up sure looks questionable to me, and it's not as good a subject as the one used for the aperture grille example. —Preceding unsigned comment added by 206.224.83.59 (talkcontribs)

fixed --h2g2bob 01:21, 22 October 2006 (UTC)

Disposal of CRTs[edit]

hi, i just added a section on how to dispose crts. Someone might want to add to it. I am kind of new to wikipedia. —The preceding unsigned comment was added by Falcon866 (talkcontribs) .

I won't put this in the article, but one thing you can do to help ease disposal concerns is to break the "vacuum tip" (the tiny little glass tip centered within the socket pins) on a dead CRT, allowing the atmosphere into the bulb and completely eliminating the implosion hazard that a CRT represents. At that point, the ex-CRT just becomes a big bottle made of leaded glass.
Along these lines, does anyone still remanufacture CRTs? Ages ago, they used to do that, expecting you to turn in "the dud" when you purchased a replacement CRT. Those guys wanted the dud to still be "under vacuum", though, so you couldn't do the safing trick that I've described above.
Atlant 18:04, 17 November 2006 (UTC)
A year or two ago I did a web search looking and found one outfit that still would re-manufacture B&W tubes, they were aiming at mostly industrial users but would do tyhem for TV collectors such as the folks who use Philco Predicata sets. About 2 years ago I also noted one fellow who was trying to sell a complete CRT rebuilding shop on e-bay.
My understadning is that the Phosphors don't like being exposed to the air for any lenth od time, and so the rebuilders have to reneck the tube and getting starting to pump down in a short time.
My tube collection includes a 21ZP4 with a sharp line where the neck splice was not done well.cmacd 20:37, 17 November 2006 (UTC)
Thanks! I'm sure they also don't like how the rapid intrusion of air caused by hacks like me blows the phosphor right off the center of the screen ;-) !
Atlant 20:50, 17 November 2006 (UTC)
When I was young, I would sometimes see a TV put out as garbage behind a local service shop. They seemed to have a habbit of just severing the neck, and so the screens normaly had a clear patch in the middle!
My understanding is that the rebuilders would either file a notch in the exhast tip or place the tube in their oven and pump the oven down before using a heated wire to crack the old neck. They could then let air in the oven, and splice in a new neck, install a gun and bake the tube to be sure it was dry inside before pumping it down.
RCA and Sylvania (among others) used to sell rebuilts that they had re-screened (according to their ads). Sylvanaia also pushed that their "silver screen 85" rebuilts were all aluminized. It is not practical to re-screen a colo(u)r tube. cmacd 13:31, 22 November 2006 (UTC)

Dismantled[edit]

just tried to dismantle a crt, messed it up and gas escaped.

I came t owikipedia to see if I'm gonna die. Perhaps details on barium or other gases used inside should be included?

—The preceding unsigned comment was added by 82.33.8.127 (talkcontribs) .

Must have been a stange CRT if Gas "Escaped" as to work they need no air inside. A dismatling attemp would likly have resuted in Flying Glass exerywhere. Their is likly a small quanity of barrium metal inside but that would quickly turn into barrium oxide.which is relativly inert. The residue would be considered hazardous, as it would conatin LEAD which can leach Slowly into the enviroment, even though most of it is in the Glass. The phosphors might be toxic. cmacd 17:33, 17 November 2006 (UTC)
Been a while I know, but the phosphor is very toxic. If anyone wishes to dispose of an old CRT, it is a good idea to let the vacuum down, to remove the risk of implossion. It can be done easily like this. Turn the monitor, TV or whatever, screen downwards. Wrap something suitable such as a blanket around the cone of the tube leaving a short length of neck protruding. Wearing safety goggles, carefully knock the evacuation entubation off with something like a pair of pliers (this is usually in the middle of the connection pins). Ninety nine times out of a hundred, the air will enter via this breach without any further damage. Occasionally, an implosion may occur, particularly if there is a flaw in the glass. The blanket will contain most of the flying glass and your safety goggles will protect you from a fragments from the neck. 109.153.242.10 (talk) 18:32, 11 January 2012 (UTC)

High Definition CRTs[edit]

I'm not an expert in the subject at all, but I think that this article needs to have information about HD CRTs and why they are still preffered by some consumers over plasma, LCD or DLP - in particular, I've heard it said that despite disadvantages such as size, weight and sharpness compared to those technologies, they still have better color reproduction, color depth, and contrast ratio without the viewing angle, dead pixel, and burn-in issues that the others have, as well as being better at showing fast motion without blurring. Esn 11:28, 23 November 2006 (UTC)

Not to mention better lifespan. I was talking to a fellow from a school board and he says he can get 10 years out of a CRT Cmputer monitor in School (rugged) use and half that from a LCD unit. cmacd 14:38, 23 November 2006 (UTC)

About the merge suggestion[edit]

This is an aboration. Give a noob an article and they will merge it into unrelated articles. If I wanted the history of electronic display I would visit CRT Monitor or CRT Telivision.

Moved from top (please follow the notices). Can you explain how the articles are different please? --h2g2bob 10:15, 6 December 2006 (UTC)
Somewhere else, I already stated strong opposition to this merge, but I can't find it today so I'll re-state it here. The Crookes tube is arguably the progenitor of all vacuum tubes, but has relatively little in common with the modern device we call a cathode ray tube, and it has at least as much in common with the modern device we call the X-ray tube. Calling for a merge seems to me to be the equivalent of calling for a merger of an article about the Wright brothers' airplane with the F/A-18 article; they both fly, but are otherwise a bit different. Atlant 12:13, 6 December 2006 (UTC)
Fair enough, I've removed the tag. --h2g2bob 13:25, 6 December 2006 (UTC)
Thanks! Atlant 13:35, 6 December 2006 (UTC)
First time I have seen democracy actually work. Usally Wiki is run by an Oligarchy. Oh, and if I want to broadcast my current IP, I would ~~~~ but I don't. And signing in is only if I want to do a move or create an article. No reason to sign in if just making a few small changes that will get reverted because the wiki oligarchy is full of idiots.
On the side note, I ask, H2g2bob, do you know anything of either article, besides what you read in wikipedia? The most common reason for a merger is because someone doesn't understand what an article is actually about, and no one cares enough about the article to correct the merger. I have been saying this for some time...
If you are not a 'true' expert on the two articles you wish to merge. Don't do it. If you can not truely say that two articles are actually one and the same, and not only relate because of a common thread. Don't do it. To many articles are merged together for no reason, -phob-, for instance, has incorporated a list of phobias even though phobia is only one possible combination of prefix and suffix of the thing. The list has nothing to do with the article, and should be torn from it.
Worse is when other articles (albeit useless) are merged into this monstrocity, which is demonstrated by the merger of 'fictional phobias' into the article as definitions, these definitions are even reduced definitions then the original articles which they were dervated from.
The end run, just don't merge unless you know what you are talking about. I am not happy with the condition the majority of articles on wikipedia are in, and people like you, merging without propper reason, are not making the situation better.

