Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [crt]

Anything related to Cathodic Ray Tubes (CRTs), i.e. specially built electronic vacuum tubes where an electron beam is focused and deflected on a phosphor-coated surface in order to display an image.

Anything related to Cathodic Ray Tubes (CRTs), i.e. specially built electronic vacuum tubes where an electron beam is focused and deflected on a phosphor-coated surface in order to display an image. Until about year 2000 CRTs were the electronic component used as screen in most TV sets and computer monitors, nowadays they are largely superseded by other technologies.

See also Wikipedia on CRTs.

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Why do CRTs have 3 electron guns?

I have been wondering about this for a while: Since the phosphor will remain excited for a certain period of time, I could imagine a single electron gun could target the red, green and blue phosphors sequentially instead having 3 parallel…
Thomas
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Why wasn't interlaced CRT scanning done back and forth?

I was studying the scanning of old CRT screens and the interlacing strategy for video, and I started wondering something. The raster scan process went top to bottom on odd lines, then back to top to raster the even lines. There is therefore a…
Stefano Borini
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How did old television screens with a light grey phosphor create the darker contrast parts of the display?

Many old television screens have a very prominent "light grey" color to the glass, I'm guessing from the phosphor, create darker areas if the effect of electrons make the phosphor glow? Is it an illusion due to contrast between the brightly lit and…
Zhro
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Espionage by CRT mirroring

Quite a few decades ago (either late 70's or early 80's), I vaguely remember seeing on TV a demonstration of, what would now be called, mirroring of a CRT screen, that was over 30 meters away, without the use of any cables, fibre optics, wires or…
Greenonline
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Why don't most electrons hit the anode in a cathode ray tube or electron gun?

In a cathode ray tube or electron gun, electrons liberated from the cathode by thermal emission accelerate towards a ring-shaped anode, from the potential difference between cathode and anode. If an electron is slightly off-centre, so nearer to one…
sqek
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Troubleshooting a faulty filter circuit in a PAL CRT display

I have an old CRT monitor (Phillips CM8833) which I am attempting to repair. When displaying a composite PAL signal, it only shows a black and white image, but it is still able to display RGB signals correctly. The composite signal is filtered into…
Kaz
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Image position and size controls vs beam alignment in a color CRT

If you look at a the shadow mask of a color CRT, you can have a pattern like this: Most TVs were purely analog and had knobs to move the picture horizontally and vertically. How does the green gun stay aligned with the green phosphor in an analog…
Thomas
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Fixing old CRT oscilloscopes... what to look for first?

I've been amassing a pretty large collection of these old scopes, and it's about time I got to trying to fix them. About half of the ones I run across and buy don't have traces. I don't need to get them in perfect working order again, but I'd at…
Jared Cravens
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Why do CRT TVs need a HSYNC pulse in signal?

Could someone, please, explain how old CRT TVs reacted to input signal, specifically to VSYNC and HSYNC pulses? Do these pulses control the electron beam? For instance, if signal would consist only of VSYNC pulses, would the beam stay at its initial…
Scylurus
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Component requires specific voltage and current but the math doesn't add up

I'm trying to get an old soviet era cathode ray tube working. On the data sheet it says the heating element needs between 5.7V and 6.9V, and between 0.54A and 0.66A, but I've measured the resistance of the heating element and it reads as 1.5 ohms.…
Lethe563
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TV screen in still photo: Why are there dark, blackish bands?

I was trying to capture the scanning process of a CRT TV screen in a photo. It gave me these dark, broad bands, shown below: Fig. 1 a,b,c I'm trying to understand the cause for this banding. However, I couldn't understand it clearly in very similar…
Always Confused
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How to understand a complex diode-resistor function generator circuit?

I'm reverse-engineering a CRT anti-pincushion circuit and it uses a complex diode-resistor circuit to approximate the function X-k×X×Y², where X and Y are the deflection voltages. My question is if there's any way to understand this circuit…
Ken Shirriff
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Understanding a Single Transistor Flyback Transformer Driver?

I've been watching a few analyses of CRT flyback transformer drivers and can't understand why the transistor would shut off. To my naive perspective, it appears that the transistor should never shut off due to the positive DC voltage applied…
Sarah Szabo
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What purpose are the transistors serving in this CRT oscilloscope circuit?

So this is part of a CRT oscilloscope diagram, and I don't understand the function of the transistors on the bottom right, Q18 and Q19. Their outputs (41 and 42, crossing through the dotted line) go directly to the horizontal deflection plates.…
Jared Cravens
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How CRT allows use of ligh-guns or pens etc?

While reading about CRT on Wikipedia, an information (CRT Allows the use of light guns/pens; https://en.wikipedia.org/wiki/Cathode_ray_tube#Advantages_and_disadvantages) suddenly triggered a a vast lots of memories. Around early 1990's when I was a…
Always Confused
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