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. 148
    cj2600 Says:

    kapil,

    I have LCD goes black problem with my Sony Vaio FZ11S, already tested inverter it is working fine. I suspect strongly it has CCFL backlight got faulty. But here my question is, this 15.4 WXGA LCD screen has twin CCFL bulb so in case one CCFL bulb goes faulty other one should work Right? In that case I should get atleast some light on the screen?

    I don’t have a lot of experience with dual lamp screens, but it’s possible the dual inverter board works properly only when it’s loaded by two working backlight lamps, not just one lamp. Thus if one backlight lamp fails, the inverter board doesn’t get enough load and shuts off. Consequently the remaining working backlight lamp also stops working. This is my guess.
    If you absolutely sure the inverter board is good, I guess you’ll have to replace the screen.

    Is it possible that both CCFL goes faulty at same time?

    I think it’s possible but very unlikely.

  2. 147
    kapil Says:

    Hi, I have LCD goes black problem with my Sony Vaio FZ11S, already tested inverter it is working fine. I suspect strongly it has CCFL backlight got faulty. But here my question is, this 15.4 WXGA LCD screen has twin CCFL bulb so in case one CCFL bulb goes faulty other one should work Right? In that case I should get atleast some light on the screen? Is it possible that both CCFL goes faulty at same time? Please suggest how twin backlight works.

  3. 146
    boetix Says:

    I have acer aspire 4715z with problems on the lcd, which only shows a white / light without seeming the least writing or drawing.
    approximately situated where the damage? on the lcd, the inverter or something else?
    thanks for the reply.

  4. 145
    Josh Says:

    I Have a preasrio v2000 I am having problems with the screen being solid white on the outer edges and in the middle a hazey white with white dots. I replaced the mother board thinking it was that. It still does this. any suggestions?

  5. 144
    dinobandhu Says:

    i have a Lenovo Y510 laptop with me.
    i work fine but from we days my laptop flip is not stand in 90 degree position it totally get flat 180when i open my laptop . i have give support from backsight to keep it in 90 degre position

  6. 143
    Bubba Says:

    Boy oh boy what a nightmare it can be figuring it out. My dell inspiron laptops screen went dark and I could not figure it out. Thank G-D for this article, at least I knew that the only way to know for sure is to get either a backlight or inverter so I figured I will go with an inverter first , found mine, installed it and viola, it turned out being the inverter. Now shes working like a charm. Thanks guys

  7. 142
    Kris Says:

    Hi! I just replaced a bad ccfl in my laptop. It went well. Next problem- when I turn it on with the lcd unplugged the whole screen lights up white but when i plug the lcd in and turn it on everything stays black. Is this a common symptom of a bad inverter? I don’t know if this helps but when I opened up the lcd the old ccfl was in two pieces and all black where the pieces met. The area over the inverter was getting really really hot. That makes me think that the inverter got too hot and broke the light. Any ideas on where the problem might lie?

  8. 141
    raghav Says:

    Hi, I had ordered a new 15.4 inch screen for my Toshiba A 105. I noticed that the wired from the backlight of the new screen is of the “BIG” type … whereas the inverter itself accepts only the “SMALL” type. Do you have any suggestions on how I can replace the wires from the backlight? Thanks.

  9. 140
    cj2600 Says:

    Young,

    I have a spare wsxga+ 15.4″ lcd screen pulled from a thinkpad t61, and is manufactured by samsung. I tried to install samsung lcd to my toshiba, but the screen would not light up. I switched back to the LG and it works fine. what would be the problem?

    The ThinkPad screen might require a different video cable.

  10. 139
    cj2600 Says:

    Tester,

    I have a toshiba A135. Everything works except that the LCD is mostly a green hue. I replaced the converter and still same prob.

    Did you mean the inverter board? You were wrong, a green hue on the screen cannot be caused by the inverter failure. Only the LCD screen backlight could be affected by the inverter failure.

    Then I purchased a broken A135 for parts and replaced the entire LCD screen and it is still doing the same thing. Output from the VGA connector is fine..

    Did you replace just the LCD screen or you replaced LCD and video cable?

    I have to assume the problem is with something on the motherboard ?

    If you replaced the LCD screen and video cable, then you are correct. Most likely this is the motherboard failure.

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