How does the colour gun in the T.v work?

Question

In answers to my question I got to know from 'oddball' and 'realist 2006' (to whom I am thankful) that the colour guns fire on the phosphorated plates on the CRT screen plate to show different colours. Please tell me how these three guns work. Thank you.

My question still remains, O my new electronics teacher realist 2006. Lets enter into even deeper waters. How do the colour guns emit whatever they do? Whatever you told was there in our 7th standard English textbook. O my teacher help.

Answer 1

As was explained earlier there are three guns in color CRT (red, green and blue) These guns are all identical with the only difference being physically where they are positioned. The are located side-by-side at the end of the neck (the far end of the tube away from the face). Each gun has a cathode, a grid, and a heater. Each gun emits a streams of high speed electrons from the heating of the cathode inside a vacuum tube, and the grid is used to control how large or small the beam of electron is. On the face of the CRT (anode) a high positive voltage is applied (around 32,000 volts). You can feel the affect of this high voltage if you place your arm next to the tube and you feel the hairs rise. The released electrons (negative) form a beam within the tube drawn towards the positive charge. If nothing else was applied you would see three very closely dots on the face. The three separate beams would take the closest path to the face of the tube, and just before it got there it would find the shadow mask. This is very much like a slotted screen. It lets each stream of electrons go through a small hole and since each gun is physically in a different starting place each stream will hit in a different part of the face. The face has three different types of phosphor that when excited (hit) by the electrons they each glow a different color. So the gun that is on the right will hit slightly to the left on the face and it will hit a red phosphor. the center gun will hit the center green and left will hit the right blue. But we can vary the direction of this beam either by a magnetic or electric field and we can force them to trace over the inside surface of the phosphorescent screen (anode). So over the neck of the tube there is a deflection yoke. There are two separate windings, one is to control the beam in the up/down direction this is the vertical windings, and the other one controls the left/right this is the horizontal windings. With the proper waveforms applied to the deflection yoke and the same voltage applied to the cathode you would see a white screen. The vertical section of the yoke would slowly direct the the beam of electrons from the top of the screen to the bottom, while the horizontal section would rapidly scan left to right hitting each individual pixel. Now all you do is modulate the voltage on the grid with signal that represents the picture you want to paint (scan). As you change the bias for each gun it varies the intensity of the that guns beam and that will vary how bright the associated phosphor segment glows. For instance if you wanted to watch a landscape. The red and the green might be nearly turned off while it was scanning the top and the blue would be on hard to show the blue sky. As the scanning got down towards the center you may see the red turn on and the blue turn off to show the red peaks of an Arizona mountain. And as it goes to the bottom the red may turn off and the green turn on to show the trees and grass. There are also focus plates and G2 plates, etc. I hope this helps a little. Fire your professor and check out the link listed below.

Answer 2

I will try to keep it brief , start in the TV studio with a colour camera, thru coloured filters inside the camera the scene being televised is split into separate colour signals corresponding to the basic colours, these colours signals or channels are all transmitted as separate channels , ( the colour signals are transmitted together but are phase related , getting into deep water here though ) meanwhile over to your house with the CTV in the lounge room , your CTV has in its circuitry a phase detector that picks out and separates the colour channels which are then applied to the three guns inside the CRT which then as described in an earlier answer light up the phosphor dots on the screen , thus your 3 guns are following the three guns in the camera in the studio . Phew ! I think that might do it , I do hope it makes some kind of sense to you . Ok then my electronics pupil, in your 7th grade text book you must have also read about the principles of Thermionic Emission , the old vacuum tubes work on the same principle but no need for me to dwell on that as you will already know !!