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.
April 16th, 2010 at 10:37 pm
Hi Repair Man,
Similar problem to what I have read so far. Just got a Toshiba Netbook NB305, and it took a lot of pressure to the top cover. Basically, it got sat on while it had some stuff on the cover (keys, pocket knife, etc.). It looks like the “point load” exerted itself on the little board that’s taped to the back of the LCD screen. The LCD screen itself doesn’t look traumatized.
So here’s the problem: At first, when powered up, the screen locked “washed out”; quite bright, but no contrast. I thought “uh oh, big problems”. So while the unit was powered up, I gave the screen a bit of a “twist”; basically held both top corners and gave it a bit of torsion, but nothing outlandish. The screen responded by flashing “normal” colors a couple of times, but now, the colors look like they are “inverted” with a little loss of brightness to boot. And “twisting” the screen no longer has any effect.
I took it apart and powered it up, and the back side of the screen looks quite bright, it looks like the backlight is workng fine. I can even navigate on the screen, but the colours look reversed.
Question: did my LCD sereen bite it (even though it shows no sign of “cracks” etc.), or is it the little board attached to the back of the screen the has a toasted chip because of being squished by that point load?
Any tips would be very helpful, cheers.
April 15th, 2010 at 10:19 pm
Cory,
If you used 24V instead of 19V, it’s possible that you damaged the motherboard. I cannot tell if that’s the case without looking at the laptop.
In one of the previous comments you wrote:
This sounds like the motherboard failure but I could be wrong.
April 15th, 2010 at 3:39 pm
Hey Repairman
It’s with a red face that I write this –
I have a secondary power supply that goes with me for occasional use, and its adjustable. I’ve just found that the last time I used this adapter, was just as the original screen problem popped up.
I’ve found that the switch had migrated to 24V instead of 19V.
Is there any chance my problems are contained to ? one part that I could replace? Otherwise it seems its time to buy a new laptop :/
thanks
April 15th, 2010 at 2:45 pm
Hey Repairman,
Thanks for the quick reply. I tested the laptop with each SIMM, and with no SIMMS, and also with no hard disk. Behaviour was the same.
One interesting thing that I did not note before, is, when first turned on the fan comes off, then shuts off with the notebook. But when it then enters its try-try-again power-off-power-on loop, the fan does not come on.
Do you think I have shorted something in the LCD/inverter setup? Or have I just got really bad luck and everything is failing all together?
thanks
April 15th, 2010 at 1:45 pm
Cory,
That’s strange! I doubt that your second problem is related to the inverter board.
It’s possible you have two separate issues.
Maybe memory is bad? Try removing memory modules one at a time. Test your laptop with each memory module separately. If one of the modules is bad, the laptop will start properly when the bad module is removed.
April 15th, 2010 at 1:41 pm
Cory,
It’s hard to tell which one is causing the problem without testing the laptop. Could be bad backlight lamp or faulty inverter board.
I guess you’ll have to wait for the inverter board and try replacing it first.
April 15th, 2010 at 1:09 pm
Further to my last post, I opened up the bezel to check the inverter connection, and peer in to see if I could see the CCFL’s.
I put it back together without issues. A few hours of use later, while using it on an external monitor, it just stopped dead.
Powering it on causes it to turn on for about 2 seconds, power off, then reboot itself a few seconds later, continuously until I pull the battery.
Any advice appreciated! This is the new priority unfortunately.
Does this mean that the lamp is gone? Can I replace that myself? I have already ordered the inverter board.
April 15th, 2010 at 10:40 am
I have an ACER 5520, and it has developed symptoms as you describe — the backlight flashes on for a moment if I force it by toggling the laptop “external/internal screen” button, but its main state is so dim that it looks black unless you look very very closely and you can then see the pixels are actually there. However, it seems like only the right half of the screen lights up, all or most of the time.
Does this mean that the lamp is gone? Can I replace that myself? I have already ordered the inverter board. Any hints would be appreciated!
Thanks
April 15th, 2010 at 8:50 am
Omarey,
It’s possible that while replacing the inverter board you accidentally pulled the LCD cable and disconnected it from the LCD screen or motherboard.
Try reconnecting the LCD cable on the back of the LCD screen and on the motherboard. It might help.
April 15th, 2010 at 8:25 am
D Bowman,
You are correct, this is not a software related problem.
I believe this is the LCD screen related failure and I’ve seen it happening before. Most likely replacing the LCD screen will fix the problem.
Yep, it’s not the inverter. The screen still has light, so the backlight lamp and inverter board works properly.
Apparently he damaged the LCD screen.
I’m 95% positive that replacing the LCD screen will fix the problem.
Just in case, try reconnecting the LCD cable on both ends – on the motherboard and back side of the LCD screen. There is a chance of loose connection but I don’t think so. Again, try reconnecting the LCD cable before buying a new screen and if it doesn’t help, replace the screen.
April 15th, 2010 at 8:17 am
Bernie,
I believe this is just a different connector type, but the backlight lamp should be the same. Replacing the existing connector with a new one shouldn’t affect functionality of the backlight lamp.