The introduction of this article was almost phrased like CRT is obsolete and only relics of CRT technology remain while I would dare say the majority of display devices (TV) in the world still employ this technology. The phrase "well into the 21st century" sounded like we're living in 2048.

To anon: I'd like to point out that trying to hide your IP address as anon is pointless, since it's logged in the history for all the world to see. If you want to hide it, then log in. Hairy Dude 21:15, 19 January 2007 (UTC)

Obsolescence[edit]

I removed the unsourced statement about CRTs being obsolete. They are actually superior to LCD screens because they display better coloring and render moving images better. They keep their picture when viewed from an angle — which can be an issue in living rooms. I added a note about the angle phenomenon and the moving-image thing.

Also, the paragraph mentioned that CRT shelf life is 5 years, but do LCDs last longer? I read that LCDs last about 25,000 hours, which should equate to around the same lifespan. So, I removed that statement, also.—ЦпғогуетаЫе 05:38, 19 February 2007 (UTC)

I do not believe that LCDs are actually superior to lcds. That may have been true seven years ago when lcd was still emerging as a mainstream technology, but now it has pretty much surpassed CRT. It has certainly surpassed CRT in terms of resolution, range of size (even small lcds can display astonishingly high resolutions), colour balance, pure digital display, 1:1 digital pixel mapping, higher more accurate ranges of balance adjustments and such. Even the old chestnut of lcds not being able to display real "blacks" has been overcome. CRTs had reached their limitations, either their technical peak or their peak of people wanting to use them, either way LCDs are ahead and CRTs are and have not really been developed and improved on as much in comparison. I think there is way too much bias of CRT being "better" in this article, based on the old idea that lcds couldn't to as good a job, which simply isn't true anymore. Some people just can't let go of that old ideal, either someone once told them that CRTs are better, I don't know, but for some reason they can't let it go JayKeaton 01:27, 5 April 2007 (UTC)
Taking into account you're comparing LCDs to lcds (what's the difference?), most if not all of your post is just ignorant and uninformed bias.
LCDs have been in development in some shape or form for over 50 years and have just barely been able to match CRTs in some areas within the recent years. LCDs can't touch response times or color vibrance of a CRT and have just recently been able to match screen resolution (in pixels, not physical screen size.) CRTs have been able to do 2560x1600 for over 20 years, something which LCDs have only recently been able to touch. You fail to mention the big downsides of LCDs in your post, which include stuck / dead pixels, terrible viewing angles (not only on the left / right but also up / down), inability to change resolutions without having the screen get stretched / blurred or cut-off, backlight woes (dead backlights or horrible light bleeding) and the list goes on. I don't see how you list "small screens with high resolutions" as a pro. a 15" screen stuck at 1920x1080, who wants to use a magnifying glass to see the start menu in Windows?
It is true that most if not all manufacturers have halted development on CRTs, but not because they are outdated, it's because of market forces. If someone really wanted to, they could put R&D back into CRTs (which could happen some day) to make a better and more environmentally friendly CRT. The potential is there, someone just has to tap into it.
But as for people saying they prefer CRTs over LCDs because they're better, it's more or less the truth. If you can put up with the weight, heat and slightly higher power usage, you can advert all of the woes I listed above.66.68.116.78 (talk) 06:43, 25 October 2009 (UTC)

CRTs are obsolete in most market segments. Analog oscilloscopes are perhaps one of the last places they are not. Obsolescance does _not_ mean that they are better or worse than the technologies that replace them. Simply that they are no longer widely available. --Speedevil (talk) 15:15, 25 October 2009 (UTC)

It's funny reading the above comments from 2007 that CRT is not yet obsolete. Now it's 2010, and CRTs are even more obviously obsolete, and a mention of that fact is conspicuously absent from the introduction to the article. Compare the article for phonograph which starts with "The phonograph, record player, or gramophone was the most common device for playing sound recordings from the late 1870s until the late 1980s.". We can say the same thing about CRTs. Now they are far from common (the article has various numbers). The fact that some people continue to use them, and even prefer them, doesn't make CRT not obsolete, any more than the fact that some people still prefer phonographs means that they are not obsolete.
Nyh (talk) 13:05, 21 April 2010 (UTC)
The main article section dealing with consumer CRT televisions has not been updated for 3 years. It's now 2013 and as far as I am aware no new CRT televisions are available. Perhaps article should be brought up to date - for example are low end CRTs still being made for any Third World markets? --MichaelGG (talk) 06:55, 26 July 2013 (UTC)

Radiation[edit]

Any knowledgeable person please help shed light on this:

"Sitting in front of a monitor is pretty safe (because of the shielding) but a lot of radiation is emmitted out the back."

This is a ridiculous myth. Emission standards for displays -- which covers TVs and computer monitors -- covers emissions from ALL directions.

Comments made on http://discuss.fogcreek.com/joelonsoftware3/default.asp?cmd=show&ixPost=94323 by:

  • Almost Anonymous Thursday, December 11, 2003
  • Brad Wilson (dotnetguy.techieswithcats.com) Thursday, December 11, 2003

Lucasrangit 01:24, 28 February 2007 (UTC)

The standards have been in effect since about the 1960 era. TV sets must have engineering controls to eliminate the hazard outside the cabinet, which means that most Sets made since then have a "shutdown circuit" that will disable the set if the high voltage gets outside of limits, also display CRTS since that time have had more lead in the glass, and the notorious "Shunt Regulator" circut that caused the potential to be noticed due to x-rays being detected underneath certain GE sets has been eliminated. I understand that metalic sheilds are installed inside some tubes.
Before 1960, technical magazines had published research that indicated that x-ray emmssion was posible from the funnel area (back) of a TV CRT, having been experimentaly detected in small beams. At that time the experimenters did not detect any at the front of the cabinet, although back then most TV sets had a separate Plate Glass "safety Glass" in front of the tube.
The articles at the time recomended that technicans did not lean over a TV chassis operating outside the cabinet unless they had to to make tests and to move TV sets off the bench when operating them outside the cabinet when verifing that repairs had corrected the problems they were trying to fix. (many problems are intermitent and so the TV techs would often fix what they though was the problem and leave the set playing for a day to see if the problem returned.)
The Old RCA tube Manuals going back to the introduction of the TV CRT after WWII did contain a warning about the posibilty of x-ray emmssion if the tube was operated above 16,000 Volts. Later the same warning was added to HV rectifier tubes like the 1B3GT. HV rectifiers produced in the late 60s and later had warnings on the base and weigh more than earlier ones, which probaly means that the glass was changed to mixture with some lead content. cmacd 13:36, 28 February 2007 (UTC)

Anyone have "useable" Lifetime estimates?[edit]

My own experence includes a 30 year old tv set that is still on it's orignial tube, and I did quote a friend above about his getting twice the life out of CRT monitors vs LCD units, but has anyone seen a refererce that could be added to the page on estimated lifetimes of colour CRTs? cmacd 16:29, 16 March 2007 (UTC)

