Talk:Cathode ray tube
From Academic Kids
New comments at the bottom please
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:
- http://commons.wikimedia.org/wiki/Image:CRT_color
- http://commons.wikimedia.org/wiki/Image:CRT_monochrome
- http://commons.wikimedia.org/wiki/Image:CRT_oscilloscope
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.
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)
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 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)
