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Book Chapter 7 - Power Supplies

1. The Power Supply

What we're looking at here is an ATX-style power supply, the predominant power supply used in desktop PCs today. In this episode, I just want to do a quick run through upper supply to introduce it to you. So it's basically function and some of the connectors on it, and then we'll put it in the system. So let's start off by just taking a look at this box. So what I've got here on one end is the part that's outside, which you would see from the outside world. This is where I plug into a standard wall outlet, hopefully via a search suppressor or something. There are a couple of other things I'm going to see. There's pretty much always an on-off switch. This isn't what we used to actually turn on the computer. This is just giving the power supply juice by itself. There will be an exit button on the front for us to use. It's also a great way if you turn that off. People never think to check that, and they're like, "Why does the computer turn on?" Another thing you'll notice is that I'm going to tilt up so we can see this, this little red drawn one; it's a slider, not a connector. That's for European volts 230 volts), with North American voltages being at around 120 volts. So if I were in England, for example, I would flip that to 230 and then I could plug into English power, or if I flipped it back to 110, I could plug into the United States. These are pretty rare today as most power supplies are auto-sensing and will automatically adjust to any voltage, which is pretty cool. All right, so you're also going to probably see other things in general power supplies, like the one that the air goes through. Air comes into your case from other places and goes out to the power supply. Although we can't see more modern power supplies, there might be exceptions to that. So first of all, flies don't really supply power. The power comes from your power company. What these really are are step-down transformers that convert AC power into DC power. So, let's take a look at some of the connectors and all of these other guys that connect to your system. So I want to start with this guy right here. So this is the primary ATX power connector for the motherboard. Now if you take a look at this, you'll see it's kind of in two pieces. The original ATX standard had a 20-pin connector that plugged into every motherboard there was.Although they found out they needed more power, they added four more pins. So you'll notice on a lot of power supplies that that's two pieces and one. Now as we're looking at this, I want you to notice some colours here. There are three main types of power that power supplies provide. twelve volts, five volts, and 3.3 volts. If you see a yellow connector, that means it's providing twelve volts. If you see red, that means volts; if you see orange, that means three volts. Three. As for the other colors, well, just keep going. We'll talk about some of those other colours as we continue through. Now, in the original ATX standard, we only needed one power connector, which provided all the motherboard power. However, over time, CPUs got bigger and more powerful and needed more electricity, and we began to discover that we needed more power. So they came up with what was known as—and still is known as—At X Twelve V. The ATX 12-standard package basically consists of extensions to the original ATX power that allow us to put more electricity into the motherboard on this particular system. It's always so much fun digging through these. This is an ATX 12-V extension power cord. These also plug into the motherboard. On some motherboards, it only needs one of these. On other motherboards, it's going to use these. It really depends on the motherboard. There's a lot of flexibility here, and also, some motherboards have six connectors, and only six of these eight plug in. You can use this and it plugs in, and you can just hang there and everything's fine. So that's what actually powers the motherboard. But inside the case, you've got a lot more than that. You've got hard drives, and you've got video cards and all kinds of other stuff. and they need electricity too. So that's why we have all these other connectors on here. So I'm going to do a quick little walkthrough, making sure that you're aware of different types of connectors. Okay, here we go. This first connector right here—this is the oldest power connector that is on any system, and it's known as a molex. The Molex connector is very versatile, and the colours indicate that it can supply both five and twelve volts. They were used for many decades to power the insides of systems. They're falling out a little bit, although there's still plenty of stuff that uses Molex. This right here is what we call a mini connector. It was originally designed to run a component known as a floppy drive. The components of your forefathers' floppy drives are dead, but we still see components from time to time that need these little mini connectors to provide power. Now the one thing about these connectors you need to be aware of is that they have chamfers, which are little notches on them that prevent you from plugging them in backwards. So with power connectors, it's really easy to make a mistake. You're doing it wrong if it's not fairly straightforward. Now as we move into more modern systems, we see connectors like this. This is a set of power connections. It's primarily used for hard drives, though you'll