Modern CRTs rarely fail outright. What happens, of course, is that the cathode's emissive coating wears away, raising the work function higher and higer. The perceived result is that the screen gets dimmer and dimmer (or the user has to crank the brightness higher and higher, making it harder to maintain focus, etc.). I think that the end-of-life for a CRT is defined as the point where its brightess falls to half of the initial brightness, but having said that, I don't know how long that is. My experience, though, seems to suggest its in the tens of thousands of hours as I've never yet had a colo[u]r TV fail for lack of CRT brightness.
The surrounding electronics, of course, do fail. A whole generation of Trinitron CRT monitors manufactured for Sun Microsystems and others have all developed the same failure: Inability to blank the beam fully. I've never tracked it to a root cause, but doubt the CRT is at fault.
Atlant 16:44, 16 March 2007 (UTC)
I have yet to wear out a CRT. Based on the experience with my new Magnovox HD television, I am guessing the d*** computer will die long before the CRT even begins to fade! It hiccups, resets itself, gets out of sync, etc., etc.. I'm not sure replacing those nice reliable analog chassis with these new computerized systems was such a good idea. Think Intel and their ilk had anything to do with spec'ing the basis these new HD systems? ;-) JimScott 19:07, 21 July 2007 (UTC)
The wearing out of a CRT in modern (i.e. post ~1980) TV sets is hidden from the viewer. Prior to this time, the image did dim as the cathode(s) deteriorated. In monochrome tubes, the viewer just cranked up the brightness and didn't notice anything else until those tell tale 'silvery' areas appeared on the highlights confirming that the cathode was shot (new tube time). In colour tubes the white balance slowly moved towards a distinct colour bias as the cathodes wore unevenly. The viewer couldn't correct this but a TV engineer could. Since around 1980, there were hardly any monochrome TVs made. Colour TVs incorporated a new circuit whose function was to measure the cut off point for each of the three guns (it did this once the tube had warmed up). It then adjusted the drive so that each colour appeared as bright as it did when the tube was new. Thus the tube did not appear to the viewer to wear - that is until the beam cut off of one of the guns fell outside of the range that the circuit could control. The circuit could be seen working in some TV designs as the 'black' areas of the picture started as non black and slowly became black after a few seconds. DieSwartzPunkt (talk) 17:58, 26 March 2014 (UTC)

Health Danger Vagueness[edit]

The first paragraph of this section is too vague and seems misleading because of it.

"Some believe the electromagnetic fields emitted by CRT monitors constitute a health hazard to the functioning of living cells."

Weasle terms. 'Some' people's beliefs aren't exactly encyclopaedic or relevant. Unless they have some credible research to cite, there's no need to mention what they think in the article.


"Exposure to these fields diminishes according to the inverse square law, which describes the propagation of all electromagnetic radiation: double the distance, quarter the power; monitor and television manuals typically recommend a minimum viewing distance of 85cm (34in)."

This seems accurate, but is the justification in the manuals related to ionizing radiation or eyesight? It's implied to be the former but there's no reference.


"The EM energy is also less intense for the display's user than for a person located behind it, because the deflection yoke is closer to the rear."

Isn't that a myth? Reference required, in any case. —The preceding unsigned comment was added by 194.46.255.71 (talk) 18:20, 8 May 2007 (UTC).

This, unfortunately, is a symptom of the way Wiki works. Even though there's scant (if any evidence) that the deflection fields of a CRT pose any hazard, enough people believe this that it keeps ending up in the article and, admittedly, the science isn't absolutely conclusive yet. Personally, I'd be happier with a statement that runs along the lines of "While there remains some concern that..., there is no scientific evidence to date that supports these concerns."
With regard to "more hazardous at the rear", this comes from two separate concepts. One, of course, is that the deflection yoke is the primary source of EM relating to the CRT deflection fields so, yes, you can get closer to these fields at the rear of the tube than at the faceplate end. But I think this also gets conflated with the X-ray concerns. Because the glass in the CRT bell is curved, it can be much less thick than the (now) flat glass of the faceplate while still being mechanically "strong enough". So you can often measure a higher flux of soft X-rays coming through the bell of the CRT than through the faceplate. Also, in the ancient days of vacuum tube high-voltage rectifiers and shunt regulator tubes, TVs often emitted very noticeable beams of X-rays downward through the bases of those two tubes, and the tubes were commonly relatively far from the CRT faceplate.
Atlant 12:20, 9 May 2007 (UTC)
I've removed the fact tag from this section and put in two references. Although the second one is an advert for an electromagnetic screen and as such obviously biased, it does prove that there are concerns, valid or not, about the effects of radiation from CRT's Richerman (talk) 00:11, 1 March 2008 (UTC)

"Exposure to these fields diminishes considerably at distances of 85 cm or farther according to the inverse square law, which describes the propagation of all electromagnetic radiation." This is NOT true. The inverse square law only describes the intensity of EM waves radiating from a point source. A Gaussian beam does not fall off as 1/r^2. This should be fixed. JabberWalkie (talk) 20:06, 22 October 2009 (UTC)

Failed GA[edit]

This article has failed the GA noms, due to a lack of references as well as a section on the history and development of the item. If you feel that this review was in error fee free to take it to WP:GA/R. Tarret 00:37, 12 June 2007 (UTC)

Controlling pixel brightness[edit]

There is no information in this article on the way the brightness of pixels is controlled. There is a great deal of public confusion about this matter. Is the power of the electron gun modulated, or is there a grid to control power as in the basic triode vacuum tube? I see that there are other patented methods for fixed-power electron guns in CRTs.

The question arises in the context of Blackle.com, where some sites claim measurements of decreased power for a nearly-all-black screen, and some claim increased measured power--on different CRTs, of course.

Flat and thin/slim CRT[edit]

Just a question for those in the know really. Has anyone heard anything about a new generation of CRT displays that are rumoured to be appearing soon. These supposedly have a flat screen and come in a more slimline package in an attempt to rival display technologies like LCD. What is the common name for them? Should this be mentioned in this article? Sloman 22:01, 8 August 2007 (UTC)

You're thinking of a Surface-conduction electron-emitter display. Communisthamster 15:20, 8 September 2007 (UTC)

CRT Resolution[edit]

I imagine a black-and-white CRT, which has no fixed pattern of pixels, would be able to adjust vertical resolution (number of lines) by changing the synchronization. As for the horizontal resolution, it depends mostly on the electronics and the focusing ability of the electron gun. Otherwise, there are no pixels in B&W CRTs.

This is however not true about color CRTs which, just like LCDs, have a fixed pattern of pixels--both because of the fixed pattern of color phosphor dots on the screen, and because of the fixed pattern of holes in the grille.

So, even though you might theoretically get better resoulution watching 480p DVD on a black and white CRT (provided your electronics supports this), you won't have the same advantage on color screens. I propose to remove this part from the article.

