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.

Related articles:

Troubleshooting backlight failure.
Screen shows strange colors.
Troubleshooting video problems.

Support this site.

 

248 Comments

Pages: « 2511 10 9 8 7 6 5 4 [3] 2 1 » Show All

  1. 28
    davd Says:

    also, it’s pretty worthy to note that the inverter itself gets very warm while in use. I checked its temperature and it was up to 102 Fahrenheit, I’m thinking that is abnormally high for inverters.

  2. 27
    davd Says:

    I have a Fujitsu LifeBook C Series computer, and it is having intermittent problems, that I believe to be in the inverter. I’m looking for a opinion from more experienced folks. Every once in awhile (usually after having been off for a while), the screen will go out, literally. It will freeze the image on the screen and warp it while it goes out. Simply moving the screen on its hinges fixes the problem and puts the LCD right back where it should be – in perfect looking condition. It may take up to 3 or 4 hinge movements before it finally comes back. I’ve never not been able to bring it back. The inverter is located directly under the LCD.

  3. 26
    cj2600 Says:

    Nathan P,

    all the white colors (only true white, off white is fine) turns into this pink color with white lines and all the black (True black) turns into this green flashing color. if I move the screen about it some times gets better or worse but sadly my screen case is broken so I have to prop it up against pillows. Is this simply an issue with my screen inverter or with the wires, and is it fixable or not?

    Your problem is not connected to the inverter board. The screen is bright and you can see it, so the inverter works properly.
    I think it’s either bad video cable or LCD.
    You said, you can make it better or worse if you move the screen. I think your problem is connected to the video cable. I would try replacing the cable first.

  4. 25
    cj2600 Says:

    Brian,

    What if the screen comes on for a while then goes out. It does the same with an external monitor

    Can you boot to the desktop or it fails before the laptop finish loading Windows?
    Enter the BIOS setup menu and wait. Does it fail in BIOS?

  5. 24
    cj2600 Says:

    moteldanny,

    i just split the soymilk on my laptop, while i didn’t get a chance to shut it off, and right now, when i open my laptop, the screen is very dark, but i can still see a little,very very dark, do you think it is inverter problem or it is motherboard’s

    There is no way you can tell without testing the laptop with a known good inverter board. If you spilled milk on the keyboard (not display), probably your failure is related to the motherboard.

  6. 23
    moteldanny Says:

    i just split the soymilk on my laptop, while i didn’t get a chance to shut it off, and right now, when i open my laptop, the screen is very dark, but i can still see a little,very very dark, do you think it is inverter problem or it is motherboard’s….

  7. 22
    Brian Says:

    What if the screen comes on for a while then goes out. It does the same with an external monitor

  8. 21
    Nathan P Says:

    I have an issue with my laptop that I think is connected to the screen inverter. all the white colors (only true white, off white is fine) turns into this pink color with white lines and all the black (True black) turns into this green flashing color. if I move the screen about it some times gets better or worse but sadly my screen case is broken so I have to prop it up against pillows. Is this simply an issue with my screen inverter or with the wires, and is it fixable or not? can you recommend a good repair shop is Boise, ID that won’t tell me to get a new laptop? thank you for your time.

  9. 20
    Dave Says:

    I had computer in rain. Screen is still quit legable with some distortion of images. I ruled out motherboard and video card. So I thought it was the screen. I ordered new one hooked up the inverter to backlight backwards. Some sizzle then went dark. I then installed connector properly and screen lit up fine, but image is still garbled. Did I ruin new screen or ids the problem lcd cable. Thank You.

    Dave

  10. 19
    Cameron Says:

    Hi CJ,

    Thank you so much for your thorough review! It is very helpful!

    My Inspiron 1520 has recently had random backlight failures in
    which the screen goes dim. It always re-lights if I sleep and resume (or whenever I start an external monitor). The backlight stays on for a few minutes and then fails again.

    Does this sound like a failing inverter or could there be other explanations?

    Thanks again!
    Cameron

Pages: « 2511 10 9 8 7 6 5 4 [3] 2 1 » Show All

Leave a Reply