-: In this lesson, we are going to talk about power issues
you may experience with a system.
Now, as you start to troubleshoot issues with a computer,
the first thing we have to look at is,
does it get proper power?
Now, there are six main causes of power issues
and why a system won't boot up when you try to turn it on.
This includes, the power button
not being connected properly to the motherboard,
the wall outlet being faulty
or not providing adequate power,
the power cable
going from the wall outlet to the computer being faulty,
the power supply itself being faulty,
the power cables going from the power supply
to the components being faulty,
or there's an incorrect voltage setting
on the power supply unit itself.
Let's take a look at each of these.
First, we have the power button
not being properly connected to the motherboard.
Now, when you try to turn on a computer,
the first thing you're going to do is press the power button.
Now, when you do that,
the power button is going to send an electrical signal
from the button down to the motherboard,
and, therefore, it has to be actually connected
to the motherboard.
The buttons on the computer case
have to be connected to the motherboard
in order for this system to be able to boot up properly.
And, if that wire becomes unattached to the motherboard,
it's not going to be able to send that signal
or have the signal received by the motherboard.
So it's important to check this.
If you push the power button on the front of your computer
and it doesn't turn on, this could be an indication
that that wire is no longer connected to the motherboard.
In order to troubleshoot and identify this as the problem,
you're going to have to open up the computer.
So you want to make sure
you unplug the computer from its power source,
such as the wall outlet,
and then you can open up the computer,
and follow the wire from the button to the motherboard,
and verify it as properly connected
and fully seated into the motherboard's connector.
Second, we have the wall outlet itself being faulty.
Now, when this happens,
this means you're not getting adequate power
from your building into your computer.
So to test this,
you're going to have to use a multimeter or voltmeter
to be able to test the power outlet
and verify you're getting the proper amount of voltage
at the right hertz cycle.
Now remember, wall outlets
will provide two different levels of voltage
depending on where you're located in the world.
If you're in the United States or Canada,
you should expect to see somewhere
between 110 to 120 volts AC, at 60 hertz.
But, if you're in Europe or Asia,
you should be expecting to see
220 to 240 volts AC, at 50 hertz.
In order to test your wall outlet,
you'll simply connect your red and black leads,
which are your positive and negative,
to the appropriate terminals on the wall outlet
and read the amount of voltages being output
by looking at the display on your multimeter or voltmeter
to verify that it is the correct amount that you expect.
Now, the third power issue often occurs
because the power cable
going to the computer from the wall outlet
has become faulty or frayed over time.
To test this, you want to disconnect that power cable
from the wall outlet and the computer,
take your multimeter and run a resistance check across it.
To be able to do this, you'll simply place one of your leads
on one of the prongs on the cable
and the other lead into the hole
on the other side of the cable.
This will be able to verify
that you have full continuity across that cable.
Now, when you do this,
you need to do this three separate times,
once for the positive pin,
once for the negative pin
and once for the grounding pin.
Now, once you verify there's proper continuity
across each of the three wires inside of that cable,
you know that that cable
is no longer the issue of your power problem.
Now, when you're reading the resistance
across each of these wires inside of the cable,
you should be expecting to get zero ohms
or very close to it.
On the other hand, if there's a break in one of those wires,
you're going to get infinite ohms read on your display
or an extremely high number.
Anything that is not close to zero
is going to be considered a broken wire
and you should replace that faulty cable
with a new one to solve your power issue.
Now, the fourth issue we have,
is when the power supply itself is faulty.
Now, remember, when you're dealing with a power supply,
its entire function
is to take high voltage AC, or alternating current,
as its input from your wall outlet,
and then convert that
into low voltage DC, or direct current,
for use by the various components in your computer.
Your power supply needs to provide three levels of voltage.
This includes 12 volts DC, five volts DC, and 3.3 volts DC.
If your power supply
is not providing those three voltages at a stable level,
that means your power supply is faulty.
Now, when it comes to power supplies,
you should never attempt to open them up
and work on the inside of them.
This is because
there's a lot of high voltage components in there,
including capacitors,
that could provide an electric shock to you
and either hurt you or kill you, in severe cases.
So when you have identified
that the power supply is the problem,
you will simply take it out and replace it with a new one.
In order to test your power supply,
you can use a power supply tester.