Bartosz (talk) 21:27, 1 January 2008 (UTC)

The dots on the shadow mask aren't subpixels, because the brightness must not be constant over the whole dot (which you can sse i.E. on File:Aperture_grille_closeup_teletext.jpg). You can increasse the resolution indefinitely in theory, although the picture won't look very good, if the resolution is much bigger than the hadow mask resolution, because this will make some subpixels be absorbed by the aperture grille (I dind't notice this effect using 2048x1536 on my 22" CRT, which has 20" visible and an aperture grille (better known as trinitron, which is actually a brand name by sony) w/ 0.24mm, which would match a horizontal resolution of 1924 pixels in the visible part of the tube and because it's an aperture grille, there is only a horizontal arrengement, not a vertical, so the vertical resolution is really unlimited). You actually can't exactly match the shadow masks resolution, because CRTs don't have a fixed size of the image, normally you make the image somewhat smaller then the CRTs size, because the visible size of the tube is normally about 1"-2" smaller than the actual size. But i.E. if you have a 19" CRT w/ 0.23mm dotpitch, you will have about 1679x1259 dots (or about 1600x1200 in the visible part, if about 18" are visible), but the picture won't look better, if you use 1600x1200 than w/ i.E. 1024x768. If you use 1024x768 on a 1600x1200 LCD the picture will look much worse than w/ 1600x1200. --MrBurns (talk) 10:09, 16 February 2009 (UTC)

I think the initial comment is worthwhile, as is this section on resolution. What it lacks is a distinction between mono-chrome and colour. As I understand it:

Horizontal resolution:The horizontal resolution of a mono-chrome (black and white, black and green, amber etc.) is continuous (analog) and hence theoretically infinite. The pracical limit is how fast one can alter the intensity of the electron beam. The horizontal resolution of a colour crt can be said to be fixed, in the sense that it must conform to the pattern of red,blue and green areas applied to the inside of the crt in the factory. It is possible to vary the intensity within each area, although the result is neither a simple increase in resolution, or easy to describe in text.

Vertical resolution. The vertical resolution of a monochrome monitor is theoretically infinite, just as with the horizontal, but one must remember the electron beam and resulting "dot" have width. For colour there are two types of mask to consider. In the first type the coloured areas are not continuous verically, and the resolution is constrained in the same way as the horizontal colour is above. In the second type the coloured areas are continous vertically, and the resolution is not constrained, the the sense of vertical mono-chrome above. This type of crt was introduced and used exclusively by Sony under the name "Trinitron", until the patent expiried, after which many manufacturers used it. Antifesto (talk) 00:00, 20 March 2014 (UTC)

The assumptions expressed here about dot pitch constraining resolution are mistaken.... very common, but mistaken. It is simply not the case that the phosphor triads on the screen match 1:1 (or close to that) with pixels, or that the number of triads constrains the number of pixels that can be displayed.
If that were the case, then on the color CRT you would see very obvious aliasing effects (like moire patterns) when you attempted to use pixel counts that were much higher than about half of the triad count... particularly when you came close to the actual triad count (Nyquist!) To eliminate this you'd have to display exactly as many pixels as you have phosphor triads, and to make that work there would have to be precise synchronization between the electron beams' arrival at the triads and the pixel times in the input signal, and this is just not practical. There isn't even a "dot clock" in the VGA signal, and there is considerable tolerance in the "front porch" duration, so there is really no way to determine just from the sync pulses exactly where each pixel is within the horizontal scan interval. And small adjustments to your H and V size and position controls would throw off the alignment completely. (Those controls do not work in increments of one pixel, or one triad!)
It would also have to be the case that each beam lit up exactly one phosphor dot or stripe at a time, and that isn't true either; electron beams in CRTs cannot be focused that finely.
Instead each beam illuminates a considerable number - a dozen or so - of the dots or stripes of its color (the shadow mask or aperture grille ensures that each beam falls only on phosphors of its intended color, and of course there is some spillover, esp at high beam intensity), with falloff toward the outer edges of the beam. The beam of course sweeps from left to right, and it is varied in intensity according to the input signal. It doesn't matter in the slightest if the beam happens to be "right between two triads" when information arrives for a particular pixel, because what you see as "the pixel" is simply the average of the brightness of the triads in that area. It's all very stochastic. Jeh (talk) 02:48, 20 March 2014 (UTC)
This is fascinating information, but I'm having trouble understanding how the triad density does not constrain horizontal resolution in an aperture grill display. Your description suggests that multiple phosphor triads are energized for each "pixel", but how is it possible to have a horizontal resolution that exceeds the triad density? For example, suppose that there are 1000 triads across the display width. I can't envision how this display could successfully resolve an image that has 600 alternations of red and green lines (e.g. 1200 lines in total).Spacediver (talk) 03:54, 13 July 2014 (UTC)
The resolution cannot exceed the density of the colour phosphor triads. The point is: that for the normally encountered television resolutions, the triad density is larger than the resolution disctated by the bandwidth of the (analogue) signal. Tubes with much higher triad densities were produced for the computer monitor market. They were also developed for television sets designed to display high definition pictures (in both the 720p and 1080i variants), but these never made it to market as they were headed off by flat panel displays. DieSwartzPunkt (talk) 16:42, 13 July 2014 (UTC)
You appear to have missed the point. There will be no moiré effect if you, "attempted to use pixel counts that were much higher than about half of the triad count". This is precisely because the picture in a cathode ray tube is not composed of pixels. All that the density of the colour triads does is to present an upper limit to the (analogue) horizontal resolution of the tube - the vertical resolution being fixed by the scanning lines. DieSwartzPunkt (talk) 16:50, 13 July 2014 (UTC)
Conversely, this is why LCD displays with VGA inputs do have fine "sync" and "phase" adjustments. Assuming that the input signal pixel count matches the display resolution, then each pixel on the screen is controlled individually, from the input signal at a time that is assumed to represent the corresponding pixel. Most modern LCDs can do a pretty good job of finding the line rate and the first and last pixel on a line by themselves, but this is very dependent on the image being displayed. If the timing is off by more than a quarter of a pixel or so you will get very obvious moire patterns when displaying fine detail. You just don't see that on a CRT. And that's all the evidence you should need that color CRTs just don't work that way. Jeh (talk) 01:55, 23 March 2014 (UTC)

The true successors to the CRT[edit]

The Field Emission Display (FED) and Surface-conduction Electron-emitter Display (SED). Both provide all of the benefits of CRT displays not found in LCDs, but in the dimensions of typical LCD and Plasma displays. The number-one complaints of LCD-critics will be satisfied, since they don't experience dead pixels, can display high-fps video, and have the same richness of color that traditional CRTs have. Furthermore, it is cheaper to make them since no back light is required. This needs to be mentioned in this article. Contrary to popular belief, CRT technology is not dead, it just got smaller. The word is that Sony will be resurrecting its Trinitron line with this technology sometime in 2009. --130.127.121.188 (talk) 19:37, 1 April 2008 (UTC)

No, they don't have all advantages, that normal CRTs also have, because they have a native resolution, which normal CRTs don't have. So they don't allow free resolution scaling w/o picture quality losses. --MrBurns (talk) 09:43, 16 February 2009 (UTC)

I wondered, does anyone know what the future plans of CRTS were? I.e, if LCD and plasma hadn't taken over, how were companies planning to devlop CRT technology? I know there were Samsung slim CRTs and maybe some HD though I do not think these had a chance to take off. --Gm33223 19:49, 3 April 2009 (UTC) —Preceding unsigned comment added by Gm33223 (talkcontribs)

Some 100% true facts about crt.[edit]

CRTs can have significantly more contrast, colour etc. just by changing the voltage of the beams, which can be done by many programs, without damaging the CRTs. The only thing you can’t change with out shortening the lifespan of the CRTs is the brightness.

