Tuesday, January 11, 2011

Why laptop turns off or freezes?

My computer runs very hot and eventually turns off or freezes – this is one of the most common complaints I have been receiving from my customer for many years.
Why it’s happening? Is there an easy fix for that?
Most likely this problem is heat related. Take a look at the following picture.


Any laptop has a cooling module which includes two parts: the heat sink and cooling fan. When it works, the processor (CPU) heats up and the heat sing heats up too. At some temperature level, the fan kicks in and cools down the heatsink.
The problem starts when the cooling module collects too much dust inside. The dust kills normal airflow inside the cooling module. Eventually, the processor overheats and the laptop turns off unexpectedly or freezes.
This problem can be fixed by cleaning the cooling module.
Cleaning the cooling module.
Some laptops give you an easy access to the heatsink and fan. In laptops like that you can access the cooling module through the bottom cover.

In my example I had to remove the cooling module. Otherwise, I wouldn’t be able to remove the fan and access the heatsink.
In some models you can remove the fan without separating the heatsink from the CPU.
After I removed the fan, I found a thick layer of dust inside. Cleaning it up will fix the overheating problem.

Apply thermal paste on the processor.
You should apply new thermal paste before installing the heat sink back in place.

Remove old thermal paste from the processor and heatsink using alcohol swab.
WARNING: In some models the heatsink also covers the graphics chip. The part of the heatsink which covers the graphics chip might have thermal pad on it instead of regular thermal paste.
Do not replace thermal pad with thermal paste! Do not apply thermal paste on the thermal pad! Just leave thermal pad alone and apply thermal paste only on the processor.
I usually use Shin-Etsu paste which is relatively cheap and performs well.

After applying new paste, install the cooling module back in place. Do not forget to connect the fan cable to the motherboard!
What if the cooling module cannot be removed easily?
In some laptops the cooling module is buried deep inside the case and cannot be easily accessed and removed. In order to remove it you’ll have to disassemble the whole laptop but it’s only for experienced users.
In this case you can use the following technique. It’s not perfect but works very well.

Buy a can of compressed air or use a compressor.
1. Blow air into the fan grill on the bottom.
2. Blow air into the fan grill on the side.
Switch direction a few times until all dust is gone. Most likely this quick cleaning will fix your problem too.

Friday, January 7, 2011

Screen shows strange colors

The screen started showing strange or wrong colors. What could be wrong? I’ve been asked this question many times and today I’m addressing the issue.

In this post I explain some basic troubleshooting techniques in case if your screen started showing strange or incorrect colors.
You have to know how to disassemble your computer in order to use following troubleshooting techniques.

TEST WITH EXTERNAL MONITOR
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…
WHAT VIDEO ON EXTERNAL MONITOR CAN TELL?
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.
Also, you might be interested in the following posts:
Troubleshooting backlight failure.
How to test screen inverter.
Bad video on the screen. What is wrong?
Fix video problems.