- [Instructor] Clean, well-planned power
is vital for a computer system.
As far as the typical A-plus technician is concerned,
power starts at your building's electrical panel
and continues on through to the AC outlet,
power protection equipment,
and then the PC with the power supply,
and then internally with the DC power connections
inside that PC.
Now, the A-plus exam is most concerned
with the power supply and the internal power connections.
Generally, a 500-watt power supply,
like the one shown here,
is enough for basic systems.
But not if you're doing some powerful computing.
Then, you might need 600 watts or 750 watts
or even 1000 watts or even more.
Underpowered systems can lead to all kinds of failures,
intermittent failures or permanent failures.
The power supply must meet the requirements of your computer
and then some.
A good engineer always over-plans
at least a little bit, right?
So power planning should be right up there
with the choice of CPU, RAM, and motherboard.
It's all intertwined.
Most of the time, I will refer to the power supply unit
as either power supply or PSU,
and PSU stands for power supply unit.
And CompTIA will sometimes use that acronym as well.
Now, the power supply unit in a PC
is in charge of converting alternating current, or AC,
which is drawn from the wall outlets,
into direct current to be used by the computer,
and that direct current's gonna come out of all these ports.
The PSU, the power supply unit,
then feeds the devices in the computer.
For example, the 24-pin connection to the motherboard,
a six or eight-pin PCI express power connection to the GPU,
SATA connections,
15-pin SATA power connections
to the hard drives and optical drives.
You've also got the CPU fan and other case fans,
and also the eight or four-pin CPE connection for power
as well.
So the power supply unit feeds everything
inside that system.
Use a certified and reliable brand.
Make sure that the power supply unit
meets the standards that are set by organizations
such as the IEC or the FCC or UL and so on.
And also that it meets the ROHS Directive, R-O-H-S,
for things like lead and mercury.
So you wanna remember to plan accordingly.
You should know the type of power supply you need,
for example, ATX most of the time,
and the compatibility of that power supply
with the rest of your system.
You also wanna know the wattage and capacity requirements,
and you can use a power calculator for that,
and I'll show that in another video.
You also wanna know the number and type of connectors
that you'll be using.
So remember the power supply unit, or PSU,
converts AC to DC,
and it feeds that direct current
to all the stuff inside the computer.
Now, let's look here, on a typical power supply unit,
at the different parts here.
Okay, here we have the back,
and what we're looking at here...
We have a port.
That is the C14 inlets for the IEC power cable,
which is defined in the IEC 6320 spec, right?
And so the cable itself connects to this
with a C13 line socket.
And on the other end, it goes out to the AC outlet
with a three-prong connector.
Here, we have a shutoff switch, also known as a kill switch.
If you turn that off, then no power will come to this.
It'll block this altogether.
But it's still a good idea to unplug the computer
before you do any types of work.
And over here, we also have a voltage selector.
And right now it's upside down,
but this is set to 115,
which also is the same as 120 volts AC.
In other countries, you may have to select 230.
So what this indicates to us
is that this is a dual voltage power supply.
Again, should be set at 115 volt in the United States
and some other countries,
but it has that 230 volt for other countries,
and an additional adapter might be necessary
for the different wall outlets that you might encounter.
Never change the voltage selector switch
while the computer is running or plugged in,
and be sure to check this setting
before you initially use the power supply.
Now, back in the day, all of the cables
came directly out of the power supply unit,
and you had little control.
More and more though, today, power supplies are modular,
meaning that you connect the power cables
into the power supply
as well as into the other side,
with the motherboard, the CPU, and everything else.
So on the left here,
we have a fully modular power supply unit,
and all these connections, the cables,
plug directly into that.
On the right here, we have a partially modular connection.
And so we have PCI express ports here for our video cards.
Then, we have our Molex connectors,
also known as peripheral,
for our hard drives, SATA, and so on.
And that's just on this end.
On the other end, it'll look like an SATA connection
if you have the right cables.
But then you also have actual cables coming out of there.
So you have multiple options with that one.
That's a partially modular,
as opposed to this, which is fully modular.
Okay, so know the difference between those.
And let's go ahead and show
an actual power supply now and its connections.
Okay, let's talk about power connector types.
Here, we have a standard ATX power supply,
and this is what we're gonna install to our computer.
