Does a crt need ac supply or dc one?
In an lcd there's an inverter to generate an ac signal for varying the power supply to different pixels on a monitor in order to produce different colour effects,does...
Most CRT displays sold for use in the US & Canada (and probably everywhere else for that matter) require AC. This is because AC is the most popular mode as it is easily stepped up for long distance transmission and down for use in commercial, industrial and residential uses, by your local utility. Additionally, AC is affected by losses or resistance differently than its DC counterpart. All of these (and more) reasons reduce the cost of providing electricity to buildings and homes.
If the utility generated and delivered DC, then electrical devices would be set up for DC connections. Since there is 60 Hertz AC at your outlet, the CRT makes use of it, and converts it to whatever the internal requirements are. Stepping the voltage down and / or changing to DC (inside or outside the cabinet) allows for many parts of the circuit to work directly - and AC of nearly any frequency (not just 60 Hertz) can be produced as needed with electronic circuits inside the cabinet.
Colors, shading, etc on CRTs are the result of an electron gun at the back of the CRT. The gun fires electrons at tiny red, green and blue phosphorous targets on the front of the screen. When the target is struck, the phosphorous glows briefly. If the phosphorous is behind a red mask - it glows red (the same holds tru for green and blue). This same process occurs for each of the thousands of colored target on the entire screen, 60 times per second.
This is simplified explanation - there are other parts of a CRT. There are circuits that create magnetic fields the direct the electron both left and right in addition to up and down the screen. Without these circuits, there would be just one dot glowing on the screen. There are circuits for refresh rate, demagnetizing, brightness, contrast and more.
I hope this provided a good starting point for you and found it helpful.
Nov 20, 2009 |
Toshiba Tekbright 15" CRT Monitor