How to Troubleshoot, Dissemble, and Repair a Laptop Display
By Stephen Bucaro
You turn on your laptop, and nothing - just a black display. Well, the first thing you
need to determine is - is it a display problem or is the system dead? Do you hear the
hard drive spinning or the cooling fan blowing? If there are no signs of life, you can't
expect a dead computer to display anything. If you see physical cracks in the LCD
screen, it's pretty obvious that your going to need to replace the LCD.
If, when you started the laptop you heard the the hard drive spinning up, and
maybe you saw the manufacturer's splash screen or BIOS startup information being
displayed on the screen before it went dark, then you probably have an operating
system problem. If everything is totally dark and silent, you probably have a power problem.
Another thing to suspect before taking the laptop apart is a defective operating
system power saver mode. If the laptop starts normally but after a few seconds
the display goes dark, it may be going into power saving mode. Certain power saving
modes can cause the laptop to go to sleep abnormally and be unable to wake up.
Power saving modes such as "hibernation" were especially common with older
Windows operating systems. The solution is to disable all power saving modes before
the system goes to sleep.
It's important to realize that almost all laptops have a connector that supports a
second external display. Some laptops can be configured to disable the built-in display
and use only the external display. One important troubleshooting method is to connect
an external display. If you can get video on the external display, then you can eliminate
the power, the operating system, and the laptops video circuitry as being the problem.
Older systems used a tiny switch to turn off the built-in display when the lid was
closed. If you can see a tiny switch sticking up, you can put your finger on it and the
screen would go black and it will send the video to the external port. It's common
for these tiny switches to break, and not having an external monitor connected, you
would assume that your computer was dead. Newer systems use a magnetic switch,
so it's much less common for this to be a problem.
Many laptops use function keys to allow you to set if want to use the external port
for video or if you want to send video to both the built-in display and an external monitor.
To set the which display is active, you press the [Fn] key located at the lower left
of the keyboard, along with a function key. Unfortunately which function key you
press is not standardized.
Many laptops use the [Fn]-[F5] combination to toggle between the laptop LCD and
an external display. You can usually tell which function key to use by labels or graphics
on the function keys.
Another common problem with laptop displays is backlight failure. The backlight sits
behind the LCD screen, shinning through the screen allowing you to see the display.
The back of the laptop lid is lined with a highly reflective surface, such as metal foil,
to reflect as much of the light out through the LCD as possible. If you turn on your
laptop and the screen is dark but you can barely make out something on the screen
then your back light has failed.
The backlight is a fluorescent bulb. Fluorescent lights need a high AC voltage to
operate. A circuit board inside the laptop called the inverter circuit takes the lower
DC voltage from the laptop battery and converts it to a higher AC to voltage the
fluorescent back light. It's common for these inverter circuits to fail.
To replace the fluorescent back light or the inverter circuit board, You'll need to
take apart the laptop. Some newer laptops use an LED backlight, which uses DC
and is much more reliable than than the inverter fluorescent bulb setup.
If you're taking apart the laptop to check the inverter board and fluorescent bulb,
first check for loose or corroded connectors inside the laptop. Many times people
spill liquid or drop a laptop, and it works for a while, until the liquid corrodes a connector
or normal handling causes an already loose connector to separate.