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.

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248 Comments

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  1. 178
    caz Says:

    my laptop screen works okey but at times displays horizontal lines and the display hangs.on a slight touch of the plastic holding the screen it works ok.what could be the problem?

  2. 177
    cj2600 Says:

    Memphis,

    On my screen image is shown as a negative, you can see the outlines of images

    The photo you provided is bad quality and hard to see what’s going on.
    But if the image turned negative, most likely this is LCD screen failure. You’ll have to replace the screen.

    I think the inverter is not a problem because the screen lights up

    That’s right. This is not inverter issue.

  3. 176
    Memphis Says:

    Greetings!

    On my screen image is shown as a negative. I think the inverter is not a problem because the screen lights up! I think it is a flat cable, I’d love to hear your opinions!

    thanks

  4. 175
    Mike Says:

    I just found the screen by searching for Inspiron 6000 screen on Ebay, then made sure it matched up in terms of size, resolution, and WXGA. And of course the listing said it was compatible with my model. Is there anything else that has to be the same?

    I will try reseating the cables…it was very difficult to get the video cable inserted at first. I realized after a few minutes that while the actual connection was the same, the new screen was not set up for a connector that had the little locking hinges on the sides, and once I took those off it slid in fairly easily.

    Anyway again thanks for the help; if I don’t get a picture after reconnecting the cables I guess I’ll try to get an exchange.

  5. 174
    cj2600 Says:

    Mike,

    The screens are the same in that they’re the same size, resolution, and they’re both WXGA. They are different in that the new one is the more “shiny” screen that you usually see today, whereas the original was the more dull type that was around more often when I bought the laptop (approximately 5 years ago). Would that make a difference or is it more likely that the new screen is simply defective?

    Apparently, the new screen is Glossy and the old one was Matte. If both screens are identical, it shouldn’t make a difference.
    I cannot tell if your new screen is compatible. How did you find the screen?
    By the way, didn’t you check connection between the LCD cable and new screen. It’s possible the cable not seated correctly and because of that you have no image. Try reseating the cable.

  6. 173
    Mike Says:

    Thanks for the info man.

    The screens are the same in that they’re the same size, resolution, and they’re both WXGA. They are different in that the new one is the more “shiny” screen that you usually see today, whereas the original was the more dull type that was around more often when I bought the laptop (approximately 5 years ago). Would that make a difference or is it more likely that the new screen is simply defective?

    Thanks again for the help.

    Mike

  7. 172
    cj2600 Says:

    Mike,

    The bottom 3rd of my LCD stopped working completely (wasn’t getting any light etc)

    This part sounds like the LCD screen failure.

    so I just purchased and installed a replacement. Upon power up I can see that the backlight is working (the screen is lit up), but the entire screen remains black throughout startup and never changes.

    Most likely it’s either not compatible OR defective LCD screen. Make sure you are using the right screen.

    Is this a problem with the inverter then?

    No, it’s not the inverter. You get backlight on the new screen, so the inverter board works properly.

  8. 171
    Mike Says:

    Hello,

    Just wondering if anyone could point me in the right direction w/ a problem I’m having. The bottom 3rd of my LCD stopped working completely (wasn’t getting any light etc), so I just purchased and installed a replacement. Upon power up I can see that the backlight is working (the screen is lit up), but the entire screen remains black throughout startup and never changes. I know the computer is working because I can hear the sounds from Window’s starting up etc. Is this a problem with the inverter then? Any information would be greatly appreciated; thanks!

    Mike

  9. 170
    cj2600 Says:

    boadi,

    i have a laptop that i am working on it now it has a dark screen and u can not even see any thing on the screen how can i know that is the screen or the inverter or trouble-shoot LCD creen

    Can you use the laptop with an external monitor?
    Does the laptop screen have backlight? Please provide more information.

  10. 169
    boadi Says:

    i have a laptop that i am working on it now it has a dark screen and u can not even see any thing on the screen how can i know that is the screen or the inverter or trouble-shoot LCD creen

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