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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May 3rd, 2009 at 10:52 am
Nico,
That could be poor connection between the video cable and motherboard, defective video cable or bad LCD screen.
Open up the display panel so you can access the video cable behind the screen. Now turn on the laptop and when you get image on the screen carefully touch/move the video cable. Does it make any difference?
I don’t think that your problem is related to the inverter board. In your case the screen lights up and is bright. That means the backligth lamp and ivnerter work properly. Nope, it’s not the inverter problem.
Here are some troubleshooting tips:
1. Check connection between the video cable and motherboard. Make sure it’s plugged in correctly. Reconnect the cable just in case and test the laptop again.
2. Try connecting the old LCD screen back to the laptop. If you still experience the same problem with the old screen (the bottom part doesn’t work) but your new screen has a different problem (fuzzy image), the new screen is either incompatible with the laptop or is bad. Did you try connecting the old screen?
3. Try replacing the video cable.
May 3rd, 2009 at 5:08 am
Hey Repair Man..
I have a HP-Compaq NC2400 in which the screen shows color although with red tint for about 5-10 seconds, afterward, it turns dark although everything still work, internet, et cetera, all still working. The same thing happen every time I restart my laptop.
I’ve read your post and the comments here in general and so I just want to confirm. At first I thought it was my LCD inverter that went wrong, but now I started to get confused whether it is my backlight that is wrong. So, which is it?
Thanks in advance…
May 1st, 2009 at 1:59 pm
Hello
I have a hp pavillion dv2275ea laptop I dropped the laptop and the screen cracked so I replaced the screen with a new one and it is very dim, I replaced the laptop with the old cracked screen again and its also dim does this mean that i should replace the inverter with a new one? and what could hace caused the inverter to go bad static from my fingers while I replaced the screen because i changed the screen while it was all powered up or do i need to change any settings as laptop was connected to external monitor for a week or so?
May 1st, 2009 at 1:51 pm
Hi
I have a hp pavillion dv2275ea laptop I dropped the laptop and the screen cracked so I replaced the screen with a new one and its very dim I replaced the screen with the cracked screen again and its also dim should I replace the inverter with a new one and what could hace caused the inverter to go bad static from my fingers while I replaced the screen?
April 30th, 2009 at 6:29 pm
Been searching and haven’t found a symptom close to mine. I am working on a Dell Inspiron 6000. It’s first problem was a black horizontal line covering the 1/3 bottom part of the screen. Picture was fine on top. External monitor worked great. So I changed the screen. Now, at power on, the screen is fuzzy multi-color can’t see bios startup. Can see desktop but unable to read letters, very fuzzy and graphics look worse than safe mode. Now if I restart the computer, the screen goes to normal. I noticed that the inverter shows compatible p/n, and the screen I used to replace is not listed. Could that be the problem? The replacement screen p/n is LTD154EX0V.
April 28th, 2009 at 12:44 pm
shilp,
If the laptop screen lights up and you can see an image (even if it’s garbled), your inverter and backlight work properly. When inverter or backlight lamp fail, the screen is completely dark.
So, you are getting some green tint on both internal and external screens? That sounds like a problem with the video card. It’s very likely that your internal LCD screen doesn’t work because of a problem with the video card.
April 27th, 2009 at 7:16 am
Kevin,
Turn off the laptop, remove the AC adapter and remove the battery. Wait for a few minutes, plug in the AC adapter and try turning it on.
April 27th, 2009 at 2:33 am
Guys,
replaced the inverter board without taking out the battery first – now pc wont power on at all.
Any ideas?
April 24th, 2009 at 7:07 am
I have just checked my laptop with external monitor and its working fine. Now from above descriptions about LCD lamp and inverter…i am highly confused and not able to decide whether the problem is in lights or inverter. Still….while turning on the system my computer starts with florescent green color earlier it used to be blue and black)screen.I can see these green florescent tints on the desktop screen too. pink tints are also there
April 21st, 2009 at 10:27 am
Mark,
From my experience this is a problem with the backlight lamp.
Can he return the screen for an exchange? There are a lot of good sellers on eBay.
I would definitely replace the whole screen. It’s cheap. Replacing the backlight lamp is very labor intensive. You can put a few hours into the repair and there is no guaranty it will work. I can replace the backlight lamp for fun or for my own screen but I never offer this repair to my customers. It takes too much time.
Just explain to the customer that replacing the whole screen is way cheaper.
It depends on what is defective. If it has a bad controller board (image is missing, garbled, has vertical lines) but lights up, it means the backlight lamp works properly and you can use it for another screen or as a test equipment.
