What the hell is a CRT Projector?

Mad Mr H

Well-known Member
Im not sure but I have heard of 2 types of projector

1. CRT Projector

2. Cinema projector - of course this uses a film roll



There are of course other projectors - like a tank - that projects missiles but thats just silly talk.

oh!
I did once hear of someone putting a bulb in theirs, I presume this helped them see inside it, cant think of any other use.
 

Peter Parker

Distinguished Member
MadMrH said:
oh!
I did once hear of someone putting a bulb in theirs, I presume this helped them see inside it, cant think of any other use.

That's a film projector like at the cinema. :)

CRT = Cathode Ray Tube, much like your big old tv at home in case that's what the OP meant.

Gary.
 

Thunder

Active Member
So you'd like a 12" now Gordon? :D Have you seen one of these in action?
 

fortean

Active Member
A CRT projector is unique in that it projects CRT's (Carbonised Radioactive Teleromes), usually on to a black screen. The screen of course looks white because it reflects all frequencies of the visible light spectrum. As everyone knows a surface of a particular colour can not reflect light of the same colour.

When these CRT's hit the screen they change the density of the molecules at the point of impact. As the density of a molecule increases it traps more and more light until it is at almost infinite density at which point enough light is trapped to make it appear black. By varying the amount and type of CRT's at any given point an image can be created on the screen.

One of the dangers of early projectors was that when they were left on without a source signal they bombarded the screen with massive amounts of CRT's to create a black image. This resulted, after a few hours, in the screen achieving critical mass and collapsing in to a black hole. This black hole, ex screen, would then fall through the floor and continue until it reached the centre of the planet. Luckily a screen would reduce to less than a nanometre in diameter and so the damage to the floor, and the planet, was insignificant. To get around this problem modern CRT projectors produce a blue screen when there is no source signal present.
 

Welwynnick

Distinguished Member
:D
12" CRT - bet they didn't sell very many of those!
287 lbs, but still "only" 120 MHz RGB bandwidth - not exactly the ultimate.

Nick
 

Ed Selley

AVF Reviewer
fortean said:
One of the dangers of early projectors was that when they were left on without a source signal they bombarded the screen with massive amounts of CRT's to create a black image. This resulted, after a few hours, in the screen achieving critical mass and collapsing in to a black hole. This black hole, ex screen, would then fall through the floor and continue until it reached the centre of the planet. Luckily a screen would reduce to less than a nanometre in diameter and so the damage to the floor, and the planet, was insignificant. To get around this problem modern CRT projectors produce a blue screen when there is no source signal present.

In our case, we kept the output strong and created a stable quantum singularity that has powered the office for the last six years as well as allowing me to go on holiday to Alpha Centauri this year.
 

Thunder

Active Member
Gordon @ Convergent AV said:
Hi Thunder,

I've done a couple of them.....the pcture doesn't do it justice....it's HUGE....Think of each tube as being like a portable TV and you get an idea of the size.

Gordon

Whats the PQ like mate?
 

Gordon @ Convergent AV

Distinguished Member
AVForums Sponsor
One was run from a Faroudja3000 the other from a Faroudja 5000 an HD Leeza and now a Lumagen HDP Pro. Not seen it with the Pro...Looked nice with HD and the Leeza. With the Faroudja's they were both BRIGHT. I liked them in a clunky sort of way.

The current verson is 912 I think. Never seen one of those.

Gordon
 

Nic Rhodes

Distinguished Member
fortean said:
A CRT projector is unique in that it projects CRT's (Carbonised Radioactive Teleromes), usually on to a black screen. The screen of course looks white because it reflects all frequencies of the visible light spectrum. As everyone knows a surface of a particular colour can not reflect light of the same colour.

When these CRT's hit the screen they change the density of the molecules at the point of impact. As the density of a molecule increases it traps more and more light until it is at almost infinite density at which point enough light is trapped to make it appear black. By varying the amount and type of CRT's at any given point an image can be created on the screen.

One of the dangers of early projectors was that when they were left on without a source signal they bombarded the screen with massive amounts of CRT's to create a black image. This resulted, after a few hours, in the screen achieving critical mass and collapsing in to a black hole. This black hole, ex screen, would then fall through the floor and continue until it reached the centre of the planet. Luckily a screen would reduce to less than a nanometre in diameter and so the damage to the floor, and the planet, was insignificant. To get around this problem modern CRT projectors produce a blue screen when there is no source signal present.

Post of the day :clap: :)
 

Siamese Cat

Active Member
fortean said:
A CRT projector is unique in that it projects CRT's (Carbonised Radioactive Teleromes), usually on to a black screen. The screen of course looks white because it reflects all frequencies of the visible light spectrum. As everyone knows a surface of a particular colour can not reflect light of the same colour.

