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.

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44 views

How do I take proper voltage measurements on device with multiple voltage sources sharing the same ground?

If you recognize me, it's in reference to CRT scopes again. I don't understand how to take proper voltage readings on the circuits. An example is the heating element in the CRT. When I hook both test ...
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2answers
798 views

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 ...
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48 views

Amplifier transistors not receiving change in base voltage… do I look forwards or backwards?

So I'm working on diagnosing a CRT scope that isn't responding to the horizontal controls; the trace is off screen. The two X plates are each being driven by 2 transistors in line. One X plate has ...
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5answers
16k views

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 ...
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2answers
61 views

Does the electron beam go towards the deflection plate with the higher, or the lower voltage?

So I've started tearing apart an old CRT scope to learn everything about them, and right now looking at the voltages on the deflection plates. When the trace goes down, my vertical plates read (a)193v,...
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60 views

How can chassis ground be used for voltage measurements in a device with components of differing voltages?

The manual for my HV probe tells me to connect my ground clip to the chassis. I can see how this would be good advice for say a 12V car, because the chassis is made the ground and every component uses ...
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2answers
933 views

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 ...
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1answer
70 views

Have CRTs ever used a different raking pattern? [closed]

CRTs traditionally scan top-left to bottom-right, in a row-major raking pattern, and appear to have done so since the 1930s. This is a little unusual though, as standard mathematical orientations have ...
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45 views

CRT automatic focusing?

Has anyone ever heard of a circuit to automatically adjust the focusing anode on an electrostatically deflected CRT? Is there any way to even detect optimum focus other than by looking at the tube ...
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1answer
69 views

What receiver is appropriate for studying compromising emanations in 2019?

I'm currently reading the Cambridge Technical Report Number 577, Compromising emanations: eavesdropping risks of computer displays, by Markus G. Kuhn and published in Dec 2003. In the paper, Kuhn uses ...
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6answers
4k views

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 ...
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1answer
125 views

Why doesn’t the focusing anode diverge the electron beam again?

Consider this diagram of a focusing anode in a CRT: Question: Why does the electron beam not diverge again when it enters the focusing anode (or accelerating anode) while leaving the pre-accelerating ...
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84 views

High voltage output from CCFL backlight transformer?

I have an old television inverter board I've been meaning to turn into a power supply for a plate-deflected oscilloscope CRT *. I'm not really an expert on transformers, however, and though I have ...
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3answers
204 views

What the heck is a “radiator plate” in a CRT based oscilloscope?

I managed to pickup a used BK Precision 1474 oscilloscope for $10 and figured it would be a good gamble for the price, I powered it up and the CRT had no spot. I did some hunting and managed to find ...
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1answer
119 views

Where is Anode Cap connected in CRT?

On the expanding area of glass? Is inside of expanding area metal?
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1answer
308 views

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 ...
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2answers
204 views

TV flyback transformer replacement without RC snubber?

I need to replace the flyback transformer on my Atari SC1224 CRT monitor. The flyback I removed from this monitor has a model number of Kf4825G, and has an RC snubber attached to it, which does not ...
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3answers
252 views

Coloured coating within CRT

I have noticed that a lot of CRTs have a coloured coating inside of them that would appear to have practical purpose other than maybe protecting the aquadag. Paints and plastics tend to be avoided in ...
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1answer
103 views

Where can I get a display screen with 30 Hz or less refresh rate? [closed]

I am experimenting with a camera recording a display screen. Based on what I have read - camera recording a screen will have flicker if the refresh rate and frame rates are not synced. My mobile ...
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1answer
243 views

Could black-and-white CRT-based television sets be damaged by holding a magnet to the screen?

I know that it is possible to cause permanent (or at very least lasting) damage to some color CRT-based TV set by holding a magnet close to the screen and distorting the picture. SPECIFICALLY: it is ...
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2answers
315 views

Old portable CRT TV power socket

I found a nice old portable CRT TV (model "tele star 4004") without a power cable. The power socket on the back has six pins: I've never seen such a design before (and google is coming up short). ...
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4k views

CRT TV NOT TURNING ON [closed]

I'm a beginner in electronics repairing and I need help troubleshooting a tv which doesn't turt on, neither the power LED lights up. The board is a cheap chinese (check the attached image). When I ...
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0answers
162 views

Replace filtering(?) capacitor on CRT deflection Board

I am doing partial recap on CRT monitor Sony PVM 20m2e. (monitor was working, but RGB lines at the top of screen which should be hidden were visible and geometry is not top notch) I desoldered C584 ...
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8answers
4k views

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 ...
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2answers
3k views

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 ...
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6answers
9k views

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 ...
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1answer
1k views

EGA display converting to VGA - screen's shaking

I've recently tried to make conversion from EGA (probably, couldn't get scope to verify) to VGA to replace an old factory CRT monitor to LCD. Screen displays fine but it appears to shake vertically ...
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2answers
481 views