And you can see,
we have some cables coming out and some ports here.
Now, the main power connector
that you'll use to supply power to the motherboard
is this guy here,
and this is a 24-pin connector.
Back in the day,
these used to be known as 20-pin connectors,
and known as the P1 connector.
And it, in fact, still has the name P1 on there,
but they added four pins after a while,
and that's the standard now, a 24-pin ATX connector.
So that's gonna connect directly to the motherboard,
and this supplies positive five, positive 12,
positive 3.3, negative five, and negative 12 voltages.
Plus, you have the black ground wires.
So this is your main power connector to the motherboard.
And we'll connect that in one of the following sub lessons.
Another one of the connectors we see here...
We have a couple.
The first is the connectors for additional CPU power.
These are each four-pin connectors, and there's two of 'em.
And so these are labeled as P3.
And you can see that you got two four-pin connectors here.
So those are gonna connect to the motherboard as well
for additional CPU power.
And finally, we have another cable here,
and this is for your PCI express video cards,
and it's a six-pin connector.
And then you have an additional two pins
in case you have an eight-pin connector on the video card.
And you can see here, it says PCI-E, PCI express.
So we're not actually gonna use this
on the video card that we have on the computer
because it doesn't need any additional power.
It gets power from the motherboard.
But I most likely will upgrade
and will need a six-pin connector,
possibly an eight-pin connector.
Now, if we look here, we see we have additional ports,
and this is where we connect our additional power connectors
for things like secondary video cards.
For example, here, you can see it says
"12-volt PCI express hard drives."
You can connect a power connector to this
for an additional PCI express video card or for hard drives.
And they give you an extra cable,
and you can see this one has a red connector,
and so that's actually just gonna connect
right to the power supply itself.
And it snaps in with the little tab here
that locks it in place.
And then the other end,
this would go to the PCI express port on the video card.
And then you have an additional four ports,
and these are meant for hard drive only.
And these also use the six-pin power connector,
and they give you a cable...
Actually, two cables for this.
And you can see this.
This is the six-pin power connector
that would just connect right to one of these.
And again, with the tab facing down.
Snaps in place.
But if you look further on this,
you'll see there's three SATA power connectors,
one, two, and three.
And that's your standard 15-pin SATA power.
And so if you have three drives or less,
the one cable is enough,
but generally they give you a second one.
This way, you can add more drives,
or if you want your drives to run
on separate rails of power,
you could have one connected to this cable
and another one connected to the cable on here.
And that's what's also good
about the additional PCI express power connector.
You could have your main PCI express, which comes from here,
but then you could have a separate PCI express power
for a second video card coming from here,
and it would run on separate rails, which is good.
This way, you don't overheat the system.
And that's pretty much automatic.
You don't have a choice about that.
So that's a nice feature of this.
Okay, let's look at the back ports here.
There's just the one port, the C14 inlet,
and that's gonna be for your main power cable.
Quite often, we'll refer to this as an IEC power cable.
And the power supply should come with a new IEC cable.
Make sure you use the one that came with the power supply.
And this is known as an auto-sensing power supply,
which means that it will auto sense
what voltage you're connecting to.
In the US, this will be your your typical 120-volt outlet.
In other countries, that'll be 240.
And it might be labeled as 115/230.
It depends.
It might not be labeled at all.
But ones like this are auto-sensing.
Older power supplies would have a little red switch,
as shown in the picture here.
And that allows you to, you know,
select which voltage you want.
In addition, you see a hard on/off switch.
It's just a rocker switch on/off.
This allows you to kill the power.
Sometimes it's referred to as a kill switch.
But it allows you to kill the power
without disconnecting the cable,
which is a nice feature.
And I always get that on my power supplies.
If I'm ever doing any troubleshooting,
I really don't feel like disconnecting the power itself.
I just wanna turn it off here.
And when you're done though,
just make sure that you click it back on,
so that it does work.
And we have a fan on the bottom.
That's gonna exhaust the hot air outta the case.
And you wanna make sure you have that vent
on the bottom of the case.
Sometimes, those will have a filter as well.
Our case has a filter.
And you wanna clean that out once in a while
if you work in a dusty environment.
Really, in any environment.
And so there's your power connectors.