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- Remember that the POST stands for

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power on self test.

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And it's something that your BIOS does

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when your computer starts up.

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But what if you can't see
anything on the screen?

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Well, if you can't

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you're gonna want to use
some type of POST tester

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and we're gonna show how
to use a POST card tester,

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but you don't see these that often anymore

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for PCI express.

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However, some motherboards
include a POST tester

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and will show that on the motherboard

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within the AV editor computer.

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So let's get started.

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- [Narrator] Let's talk
about POST devices.

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The POST is the power on self test

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and we know that the motherboard does this

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the BIOS,

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or your UEFI does this.

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And it checks all your devices.

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Now what's great about the POST is

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if there's a problem

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you might get a beep code.

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You might see an indicator light in here.

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You might get a message on the screen.

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But what if you don't
get any of those things?

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And you're not sure what the problem is.

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Well, then you can use a POST device,

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a POST tester,

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to find out what the problem is,

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which is quite often

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one of the big four that we talked about,

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CPU, RAM, motherboard,

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or video card.

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And there's various types of POST devices.

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Back in the day you'd use a card,

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and the card would be a PCI card.

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And you'd connect the card,

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then boot up the system

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and there would be a readout

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with the two digit display,

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and you'd find out what the code means

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within a book or online documentation,

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or what have you.

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Nowadays you don't have
PCI slots as much anymore,

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and you're gonna be hard pressed

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to find a PCI express POST card.

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You might find one,

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you might find a USB tester.

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But I gotta be honest with you,

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they're generally not necessary.

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I've used the POST testers in the past.

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Maybe once out of every 50 computers

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that I worked on.

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And with the newer UEFI

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it's not as necessary
to be honest with you.

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But the best types of
POST device is the one

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that's built into the motherboard.

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And that's one of the reasons
I chose this motherboard

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cuz it has a built in POST tester

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and the two digit code is right here.

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So when you boot the computer,

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it'll run through a series of codes

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and it'll stop if there's an error.

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So everything is connected now.

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I connected everything back up

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from the previous lessons.

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And so we're gonna boot the system now.

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And you can see the various codes

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it's going through.

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It's testing everything.

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And generally with these POST testers

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if it ends at 00,

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or FF,

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you're in good shape.

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And that means that the
system has booted properly.

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And for this device, AA is also okay.

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That's a special code

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and that's actually all right.

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Now, if you wanna learn
more about the codes

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for your POST tester,

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you wanna look at the documentation.

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And so that might come with a book.

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If it's an external POST tester,

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or if it's say an external USB,

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or an internal PCI POST tester,

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and it might come in the book,

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the manufacturers documentation
with the motherboard.

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And this motherboard is from Asus.

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And these are known as Q codes.

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That's what they call 'em.

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So there's a whole ton of them

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a whole different list of
problems that could occur,

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but the AA is okay

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and the system will boot all right

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if it's set on AA.

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Now there's a lot of other
possibilities obviously.

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You saw there's probably dozens there.

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So I'm gonna shut down the computer

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and pull a stick of RAM,

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and then reboot

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and see what error message we get.

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Okay. So always make sure that

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the little lead light on the motherboard

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has turned off before you touch
anything inside the system.

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And so I have removed
all of the RAM sticks.

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And so now we'll power
the computer back up.

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Okay. And it goes through a couple codes,

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and right away it stops at the 53 code.

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Now this is hexadecimal by the way.

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So you can have a lot of
different options here.

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You might see numbers or letters.

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And if we were to look at

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our manufacturers documentation here,

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we'd see down here,

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50 through 53,

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is a memory initialization error.

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Invalid memory,

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incompatible memory,

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or in this case, no memory

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that's what we have in this case.

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So you can look up what's happening

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and these codes are usually right.

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If you have an issue

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with incompatible memory,

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or if you have, you know,

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two sticks that are not the same,

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two different speeds,

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or they're in the wrong slots, you know,

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you'll usually get a 50 through 53 code.

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So I'm gonna fix that right now.

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We'll shut down the system

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and it hasn't even booted properly

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because there is no memory in there.

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Wait for that lead to go out

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and I'll put the RAM back
in and boot it back up.

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Okay. So I put the RAM back in

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and always be sure to
use your documentation.

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You wanna know where your
RAM is supposed to go.

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If you're using dual channel,

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or tri channel,

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or quad channel, you know,

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there's gonna be a whole diagram

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and then description
of what the slots are.

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So make sure you're putting
them in the correct location.

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And so we'll boot this guy back up.

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Let that guy run through.

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And again, usually this is
a problem with connections

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or a device isn't there,

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it's missing or it's incompatible.

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And usually you can find
these things with your eyes.

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You can find out what
the problem is generally.

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But here we go.

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AA is the code.

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Everything's good.

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That's how this normally
boots and we're in good shape.

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So now we can use the system
to our heart's delight.

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So that's POST testing

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and this is outside of what the BIOS

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or UEFI does for you.

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This is beyond that.

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So it's diagnostics

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in the case that

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you can't see anything on the screen,

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and you don't hear
anything on the computer.

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And again, older devices,
you could use a PCI version.

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Again. I rarely use that.

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Maybe one out of every 50 computers.

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And you might see a PCI express,

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or a mini card version,

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or a USB version,

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but the best ones are the ones that built

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into the motherboard

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but they all work essentially the same.

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It's a two digit code

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and you have to cross reference that

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to your documentation,

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to find out what the error is.

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But keep in mind

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if you see something
like AA, or 00, or FF,

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generally, that means the
system's booting properly.

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And you wanna look
elsewhere for the problem.

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And so that's it for this sub lesson.