Talk:Cathode-ray tube: Difference between revisions

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New comments at the bottom please

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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:

phosphor metamerism
color gamut

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:

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

> "(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)[reply]

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

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

Fair enough, I've removed the tag. --h2g2bob 13:25, 6 December 2006 (UTC)[reply]

Thanks! Atlant 13:35, 6 December 2006 (UTC)[reply]

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.

@@ Line 134: / Line 134: @@
 :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.