CRTs consume the same power like other displaying technologies.

CRTs have a longer lifespan, because they just become duller. Unlike CRTs, LCDs and Plasmas burnout or become "greyish" instead.

The Problems of CRTs is that they take a lot more space, but the weight of them really isn’t a problem. Quote: "Sure LCDs are light weight, that’s fine until your kitty knocks over your LCD."

The other problem is that most of the CRTs have only a VGA(analogue) connector, which makes graphics processing slower, even the latest high-end graphics cards don’t go over an analogue processing speed of 400Mhz. —Preceding unsigned comment added by Govadina (talkcontribs) 21:21, 2 June 2008 (UTC)

WTF are you talking about? 400 mhz RAMDAC has absolutely no effect on graphics processing speed. The only thing it does is limit the bandwidth the card can output with the analogue signal which limits the maximum combination of refresh rate, resolution and colour depth. Nil Einne (talk) 13:06, 17 February 2009 (UTC)

History[edit]

What is the history between invention and adoption? Which came first, television sets or computer monitors? -- Beland (talk) 23:49, 8 June 2008 (UTC)

Use of the term "Shadow mask"[edit]

The term "Shadow mask" is technical jargon which is used without giving its definition. Anyone who knows what that term means is highly unlikely to be reading this article in the first place; as he or she will almost certainly know the basic workings of a cathode ray tube. The term is therefore essentially meaningless. In my opinion this is also more than a little likely to be perceived as arrogant and "showing off." There are concepts contained within the article which are based on an implicit understanding of this term. However, if I am correct that the term is essentially meaningless for most readers, that means that this problem can cause the article itself to be confusing and frustrating to read for almost all readers. A clear definition of this specialized jargon might therefore be helpful to understanding the article as a whole. —Preceding unsigned comment added by 69.127.200.152 (talk) 06:40, 30 July 2009 (UTC)

WP:SOFIXIT. Agreed, a quick definition would have been in order, but if you click on the link with your mouse, you rapidly get to the article that explains shadow masks at length.
I think a more serious problem with the article is the mish-mash between CRT as physics demonstration, oscilloscope CRTs, television CRTs, and computer monitor CRTs - we need to factor out these things. And the article has been needing references for TWO YEARS! --Wtshymanski (talk)

health risks->electromagnetic->inverse square law (Wrong?)[edit]

I think this section is incorrect. Electromagnetic dipole fields decrease in strength following an inverse cube of distance, not inverse square. I'll admit, they might be talking about another form of emission, it would be easier to tell, if this section included some references. (For example light intensity decreases with the square) 75.82.133.73 (talk) 01:56, 3 September 2009 (UTC)

Toxicity[edit]

I'd like some references here. I'm told that glasses dissolve very slowly - so even if there is lead in the glass, it's not going to leach out at any great rate. And just how toxic are the "phosphors", anyway? In the world of fluorescent lamps, the phosphors are fairly inert minerals - not good to eat, but harmless if they are dispersed. --Wtshymanski (talk) 21:18, 14 September 2009 (UTC)

Google is a wonderful thing. Still nothing on phosphors, though. --Wtshymanski (talk) 21:42, 14 September 2009 (UTC)
I think I added two extra references for the lead part of this section, but not the phosphors: they got undone in the recent edits. There follows a saved copy from the section as I left it from this old revision on 3 October. I now feel the 18.5% claim is perfectly plausible and no longer needs a citation, since [1] implies possible values up to 20%. I was mainly interested in wrapping the inline cites in completed {{cite web}} templates and having multiple cites (even for the same claim) to part-protect them from WP:Linkrot. Anyway they're in the wikicode if anyone wants to extract them. -84user (talk) 23:58, 5 October 2009 (UTC)

Toxicity[edit]

CRTs may contain toxic phosphors within the glass envelope. The glass in some modern CRTs is made from heavily leaded glass (amount varies from 1.08 pounds (0.49 kg) to 11.28 pounds (5.12 kg), depending on screen size[1]), which represent an environmental hazard on disposal.[2][3] The front panel (of CRTs in the United States) contains up to 18.5%[citation needed] of a mixture of strontium and barium oxide. Indirectly heated vacuum tubes (including CRTs) use barium compounds and other reactive materials in the construction of the cathode and getter assemblies; normally this material will be converted into oxides upon exposure to the air.

  1. ^ "Lead in Cathode Ray Tubes (CRTs) Information Sheet**" (PDF). Electronic Industries Alliance. 2001-11-30. p. 1. Retrieved 2009-09-29. 
  2. ^ Poon, C.S. (2008). "Management of CRT glass from discarded computer monitors and TV sets". Waste Management 28: 1499–1499. doi:10.1016/j.wasman.2008.06.001. Retrieved 2009-09-29. "number of studies have demonstrated that the neck and funnel glasses of CRT are hazardous wastes, while the panel glass exhibits little toxicity." 
  3. ^ Townsend, Timothy G.; Stephen Musson, Yong-Chul Jang, Il-Hyun Chung (December 1999). "Characterization of Lead Leachability from Cathode Ray Tubes Using the Toxicity Characteristic Leaching Procedure" (PDF). State University System of Florida. Retrieved 2009-09-29. "Leachable Lead concentration (mg/L) ... Matsushita <1.0 ... Phillips 1.0 ... Hitachi 13.6 403.6" 
Here ends the paragraph pasted from the 3 October 2009 old. -84user (talk) 23:58, 5 October 2009 (UTC)

CRT Resolution (bis)[edit]

A question with no answer ?

Knowing that a computer monitor CRT tube has a FIXED PATTERN of holes in the grille, how is it possible to change the resolution ? For example in my monitor I can choose 800 x 600 ; 1024 x 768 ; 1152 x 864 ; 1280 x 720 ... 1280 x 1064 and the tube always works !

