This laptop came for repair because of the LCD screen backlight failure. My customer complained that the laptop LCD screen is black but the laptop works with an external monitor.
Here are my steps for troubleshooting this laptop with the backlight failure.
First of all, I tested this laptop with an external monitor connected to the VGA port and the external monitor worked absolutely fine. I was able to get crystal clear image on the external screen even though the internal screen didn’t light up. If the external screen works fine, then most likely there is nothing wrong with the video card.
Notebook display assembly diagram
After that I took a closer look at the laptop LCD and noticed that the screen is not completely black. The laptop screen still works but the image is very very dull, you barely can see it. It means that the screen still gets data signal from the video card, but for some reason the backlight lamp doesn’t work.
From my experience I know that this problem can be related the lid close switch, faulty inverter board or bad backlight lamp. I checked them one by one.
If you have a similar problem, make sure the lid close witch moves freely. The lid switch is a small button located close to the LCD screen. This button triggers the hibernation or sleep mode when the screen is closed. If the lid close switch is dirty, it might get stuck inside the laptop case and cut off the power from the inverter board. The inverter board works as a power supply for the backlight lamp and if there is no power coming to the inverter board, the backlight lamp will not light up either.
In my case the lid button worked properly, it didn’t stuck inside the case. When I was pressing on the button very fast, I was able to light up the screen but only for a fraction of a second. The image wasn’t bright and it had a pinkish tone. A pinkish tone usually indicates a problem with the backlight lamp, not the inverter board.
Even though I suspected the backlight failure, I decided to test this laptop with a new inverter board just in case. But it didn’t help. The screen didn’t light up even after I replace the inverter board. So, I was right, this problem is not related to the inverter board.
Finally, I disconnected the screen backlight lamp connector from the inverter board and connected my test backlight lamp (I removed it from another cracked screen). For the test purpose, you can buy a new backlight lamp here. Try to find a backlight with the connector already attached to it, so you can plug it into the inverter board. Make sure the connector on the backlight lamp is similar to the connector on your LCD screen.
As soon as I turned on the laptop, my backlight lamp lighted up. Yep, that’s the problem. The laptop screen has a faulty backlight lamp.
Here’s another laptop with backlight failure
This laptop video fails in a little bit different way. In this case the backlight lamp hasn’t failed completely.
The laptop starts with video on the screen but the background has reddish tone, the screen flickers and it makes noticeable buzzing noise coming from the backlight and inverter area. After a few minutes the backlight turns off by itself and the buzzing noise stops. When the backlight is off, the image on the screen is still visible but it’s very dark.
I removed the screen bezel and connected my test backlight lamp.
My test backlight works absolutely fine. The lamp doesn’t flicker and there is no buzzing noise. So, this laptop needs a new backlight lamp.
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October 13th, 2009 at 9:30 pm
Al Green,
Have you tried reseating the video cable on the motherboard? It’s located right under the keyboard/hinge cover. Maybe the cable got disconnected from the motherboard when you dropped the laptop.
October 13th, 2009 at 9:03 pm
Hi tech guru…I was wondering if you can you help me figure out whats up with my dark screen. I can see everything but its just too dark… I have a dell inspiron 6000 and I accidently dropped it from my counter top. I have replaced the backlight and the inverter and still have a dark lit screen. My case looks exactly like your first picture on this page. I have also used an external monitor to test the video card and it works just fine. What can it be? Thanks in advanced!
September 26th, 2009 at 4:11 pm
I have a Dell Insprion 600M Notebook
The weird part is that the dim image shrink to 60% to the left. Other 40% is just blank image. I don’t have any invertor or CCFL lamp to test on. But I guess the whole lcd is the best way.
Do this 60/40 screen happen often?
September 23rd, 2009 at 8:02 am
It775,
It’s possible that the power jack inside the laptop is bad and has to be replaced. It’s necessary to disassemble the laptop and take a closer look at the power socket/jack.
In a Satellite A105 the power jack is located on a harness. If the jack is bad, you simply unplug the defective harness and replace it with a new one. That’s my guess.
Take a look at the step 21 in this laptop disassembly guide. Clock on the picture to open a big one. The red arrow points to the power jack.
I don’t know how this question is related to your question in the first sentence. I think you missed a part of the story.
Did you take the laptop to a local shop and after that the backlight stopped working?
September 23rd, 2009 at 7:50 am
My AC adapter has a short in it. The local shop tried a universal adapter with a couple of tips but nothing worked. If I I wiggle the cord on my original adapter, I can get enough power to max the battery at 100% within the usual amount of time. Two questions:
1. Is it possible that the laptop is not getting enough juice to power up the laptop LCD?
2. Could the local shop have shorted something out and caused my laptop LCD to remain black? Would that be the inverter or the backlight?
Ultimately, the computer works fine except the LCD screen. It works with an external monitor, and when the lid closes it hibernates so it is not a lid switch issue. The screen is dead black, no image at all so I am trying to narrow it down to power supply, inverter or backlight. It’s a 3-year old Toshiba Satellite A105.
Thanks,
-lt775
September 5th, 2009 at 2:29 pm
By the way, it is useful to find the service manual for your laptop before beginning disassembly.
September 5th, 2009 at 2:28 pm
Just wanted to say thank you. I would have never figured out it was a stuck laptop lid switch. I just disconnected the switch from the motherboard. Now I can’t put the computer to sleep by closing the lid, but at least the monitor works.
September 3rd, 2009 at 4:35 am
I am having trouble with my Toshiba laptop screen. It was very dark. I replaced the inverter & when I turned it back on it came on but then went dark again. I discovered that when I tapped the metal lid closed plate it would come back on. This worked for a few hours but now it is dark again & tapping does no good. Do I need to replace the lid closed plate, the backlight, screen, or is it possible I have damaged the new inverter by tapping on the plate too much?
August 30th, 2009 at 6:18 am
Your description of notebook backlight failure is exactly my problem. The screen is not completely black. I tried the first suggestion, but even a quick flick of the lid button, the notebook went into hybernation. When I started up notebook again the screen is fully lit. I tried closing down my notebook again, but on restart the same problem occurs each time, but when I depress the lid switch button and restart from hyberantion the screen is fine. Any idea what the problem is???
August 26th, 2009 at 9:28 pm
Hi Dave,
That’s me again. I already replied to your question in a different thread.
Are you talking about a 1-2 pixel vertical line? Can you upload a picture somewhere?