April 21st, 2009 at 10:07 am
karl dela cruz novaselic,
Yep, your description in the previous comment doesn’t sound like a problem with the inverter.
It’s up to you.
But in my opinion you have a problem with the LCD. I could be wrong.
You can search for the whole display assembly (LCD screen, inverter, cable, plastic covers, etc…) If you can find one, you simply unplug the old display assembly and install a new one.
Do you have a white sticker glued to the video cable somewhere close to the connector which plugs into the system board? HP usually places the part number on that sticker. Look for the SPS number. If you can find it, most likely it’s the part number for the whole display assembly. Google the part number to make sure what it is.
April 21st, 2009 at 9:45 am
Hey repairman,
I have a laptop where the screen comes on for 1-5 seconds after boot and has a red tint to it. Have you ever seen the reddish tint caused by an inverter or is it always the backlight? Second, I’m debating whether to get the light or the whole screen. I had a customer get an lcd screen from ebay before and it had a horribly obvious bright pixel. Do you have a vendor you like that sells higer quality screens and parts and are there any that I definitely shouldn’t use? The screens on ebay for this Toshiba a135 go for around $60 and it would be easier than replacing the lamp, but the customer probably won’t be happy if the screen is defective. Also, if I do get the whole lcd and it is defective can I at least use its lamp?
April 19th, 2009 at 4:45 pm
thanks for the reply.i cant see any display on the screen even when i used a flash light to illuminate it so probably the lcd inverter is not defective. what can you suggest for me to replace first,is it the lcd, the display cable, or better to change them both?by the way i tried looking for a part number on the lcd and the display cable but i couldnt find one.any suggestions as to how i could find the exact parts?
April 17th, 2009 at 12:36 pm
Guillermo,
OK, let’s go through your problem step by step.
1. The external monitor works fine and the image on the external monitor is displayed properly. That tells me the motherboard and video card works properly.
2. When you unplug the video cable from the LCD screen it turns completely white. It’s normal. The screen is bright and that means the inverter board and backlight work properly.
3. I don’t think that your problem is related to the LCD cable. From my experience, LCD cables do not fail like that. When the cable fails, the whole image gets garbled or the screen doesn’t turn on at all.
I think your problem is related to the LCD screen.
April 17th, 2009 at 11:57 am
First, congratulations for the site. I found some very valuable information.
I have a compaq evo n800c with a strange problem. The display (LCD) activates only one colum every 2 colums (consecutive colums, if “1″ is on and “O” off, it looks like 1010101010101010). Overall it looks like a loss in resolution. It is independent of the resolution selected for the video. I have dismounted the screen and (while powered on) disconnected the LCD. The result was a perfect white screen.
When connected to an extenal monitor, it works fine.
Can you help me identify the source of the problem ?
Thank you in advance.
April 16th, 2009 at 1:11 pm
Justin Lancaster,
Hard to tell why it’s doing that. It’s possible you damaged the old inverter while replacing it with a new one. I cannot tell without testing your laptop with a KNOWN good inverter. Also, it’s possible that finally your backlight failed.
If the screen has reddish glow, most likely it’s related to a failing backlight lamp.
April 16th, 2009 at 6:30 am
Hey Repairman,
First thanks for your help, this site is great!
I got the inverter board in and replaced it and now the screen doesn’t come on at all. I can still see a faint image if I shine a flashlight at the screen though.
What should I do? Try to replace the bulb next?
I also tried putting the old inverter board back in and it does the same thing, doesn’t light up at all. Before I replaced it, it would come on for about 10-30 seconds and shut off. The screen also had a reddish glow to it.
Thanks in advance!
Justin
April 15th, 2009 at 8:11 pm
karl dela cruz novoselic,
I think there is a problem with the LCD screen. With a bad cable you can get distortion on the screen but it would not divide the screen into 4 images.
When inverter fails, you still should be able to see a very faint image on the screen. Can you?
April 15th, 2009 at 6:17 pm
i just stumbled upon your site and found it informative and helpful.a friend brought a compaq c500 laptop to us for repair, the problem is the white,moving lines which is about 1 centimeter thick.i dont know if the word “fuzzy” is a right adjective for it(sorry for im not a native english speaker).but when i disassembled the unit and reseated the display cable, the display was divided or tiled into 4 parts and when i tried reseating it again the display was totally lost(display on an external monitor is fine).further reseating didnt solve the problem and i am thinking that it might be related to the inverter or the display cable.any ideas?thank you in advance
April 7th, 2009 at 7:15 pm
James,
Most likely your problem is related to the backlight lamp which is located inside the LCD screen. You can try replacing the backlight lamp yourself but it’s not easy. If you cannot do that, I would suggest replacing the whole LCD screen.