see it on opedia and other sites that might also use it for power. And the last one I want to show you is what we call a PCIe connector. These connectors are used for video cards. Higher-end video cards need their own little extra bit of juice. And these are dedicated connectors that you plug straight into your video card to give your video cards just that little bit of extra power that they need. Now, if you take a look at the power supply, you'll see that all these cables are just soldered onto the system. So what if I have a smaller system that doesn't need all this? Well, you used to wind these up with some guys and try to hide them as best you could. However, what's very popular today is something like this. So this is what we call a modular connector. Note that it's got a lot of connectors here. There's no cable coming off of it. That's because also in the box it came with are all these extra cables that you can choose to use or not use based on what your system needs. Now, I'm definitely going to need some motherboard power, so it's got its own little dedicated connection here. I'm going to plug this in. And again, they're chamfered, so I can't put them in backward, but they can be a little perch, Nicky, especially with a brand new power supply like this. And I know I'm going to need some supplemental power for my motherboard. And this one has one of these. As I've just done here, I just want to make sure you see the connectors here. You'll see that I've plugged in my ATX power motherboard connectors, so they're on and ready to go. In terms of anything else, one of the nice parts about modular power supplies like this is that I probably won't plug anything else into the back of this power supply until I know what that particular motherboard needs. And in order to do that, let's go ahead and mount this power supply into a case.

2. Mounting a Power Supply

Look at this big case, and we've got to mount this little power supply in here. So what I'd like you to do is take a look at this case and guess where you think that power supply is going to fit. The answer is probably way down here. So it's going to be coming out the back of my system. And if you'll notice in this particular case—and this is something we see more and more of—the power supply is actually separating the rest of the system. So it does its own cooling, which is actually kind of a nice feature. The downside to a feature like this is that unlike in a simple case, we just reach inside and drop in our power supply, and it's going to take a little bit more energy. So if we take a look back here, this is where we're going to mount the power supply. In order to get this fella in, I've got to unscrew these four thumbscrews. Then I'm going to mount it to the back of the power supply and slide this in and remount it with these. And then that's actually the power supply in.So let's do that really quick. Thank you. Look, every power supply is going to have a little bit of a different way to mount into the case on this particular power supply, and pretty much all ATX power supplies require you to remember that heat blows out the back. Now if you come and look inside this case right here, you're going to see there's a bunch of ventilation. So in this case, if I want to, I could actually pull heat from the case and come out here. It's even got another fan at the bottom of this power supply unit, and that one's pulling air into the power supply. I could turn this upside down and draw air through the power supply and out of the motherboard area case. In this case, I'm going to cool my motherboard area with its own cooling system. So what I'm doing here is flipping the fan so it's pulling cold air from the bottom of the room outside and then pointing it that way. In this particular case, the power supply is in charge of cooling itself. Now, I want you to take a look at one more thing as we look inside this case. Let me tilt this a little bit for you guys. You'll see that I have power connections way over here, and here's my primary connection. So the trick here is to get the connectors out of that little power supply area. I've got this handy-dandy little space where I pulled them through. I've already got them started here, so I'm going to pull them through and plug them in. You notice this little connector on the outside here—a little latch that's going to correspond to a little notch on the side of the connector itself. And I've got it plugged in now on this other connector. If you look closely, you'll notice that this has two sets of these connectors. So for right now, I'm just going to plug one in on this particular motherboard by reading the documentation. I don't have to plug both of those in, mainly because I'm only running one video card. Okay? So I went ahead and connected all of my power. Now, if I need to put any more power on here, for example, if I've got a couple of power supplies that are going to need SATA power, it's at this point where I'm going to go ahead and plug it in and then put those cables in as well. Or, if I have a video card, I'll plug it in from all my nice modular collectors, plug it into the back of the power supply, and then feed that video card. That's kind of the beauty of these modules—you're not stuck with having lots of extra cables laying around doing nothing. Now the only thing to do at this point is to actually give it some electricity and give it a test. But I'm going to sit for a whole other episode where we test our power supplies.