--AXRL (talk) 18:38, 21 September 2010 (UTC)

OK see Talk:Cathode ray tube#CRT Resolution
--AXRL (talk) 18:51, 14 August 2011 (UTC)

Information on selling recyclable metals from CRT[edit]

Hello, Why is:

http://scrappingmetal.blogspot.com/2010/10/copper-in-crts-dont-just-cut-their.html
and 

http://scrappingmetal.blogspot.com/2010/11/copper-in-crts-follow-up.html

not a allowed resource regarding the harvesting of recyclable materials in CRTs? —Preceding unsigned comment added by 67.194.45.168 (talk) 21:11, 7 January 2011 (UTC)

See WP:RS and WP:SPS about Wikipedia's policies with regard to reliable sources and self-published sources. It is unlikely that this blog can meet the necessary criteria. Apart from falling short of Wikipedia requirements, the information in this blog encourages recycling "CRTs" without providing any explanation of the significant hazards associated with disassembling CRTs. There is potential for high-vacuum implosion (flying glass and materials), severe electric shock, and toxic poisoning. Any recommendation of do-it-yourself recycling of CRTs (or TVs or monitors) should make the safety issues clear, and this blog does not do so.
Example of poor wording: "All CRTs are made of leaded glass and (none the less) often thrown in the garbage. One way people make money from these material rich products is to rip them apart to harvest their insides." Rip apart a glass CRT tube to harvest its insides? Not a good idea for most people. This may not be what the text intended, but that's how it reads. Wildbear (talk) 21:39, 7 January 2011 (UTC)

Cadmium in CRTs[edit]

It may be true that manufacturers stopped using cadmium in CRTs in the 1970s; however, Wikipedia needs a reliable source reference if it is going to make that assertion. I did some searching and didn't find anything which adequately supports an assertion that cadmium is a non-issue with all but very old CRTs. I did find one reference, from an electronics demanufacturing company, which tends to indicate that the possible presence of cadmium should still be given consideration in the handling, disassembling, and disposal of CRTs.(ref) A quote from the referenced article: "There has been much less rigorous study of cadmium concentration levels, though, it is known that many fluorescent coatings of CRTs contain cadmium. One study providing TCLP analysis on CRTs for cadmium reported a concentration of 0.099 mg/L, with the US EPA TCLP threshold for cadmium being 1.0 mg/L." According to the report, the company conducted a study of toxins in the work area where CRTs are being disassembled. The quantities of cadmium found were low enough to pass safety requirements (as they should be if dust from the disassembly process is being adequately controlled), but not zero. Together with lead, cadmium appears to be a toxin of primary concern for this CRT demanufacturing company. Wildbear (talk) 06:33, 20 January 2011 (UTC)

Analog CRT software emulators[edit]

It would be nice to accumulate some information about the existing software emulators that aim to reproduce analog CRT artifacts; i.e. to more reliably display old games on modern displays. Some combination of high resolution+fps capture hardware and interpolating display software is also possible... 66.11.179.30 (talk) 03:47, 29 October 2011 (UTC)

Wayback Machine link[edit]

The link [2] in the references doesn't work, maybe someone should try if any of the links here works, I don't have the time to try them all now. --MrBurns (talk) 06:01, 31 March 2012 (UTC)


Error in Article[edit]

Something is inconsistent in the history part of the article. Western Electic made a commercial product in 1922 , yet the article also says that the first commercially made electronic television sets were manufactured by Telefunken in Germany 1934. Somebody who knows should fix that, or if it's true but makes sense a certain way, let me know of that as well. Either way let me know. –Dre-Velation (talk) 02:43, 9 April 2012 (UTC)§

This may not be an error, CRTs can also be used for other things than television (e.g. an oscilloscope) and in the articlkle it is not stated, that it was used for a television. --MrBurns (talk) 12:00, 9 April 2012 (UTC)

CRT vs LCD Power Usage[edit]

The article states, quite clearly, that many CRTs consume less power than most LCDs. As of when I am writing this I did not see any references to prove this. I don't need to add that this is contrary not only most manufacturers claims, we can all site a large number of their claims as well as a few benchmarks, but also that the article makes a passing reference to an infrequent number of LCD with LED backlights. Given the number of LCD manufactured with LED backlights today this sounds like it was written quite some time ago and may not be relevant anymore. If it is still relevant could someone please cite some reliable third party sources, id est: no long-running forum threads that anyone can respond to.

Thinkincode (talk) 00:05, 12 February 2013 (UTC)

I spotted this claim and tagged it before I saw your comment above. The claim even points out that the manufacturer's themselves claim the opposite. Manufacturers data are a valid source of references, so unless someone can produce a reliable and verifiable source for this extraordinary claim, deleted it will be. It should be noted that a CRT has three relatively high power heaters (one for each colour) for the cathodes in the tube. An LCD display with CCFL backlight lacks any such heaters, so something in the LCD display would have to consume a lot of power to match those three heaters (and it certainly isn't the CCFL backlight - although they get hot they do not reach anything remotely like red heat). Rememder: laptops contain CCFL tubes which contribute to only a small fraction of the power taken from the batteries. Using LED backlight doesn't produce a laptop with significantly greater running time. 86.166.71.0 (talk) 16:52, 26 February 2013 (UTC)
Very good points 86.166.71.0; I came here after seeing similarly outlandish edits on the Comparison_of_CRT,_LCD,_Plasma,_and_OLED#LCD page. The edits were made by‎ 81.90.254.28 on January 9, 2013. Since there is no truth to these type edits, I will be reverting them (and writing truthful text to the opposite) as soon as I finish writing this.
76.6.164.233 (talk) 22:36, 25 March 2013 (UTC)

Image of CRT or LCD?[edit]

Is this closeup of text on a CRT or LCD?

The image shown here has been removed from the article three times. Once by another editor, and was restored by yet another editor solely on the evidence of the caption (probably not unreasonable) I modified its caption to report that it was a slot aperture grille (slot mask) tube which I intially thought it was. However, it dawned on me that the phosphor pattern was wrong for such a tube and so I removed it again. Unfortunately, another editor has confused the 'phosphor' pattern with the slot mask tube, but has wrongly declared it to be a trinitron.

There are three principal types of colour CRT display. They are (in order of development), the shadow mask (also known as delta gun) tube; the aperture grille (also known as trinitron) and the slot mask (also known as slot aperture grille or even in line gun) tube. Each type is characterised by a specific pattern of the three colour phosphors that make up the screen. The pattern shown in the picture is not one of them.

