Troubleshooting backlight failure

This laptop came for repair because of the LCD screen backlight failure. My customer complained that the laptop LCD screen is black but the laptop works with an external monitor.

Here are my steps for troubleshooting this laptop with the backlight failure.

First of all, I tested this laptop with an external monitor connected to the VGA port and the external monitor worked absolutely fine. I was able to get crystal clear image on the external screen even though the internal screen didn’t light up. If the external screen works fine, then most likely there is nothing wrong with the video card.

Notebook display assembly diagram

After that I took a closer look at the laptop LCD and noticed that the screen is not completely black. The laptop screen still works but the image is very very dull, you barely can see it. It means that the screen still gets data signal from the video card, but for some reason the backlight lamp doesn’t work.

From my experience I know that this problem can be related the lid close switch, faulty inverter board or bad backlight lamp. I checked them one by one.

If you have a similar problem, make sure the lid close witch moves freely. The lid switch is a small button located close to the LCD screen. This button triggers the hibernation or sleep mode when the screen is closed. If the lid close switch is dirty, it might get stuck inside the laptop case and cut off the power from the inverter board. The inverter board works as a power supply for the backlight lamp and if there is no power coming to the inverter board, the backlight lamp will not light up either.

In my case the lid button worked properly, it didn’t stuck inside the case. When I was pressing on the button very fast, I was able to light up the screen but only for a fraction of a second. The image wasn’t bright and it had a pinkish tone. A pinkish tone usually indicates a problem with the backlight lamp, not the inverter board.

Even though I suspected the backlight failure, I decided to test this laptop with a new inverter board just in case. But it didn’t help. The screen didn’t light up even after I replace the inverter board. So, I was right, this problem is not related to the inverter board.

Finally, I disconnected the screen backlight lamp connector from the inverter board and connected my test backlight lamp (I removed it from another cracked screen). You can find a new backlight lamp on eBay. Try to find a backlight with the connector already attached to it, so you can plug it into the inverter board. Make sure the connector on the backlight lamp is similar to the connector on your LCD screen.

As soon as I turned on the laptop, my backlight lamp lighted up. Yep, that’s the problem. The laptop screen has a faulty backlight lamp.

Here’s another laptop with backlight failure

This laptop video fails in a little bit different way. In this case the backlight lamp hasn’t failed completely.

The laptop starts with video on the screen but the background has reddish tone, the screen flickers and it makes noticeable buzzing noise coming from the backlight and inverter area. After a few minutes the backlight turns off by itself and the buzzing noise stops. When the backlight is off, the image on the screen is still visible but it’s very dark.

I removed the screen bezel and connected my test backlight lamp.

My test backlight works absolutely fine. The lamp doesn’t flicker and there is no buzzing noise. So, this laptop needs a new backlight lamp.

Link Ref : http://www.laptoprepair101.com/troubleshooting-laptop-with-backlight-failure/

How to replace backlight lamp (CCFL)

In this guide I will disassemble a laptop LCD screen in order to remove and replace the backlight lamp (CCFL).

Replacing the backlight lamp is not an easy task even for experienced technicians. If you do something wrong you will permanently damage the LCD screen and have to buy a new one. Proceed on your own risk and do not blame me.

Some recommendations before you start:

1. Work in a clean room. You don’t want dust and lint inside your LCD screen.

2. Make notes, so you know how to assemble your screen back.

3. Take pictures.

4. Before you remove something, take a closer look at the part and memorize how it is assembled.

5. When you are assembling the screen, remove dust and lint with compressed air. Do not use cloth.

The backlight lamp (CCFL) is located inside the LCD screen, so we are going to take it apart. In this article I’m not going to explain how to remove LCD from a laptop, it’s been covered before.

Remove sticky tape and foil from the back of the screen and glue it somewhere so you can reuse it later, when you assemble the screen.

Removing tape from the backlight cables.

On my screen the green circuit board was glued to the plastic frame with a double sided tape. Carefully unglue the circuit board. Be very careful, do not flex or bend the circuit board.

The circuit board has been unglued.

Place the LCD screen on the side and start removing the metal frame witch secures the LCD to the plastic frame. There will be many latches on all sides of the frame, you can unlock them with a small screwdriver.

Continue separating the metal frame from the plastic base.

