Talk:Cathode-ray tube

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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

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.

I have no idea when this was added, but I felt some sort of response was in order. The brightness of the displayed picture is controlled by varying the beam current using a control grid in the electron gun (as you note) in the same way as the vacuum tube.
On the face of it, displaying a predominantly black picture would require a lower average beam current than a predominantly white one. Unfortunately, there is an issue which makes the claim false. The EHT supply for a colour tube has to be stabilised. Since they exclusively use shunt stabilisation, any current (and hence power) not required by the CRT is absorbed by the stabiliser, so that the EHT current (being the tube beam current plus the stabiliser current) remains practically constant. Thus displaying a complete black picture requires the same power as a complete white picture and no energy saving results. I suspect Blackle calculated their claimed savings on the tube beam current alone.
An LCD display also will have no savings because the backlight operates at a constant output giving no energy saving when the black pixels simply block the light. 86.149.142.3 (talk) 17:07, 25 June 2018 (UTC)

Advantages and Disadvantages Section[edit]

I removed the Advantages and Disadvantages section as it was clearly non-neutral (to such an extent which I doubt anything short of a complete rewrite would fix the problem) and had been flagged as non-neutral and not fixed since 2012. I have no special knowledge about this subject, but a appropriately balanced advantages and disadvantages section could be a good thing to include in this article. --Nogburt (talk) 05:21, 11 September 2016 (UTC)

While neutrality issues may have their importance, I find this article lacking information on real-life performance of CRTs when compared to flat panels (LCDs, etc). Anybody with reasonably healthy eyes and no bias, will instantly recognize the terrible color rendition, edge rendition and moving image rendition of most "modern" displays when the signal does not correspond to the native resolution of those modern displays, for example, when viewing a standard ("low definition") cable signal or DVD on an LCD with higher rated resolution: the CRT image will be slightly blurred perhaps, but EVERY OTHER aspect of the perceived quality of the image will still be much better in the old and relegated CRT. The fact that modern displays require a different from "standard def" signals is seldom recognized. That is the reason why I keep my old Toshiba 32" CRT TV bought in 1997: it simply looks much better than ANY modern display when looking standard definition cable-TV or DVDs, except perhaps that the Channel logotype is slightly less defined in the CRT (everything else in the image is MUCH better!). Amclaussen. — Preceding unsigned comment added by 201.141.2.236 (talk) 17:10, 11 January 2017 (UTC)
The color palette on 2K LCD TV's is/was limited, in some cases as bad as the equivalent of 6 bits per color using computer monitor terminology. OLED TVs were introduced with a much better color palette, and 4K LCD TV's also increased color palette in order to stay reasonably competitive with the OLED TVs. Despite the shadow mask, since a bean can move across part of a "native" pixel, or change intensity "mid-pixel", the native resolution of a CRT is related to the size of the individual phosphors on a screen, so CRTs, especially computer monitors, are able to handle a wide variety of resolutions. In the case of rear projection CRT TV's that use 3 CRTs, (one red, one blue, one green) there is no shadow mask, but these require adjusting convergence about twice a year. As for standard definition display, the main issue is that "pixel" aspect ratio is 8/9, which is a problem for a digital display, but not an issue for a CRT since it can just change the beam effective thickness and sweep rate. CRT based rear projection HDTV's support both 480p and 1080i as "native" modes. Rcgldr (talk) 06:33, 26 July 2018 (UTC)

I have restrained myself from opening an account on Wikipedia for ages, but I couldn't control myself on his one. I have read that section before and read nothing that could be considered non-neutral. In fact, it was very neutral indeed, based on cold scientific facts. The user that flagged it as non-neutral, did he changed it? Did he tell why he flagged it? What about you, what did you consider as non-neutral and why didn't you fixed it in the first place? It's obvious that LCD displays make sense for most users and applications. But for professionals in several fields (like graphic design, cinema or photography), as for more demanding users, is there a match for the best CRT monitors and TV's? The user that replied to your post says it all. Or maybe not. There was more in the section you deleted. — Preceding unsigned comment added by Dpmaf (talkcontribs) 12:50, 22 October 2017 (UTC)

Last CRT computer monitors made?[edit]

I think the last CRT based computer monitors were made by Sun / Oracle, and these probably were continued to be made after CRT based TVs were no longer made. I haven't been able to find the last year that Sun / Oracle made CRT based monitors. These were popular for graphics workstations because the LCD monitors at the time didn't have good color depth, some of which were not much better than the equivalent of 6 bits per color. VGA computer monitor cards supported up to 10 bits per color (30 bit color mode), although it wasn't that popular other than graphics environments. Some computer games, such at Tomb Raider Angel of Darkness (2003) support 30 bit color mode. Rcgldr (talk) 06:47, 26 July 2018 (UTC)

A Commons file used on this page has been nominated for deletion[edit]

The following Wikimedia Commons file used on this page has been nominated for deletion:

Participate in the deletion discussion at the nomination page. —Community Tech bot (talk) 04:36, 16 October 2018 (UTC)

False alarm - the nomination was vandalism on Commons. Maybe I've saved you a mouse click ? --Wtshymanski (talk)

Williams tube[edit]

IBM 701 has a link to CRT, but that section is gone, and in fact the use of cathode-ray tubes as memory seems to be completely deleted from this article. If nobody else is interested, I'll try and pull that from the history.--Prosfilaes (talk) 23:19, 8 May 2019 (UTC)

It was there, but buried under oscillscope lore. I moved it. Willams tube has a main article. --Wtshymanski (talk) 17:33, 13 May 2019 (UTC)

Convergence contradiction[edit]

all three hit the same spot (and nominally pass through the same hole or slot) on the shadow mask

However, it was previously established that the purpose of the mask is to stop the three beams from hitting the same spot, passing through separate holes to their respective phosphors. OrangeDog (τ • ε) 15:56, 5 August 2019 (UTC)