3. Choosing a Power Supply

When we're buying a power supply, we buy it based on watts. Now, before I get into detail on WATTS, I want to kind of correct something I said that wasn't 100% true earlier. When we talk about electricity, we always say volts times amps equals watts. Well, that is absolutely true, but only in a perfect world where we have 100% efficiency. What's really happening is that power supplies, like anything on Earth, are not perfectly efficient. So when you plug into your wall outlet, only a percentage of the tricity that you're getting from the wall outlet is being converted into the DC voltages that your PC needs. The rest is lost through heat resistance and other things like that that prevent all the electric goodness that you need. And this has been a big problem with our supplies over the years. So, first of all, when you're looking at power supplies in the store, you can see they've all got these wattage ratings on them. So on these two in particular, you can see one of them is 460 watts. The other one is 750 watts. So the big first question I get from everybody is, "Well, how much wattage do I need?" And I refuse to answer that question. In fact, you will not be quizzed on that question on the copy exams because everybody understands that this is a very subjective question. There are wonderful websites that you can go to all over the Internet that help you figure this out. So basically, how much does your motherboard need? What kind of video cards are you using? That's a lot in terms of your total wattage and how many hard drives you have installed on your system. It's surprising how little wattage most systems need today, unless you're doing something like, for example, using a really high-end processor or using really, really high-end video cards. So don't worry about the wattage you need for your system in terms of an A-plus question. But do be aware that that can be an issue for anybody buying a system. And the answer is, do like I do. Go online, find one of these wattage calculators, and then make your best guess. Add in 20%. So that's the other thing to keep in mind. So let's just say you go through these calculations and you decide that your system needs 700 watts of power. Well, you're only going to need seven watts of power when everything's running off the power supply. He can provide wattages up to these wattages.But for the vast majority of the time on your computer, unless you're constantly playing high-end video games and constantly accessing your hard drive, there's only going to be a percentage of that particular number. So it's always fun. Guys like me want to buy, like, super high-wattage power supplies. Right now, the highest commonly found power supply would be 1500 watts. And they're huge, and they look cool, but I doubt I'll ever need that much power. So the important thing to take from this is to get the wattage that you need and give yourself a little buffer. The problem that you can run into is not having enough. So don't be afraid to turn that up a little bit. And if you're like me and buy almost nothing but 750 to 1500 watt power supplies, then I've never seen you run into that problem. Okay, so going back to the Affidi issue, this is a big problem on older power supplies like this one. If I had even a 60% efficiency, that would be good. So this one was rated at 575 watts. So 575 watts is all you need, are you ready? Room temperature. Okay? And I assure you, inside this power supply, after running for 30 seconds, it's a lot hotter than room temperature. And heat reduces efficiency in a big, big way. Also, in terms of quality, electronics can be a big issue. And the bottom line is that if this thing is only putting out 60% efficiency, that'd be 575 watts on the box. But that is only when everything is absolutely optimal. At 60% efficiency, it's probably going to be just a little bit over 300 watts when everything's working really hard and when it's in a less than optimal situation. So you need help with that. In fact, it was such a big problem that the power supply industry on its own came up with what they called the "80 Plus" rating system. If you look at this very nice Antec power supply that I got right here, you'll notice that it has an 80 plus rating. The 80+ rating is a godsend for people like me who want high-efficiency power supplies. Now, there are a number of rooms within these 80 or so. Let me show you those. So, as you can see from the chart, there are several types of 80 plus. So at the very base, we have what's just known as "80 plus." And if you take a look, you'll see it's talking about the percentage of rated lows. So that means if I'm only using 10% of the watts that this guy could provide to me, or 50, or all of them, what is my efficiency? So with 80 plus, which is the base boast, they guarantee that you get 80% efficiency. And, as you can see, we are increasing our efficiency. bronze, silver, gold, platinum, and titanium, where the efficiencies continue to improve. Keep that in mind when you're choosing a power supply. You