On the following picture you can see that frame, LCD with the circuit board and screen base have been separated. Be careful, do not touch internal components with your fingers. Handle all internal components by the sides.

Place the metal frame and LCD with the circuit board aside. You’ll need them only when you assemble everything back together.

There will be a few transparent layers inside. Carefully remove them from the screen base. Do not separate the layers, just put them aside together.

Keep everything organized, so you have no trouble assembling the screen.

Start removing the metal cover from the backlight lamp (CCFL).

The backlight cover has been removed.

The backlight lamp (CCFL) cables are routed through small plastic hooks.

Unroute the backlight lamp cables.

Now probably the hardest part in this disassembly process – removing the backlight lamp and reflector. The backlight lamp is secured inside the reflector so you have to remove both and then separate them.

Before you remove the backlight lamp and reflector take a closer look how it’s assembled and mounted to the screen base. Fitting the backlight and reflector back in place could be a very challenging task.

The reflector is glued to the screen base with a double sided tape.

After the reflector has been unattached from the screen base, you can start removing the backlight lamp. As you see on the picture, I marked the left side of the reflector with a red dot so I know where the red cable goes when I assemble everything back together.

The backlight lamp (CCFL) has been removed from the reflector.

In order to access the backlight lamp leads you’ll have to remove the rubber caps from both side of the lamp. I’m not sure if you can touch the backlight lamp with your fingers, so I would use rubber gloves.

Cabled on both sides of the backlight lamp are soldered to the backlight leads. In order to access the leads you’ll have to remove the black insulator on both side of the lamp.

Unsolder both cables from the old backlight lamp and solder them to a new one.

You can test the new backlight lamp (CCFL) before you install it back into the screen. Connect the backlight lamp into the inverter board and turn on the laptop. The backlight lamp should light up.

From my experience, on some laptops the backlight lamp will not light up until the video cable is connected to the LCD screen. In this case you’ll have to assemble the LCD screen and then test it.

Link Ref  : http://www.laptoprepair101.com/replace-laptop-backlight-ccfl-lamp/

Display assembly diagram

Here is a simple diagram that will help you to understand how a notebook display assembly works and how an image appears on the screen. I’m not an artist and I tried my best drawing this diagram, so if you cannot see a laptop in this picture, don’t be mad.

A generic display assembly includes a very few parts and knowing them will help you to understand witch part can cause a problem if you laptop video not working properly.

Video cable. A video signal from the motherboard goes to the LCD screen through the video cable. The video cable connects to the motherboard (or video card) through the connector 1. The video cable connects to the LCD screen through the connector 2. The video cable (in most cases) is also responsible for supplying a necessary voltage for the FL inverter board. The video cable connects to the FL inverter board at the point 3.

FL inverter board. This board is responsible for converting low voltage DC power (point 3) to high voltage AC (point 4), necessary to light up the backlight bulb. If the FL inverter board is bad, the LCD screen (backlight bulb) will not light up when you turn on the laptop, but you still should be able to see a very dim image on the screen.

CCFL (backlight bulb). When the backlight bulb lights up, you can see an images on the LCD screen. In most cases the backlight bulb is a part of the LCD screen and if it’s bad, the entire screen has to be replaced. By the way, some specialized repair shops can replace the backlight bulb itself.

Lid close switch. The lid close switch is a small button that locates close to the display hinges. On some newer models there is no button, because the switch is magnetic. You can set up your laptop to go to a hibernation mode or to a standby mode when the LCD is closed. It’s done through power management software. These modes are triggered when the display is closed and the lid close switch is pressed down. If the LCD screen on your laptop will not light up when you open the display assembly, check the lid close switch is stuck inside (it might happen because the switch is dirty).

Link Ref : http://www.laptoprepair101.com/notebook-display-diagram/

How to test screen inverter

In this post I explain how I test the inverter board in a laptop.

The inverter failure is very similar to the backlight lamp failure. In both cases the screen gets very dark and the image becomes very faint, barely visible under a bright light.

There is only one reliable way to test the inverter – replacing it with another one and see if the screen lights up after that.

Alternatively, you can connect a new backlight lamp and see if your presumably bad inverter lights it up.

In most cases I go with the second method – using my test backlight lamp. Why? Because the same backlight lamp will work with many different inverters as long as they have matching connectors.

