Talk:Cathode-ray tube

New comments at the bottom please

Older Comments

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

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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?

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To do:

• phosphor metamerism
• color gamut

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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

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:

• http://commons.wikimedia.org/wiki/Image:CRT_color.png
• http://commons.wikimedia.org/wiki/Image:CRT_monochrome.png
• http://commons.wikimedia.org/wiki/Image:CRT_oscilloscope.png

User:Peo, from danish Wikipedia - again!

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

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"...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)

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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

> "(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

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 2^nd 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)

Faraday???

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

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 (talk • contribs)

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

Disposal of CRTs

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 (talk • contribs) .

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

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 (talk • contribs) .

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)

High Definition CRTs

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

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

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)

Radiation

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?

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)

Health Danger Vagueness

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)

Failed GA

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

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

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

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)

CRT Resolution (bis)

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

axrl0016@gmail.com Thank you for responding.

Thanks, Mario —Preceding unsigned comment added by 83.186.15.67 (talk) 23:45, 22 March 2008 (UTC)