need to make sure that whatever its peak wattage is, it shows. Take a look at the 80 percent plus efficiency, and that's the real wattage that you're going to get out of that system. Thank goodness for people over the age of 80. It's really made our lives easier when it comes to choosing power supplies. Now, for me, the only other issue when it comes to choosing a power supply is going to be modular versus soldered modular, where we can plug in and choose our different types of cables. I really like those. Although many people claim that you actually reduce efficiency, that connection does have a minor impact on your efficiency. Some of us believe that soldered permanent connections are always preferable to modular ones because they are more efficient. Personally, I love the convenience of modular power supplies, and if I lose 5% efficiency, I'm going to be perfectly happy with that. The last thing I want to mention when it comes to power supplies is that the standard ATX size covers the vast majority of systems. Even a lot of the small form-factor systems still fit that full-size power supply that you've seen. However, do be aware that there are smaller power supplies out there. They still need the ATX standard, but they're very, very small form-factor systems. There are a bunch of them on there. They're not on the exam. However, if you're looking for a small system, there may be a smaller-sized ATXpower I that will be ideal for your needs.

4. Cooling Your PC

The one downside to CPUs is that they generate heat. In fact, your entire system makes heat, and your CPU makes heat. Your RAM makes heat, your motherboard makes heat, your drives make heat, and your Vic Hards make heat. Everything in here is generating heat—and heat is a bad thing. want to minimise the heat as much as possible. Now, in other episodes we talk about things like the CPU, and that's great, but in this episode I want to make it a little bit more holistic. I want to talk about cooling the entire system. So first of all, let's make sure we understand how we give heat. The number one thing that we're going to use on anything that generates heat is going to be something called a heat sink. Now, if you take a look at this cooling system I have right here, Now this is a CPU cooler, but I could be cooling anything and I would have the same situation. If you take a look on top here, I've got a big copper block, and this thing draws the heat from the CPU itself because it's not as hot as the CPU. So the heat transfers into this big metal, which is a heat sink. So anything that can take heat from another device is a heatsink. Now, once we have a heat sink, we've got to get rid of the heat in the sink. And then we go through heat dissipation. So on this particular one, it's got these cool copper tubes. These are hollow tubes, and the heat will transfer through the tubes. And on this particular one, you have all of these wonderful cooling fins. So all of this actually takes the heat away. In some cases, that's not enough to get rid of the heat. And the way we get rid of the heat is that we have this huge area exposed to the air, which is cooler than the fins. Therefore, the heat transfers from the fins out into the air. But in order to make it even cooler, on this third device we have the active cooling function of a fan itself. So we use heat sinks to draw heat away from whatever is generating too much heat. And then we use different types of ways to paint that heat out of it and out of the system completely, which is the idea. So this system right here in front is a pretty good example of good heat dissipation design drill set.In general, there are exceptions to this, but in general, the whole idea is that you pull cooler from the front and from the top of your system. Over here's the front on this guy. So you pull air in, and then you push the hot air out somehow. Normally we use a power supply as yourmain push the heat out type of situation. Let me take a look at this here. So on this particular power supply, it's got a couple of holes, and it just pushes all the heat out this way. One of the other things that happens on more modern systems is that we'll seeand this one is no exception. It's completely separated from all this. So he's actually pulling cool air from the bottom and just pushing it out the back. So really, the power supply is kind of an island unto itself here. So on this particular system, what I have are a number of fans. Now, if you take a look here, you'll try this at home, but you can see these fans are oriented to pull air down from the top of the system, and they're actually pulling air through this liquid cooling radiator system. I've got pants in the front that are also pulling air in. Now, I could easily, if I wanted to, install it in the back to push air out. I just have lots of holes in the back. And I feel that that's more than enough on this particular system to make the air move. And that's what it's all about: making air move. The big thing that people need to watch out for is that when you start stamping in