The shadow mask uses circular shaped phosphors arranged in triangular triads (shown in top illustration in the article). The trinitron tube uses vertical stripes that are continuous from the bottom of the screen to the top. You may observe one or two horizontal lines on a real tube, but these are support wires stretched across the aperture grille to minimise the effect of vibration (shown in the lower illustration in the article complete with a support wire). The slot mask tube uses short phosphor rectangles (actually with rounded corners) arranged in groups of three. In the horizontal plane each group of phosphors is staggered from the previous one as this improves the structural integrity of the slot mask, though they are in line vertically. A good illustration of the layout is here (about halfway down the page) The image to the right is not of a CRT but of a LCD because each group of three 'phosphors' is in line, as they are in LCD displays (and hence are not phosphors as LCDs do not use phosphors). Further, the slot mask tube was never available in as fine a resolution as the shadow mask or the trinitron (and certainly not as fine as in the picture), which is why the latter two dominated the computer display market, with the slot mask tube remaining firmly in the television market where the relatively coarse resolution of the coloured phosphors was not an issue. The slot mask was liked by TV manufacturers because, unlike the other two CRT types, the slot mask required little in the way of setting up on the factory line beyond purity and static convergence of the three images, a simple task. The dynamic requirements were the same between different examples of the same tube type and size and could be magnetically 'printed' into the deflection coil assembly. Contrast the shadow mask tube which required a high degree of skill to successfully converge the three images and the trinitron which required a moderate skill. I B Wright (talk) 15:56, 20 March 2013 (UTC)

Mostly correct... but I don't see why you're saying the picture can't be of a Trinitron. (note cap, "Trinitron" is, or at least was, a trademark of Sony) The horizontal lines that appear to break up the vertical stripes of phosphors are the gaps between the horizontal scan lines. The one argument for "not a Trinitron" would be the sharp degree of cutoff around the pixels, but since we don't have anything to give us a sense of scale, we can't know how whether this is really pushing the sharpness limits of a well-converged Trinitron. By the way, there is only a tenuous relationship between dot pitch and usable display resolution. Consider that a monochrome CRT has no "dots" at all... Jeh (talk) 19:15, 20 March 2013 (UTC)
1. If they were the gaps between the scanning lines as you suggest, then from the text size and 'phosphor' pitch comensurate with a trinitron computer monitor tube, the display would be displaying around 1000 scanning lines (which would fit with the standard vertical resolution of 1024). As you note, the text is far too well defined to be displayed on any sensible sized (analogue) CRT display operating at that resolution (even given that the photograph is slightly out of focus). It is impossible to focus an electron beam that tightly due to the mutual repulsion of the electrons in the beam (at least with the 20 to 25 kV accelerating voltage normally encountered in computer displays).
2. Looking at black text on a white background on an LCD computer monitor, it appears almost exactly like the picture above (the font size would appear to be about the size of this text). There are no focussing problems on an inherently digital LCD display.
3. Looking at the same black text on a white background on the one remaining Trinitron monitor that we have left around here (one of our engineers will not give it up), the letters are nowhere near as well defined, the edges blurring across two or sometimes three stripe triads. Further, the gaps between the scanning lines are barely discernable (I presume because the beam size is similar in size to the line width and if so is larger than the width of three stripes). The monitor was operating at 1024x768 resolution, the nearest I could get to around 1000 'lines'.
4. The photograph appears slightly out of focus, but each letter seems to occupy an exact integral number of colour triads, just as it would on an LCD display. The 't' occupies exactly four and the 'o', exactly six. This is not a characteristic of analogue displays. The trinitron monitor from 3 above shows the letters occupying a definately non integral number of colour stripe triads, the 't' occupying slightly more than six, and the 'o' about nine and a half. It is difficult to be more exact than that because the letter edges are far from sharp - I am estimating from mid blurr! The fact that the blocks of the letters exactly occupy the vertically positioned colour triads betrays also that the image cannot be of slot mask tube for the same reason.
My only slight concern is that the gaps between the triads vertically are alternately wider and narrower. This might be explained on a CRT display by poor interlacing, but computer monitors are rarely, if ever, run in interlaced mode - but there is still that focussing problem. It could be that someone has manufactured a LCD panel with that pixel pattern. I guess we will never know. I remain convinced that it is a LCD display in the picture. Since the article contains a picture of the stripes on a trinitron display, do we really need another picture? I B Wright (talk) 12:48, 21 March 2013 (UTC)
The photo is not a Sony Trinitron TV. I still own a 35" CRT unit and there are three colour phosphor bars and then about half a bar width of blank / black / no phosphor. I couldn't get a good photo of it in macro mode on my camera as the digital auto focus would not settle on the jittery picture. The phosphor bars are vertically continuous and no breaks could be observed between them except for the electron scan illumination line gaps. 174.118.142.187 (talk) 22:10, 21 March 2013 (UTC)
You are correctly describing a Trinitron television CRT. The large gap between the three colur stripes is because the aperture grille used relatively wide sheet metal vertical obstructions in the aperture grille. Trinitron computer monitors used fine wires instead to get the desired fine resolution. Both types required support wires (and your 35" display probably has two). Sharply tapping a Trinitron computer monitor causes the wires to vibrate enough that false colour patterns will appear on the display. The mask in a television tube is much more rigid and you would have to hit it fairly hard to get any colour pattern. And following your cue, I could have added another reason that the picture is not a slot mask CRT.
5. Using fine wires in a slot mask tube would have made the cost prohibitive which is why that CRT type remained the preserve of television displays where the slot mask can simply be etched from sheet steel. I B Wright (talk) 13:23, 22 March 2013 (UTC)
Also rectangular dots with sharp corners did not make good monitors as the sharp corners of the dots caused visible "jags" on rendered objects, to the user. Round dot corners got away with much courser dot pitches. 174.118.142.187 (talk) 15:22, 22 March 2013 (UTC)
While you may be right, the reason for the rounded corners on CRT masks was more likely to be down to the impossiblility of producing sharp corners using conventional etching techniques as applied to shadow masks and slot masks of both types. Rounded corners or otherwise was not an issue with Trinitron masks. However, the colour dots on LCD displays appear to be rounded as well, possibly for the reason you give. I have tried to find a camera to photograph the LCD pixels, and eventually realised that one of my video cameras is able to focus right down to the lens surface. By under exposing the picture, I was able to determine, that the pixel corners (or more correctly ends) are indeed rounded. I B Wright (talk) 18:08, 22 March 2013 (UTC)
I have just been looking into this dot shape business, and was slowly coming to the conclusion that the image is probably from an LCD display. Mr Wright's reasoning of his 5 points are reasonable, though point 1 is a bit nebulous and 2 and 3 are subjective. Points 4 and 5 are the clinchers in my view.
I too was worried by the alternately differing gaps between the dot triads, and I am unaware of any CRT that would have that feature (and certainly cannot think of a reason for it). The problem was that I could not envisage why an LCD display would feature it either. I looked at several LCD displays through a good magnifying glass.
And then - I found it! The photograph is of an LCD display. Specifically, it is of the display used in the Apple iPad2 which features exactly that dot pattern. The two triads with the narrow gap between them seem to operate as a single 'pixel' for resolution purposes (and for all I know, may indeed be driven as a single pixel). With that discovery, I was able to easily reproduce the photograph above, except mine was in focus. 86.157.172.38 (talk) 17:15, 22 March 2013 (UTC)
Brilliantly spotted. You are dead right about the iPad2 display. I checked it on an original iPad2 and they do indeed have the pattern illustrated. I do not know if the later iPad2 exhibits the same pattern. I B Wright (talk) 18:08, 22 March 2013 (UTC)

