How to test screen inverter

posted in: Screen, Troubleshooting | 253

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.


253 Responses

  1. cj2600

    @ Lauren,
    What is wrong with the laptop? How it failed?

  2. Lauren

    I do not think this helped none of it did I don’t think I did anything wrong but it just does not work on my laptop same thing happened last time.

  3. kipkoech

    ma hp monitor 19 inch have problem in start its display quickly and desspeared that happen after every step till the time im requested for password its dssappears completely in starting and switching off the monitot there is displays and goes dark again testing ma vga cable ok and monitor ok whats the problem?

  4. Rosa Bellis

    pls help <3 Samsung i7 17nchs 2nd gen..
    there are instances wherein it blinks continuosly. once it starts, it wont stop anymore. it blinks 4 times per second. ive tried to adjust the settings of the definition but nothing happens. blinking though doesn't happen frequently.

    oneday i was watching but then afterwards i closed the player. right after then, the backlight went dim and the blinking of the screen started.

    im sure it's not just out of battery cause it still happens even if my laptop is fully charged. ive been using my laptop for four days now without battery and just connecting it to the charger and it hasn't blinked even once. is there another way to fix it?.. or a part of my laptop got damage or should be change? if yes then what should that be?

    pls help me, i will really appreciate it <3

  5. cj2600

    @ Carlos R.,
    Sounds like you have an intermittent failure. One of the components (probably inverter board) is failing.

  6. Carlos R.

    Hey.

    I have a laptop Asus A53SV-XE1. Last week when I turned it on the OS went up as usual, but a few seconds later the screen went very dim, at a point that you couldn’t see anything, but it wasn’t a black screen, just as I said; really dim. I immediately thought it was the screen inverter, but just to make sure I made a few tests to see if my video card was alright. Everything was fine. I used it with an external monitor for the past week, but yesterday when I turned it on again, the screen went on perfectly, but it stayed on for about 10 minutes, then dim for 5 (or something like that). This happened for like half and hour. However I kept using it for a couple more hours and the intermittence stopped and now the screen hasn’t gone dim again, not even for a few minutes, it doesn’t matter if I try shaking it. I want to know what happened and see if I have to take some sort of precaution.

    I’m a laptop technician from DR, but I’m amazed by what happened and I want an explanation.

  7. cj2600

    @ Dražen Šarić ,Croatia

    I have problem with my lenovo 3000 N200 ,when i turn on laptop after while i can hear windows sound ,but can’t see anything on laptop lcd neither on external monitor .Is it graphical card on motherboard …

    If you can hear Windows sound probably the motherboard works properly.
    Take a closer look at the screen. Are you sure there is no video on the screen? Maybe the image is very dim?
    If you can see a dim image, it’s either bad inverter board or failed backlight lamp inside the LCD screen. Try replacing the inverter board first.

    NOTE: some laptops will not display on external monitors on startup. In order to test video on the external monitor properly it’s necessary to unplug the video cable from the motherboard. Can you do that? Can you get image on the external screen when the video cable unplugged from the motherboard?

  8. Dražen Šarić ,Croatia

    Regards !
    Please can you help me …. I have problem with my lenovo 3000 N200 ,when i turn on laptop after while i can hear windows sound ,but can’t see anything on laptop lcd neither on external monitor .Is it graphical card on motherboard …
    Thanks in advance …

  9. Why I power my laptop Hp pavilion dv5,It brings purple colour,wat could be the problem.Thax

  10. i have one laptop before 2 days one problem created in it, now it is complately on but its display light come (not brightness) , i attech it with other crt or lcd monitor it is working properly

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