lots of cards and stuff, you can actually block air movement inside your system. There's no magic system to this other than looking at it and making sure you have good airflow. If your system overheats, it does one thing: It reboots. That's your cue. If you have a system that reboots, it's overheating. And to fix that, you have to put in more fans or switch to liquid cooling, or whatever it might be. But I will tell you, 95% of desktop systems, thatwhen you snap them together, unless you do something terrible,like leave a piece of plastic on the front ofa case, whoopsie, I did that once. You're going to have good airflow. So we move air through fans. So I've got a couple of examples of fans here. fans, all these different sizes. This is what we call a 60 millimeter. This is a 120 millimetre fan. And the idea is that bigger fans don't have to turn as fast, and therefore they don't make as much noise. Because that's the big downside to fans, folks: they make noise. So we would like bigger fans to turn more and move the same amount of air as smaller fans that turn faster. Now, if we take a look at this board, I have all kinds of connectors on the motherboard that are designed to do nothing but power the components on this particular motherboard. Now, if we take a look, well, I can see them, but you can't. But, luckily for me, I brought something along that'll make it a little bit easier for us. So if you look on this particular motherboard, you'll see that there are three or four pin connectors. One of them says CO, and the other two just say system fans. So you'll notice that there are four pin connectors, and that's fantastic. The idea behind a four-pin connector is that CPUs are so important that they stay cool that we need the CPU to be able to talk directly to the fan and to be able to say "spin up" or "spool down" depending on what its needs are. So those four pin connectors, better known as PWMconnect, will allow us to do exactly that. Now, all you other fans, let's take a little peek right here. All the other regular fans don't have that direct connection. They kind of let the CPU manage its own temperature by making the fan go faster or slower. So they just have little three pinters and wecan go ahead and just plug them in toa four and they work absolutely fine. So we've got all this stuff plugged into our system. So what, in terms of control, will cool our PC? Well, number one, you don't have to control them at all if you just want to plug them in and let 99.9% of all motherboards go. If you don't tell me otherwise, I'm going to run that fan full speed all the time. And for a lot of people, that's great. Just let it run. Cares? Well, I care because noise drives me bonkers. So if the goal here is that we want to adjust our system in such a way that it's running the fans just fast enough to keep it cool enough to keep it from rebooting, Now that can be a challenge, but it's actually not that hard with a couple of tricks. Number one, most modern motherboards have functionality built into them that will automatically handle all this for you. What I have over here is a sample system setupand let's just take a look at that and showyou some of the typical types of settings you're goingto see that allow us to actually control the fans. I'll let you in on a secret. We don't really have fans as much as we control the temperatures. I'll show you what I mean right now. You'll see, I've only got two functional fans. There's one fan that's running on the CPU itself. There's another fan, which is called the second system fan. I got to warn you folks: I've got a lot of different systems here, and we're going to be looking at a lot of different scenarios. So this one has a bazillion fans on it.We'll look at him in a moment. But for right now, I want to keep it simple to help you understand how fans work. So let's get back to this. One of the big things I can do is set warning temperatures. In this particular case, we'll make the system beep through my little, tiny system speaker depending on what temperature I want in these types of situations. Usually you actually do a little research on your CPU and you'll see what its design temperature is, and you just set it a little bit below its maximum. In that interim, some CPUs can run as hot as 90 degrees. That's Celsius. So we can also do anything if the actual internal case itself gets a little hot. Here's another one that's actually very important. And this is the CPU fan fail warning. If, for some reason, the CPU fan just stops turning, I want it to beep and give me a little bit of a clue. Now, if for some reason you wanted to manually control the CPU fan, this would be one way to do it. So I set it to you all and then I can say whatpercentage of its maximum temperature do I want it to run at? So this is just something you play with a little bit. In my own experience, in most cases, I'm going to set that to something normal, and I'm going to let the actual system itself control those speeds. If you're going to be messing with your fan controls and your systems, be