Instructor: In this lesson
we're going to talk about POST issues.
Now, POST stands for the Power On Self Test,
and the Power On Self Test is a diagnostic program
that exists inside the system's firmware,
and it's going to check the hardware
to ensure that all the components are ready
for you to be able to boot up the PC.
This includes things like the processor, the memory,
an input device like the keyboard
and an output device like a video display.
On older systems, these POST messages
would be displayed to your monitor,
and that still happens on modern systems,
but it happens very quickly
so you're unlikely to actually see those messages
on your display if everything is working properly.
If things aren't working properly
then it would actually show that display message
and pause the booting up of the computer
and that way you can start determining what that error is.
But in addition to that visual indication on your display,
there's also an audible indication that comes
in the form of a series of beeps.
Each of these beeps indicates different things,
based on the Power On Self Test and its results.
For example, if you hear one short beep,
this means there's a normal Power On Self Test
and everything is okay with the system
and it's going to be able to boot up.
Now in most modern PCs inside of your UEFI or bios,
you can actually configure whether or not
you want to hear this beep on a regular basis.
By default, this beep is normally turned off
by your system manufacturer,
but if you go into your UEFI or BIOS,
you can enable that
and be able to hear that Power On Self Test
every time you boot on the computer
by hearing that single short beep
that tells you everything is working fine.
Now, there's lots of other beep codes as well
but each beep code is going to be set
by the manufacturer of your motherboard.
Remember, the Power On Self Test diagnostic tool exists
within your UEFI or BIOS as part of the system
firmware that has been installed by your manufacturer.
So the ones I'm going to go over right now
are actually some of the original ones
that were created by the first IBM PCs back in the 1980s.
And most manufacturers use these
or something similar to them.
For the exam, you don't have to memorize
what each beep means.
For example, if I said two short beeps,
you don't need to memorize
that that means that there's a POST error
and therefore you're going to see
some kind of an error message on the screen.
But I want you to be aware of this
because as you're troubleshooting systems
you may need to use these POST codes
if you don't have any kind of output on the screen,
or something is going wrong during the boot up process.
Now, if you hear no beeps
this means you have some kind of a power supply issue.
Why, because there's no power
and therefore there's no Power On Self Test or beeps.
In addition to this, if you have a faulty speaker
you may also not hear the beeps,
even though the computer is booting up.
So again, you have to take all this information
and then decide what is happening
based on your troubleshooting.
Another thing you might hear is one long continuous beep.
Now, when you hear a long continuous beep,
this usually indicates some kind of a memory problem.
This could be the memory controller on the motherboard
or the memory modules itself that have gone bad.
In either case, if you hear this long beep,
that would be something you'd want to investigate
in terms of memory.
Another thing you might hear is a series
of beeps that just continually repeats
and this is usually going to be short beeps,
so it'll just be like, beep, beep, beep, beep, beep.
And when you hear that over and over again,
that usually indicates there's a motherboard problem
or some kind of a power supply fault
where you're getting some power
but not all the power that you need
to be able to run the full system.
Another indication of a motherboard problem would be
if you hear one long beep followed by one short beep.
In addition to that, you might hear things
like one long beep followed by two or three short beeps,
and this would be a video adapter error.
And in this case, you're not going to see an output
to the screen because your video display
is not being able to be controlled by that system.
And so this can be one of those important
POST test beeps that you're going to be listening for
because you're not seeing anything on the screen.
Another issue you might have is
if you hear three long beeps.
Now, three long beeps means
there's an issue with your keyboard.
Now, most of the time this indicates
that the system can't detect the keyboard,
but the other thing that might happen is
that that keyboard is getting incorrect or unexpected input.
For example, have you ever had a pile of books on your desk
and one of them falls on your keyboard
and it's holding down one of the keys?
Well, if you have,
and you try to boot up your system
with that key depressed the entire time,
that could actually cause this three long beeps to occur
because that's seen as a keyboard issue.
So if this happens,
just make sure you move everything off the keyboard
and that there's no keys being stuck down.
This can also happen if you have
some kind of a sticky residue on the keys
that's holding it in place
instead of that key being able to release itself
back to its normal position.
So you may need to change out your keyboard
or clean the keyboard to solve this issue.
Now again, I want to remind you
that all these beep codes are from the original IBM PC
and they're not something you have to memorize for the exam.
But you should be aware that beep codes are associated
with Power On Self Tests or POST.
And these Power On Self Tests are used to check the system
before it boots up, to ensure that everything is in place
that it needs to be able to run a basic system.
This again includes things like your processor,
your memory, your input, and your output devices.
Also, remember that these POST beep codes
are going to be specific to your motherboard
and that manufacturer is going to control it.
So always check the manufacturer's documentation
to be able to understand what the beep codes mean
for your specific motherboard.
Now, the final thing we need to talk about
when it comes to the POST test is the fact that
there is also the ability to use an expansion card
to give you even more detailed information.
For example, you can get a PCIE x1 card
that will plug into one of your expansion slots,
and on that card it's going to have a series of LED lights
that will indicate what problems
may exist with your motherboard.
And some of the more detailed POST expansion cards
will also have a two digit display on them
that you can use to be able to see codes
from 00 to FF, written in hexadecimal format.
This can provide up to 256 unique error codes for you,
that can give you a lot of detailed information.
So instead of just hearing a beep
and knowing that there is a motherboard issue,
using one of these POST test cards
can actually tell you specifically
what is wrong on that system.
Now, as a general technician, you're probably not
going to be going that specific to identify the exact component
on the motherboard that's broken
because you're not going to be unsoldering different resistors
or capacitors on that motherboard and replacing them.
But if you are working
in a micro miniature electronics field, you could use things
like a POST test expansion card
to be able to identify exactly which component
on the motherboard is faulty and needs to be replaced.
But for most of us working as an entry level technician,
we are not going to be going down to the component level,
and instead we just need to identify
that the motherboard has a problem and needs to be replaced.