The
main troubleshooting step is testing the video output on an external
monitor (or TV). You can connect your laptop to an external monitor
using VGA cable, DVI cable, HDMI cable or S-Video cable, it depends on a
type of connector you have.
Most models have a VGA connector, so
it would be the most common way to connect.Some laptops detect external
monitor automatically and start showing image on both screens right
from startup.
Other models can detect the monitor but
display image only on one screen (internal or external). In this case
you’ll have to switch video between internal and external using the Fn
key and one of the F* keys in the top row of the keyboard. This
combination varies for different brands, for example it’s Fn+F5 for
Toshiba, Fn+F4 for HP, Fn+F8 for Dell, Fn+F7 Lenovo etc…
FACTS VIDEO ON EXTERNAL MONITOR CAN REVEAL
If
both, the internal screen and external monitor (or TV) show strange or
incorrect colors or any other image distortion, this is the graphics
card failure.
If only the internal screen shows bad video but
external image appears to be normal (as in my example), the problem is
somewhere inside the laptop display. This could be bad connection, bad
LCD cable or bad LCD screen.
Let’s narrow down the problem one by one.
TRY RESEATING LCD CABLE CONNECTOR ON MOTHERBOARD
The
screen receives data signal from the motherboard via LCD cable. If the
LCD cable not making good connection with the motherboard, it might
cause image or color distortion on the screen. Try reseating the LCD
cable connector and see if it fixes the problem. Make sure the LCD cable
connector plugged correctly.
In most laptops the LCD cable
connector located under the keyboard bezel (aka keyboard cover). If it’s
not there, most likely you’ll find it somewhere under the keyboard.
WIGGLE THE LCD CABLE
The LCD cable
runs inside the display panel, under the screen. For this test it’s
necessary to disassemble the display, so you can access the cable.
A pinched or damaged wire inside the cable also can cause color distortion.
Wiggle
the cable while the laptop is running. If moving the cable affects
image on the screen in any way (it starts shown different colors, lines,
or image clears to normal, etc…) most likely the cable is defective and
has to be replaced. Try replacing the cable.
On the other hand,
if moving the cable doesn’t affect image at all, most likely the cable
is good and you have a failed screen. In this case you’ll have to it
with a new one.
APPLY SOME PRESSURE TO THE DISPLAY
Try applying some reasonable pressure to the top part of the display assembly. Squeeze it with your fingers.
If
the screen starts showing different colors, lines, or clears to normal
when you squeeze the top part of the display panel, most likely this is
screen failure. In this case you’ll have to replace the screen.