Instructor: In this lesson,
we're going to talk about physical cabling
and source selection issues
that may cause you to have issues with your video
or audio signals.
Now, when we talk about physical cabling issues,
this usually refers to the fact
that the cables will wear down over time,
especially if you connect and disconnect them repeatedly.
If you're connecting to an external display
using a cable that carries a digital signal,
something like HDMI, DisplayPort, Thunderbolt or DVI-D,
these cables, when they fail,
will completely make the signal disappear.
On the other hand, if you're using a physical cable
that's carrying an analog signal,
something like VGA or DVI-A,
these cables could deteriorate or break over time
and when they do, you'll still get a display image
but that display image will look wrong.
For example, VGA cables use 15 pins
that are connected to 15 individual wires
inside of the VGA cable.
If one of those pins or wires inside of that cable breaks,
you can have issues such as the horizontal hold
not being able to hold the image in place
or entire colors that will disappear,
such as the red, blue or green,
since it uses a composite image using this analog signal
over these cables.
Now, luckily for us, these days
most of our cables are going to be used with a digital signal
like HDMI, DisplayPort, Thunderbolt or DVI-D or DVI-I,
which is DVI Digital or DVI Integrated.
All of these carry digital signals,
so when these cables deteriorate
the entire signal is going to go away
and this makes it a lot easier to troubleshoot
that it's an issue with that cable.
If you come across a system
where the display is no longer displaying to the monitor,
this could be an issue where the cable is the problem.
Now, when you look at the cable,
there are several different things
that could be the issue here.
The first is that the cable itself
could have been broken over time.
This commonly occurs in an office environment
when you're using longer cables
and somebody rolls their office chair over the cable
and if this happens repeatedly,
the wires inside of that cable will break
and this will cause the signal
to not be able to reach the distant end,
which has your display.
If this occurs,
the best thing to do is to physically inspect the cable
and if you notice that it is physically damaged,
you would simply replace that cable.
Another thing that can happen with your cables
is when they're not properly inserted
into the connectors or ports.
Let's take the example of an HDMI connector.
You need to connect that cable into two places
in order to have a valid signal.
One is your source,
which would be the back of your computer
using your video graphics card
or the integrated HDMI port on your motherboard cluster.
The second is into the back of your monitor or TV.
Now, if the cable is not properly inserted
into the port on both of those areas
and it's not fully seated,
you're going to have an invalid connection and the HDMI signal
will not be able to move across that cable
and get to the display.
So, if you're having display problems,
you should check and make sure that both ends of the cable
are properly seated into the appropriate connections.
The third issue you might come across with a physical cable
is that that physical cable was a cheap quality cable
to begin with.
In this case, you may be limited at the top speed
that can be sent over that cable
And in the case of something like HDMI or DisplayPort,
if you don't have the top speed,
you're not going to be able to have the top resolution.
For example,
if you're trying to send 4K data over the cable
but you have a very inexpensive HDMI cable,
it may only support 1080P instead of 4K.
In these cases, you're only going to be able to get a HD image
and not a full 4K image.
If you're using a very high quality display or monitor,
you may notice that blurriness to it
because you're now using 1080P instead of a 4K image.
To be able to fix this issue,
you want to move up from a basic HDMI cable
into a high-speed rated cable instead
which can support those higher bandwidths
and be able to give you the full picture
that you're seeking.
For these reasons, when I'm working as a technician,
I always carry a couple of spare cables with me.
This way I can simply detach the cable
from the customer's computer and monitor,
replace it with one of my known good cables
and verify that it's not an issue with the monitor
or the video card and instead it was just the cable.
If this was the issue, we would then have to buy a new cable
and replace it for that customer's computer
to make sure we can get them back up and running fully
or we can leave our known good cable with them
and purchase a new one for ourself.
Now, it's also important to remember
that when you're dealing
with a lot of these digital standards like HDMI,
DisplayPort and Thunderbolt,
they can also carry audio over that same cable.
So, if the end user's having issues
hearing the sound from the system,
it could be an issue with that cable as well
and this would be another case
where you'd want to replace the cable with a known good cable
and see if this fixes the issue.
If you're using VGA or DVI cables though,
these cannot carry sound and in those cases
the audio issue you're experiencing
would be tied to the fact
that they don't have a proper cable connected
for the audio connection.
In these cases, you want to verify that the audio cable
is connected from their speakers
into the back of the computer
using the 3.5 millimeter jack or the SPDIF connection
if you're using a digital fiber optic connection
to your audio system.
Another issue you may come across
is when you have the incorrect data source selected.
This can happen a lot when you have a display
that supports multiple HDMI or DisplayPort connections.
For example, I have a 4K monitor
that has two different HDMI ports on it and one DisplayPort,
so it has three source inputs
that they label input one, two and three.
If I connect my computer into the HDMI port
that is labeled as input one but I've selected input two
or three on that display, I'm going to see a black screen
and it's going to say, "Missing source."
In these cases,
you simply need to be able to change the setting
on that monitor to be able to select the right input.
Normally, the monitor will have a button on it
that's labeled as input or it'll be a little square
with an arrow pointing into the square
that indicates this is the input selector.
In these cases, simply switch to the input
where your cable is plugged into
and this will be able to show the image
on the display properly.
Now, the final thing I want to mention
is that sometimes you may have an issue
when you're dealing with HDMI devices
going from a computer to a TV
or from some sort of a set top box to a TV.
For example, if you have a smart TV device like an Apple TV,
Amazon Fire or Roku device
and you plug it into your TV over HDMI,
it actually uses a content protection system
over that connection to be able to make sure that the TV
and the device are authenticating to each other.
This is known as HDCP
or High-Bandwidth Digital Content Protection.
Now, this was a type of coding scheme
that was developed by the manufacturers
to protect the audio and video signals
that are going between the systems over HDMI,
DisplayPort and other technologies like this.
The whole purpose of this system
is to prevent people from being able to copy
or illegally intercept the signals
from a streaming video session.
Now, all that being said,
sometimes it doesn't work perfectly.
In those cases,
you need to understand how to troubleshoot issues with HDCP.
Now, the first thing I want you to do,
if you're having an issue with HDCP,
is simply turn off the TV and turn off that device
and then turn on the TV and then turn on the device.
By doing this and making sure the TV is on first
and then the device, it will allow the handshake to occur
and usually this will fix about 75% of the issues you have
with HDCP.
The other thing you can do if this doesn't work
is upgrade the quality of the HDMI cable
that's being used between the two devices.
Again, this is an area,
where if you're using a very inexpensive type of cable,
you can have issues
because the signal's not being properly sent
and there's not going to be that copyright handshake happening
over HDCP properly.
So, if you find that you're having this issue a lot,
what you're going to want to do is replace that cable
with a higher quality HDMI cable
that can support higher bandwidth operations
and that is made of a higher quality,
like a gold plated connector
to ensure you're getting a proper signal between the two
and there's no interference during that handshaking process.
Keep this in mind if you're working
with any kind of set top boxes, smart TV devices
or even game consoles
because all of these do use HDCP
and if that handshake doesn't occur properly,
you're not going to be able to get it onto your display
and be able to use those devices.
And instead, you'll get an error saying, "HDCP Error.
The device you're trying to connect
is not authorized for use on this system."
So remember, when it comes to display issues,
usually this is going to come down to one of two main areas.
It's either going to be a physical cabling issue
such as the cable is of low quality
or not properly seated into the connections
or you've selected the incorrect data source on the display
and therefore, it's looking on input two or three
instead of input one and showing the wrong image
or no image if nothing's connected to those ports
on the display.