ready for a lot of tweaking and adjustments, and be ready for a lot of beeping when you set them. So the fans aren't turning fast enough. People are increasingly foregoing system setup in favour of features that allow them to control their fan settings directly from within their operating system, which we're seeing more and more of these days. Let's switch over to the white box and I'll show you how some of those work. I am on the desktop of my white system. Now, there are a lot of tools you can use, but here's just one that I like. This one's called Speed Fan. It's been around for a long time; it works perfectly well. Now, first of all, on its main screen, notice that it shows us all kinds of fans here. These are the actual fans that went in my motherboard book. It would say the same names that are on my current system. Notice it's a zero. Just because there's an interface on your motherboard for AFN, that doesn't mean you have to use them all. If you're getting enough one fan,ignore the rest, who cares? So these are the ones that I've chosen to plug in, and we'll see a couple of themon running, and that's not a problem. So if I want to, I can actually go into these, and you see where I can go in and select and configure different fans. A cooling system is either a complete nonissue or a complicated mess, depending on your choices. For the vast majority of systems, if you just snap in the default fans that come with your case—the default OEM fan that comes with your CPU—you're going to run just great. You're not going to have any of it all. But if you're someone like me who likes to mess with the fans, I like to keep my fans quiet. Be prepared to spend an inordinate amount of time either on your system setup or using specific software for your system to get it just the way you like it.

5. Troubleshooting Power Supplies

Power supplies are the most likely component inside your computer to fail. Keep in mind that power supplies are in desktops or laptops or tablets, and they are the one piece of equipment that takes the most abuse, primarily from the electricity that's coming from your electrical provider. So power lines really are a big problem, and there's something that we need to be comfortable troubleshooting. So let's talk about the scenarios that we run into when we're troubleshooting power supplies. The big thing we need to remember above all else is that power supplies are going to die in one of two ways. They are going to die really, really fast, or they will die really, really slowly. And when they die quickly, no man, no man, will you know. You'll get horrifying smells. Almost anytime you get a burning smell coming out of a system, the first thing you need to be considering is the power supply. You can get smoke, which is absolutely terrifying, especially if it happened to me at 38 ft. But the important thing is that if you get that type of reaction, the system is dead. You're not going to be doing anything. Make sure it's unplugged, and then you need to open that up and get that power supply out if you haven't already damaged other stuff. So that's the big issue. I wish more power supplies died quickly. Well, not at 380, but I wish they did die more quickly. Because the other way they die, the slow death, is far more common, far more nefarious, and harder to diagnose. But we need to talk about that too. The best way to tell if a power supply is dying is to test it. Now, for the first thing, you're going to get more. Anything else will result in unexpected shutdowns or booting up with no power. And then you shut it off, and then you unplug it from the wall and plug it back in. Then suddenly, it works for a while. So those kinds of things are a good indicator that you're approaching what we call the slow death. What's happening in here is that there are massive capacitors that act as the primary surge protectors for your system. That's right. Power supplies have surge suppressors built into them. And as the capacitors start to break down after lots of surges, you start to get this very slow death. If you think you're having a slow death or if you're seeing these unexpected shutdowns, you have to test it. There are a lot of different ways to test a power supply. My favourite way to test a power supply is with a power supply tester like this guy right here. So, in order for me to test him, take a look at this little power supply tester right here. I just plug in my primary ATX power and I can see all the different outputs. One of the things it's saying is that MyPlus 12 V-2 doesn't have enough juice. So basically, what we need to do is identify exactly what the problem is here. He wants to plug the secondary connector in. There we go. And I want you to take a close look at the outputs you're seeing there. In particular, look at the twelve-volt ones. So you'll see it says twelve, two, and twelve, two. There are two different twelve-volt outputs. Power supplies come from the factory a little over bolted.So if it's a twelve volt to comeout twelve point 212.312.4 even, that's okay. They