Usually the inverter is mounted inside the display panel below the screen. In most cases you can access it after you remove the display bezel. The inverter has connectors on both ends. The left side connects to the LCD cable. The right side connects to the backlight lamp which is mounted inside the screen. Check out this display diagram.

To make sure that inverter gets power from the motherboard (via the LCD cable), you can test it with a voltmeter. In my case I connected the “+” lead of the voltmeter to the pin 1 and the “-” lead to the ground trace around the screw hole. I got about 19.4V DC on that side of the board, so it’s getting power from the motherboard.

WARNING! If you accidentally short something on the inverter while testing, you can damage it. Proceed on your own risk! Not sure? Don’t do that!

So far we know the inverter is getting power from the motherboard, but the screen still has no light. Apparently, it’s either bad inverter or failed backlight lamp.

Now let’s test it with a known good backlight lamp.

1. Unplug the screen backlight cable from the right side of the inverter.

2. Connect a known good backlight lamp.

Turn on the laptop.

1. If the test backlight turns on, the lamp inside the screen is bad. In this case you’ll have to replace the screen. Also, you can replace the backligth lamp which is not easy and not recommended.

2. If the test backlight doesn’t turn on, most likely we have inverter failure. Replace it and test the laptop again.

There are two different types of backlight connector, you can see them on the picture below. The top one (big) is not as common as the bottom one (small). I mostly use lamps with a small connector.

IMPORTANT! When you buy a new lamp for test, make sure the connector fits your inverter.

On the following picture you see how I’m testing the laptop with a new lamp.

Link Ref : http://www.laptoprepair101.com/how-test-lcd-screen-inverter-in-laptop/

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.

Link Ref : http://www.laptoprepair101.com/laptop-runs-hot-turns-off-freezes/

How to reinstall factory OS

How to reinstall factory OS

In this post I explain how to reinstall factory operating system. This should work for most laptops running Windows Vista or Windows 7 OS.

This could be useful if your OS stopped working properly, got corrupted or infected with a virus.

WARNING! Running system restore utility will erase all personal data on the hard drive and re-image it back to factory defaults. Make sure all personal data is backed up before reinstalling the OS. Also, make sure the laptop is running on AC power during the recovery process.

These days most computers are sold without recovery discs. Instead they have a hidden (or visible) recovery partition with the factory image. In order to re-image the hard drive back to defaults it’s necessary to initiate the recovery wizard and it’s very similar for many different brands.

As an example I’ll show step-by-step operating system re-installation process on HPs.

How to start Recovery Manager on HP laptops.

STEP 1.

Turn on the computer and press the F8 key when HP (or any other brand) logo appears on the screen.

STEP 2.

On the next screen you should see Advanced Boot Options.

If for some reason you don’t get this screen, restart and try the F8 key again.

From all available options select the very first line: Repair Your Computer and press on the Enter key.

STEP 3.

This should take you to the System Recovery Options.

Select available language and keyboard layout. Press on the next button.

STEP 4.

On the next screen select your user name (must be user with administrative rights) from the drop down menu.

Enter the user password and press the OK button.

STEP 5.

This will take you to the next System Recovery Options window.

The last option will be HP Recovery Manager. Click on it.

STEP 6.

This will take you to the next window: HP Recovery Manager.

There are many different options here and one of them – System Recovery (Restore your computer to its original factory conditions).

Select this option and follow the instructions on the screen.

How to start Recovery Wizard on Toshiba laptops.

In order to start Toshiba Recovery Wizard you follow STEPS 1-5.

This will bring you to the same System Recovery Options with Toshiba Recovery Wizard at the end.

Click on the Toshiba Recovery Wizard button.

On the next scree you’ll see Toshiba warning about data deletion. Click the next button.

In the next Toshiba Recovery Wizard window you can select Recover to out-of-box state option.

Click on the next button and follow instructions.

How to start Backup and Recovery Manager on Dell laptops.

Here’s another example.

Again, follow steps 1-5 and on the System Recovery Options select the very last option: Dell Backup and Recovery Managers.

This will take you to the next window where you can start the operating system re-installation process. Follow the instructions.

Other options.

If the above mentioned way doesn’t work, try this.

Hold down the “0” (zero) key and turn on the computer. Do not release the key until the recovery interface starts loading.

Link Ref : http://www.laptoprepair101.com/reinstall-factory-operating-system-on-laptops/