Now, a power supply tester is a small handheld unit
that allows you to connect the output from the power supply
using its different cables
and be able to test the amount of voltages
being received over those cables.
For example, if you take
the 20+4 pin motherboard connector,
or 24 pin motherboard connector
depending on your power supply,
and connect it into this power supply tester,
you should see that you have around 12 volts DC,
five volts DC, and 3.3 volts DC.
Now, you don't necessarily have to have exactly 12.0 volts,
or 5.0 volts, or 3.3 volts
for that power supply to be considered good.
There is a small variation or tolerance to this.
But, essentially, it should be very close to those numbers.
So for example, if you have 11.9 or 12.1,
that is considered 12 volts DC
for the purposes of a power supply tester
and saying you have a good power supply.
On the other hand, if you come back with something
like, seven volts DC or nine volts DC,
this is much lower than the 12 volts DC you're expecting
and your computer will not operate properly.
So make sure you keep this in mind
when you're using a power supply tester.
Generally, a power supply tester
will have connections on both sides of the tester.
Normally, the one on the bottom is the largest connector
and that's going to be able to connect your motherboard power.
On the top, you'll have four, six, and eight pin connectors,
as well as SATA power connectors and Molex connectors
in order for you to test all the variations
of different power components
that are coming from your power supply
to ensure you have the right low voltage DC
that's being provided by that power supply.
Now, the fifth cause of a power issue
could be that the power cables
is going from the power supply unit
to your different components, is faulty.
Now, if you have a power supply unit
that has cables that are able to be detached,
you can actually test each of those individual cables,
just like we did the power supply cable
going from the wall outlet to the power supply.
You're going to be able to do this using a multimeter
by measuring the resistance across that cable.
Again, you want a very low resistance level,
somewhere around zero ohms or slightly above that.
If you get a very high resistance level,
this means there's a break in that cable.
Now, when you're testing each of the detachable cables,
you will have to check each pin on each side of the cable
to verify you have full continuity.
Now, for example,
if you're using an eight pin CPU cable that's detachable,
you're going to have to test eight individual wires
based on the pin outs of that entire cable
to verify that the entire cable is good.
If even a single one of those eight pins
or eight wires inside of the cable is bad,
you're going to have to replace the entire cable.
Now, the sixth and final power issue
you might come across in the field,
is when you have an incorrect voltage setting
on that power supply unit itself.
Now, this isn't very common in newer systems,
because most newer power supply units
do have auto-sensing voltage
and there is no actual physical setting
on that power supply unit.
But in older power supplies and older servers,
you may still come across this voltage setting
on the back of the power supply unit.
When you look at the back of the power supply unit,
there will be a small switch that will allow you to set
either 110 to 120 volts AC or 230 to 240 volts AC.
Most commonly, this is going to be written as 115V or 230V.
If you have the incorrect setting on the power supply unit
and you plug it into a wall outlet
that's providing the incorrect type of power,
this can actually cause damage
to the computer or the power supply unit,
or it will just cause nothing to happen,
because there's not enough power.
For example, if you are in the United States
and you're using 110 to 120 volts AC
as your wall outlet supplied power,
but your power supply unit is set to a 230 volts setting
on the back of it,
this will actually cause nothing to happen,
because the power supply unit is expecting 230 volts
and you're only providing 110 to 120 volts.
So it's not enough power to turn on the computer
and nothing will happen.
Alternatively, though,
if you take a computer from the United States
set 110 to 120 volts AC,
and you plug it into a 230 volt wall outlet
in Europe or Asia,
this will actually damage the power supply unit
and it could cause a fire.
This is a really dangerous thing, so it's important
that you always check your power supply unit
and determine if it has one of these voltage settings.
If it does, make sure
you're selecting the right voltage setting
based on the area of the world
that you're going to be operating this computer in
and make sure it matches the wall outlets voltage output
to ensure you're not going to damage the system.
Now remember, there are six main causes of power issues.
First, your power button
might not be connected properly to the motherboard.
Second, the wall outlet
is not providing the right amount of voltage
or the wall outlet is faulty.
Third, the power cable to the computer is faulty.
Fourth, the power supply unit itself is faulty.
Fifth, the power cables
from the power supply to the components is faulty.
Or sixth, you have incorrect voltage
being set on the power supply unit
based on what your wall outlet is providing to you.
Remember to keep all this in mind
when your troubleshooting power issues on a system.