designed the factory. In fact, most systems run fine with a power supply. With twelve-volt outputs dropping below 12 volts, you can plug in what seems to be a perfectly good power supply running at about 611 volts. You're like, "Well, that's not 12 volts." Well, it's good enough, and the system will continue to run. However, it could be a clue that your system is suffering as that voltage continues to drop more and more. You're going to get more of these unexpected shutdowns and crazy reboot scenarios where you're just going to have to jack up that computer and slide it into a new power supply. So having a voltage tester like this is really great. By the way, I can also use this to test just about any individual plug that does happen. Sometimes, with the pliers, you might have a molecular or a SATA connection that's physically broken, and plugging it into a guy like this is a great way to verify an individual connection as well as the entire power system itself. However, we don't always have these guys laying around, and that can be a challenge. To take care of that, there are a few things we need to do. You don't really have an onswitch with these X power supplies. That switch at the back just gives juice to the system. We have to emulate turning on pewter. And that's where we take advantage of something like this. This is nothing more than a carefully bent paper clip. The only thing I can test here is the fanning inside the power supply itself. Although every now and then you run to the power supply with an "I'm ready to go light" Most of the time, the only way to tell if it's running is just to do this. So what we've done is linked the green power grid to any black ground. It doesn't matter which black one I connect to for a nice little spin of the fan. This is a quick and dirty way to verify that at least the power supply is on when it's supposed to be on. Now to test voltages, you're going to need a spare motherboard lying around. So what I like to do is just get an old mug—not that old, but a pretty good one. And what I'm going to do is plug it in. So notice I don't have a CPU in this or anything. I don't need it for what I'm about to do. I just want to test the voltages. So in this case, I don'teven need my special paper clip. What I'm going to grab is a voltmeter. On a voltmeter, you're going to see a V with a little squiggle like this, and then a straight line with three dots underneath it. This is for AC power. I'd use the V with the squiggle if I were plugging a plus voltmeter into a wall outlet, because I've just plugged it into a board. To test the power supply, I'm going to use the V with the three dots. Now take a look here. You'll see it says 220, and on this 1300. So the V with the straight dots means it's DC power. So I know that the highest voltage on this volt metre is 12 volts. So I'm going to set it to the number above the 12 volts I've got. And on this one, it's 20, right? So let's go back over here for a minute. And what I'm going to do in this particular example is use my red and black probes, and I'm going to shove this red probe into one of these 12 volts like this. Then I'm going to pick an arbitrary black background and shove it in like this. So what I actually did there is I actually just press the on button. I hit the two little wires that are connected that wouldn't be connected to the button in the front, and I just dragged something metal across it. and I've turned the system on. I can feel a little fan. And what I want you guys to look at is this right here. So you're seeing that I'm outputting. The connections are a little wobbly. That's why it changes a little bit. But you can see I'm outputting just a little bit of 12 volts, so I know that this system is okay. The big challenge to testing a slow-dying power supply is coming up with a way to handle the voltage on the twelve-volt side. You could do the same thing with the five volts or the 3.3 volts, but with the twelve volts, being the highest voltage, you can get a little bit better view of a slowly decaying power. So I like to use the twelve-volt system. You could use it for five if you wanted, but a twelve-volt system works for me. There is a point. If I have any power supply, no matter how good it is, the twelve is only putting out eleven and a half. I'm yanking it out, and I'm going to go get a new power supply, and I'm going to snap it in. There must be a reason I'm doing this test. There must be symptoms that this thing is doing something wrong that motivated me to do this. And if I'm in here, I'm just going to go ahead and see if I've seen eleven and five. Some guys say 11:07 p.m. They're just going to replace it. By the way, the exam itself isn't going to test you with these numbers, but they're going to ask you things like, you see, the voltage is decreasing. What do you do about it? You buy a new power supply. I'm sure there are people out there who know how to solder and things like that. I don't. I yank it out a new one in and life's good for me. So basically, those are the big things to watch out for.