Screen inverter board
Laptop inverter boards (also know as LCD inverter, FL inverter, screen inverter, backlight inverter) come in different shapes and sizes. On the picture above you see some typical looking inverter boards found in laptop computers.
The inverter board works as a power supply for the backlight lamp mounted inside the LCD screen. The inverter board converts low voltage DC power (few volts) supplied by the motherboard to high voltage AC power (few hundred volts) needed for the backlight lamp.
When the inverter board works properly, the backlight lamp gets power and the LCD screen lights up. As a result, the image on the screen is bright.
HOW INVERTER CONNECTED TO LDC SCREEN
On the picture below you can see a typical laptop display assembly which includes the LCD screen, video cable and inverter board.
One side of the inverter board connects to the backlight lamp and another side to the video cable (LCD screen cable).
HOW INVERTER MOUNTED INSIDE LAPTOP DISPLAY PANEL
In most laptops the inverter board is mounted below the LCD screen as it shown on the picture below. You can get an access to the inverter board when you remove the screen bezel – a plastic frame around the LCD screen.
TYPICAL INVERTER FAILURE SYMPTOMS
Usually inverters fail in one of the following ways:
1. When you turn on the laptop, the screen lights up for a short period of time and then goes dark. You still can see an image but it is very dark, almost invisible and definitely not usable. When you restart the laptop, the screen lights up and then goes dark again. The laptop works fine with an external monitor.
2. Your laptop turns on but the screen remains dark all the time. You still can see a very dim image outline. The laptop works fine with an external monitor.
3. The laptop screen works fine for hours or even days, but sometimes it goes very dark as it mentioned above. When you restart the laptop, the screen works fine again.
Inverter failure symptoms are very similar to backlight lamp failure symptoms and in most cases you cannot tell which one is causing the problem until you replace either the inverter board or the backlight lamp. From my personal experience, inverter boards fail more often than backlight lamps. If you have to guess, replace the inverter first.
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February 24th, 2009 at 8:56 pm
Roman,
It’s hard to tell which one is causing the problem, the backlight lamp or inverter board.
Here’s what you can try.
Try reducing the LCD screen brightness for the AC mode (when the AC adapter is plugged in). On some laptops you can do that through the power management software in the control panel, on other laptops you can do that through a keyboard shortcut or in the BIOS settings. Make the LCD screen a little bit dimmer when the laptop is plugged into the adapter. Will it help the backlight to stay on all the time or it still turns off even thought the brightness is reduced?
February 24th, 2009 at 8:48 pm
Gareth Bradley,
If I understand correctly, you bought a new LCD screen but the backlight will not light up? Try installing the old (cracked) screen back into the laptop. Will it light up?
If the backlight works fine on the cracked screen but not on the new one, apparently it’s either defective LCD screen or the screen is not compatible with the laptop.
February 20th, 2009 at 4:18 pm
Same problem as Bradley here
Guys I have been googling since 2 days to find a solution to my strange problem.bingo! i hit this page.I am experiencing the same problem as u Bradley.No enough power to the inverter from the motherboard! I read some where for IBm laptops there is something called LVDS board which they can replace(where the female pin for the video / inverter cable fits).Do we got any for our acer aspire 5100? .or can we shunt power some where else from the motherboard?
February 19th, 2009 at 6:38 pm
Hi.
Whenever I have my laptop plugged in to the AC Adapter, my backlight will eventually turn off and will not turn on until after I have restarted or place the computer in sleep mode. However, when it runs on battery, I have yet to see my backlight turn off. Could this still be an inverter problem?
February 1st, 2009 at 2:46 pm
Original fault was cracked LCD, the backlight did work it was just the screen that was cracked, I’ve still got it and plugged it back in but the backlight on that will not light up. That’s why this is strange, I’m at a complete loss with this one, the only over thing I can think off is to replace the motherboard but that’s too expensive so that’s a no no
February 1st, 2009 at 2:38 pm
Gareth,
Did the backlight worked after you cracked the screen? Do you still have the cracked screen (hopefully with a good backligth) lamp?
Can you install the cracked screen back and see if the backlight still works?
February 1st, 2009 at 2:30 pm
This is strange, when I got the new LCD display I just connected the cables to see if it worked and it was fine, the following day I fitted the screen in the laptop and this is when the problem occurred, I can’t understand why it has gone dim, when that was the oringinal fault it was a cracked LCD
February 1st, 2009 at 2:25 pm
Gareth,
Yep, 16volts sounds normal.
I guess there could be a problem with the motherboard. For some reason it’s not providing enough power for the inverter board and because of that the backlight will not light up. That’s my guess but I could be wrong.
I don’t think it’s a cable related problem. With bad cable you would get no voltage at all, but you are reading 3volts. Apparently it’s not the cable.
February 1st, 2009 at 2:16 pm
Yep took a reading of another laptop and getting around 16volts any ideas???
