Join Mike Meyers for an in-depth discussion in this video How monitors work, part of CompTIA A+ Exam Prep (220-901) Part 4: Displays and Printers.
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- If you want to understand how monitors work, we've got to take it down to the very base level to the most core piece of your monitor, the pixel. This is a pixel. Now mine's actually you could walk through it, but in the real world this is actually made from liquid crystal display or LCDs. Now a single pixel on an LCD is actually composed of three pieces. Each one of these pieces is called an element. Now the reason we use three pieces is because we need colors.
So what I'm gonna do here, it's not gonna be a very pretty pixel but it'll work. There we go. So what I've got here is a pixel that's broken up into three distinct pieces of LCD. You see LCDs have a really cool feature. With an LCD, if you give it electricity, you can see through it. But if you turn the electricity off, you can't see through a part of the LCD pixel. So we can take advantage of LCD technology to make a pixel. So what I'm gonna do is I'm going to take an LCD panel and I'm gonna put it over red, green, and blue filters.
Now the important thing that you need to appreciate here is that behind these filters is a backlight, and the backlight is just a regular fluorescent light. It's actually called a CCFL. And the beautiful part about this system is that if we adjust the amount of electricity over the blue, red, or green filters, we can make any color of the rainbow. If you want to make red, we'll just turn the electricity off on the blue and the green side.
If you want to make green, well, just turn off the red and the blue. Now the cool part about this is that we can make almost any color of the rainbow because light is an additive technology. For example, if we want white, we just turn all three of them on all the way. If want a dark red, I'll turn off the green and the blue and just turn the red on a little bit. So we can make literally billions of colors using LCD technology. Now the problem here is that I've only got one pixel.
That's not gonna be good enough. In order to make this technology work, we have to create LCD panels that aren't made out of one pixel, not made out of four or 16 or whatever it might be, but literally millions and millions of pixels. The larger the number of pixels, the finer the resolution and the larger the screen so that you can make LCD technology work for you. So now that you understand LCD technology, let's take a look at a real LCD monitor. All right, now I've got a gorgeous monitor here, top of the line, cutting edge monitor, and in order for you to appreciate how all these pixels light up and everything, how LCD technology allows us to enjoy these great monitors, well, we're gonna have to rip this thing open.
You know what? I like it but not that much. Don't worry about it. I took an old one apart just for you. Okay, let me get these pieces, a couple of zillion screws laying around. Do not try this at home. But this is the part I'm interested in showing you. The rest of this is all just junk. All right, now this is the backside of an LCD screen.
If I put this over, you're not gonna be able to see much. And the reason is simple. It's because the LCD doesn't have any electricity. An LCD by default is without electricity. It doesn't let any light through. So what we have here is an LCD screen. Then we have those little, tiny red, green, and blue filters and then behind that we have a backlight, which is cold cathode fluorescent lamp or CCFL. Now in order to make all of this work, we've got a number of parts here.
First of all, this particular monitor uses an AC adapter, just like you'd use for so many other different things, and he would plug in right here. So from the AC adapter, what we have, and here's my VGA connection, and the AC power is converted into DC power by the AC adapter, so it comes in here as DC, and the DC power runs out to all the circuitry and this is what lights up all the different little pixels on the LCD screen itself.
Now the number of pixels on this particular screen is exactly 1,280 by 1,024. And those are fixed at the factory. We call that native resolution. So this circuitry right here is actually controlling all of those slightly over one million pixels on the screen and it's taking commands from the computer to do that. And that works great, but the other problem is is we have to backlight this thing. So to backlight it, we've got two CCFLs, and they're running all the way across the top and the bottom.
These wires are actually just lighting up the two CCFLs. Now fluorescent lamps are interesting because fluorescent lamps have to have AC power. So remember this AC adapter converted everything to DC, so now in order to run the CCFLs, we have to have this guy right here. And this is one of the problem children of LCD panels. This is called the inverter. Inverters convert DC power to AC, and that's his job. So one of the problems we run into with LCDs is that if the screen goes black, one of the places we look is a bad inverter.
And these are actually surprisingly easy to replace. It only costs maybe $30, $40 bucks. I can't tell you how many times I've fixed a monitor just because the inverter went bad. The interesting part about LCDs is that when your screen goes black, it's usually simply a factor that well, you blew a light bulb. So if your inverter goes out or if you CCFLs burn out, your screen's gonna go black, but it's very obvious because you can actually hold the screen up to a bright light source and you can still see your windows and everything is still working.
That's a big clue. You don't have a big problem with your LCD. It's repairable. You can buy inverters. You can buy CCFLs. It's a lot of screws, but it's not that hard to fix, and I know people who make a good living doing it. So understanding the idea of pixels, LCDs, and backlights are the cornerstone of appreciating how we use the LCD monitors on everybody's computer. (upbeat music)
The CompTIA A+ 220-901 exam is comprised of six key parts. The fourth, peripherals, is covered by this course. Instructor Mike Meyers explains how to manage monitors and display technologies, including how to work with connectors and ports like VGA and DVI. He also shows you how to maintain printers and multifunction devices, both as independent devices and as devices connected and configured to a computer.
Note: The six courses designed for the CompTIA A+ (220-901) exam preparation include core processing, core hardware, peripherals and building a PC, displays and printers, networking, and laptops and mobile devices.
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- Configuring display technologies
- Working with Plasma and DLP monitors
- Setting up video connections, graphic cards, and projectors
- Using dual displays
- Troubleshooting video issues
- Maintaining printers