Purpose of low voltage pins on TV power switch

I am building an arcade machine, using a CRT television. I am wishing to replace the television's front panel power switch with a toggle switch on the outside of the cabinet but am concerned by two ...
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352 views

Oscilloscope only using middle of CRT

I recently picked up a faulty Hitachi V-1150 'scope and after fixing a problem in the power supply it now starts up. However, it only uses the very middle of the screen vertically, and goes wild if I ...
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1answer
5k views

How does a CRT television flyback really operate

I am surprised that no-one has already asked this question (unless I've missed it), because it affects all those DIY guys dealing with high voltage. I have spent hours on the web to find how to use a ...
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2answers
213 views

Horizontal overscan on NTSC

How much horizontal overscan is there on a typical NTSC CRT television set? Vertical overscan, there are nominally 240 scan lines per field, of which you can reasonably count on having slightly more ...
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1answer
76 views

Cost of early color monitor versus TV [closed]

Back in the seventies and eighties, an important design choice for a desktop computer was whether to use a television or a dedicated monitor for display. A monitor could give better resolution; on the ...
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2answers
1k views

What advantages do CRTs still have over more modern display technologies? [closed]

Are there any uses for Cathode Ray Tubes in modern world. TVs and Monitors were first, then Oscilloscopes, I am not sure about Radar but are there any applications which will only work with CRTs or ...
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1answer
826 views

Melted CRT anode cap [closed]

I'm sorry it may not be the right place to post this but i'm not familiar with CRTs and old electronics so... here's my question: This crt made a loud noise so i opened it and found this when i tried ...
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6answers
3k views

How to function a TV electron gun for experiments [closed]

right to the point, I'm study physics and I want to do some experiments like q/m, oscilloscope, etc and I needed an electron gun. I had an old crt TV and I took out it's electron gun and vacuum tube ...
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1answer
437 views

5.5" portable CRT television with several black lines

I have this monochromatic chinese television largely manufactured in the past decade, marketed under several brands (Coby, Curtis, Precision, etc). This one in particular have a external AC DC ...
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2answers
1k views

My CRT Television had blue patches when turned ON?

My CRT Television had blue patches on screen when turned ON, what could be possible reason? After moving speaker magnet(BIG) around the screen, it was possible to pull the blue patches from ...
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4answers
1k views

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,...
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1answer
431 views

Purpose of copper coils encountered in TV

I was recently working on an old TV similar to the one in this video here. I began to open it and encountered a part on the TV which I have never came across, I believe it functions similarly to a ...
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1answer
2k views

are there 2 basic-type of CRT deflection-yoke coil?

Deflection coil inside TV, deflects the electron-beam, using magnetic field. However this-deflection is not as simple as electrostatic deflection. What is the actual mechanism behind working of ...
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4answers
2k views

Television flyback transformer: does it do 2 tasks ie. horizontal flyback and E.H.T.?

Television EHT transformer is also called Flyback-transformer? E.H.T. (Extra High Tension) generates the cathode ray; ie. acts in same direction of the main pathway of running electrons, i.e. "...
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3answers
811 views

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 ...
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1answer
10k views

What is the function of “Picture tube charger”?

There is a bizzare device called picture tube charger or CRT-Charger. Here I attach the some diagrams of it from a circuit-book. Now, what is its function? what changes it create inside the CRT? ...
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2answers
8k views

How does television EHT Transformer (that connected to anode) operates in DC?

A step-up transformer takes AC input and gives AC output. Then, how does the E.H.T (Extra high-tension transformer) create 18 KiloVolt or more, DC-output on the CRT (enough to shot the electrons on ...
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2answers
614 views

Composite video (one channel) to RF input of an old CRT TV [closed]

I want to convert HDMI signal to RF signal(antenna input) for my old TV (AV is input broken). If I connect Composite video (one channel) to RF input of an old CRT TV, does it work? Audio to TV is not ...
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1answer
835 views

How dangerous are portable CRT televisions?

I want to use an old portable CRT for a project, but I don't know how dangerous the capacitors are, and if they'd be as bad as the ones inside a normal CRT. It takes in 12v dc via adapter, or 8 D ...
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3answers
157 views

is there any impact of Electron's spin in CRT?

fact-1. Electron's (or any-other particles) magnetic behavior depends upon mass, charge and spin. fact-2. All electrons are not the same. Though all electron have the same mass and charge; an ...
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1answer
1k views

Should I open the CRT monitor?

I have a CRT monitor which I was looking to open to acquire CRT for a project I am working on. I know its probably not the best idea but I have taken some safety measures. They are as follows: 1) ...
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1answer
2k views

Generating Sync Signals [closed]

Normally any sort of video signal received by means of RF,contains a Hsync and Vsync component for instructing the electron beam.My question is ,how does the television do this using external sync ...
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1answer
17k views

What is Front Porch and Back Porch of a video signal in CRT display? [duplicate]

What is a Front Porch used for? What is a Back Porch used for? What does it mean by active video?