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Common causes of no power, no display, or shutdown in LCD monitors and television sets:

The most common cause of no display is a faulty back-light. Liquid Crystal Displays work by selectively blocking light. In most cases, the light source is a pair of fluorescent tubes that run quite hot and are prone to failure. Smart chips which sense any over or under-current then shut them down. Sadly, most tubes are difficult to get at, and require a clean-room to replace, unless you don't mind staring at a screen full of dust.

The transformers that generate high voltage to run them can also fail. Bad solder joints are becoming less common but can still happen. Typically, connections fail wherever there are high levels of heat, current, frequency, or voltage. The back-light circuit has all of the above.

No power at all is usually caused by one of two conditions: either the standby voltage that runs the microcomputer is too low, or there is no voltage at all. The former is almost always due to a bad filter capacitor, while the latter can be anything from a blown fuse to a weak start up capacitor.

Switch mode power supplies or inverters work by using transistors to produce their own alternating current (AC) at much higher than the line frequency. This allows them to convert a lot of power with a very small transformer. Filter capacitors act like a reservoir soaking up rapid pulses of current and turning them into a steady voltage. Unfortunately, the high frequency they run at (typically 30 to 50 kilohertz), generates a lot of heat which causes them to wear out more quickly. Sometimes they even blow their tops! A startup capacitor gets everything going by sending a burst of power to the switching transistor kind of the way the starter gets a car running. If it wears out you won't know it until after the next power failure.

Blown fuses fall into two categories: melted and vaporized. A vaporized fuse means you have a shorted component with access to a lot of current. Common causes are switching transistors, rectifier diodes (one way valves that turn AC into DC), filter capacitors, and anything across the AC line such as surge protectors and transient suppressors. A melted fuse can be more tricky to diagnose, since it can be anything from a shorted component to the gradual rise in current caused by aging.

Filter capacitors become less efficient over time, causing the whole set to draw more current. Fluorescent lamps also draw more current as they age. A good design will use micro-fuses or fusible resistors to protect the drive circuit.

If all the power supplies are there and it still won't turn on, you may have a bad switch. Membrane switches have been known to fail altogether.

Finally, as reliable as they are, microcomputers, signal processors, and multi-layered circuit boards all have one mortal enemy: heat. Even a soft metal such as copper can only take so many expansion and contraction cycles before metal fatigue causes it to break.

Tip: Turning the back-light intensity down just a little bit can make it last a lot longer.

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my hp lcd monitor screen is accidently suffered a pin hole. how to plug this pin hole to make screen normal and prevent white light from escaping from screen and read words on that part of screen which get lost presenly.

LCD is Short for liquid crystal display, a type of display used in digital watches and many portable computers. LCD displays utilize two sheets of polarizing material with a liquid crystal solution between them. An electric current passed through the liquid causes the crystals to align so that light cannot pass through them. Each crystal, therefore, is like a shutter, either allowing light to pass through or blocking the light.

If you have a "hole" in it then you will most likely have to replace the display.

Aug 29, 2013 | HP Computers & Internet

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Whats the difference between Backlight inverter and LCD??http://www.fixya.com/PostQuestion.aspx?dm=1&ref=thask

Liquid Crystal Display commonly known as LCD is an
electronically modulated optical device made up of any number of pixels filled with crystal.. The one you called the screen.. facing you when you are in front of the lcd monitor
It needs light source for this to have display... the light source whose responsible for the image to be displayed is the backlight inverter.. Its in the form of a cold cathode lights...frequently located at the upper and lower back edge of the LCD screen..

Hope i clear things out for you...

Much appreciated if you rate this help..thanks..

LCDs therefore need a light source and are classified as "passive" displays
LCDs are more energy efficient, and offer safer disposal, than CRTs. Its low electrical power consumption enables it to be used in battery-powered electronic equipment. It is an electronically-modulated optical device made up of any number of pixels filled with liquid crystals and arrayed in front of a light source (backlight) or reflector to produce images in color or monochrome. The earliest discovery leading to the development of LCD technology, the discovery of liquid crystals, dates from 1888.[1] By 2008, worldwide sales of televisions with LCD screens had surpassed the sale of CRT units.

May 23, 2010 | IBM ThinkPad T20 2647 Notebook

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Broken screen casing

LCD displays do not emit any radiation. This is the same as LCDs that are used on laptops and on LCD High Definition TVs but these are much larger screens.
LCD are liquid crystal display just like the display on your digital watch, but it uses three lots of color crystals (red, blue & green)where as the digital watch uses one black crystal. The DVD player also a backlight panel to provide light behind the liquid crystals so you can see the movie images.

There is no danger in unscrewing the case etc, just don't have it turned on when you do this, because you may cause an electrical short to some components, even if you do it won't harm you (the elecrical voltage is too low) but it is enough to possibly damage the unit.

Mar 05, 2009 | Panasonic DVD-LS80

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