New backlight lamps are sold without any connectors, so it’s up to you which connector to use.
If you do everything correctly, the LCD screen should work properly with a new connector.
April 14th, 2010 at 7:57 pm
Hello! I’m trying to save a bundle on shipping by not having to send a very slightly wrong Toshiba laptop screen back. I ordered a replacement for a dropped and cracked Toshiba Tecra a8 PTA83c LCD, without taking it apart first. After the part arrived I took the bezel apart and found the screen fit each of the mounting screws and video cable, but the inverter connection cable ends are not compatible. The broken one is a Samsung LTN154×3, the replacement I was shipped is an LGPhillips LP154wx4. Am I going to screw something up if I clip the old and splice it onto the new? Do the different shaped pins mean that much?
any assistance would be helpful, as the shipping there and back will be as much as I paid for the screen to begin with!
it using the model of the machine (Toshiba Tecra a8 PTA83c), and the actual screen inside was a Samsung . The The , but will it work if I take the old connector and put it on the new wires how fussy are backlight
April 14th, 2010 at 6:53 pm
I have a HP nc6400. The LCD screen is very bright and does not flicker – basically I can see everything fine – but – the colors seem to be inversed. Its as if it were a negative image of the monitor. I checked all the setting in the Accessibility Options, I checked the video controller settings and even reinstalled the correct video drivers, and set the BIOS to all factory default settings. It’s DEFINITELY a hardware issue and not a software issue. I hooked it up to an external monitor and it works great – I took the LCD case apart and made sure all the connections were in tact. Still – nothing fixed. Would also like to note that even at startup – before windows loads – the HP splash screen is also the wrong colors and the BIOS screen is the wrong colors. Based on what I have read here I would not think its the inverter.. Someone correct me if you think I am wrong.. Could it just be the LCD needs replaced? I received the laptop for free when these symptoms started occurring.. The guy who I got it from said it fell of his bed, while closed, about a foot from the ground and this has been happening since.. I don’t want to buy a new screen if it could possible be something on the mother board, graphics card, or possibly the inverter.. Anyone have any suggestions or ideas?
April 12th, 2010 at 4:35 pm
I have a Toshiba Satellite M55-S135. I found information that led me to believe I was having a problem with my backlight inverter. On startup the picture would flicker for a few seconds then go out. I ordered a backlight inverter for my laptop and it did not illuminate the screen. The old one did but continued to go out. I got another one and installed it. The backlight now seems to illuminate the screen but no images come up. I can here the computer starting up and the sound of the windows screen sounds but nothing shows up on screen. Now when I tried reinstalling the old inverter it does the same thing as the new one. Any suggestions?
April 12th, 2010 at 7:59 am
Dease,
Test your laptop with an external monitor. Can you get video on the external monitor? If yes, check connection between the LCD cable and motherboard. Maybe the cable is not plugged correctly.
If there is no video on both the internal and external screens, check memory modules. There is a chance that one of the memory modules (or both of them) not seated correctly. Try reconnecting memory.
April 10th, 2010 at 12:20 pm
Gauntlett,
Test your laptop with an external monitor. Can you get video on the external screen? If not, check the memory modules. Maybe memory modules are not seated correctly.
If external monitor works fine but there is no video on the internal screen, check connection between the video cable and motherboard, LCD screen.
It’s possible the video cable is not making good contact. Reconnecting the cable might help.
April 10th, 2010 at 12:14 pm
I took my HP Pavilion Laptop apart and put it back together. Everything works but the Screen. Screen does not light up or show any image. Ideas? my
March 29th, 2010 at 2:23 pm
Anil,
1. Wrong type of the inverter installed.
2. The inverter is defective.
3. Could be bad connection between the inverter board and LCD cable.
4. Not sure about this one, but it’s possible that the backlight lamp is not working properly and drawing too much power from the inverter.
First of all, make sure you are using the right inverter for this laptop.
March 29th, 2010 at 1:44 pm
Kyle,
If the laptop works fine with an external monitor, most likely the video card and motherboard work properly.
Can you see a very faint image of the desktop on the screen when the laptop is on? If not, this failure is not related to the inverter board.
You can try reconnecting the LCD cable on both ends – on the motherboard and back of the LCD screen. Maybe this is connection related issue and reconnecting the cable will fix it.
It’s necessary to take apart the display panel and access the back side of the LCD screen.
Another end of the LCD cable is connected to the motherboard. This connection is located under the keyboard cover, close to the left hinge.
Take a look at this guide for the keyboard cover removal instructions:
http://www.insidemylaptop.com/remove-hard-drive-memory-wireless-card-keyboard-hp-pavilion-dv9000/
March 29th, 2010 at 10:58 am
Andrew Hall,
It’s hard to tell. It’s possible you purchased a defective inverter.
If you still experiencing the same problem after replacing the inverter board and LCD screen (I assume both parts are good), most likely the failure is related to the LCD cable or motherboard. You cannot tell with one is causing the problem without replacing them with known good parts.
Maybe the LCD cable is bad and it fried the first inverter? This is just a guess.