────────────────────────────────────────────────────────────────────────────────────────────────────The fact that you have observed the colour pattern on an iPad2 display does not prove that the photograph is of an iPad2 and in any case probably falls under original research. I do not believe that someone uploaded an image of a LCD with intent to pass it off as a CRT (though it's not impossible). The uploader's editing history can often provide a clue in these matters. In this case Greg5030 is a prolific uploader of high quality images and a minor editor of articles. The lack of technically related pictures and the almost absent editing of technical articles suggests that if the picture is of a LCD, then it could be a good faith mistake. I am surprised that no one has taken the initiative to ask the photographer, and to that end I have placed a question on the photographer's talk page, inviting his contribution. DieSwartzPunkt (talk) 11:35, 24 March 2013 (UTC)

As the uploader, I have some responsibility to clarify this topic. Unfortunately, I cannot say with certainty whether the image is of a CRT or LCD - please let me explain. The image was taken in 2007 (4 years before introduction of the iPad 2 incidentally) to test the capability of a new macro lens. I was pleased at the ability of the lens to pick up the dot pattern shown in the image. The image was posted in 2011 based on my recollection that it was taken of a higher end ViewSonic CRT (model unknown) in use in 2007.

The ViewSonic was eventually replaced by an Envision G218a1, currently in use. In reviewing the controversy, it initially seemed unlikely that the Envision was in use in 2007. Several sources report that the Envision LCD monitor was indeed introduced in 2007 and this image could well be of it. Given the possibility that this may be an LCD image, I am removing it from the article. Greg5030 (talk) 16:37, 24 March 2013 (UTC)

This photo also appears modified and not authentic. Notice the black character dots do not line up with the colour mask dots in groups of three (RGB) dots. Some dots only blank out two of the three colour bars. Either the characters were a multicoloured font (not likely) or this photo has been modified from reality. The phosphor dots are too clear to be raster phosphor smear / bleed. 174.118.142.187 (talk) 02:53, 25 March 2013 (UTC)
The alignment issue you're seeing is characteristic of CRTs. There is nothing that requires or even makes possible the alignment of pixels in the signal with the RGB phosphor groups on the screen (this is true of all color CRT types: triad, Trinitron, and slot-mask). For that matter there is no requirement that the number of RGB groups has to match, or even come close, to the number of pixels in the input signal. The alignment between pixels in the input and phosphors on the screen will vary with each change in resolution and with every minor adjustment to raster size and position. And if it's an LCD, then the "some colors but not others" is characteristic of subpixel rendering, eg. ClearType. Jeh (talk) 03:01, 25 March 2013 (UTC)
I think that that is just another way of making one of the points that I made. In any case the original uploader has conceeded that he cannot be certain whether the image is of a CRT or a LCD. Viewsonic were early adopters of LCD technology and introduced their first LCD monitor in the 1990's. The position is complicated because they continued to sell CRT based monitors for the professional market and are still manufacturing such monitors today (March 2013), though they are accompanied by hefty professional price tags (but bargains are are always to be had on remaindered models). The relative pricing suggests that Greg5030's Viewsonic is more likely to be a LCD based monitor. His replacement Envision definitely is.
In view of the total absence of any evidence of malfeasance, we can only thank Greg5030 for at least taking the time and trouble to provide an image for the article. I note that he has uploaded a not inconsiderable number of high quality images for other articles in Wikipedia, and I can only request that he keeps up the good work. I B Wright (talk) 15:41, 25 March 2013 (UTC)

The Viewsonic was definitely a flat screen (not flat panel) CRT - the thing weighed 40-50 pounds. I believe that the photo was taken of the Viewsonic CRT, but don't recall when I replaced it with the Envision LCD. The Envision G218a1 LCD was new in the market at the time the photo was taken in 2007, so it is possible the image is of it. Greg5030 (talk) 16:58, 25 March 2013 (UTC)

A 40-50 pound monitor would be consistent with CRT technology. As I reported, Viewsonic have not ceased making CRT monitors. My concern was (and still is) that the phosphor pattern photographed is not consistent with any known phosphor pattern on a CRT, though would seem to be so for some LCD panels. In view of your own doubts, your decision that the image should not be in the article would seem be the right one as the validity cannot be verified. Your honesty in this is appreciated. I B Wright (talk) 12:01, 26 March 2013 (UTC)

Fluorescent screen necessary?[edit]

Aren't all tubes employing an electron beam in a strict sense CRTs? Not only magic eye tubes but also klystrons, traveling wave tubes, video camera tubes etc., even trochotrons and beam tetrodes? --Mkratz (talk) 14:28, 4 May 2013 (UTC)

Strictly yes. But the term 'cathode ray tube' is generally accepted as describing tubes specifically designed to process or display some sort of an image. 86.171.45.79 (talk) 17:22, 12 May 2013 (UTC)

Wikify Drive october 2013[edit]

part of October wikilink drive added links to lower sections of article, then removed tag.--Andys'edtits (talk) 08:38, 29 October 2013 (UTC)

Semi-protected edit request on 29 January 2014[edit]

Television and Cathode Ray Tube Application There are three patents on television-transmission of pictures and views (1928-30) and two patents on cathode ray tube (1935). GE research engineers at Schenectady N.Y. developed the liquid crystal display (LCD) instrument system based on the original patents of Lebanese Hasan Kamel Al-Sabbah. It is the world's largest high resolution LCD panel for aircraft. It presents information in color, and with twice the sharpness of a home TV screen. The display owes its high resolution to the large number of pixels (dots) that are activated to form an image on its screen, LCD images are normally black and green filters. Further development and modifications of the Al Sabbah cathode ray tube created new types of CRT used in electronic systems. The television would not have been discovered without this.


YOSS (talk) 14:37, 29 January 2014 (UTC)

Not done: please be more specific about what needs to be changed. I have no idea what edit you're requesting, how it fits into the article, or what sources you're citing to reference your request. Please clarify what you're looking to do. --ElHef (Meep?) 03:43, 31 January 2014 (UTC)
Appears to be a direct copy from this page at starsofscience.com. I am at a loss to understand several of the claims, like "LCD images are normally black and green filters" (true only for some types of LCD), or what a very recent high-res color LCD panel has to do with CRT development in the late 1920s. Jeh (talk) 04:59, 31 January 2014 (UTC)

Police Radar Guns are Cathode Ray Tubes[edit]

Why is there no information in this article that police radar guns are cathode ray tubes? 2602:306:C518:6C40:A131:D35B:C70E:37C0 (talk) 04:32, 7 June 2014 (UTC)

Probably because they are not. DieSwartzPunkt (talk) 09:31, 7 June 2014 (UTC)

No ghosting?[edit]

The "pros" section mentions there's no ghosting on CRTs. To the contrary, I know I've seen plenty of ghosting on CRTs. For instance, move your cursor around a black screen, or turn it off in a dark room and watch the last image slowly disappear.  Supuhstar *  19:35, 22 October 2014 (UTC)