February 1st, 2009 at 1:51 pm
Managed to get to the connection, everything there looks ok. Got the inverter of eBay so not reliable so I’ve emailed them back asking for a refund. I’ve got another laptop I’ll see what reading I’m getting with that, if it is reading higher what does that mean?? I’ve tried the laptop close switch was one off my first thoughts. Will let you know the reading
February 1st, 2009 at 1:31 pm
Bradley,
I’m not sure but 3 volts seems to be low. I don’t have a multimeter with me and cannot confirm if that voltage is correct.
It’s possible. I’ve seen that happening before. Did you but it from a reliable source?
It depends on the laptop model. On some laptops this connector could be found under the keyboard bezel. On other models it’s located under the keyboard.
No, but you’ll have to remove the keyboard bezel and maybe the keyboard too.
In your case it looks like the power is getting to the inverter, so I assume the cable is seated correctly. Again, 3 volts seems to be low. I believe when I tested it last time (a couple of years ago), I was reading over 9 volts.
By the way, do you have a display close switch on your laptop – a small button usually located close to one of the hinges. When the display is closed, the button is pressed down and there is no voltage going to the inverter. Check the button. Maybe it’s dirty and got stuck inside the case and the laptop “thinks” the display is closed even though it’s open.
February 1st, 2009 at 1:17 pm
I’ve measured the voltage on the left hand side, not quite sure which is pin1 and ground but I do get a reading of 3 volts implying power is getting to the inverter, maybe the new inverter I’ve bought is dead??, is it easy to get to the motherboard connection? Do I have to take the all the back off? If power is getting to the inverter is it neccesary to check the connection to the motherboard.
February 1st, 2009 at 10:01 am
Bradley,
I think it’s possible to check voltage with a multimeter on the left side of the inverter board where it’s connected to the LCD cable. I believe you have to measure voltage between pin 1 and ground, but I’m not sure 100%. You’ll have to get some low voltage DC readings. If there is no incoming voltage, it could be bad LCD cable or motherboard.
Did you try reconnecting the LCD cable connection on the motherboard? Maybe it’s loose connection?
February 1st, 2009 at 3:32 am
My screen is dark and can barely see the picture, I’ve changed the LCD and inverter but no luck, can somebody please help!, is there anyway I can check whether power is getting to the inverter.
January 31st, 2009 at 11:19 pm
Joey,
Apparently it’s a bad screen.
It’s easier to test with a desktop monitor. Can you find a monitor for the test?
You cannot tell if it’s a bad screen or motherboard until you test the external video output.
January 31st, 2009 at 7:54 pm
Repair guy I took the bevel from around the screen off today as well as the plastic piece from above the keyboard. I fired it up and wiggled and messed with all the wires. Moving wires did nothing but as I moved the screen the display would change. It’s totally out now. I have an S video cord connection on my machine but last time I messed with it I had to set it up on the settings so I don’t know if I can just plug it in and get it to work on my TV to test it. BTW the machine is a HP DV5000 series. It’s about 2 years old.
January 30th, 2009 at 2:18 pm
ACH,
First of all, check the cable connection. Maybe it’s not plugged correctly. Try reconnecting the video cable.
When you moved your LCD screen to the Compaq laptop you tried to turn it on with the customer’s inverter, right? It means, your inverter board stayed connected to the Acer and you couldn’t damage it. Am I missing something?
Take a closer look at the LCD on your Acer. Is it completely blank and black? Can you see any faint image at all?
If you cannot see any image and reconnecting the video cable doesn’t help, apparently you damaged the screen when tested it with the Compaq laptop. Even though both LCD screens look very similar, they might require different video cables. Connecting a good working LCD screen to a laptop with incompatible video cable can damage the screen.
January 30th, 2009 at 1:46 pm
Joey,
To me that description sounds like a problem with the LCD cable, apparently it’s defective and has to be replaced. I guess could be a problem with the LCD, but for some reason it feels like bad cable.
By the way, did you test the laptop with an external monitor? Can you tell if the external video output works fine even though the internal video fails? If you are getting the same exact problem on both the internal and external screens, there could be a problem with the video card. It’s possible that when you are moving the display, you are actually flexing the motherboard and temporarily fixing the problem.
Test your laptop with an external monitor and let me know if it fails the same way as the internal screen.
January 30th, 2009 at 1:21 pm
I have a dead acer laptop with (what I thought was) a working screen. I had a customer with a Compaq laptop with a nearly identical lcd screen that was cracked. I tried connecting my screen to the compaq, but no video came up and the inverter seemed to start to heat up. I immediately powered it off and later tried plugging it back into the dead acer (bad ata controller, actually works with usb boot media)
now I get no video whatsoever on the LCD but external monitor works fine. Have I fried my LCD screen and/or inverter? any thoughts appreciated
January 30th, 2009 at 2:15 am
When ever I fire up my laptop I have to wiggle the screen back and forth to get the image to stay on the screen. Once you get it into just the right place the display is fine. It continously freezes though till you wiggle it again then it will pick up wherever you are. The issue has continously gotten worse. If you mess with it enough eventually you get all lines and a crazy display. Does this sound like a screen or a wiring issue? I already checked where the video cord plugs into the motherboard. Warranty is out and I need my laptop back! Thanks