When these CRT's hit the screen they change the density of the molecules at the point of impact. As the density of a molecule increases it traps more and more light until it is at almost infinite density at which point enough light is trapped to make it appear black. By varying the amount and type of CRT's at any given point an image can be created on the screen.

One of the dangers of early projectors was that when they were left on without a source signal they bombarded the screen with massive amounts of CRT's to create a black image. This resulted, after a few hours, in the screen achieving critical mass and collapsing in to a black hole. This black hole, ex screen, would then fall through the floor and continue until it reached the centre of the planet. Luckily a screen would reduce to less than a nanometre in diameter and so the damage to the floor, and the planet, was insignificant. To get around this problem modern CRT projectors produce a blue screen when there is no source signal present.[

I'm not sure that they do stop at the centre of the earth. Taking into account momentum and of course the gravity of a black hole you get M2 + G = C where M is momentum, G is gravity and C, of course, is the speed of light. This tells you that the black hole will go straight through the Earth and go on out into space - in a straight line.
Relevant to this is an insurance claim going on in New Zealand where a house was destroyed by a mysterious projectile emanating from the centre of the Earth. Drawing a straight line through the centre brings you out in Chorley so it seems likely that the projectile was your screen. In order to be certain we need to know the date and exact time of the collapse of your screen into it's nucleonic state. Should it be your screen the insurance company will be looking to you for recompense.
 

Peter Parker

Distinguished Member
welwynnick said:
Ho ho ho.
And what kind of contrast do you get from one of those?
Nick

If you mean from a cineam projector, then generaly maybe up to around 2000:1. Apparently the film or Hi Def cameras used are only capable of 1000:1, so if true, any CR over that is achieved via processing of the film stock for better black and higher CR, though that doesn't create any more image detail.

Gary.
 

johann1979

Banned
This is probably the dumbest and most uninteresting question anyone has asked, but I am completely new to all this and i have just been doing a little bit reading so far. I am in the market for a new projector and have been looking at LCD and DLP projectors until now...

Can somebody explain to me whether a CRT projector also makes use of lamps like LCD and DLP?

Sorry if this question seems really stupid... ;)
 

Peter Parker

Distinguished Member
No, it uses an electron beam and phosphor which is stimulated to one degree or another and will glow accordingly. Phosphors vary in performance and are not all the same.

Anyone know if the gamut range of phosphours has improved in the last 50 years?

Gary.
 

Thunder

Active Member
No they use Cathode Ray Tubes like a conventional television set. The projector has three of these, one each for red, green and blue. The light from the tube face is used to project the image through three lenses and the three images are converged onto a screen to provide a full colour image :thumbsup: No bulbs = superior contrast + three dimensional image and a much longer life span :smashin:
 

LV426

Administrator
Staff member
No bulbs = superior contrast + three dimensional image and a much longer life span

3-d image? I doubt it. Otherwise, true.

Plus, drifting convergence, inability to move the projector without having to repeat the prolonged setup routine, inability to use anything but a fixed screen, tubes that do deteriorate over time (phosphor burn), refresh flicker, rainbows (and no, I'm not getting confused with DLP)...........
 

alexs2

Distinguished Member
Thunder said:
No they use Cathode Ray Tubes like a conventional television set. The projector has three of these, one each for red, green and blue. The light from the tube face is used to project the image through three lenses and the three images are converged onto a screen to provide a full colour image :thumbsup: No bulbs = superior contrast + three dimensional image and a much longer life span :smashin:

Not sure about the longer life span either,as the tubes tend to be driven pretty hard,although maybe not as hard as those in RPTVs....maybe someone like Gordon or Roland could give an idea of average lifespan?
 

Thunder

Active Member
Well I know several people that use non fixed screens. I wouldnt say that 15000 hours is a short lifespan. Mines been up for nearly a year and hasnt needed any convergence adjustment yet. They definately give a more three dimensional image in my and most other eyes. The only one I will conceed is size and difficulty in set up. Otherwise its no contest :)
 

alexs2

Distinguished Member
Thunder said:
Well I know several people that use non fixed screens. I wouldnt say that 15000 hours is a short lifespan. Mines been up for nearly a year and hasnt needed any convergence adjustment yet. They definately give a more three dimensional image in my and most other eyes. The only one I will conceed is size and difficulty in set up. Otherwise its no contest :)

I do agree about the image and contrast,plus the lack of rainbows,but the other drawbacks like tube burn and replacement costs are irritating....I do of course speak from the viewpoint of CRT based RPTVs
 

Thunder

Active Member
15000 hours! They don't really suffer from screen burn any more than a conventional television set. I play x-box on mine regularly with no detrimental effects :)
 

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