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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March 19th, 2008 at 9:20 pm
Haluk testereci,
If a known good inverter didn’t fix the problem and the image on LCD screen is still very faint, most likely you have a problem with the backlight lamp (CCFL) inside the LCD screen.
It’s not easy to replace the backlight lamp because you’ll have to take apart the LCD screen. Most repair centers will not replace the backlight lamp, they will swap the whole LCD screen.
Here’s an example how to replace the backlight lamp.
March 18th, 2008 at 2:21 am
response 57 &58
I found out that repairmen is trying to sell me whole LCS screen. It is only problem is backlight lamb and since they dont carry the lamb he wants to sell me whole LCD secren w/lamb..So iwas right on. Besides same attitue Toshibe center has, they want to sell whole LCD screen for about USD500 when i told only backlight need to replace as other repairment diagnosed at distance, Toshiba center is even unaware or pretending as unaware there is even backlight lamb…so kind of ridiculus bussines going on here. Now i am going to on my own, try to collect proper lamb and fix it w/ myself or fix w/TV repari man who would do things more chepaer…
any help on where to fing backlight lamb and instruction to fix that would be helpfull
regards
haluk
March 17th, 2008 at 11:30 am
Hi ( Ref 57)
In addition of my question on 57
would that be reason hard to replace light bulb ofr Toshiba M70-215 screen, so they might be asking for whole LCD replacement ? Is it easy to replace light back bulb, and what is the aproximate cost on that lamb?. Is there any visiual show of that light bulb might be?
thx for any help
best regards
haluk testereci
March 17th, 2008 at 11:20 am
Hi there,
myToshiba M70-215 has faint light, i had taken to repair, they tried invertor and couldnt repaired. Now they take to far away for repair and send computer for that reason. The laptop works fine w/ external monitor, and vision on original screen is very faint , can be seen on very light environment. So i dont think my screen went totally off. However, the repairment men from where my computer send gave us estimated repair demage and cost claiming that LCD screen went off and screen need to be replaced and sure that cost 250 USD. I am having hard time to belive ( since laptop is not older than 2.5 years just after waranty end!!) that and never dropped, that screen went out. Ithey just wanted to suck me i have strong belive right now it is backlight lamb and not invertor.
As an expert would you confir me that if screen went off i would never get any vision on screen right ( besides i used to have loss of light or brightnes while computer works few months aga, any time i turn off computer then light was comming on scree. The final and resisting light loss happened while i am using computer, the vision sudenly gone, and screen can be hardly seen with carefull look. So just give me some expert information before i decide replace my LCD screen. Do you think it need to replace LCD screen or light bulb. We tested inverter by bringing new inverter from Toshiba but didint work.
with my best regards from Turkey
haluk testereci
March 15th, 2008 at 2:31 pm
Guillermo,
1. Could be bad inverter. Maybe it’s not providing enough power to light up the backlight.
2. Could be a faulty backlight.
Unfortunately, I cannot tell you witch one is causing the problem. You’ll have to test the laptop either with another working inverter or another working backlight lamp.
It’s not easy to replace the backlight lamp because it’s located inside the LCD screen. You’ll have to take apart the screen. You can easily damage the screen if you have on experience with fixing laptops.
March 15th, 2008 at 12:39 pm
I am having trouble with my satellite m35x-s111 lcd display. I can see the whole image, but the lcd brightness is very low. I also noticed that brightness is higher in the right side of the display. How can i know if the trouble is in the inverter module or in the backlight lamp? The lamp can be easily replaced? Thank you.
March 6th, 2008 at 7:30 pm
Roy,
Let’s assume that both new parts LCD and inverter are supposedly good. Here’s what you can try in order to troubleshoot the problem.
Let’s say you have the new LCD screen installed. Leave the data cable connected to the back of the screen but disconnect the cable witch goes to the inverter board and plug the old LCD screen instead. In this combination you still should see a very faint image on the new(installed) screen but the inverter board should light up the backlight inside the old screen. If there is no backlight, swap the inverter board and try again.
After that install the old screen back into the laptop. Connect the data cable into the slot on the back of the LCD, but plug the new screen into the inverter instead. In this combination you’ll get image on the old screen but the backlight will be on the new screen. If no backlight, try swapping inverters.
Also, you may try connecting LCD and inverter without mounting them inside the display panel case, maybe it’s grounding somewhere and will work outside the case.
If you still cannot get the backlight and your parts are supposedly good, apparently there is a problem either with the video cable or with the motherboard. Just in case check connection between the video cable and the motherboard located under the keyboard, maybe you accidentally pulled the cable.
If you cannot see the lid close switch, apparently it’s a magnetic one and located somewhere inside the laptop case. I don’t think this is your problem.
March 5th, 2008 at 12:40 pm
Thanks for the tip, Brad. I bought the inverter “new” directly from IBM/Lenovo, but I suppose it could be bad. However, since this was my first crack at fixing a laptop, I am more inclined to think I damaged the cable or (worse) something on the system board, because I forgot to take the battery out first. (Doh!)
March 5th, 2008 at 10:02 am
to 51 (Roy)
I thought I had a bad inverter so I bought one on ebay… guaranteed not to be DOA. It did not fix my problem. After thinking and scratching my head for a bit, I decided that the issue was still the inverter. I bought another one and this one fixed my problem. What is the point of this story? Well it is simply where did you get your inverter? and how can you be sure that this replacement part is in working condition? After all the one I bought was guaranteed to be NOT DOA but it was in fact DOA.
Your best bet is to try again or find someone with the same model that is working and try their inverter.
March 4th, 2008 at 10:15 am
The LCD panel on my IBM ThinkPad T60 (model #1953-D9U) got cracked, but with the exception of a small 2″ square area where the damage occurred (white screen), I could still use the laptop with the screen open.
However, now that I have tried to replace the screen with a new one, I cannot get the new screen or the old one to light up. I thought I may have damaged the inverter, so I bought a new one and installed it. However, I am still not getting power from the inverter to the new LCD (no backlight) and the images on my old screen are very faint…as if it was a bad inverter. (FYI – The external video still works perfectly.)
I have not tried to replace the LCD cable yet (perhaps I damaged it when removing the old one?), because I am trying to find out where the “closed lid” switch would be on this model. (My old T30 had a mechanical switch that could be depressed, but this one doesn’t.)
Please tell me the best approach for troubleshooting this problem, and if it sounds like I may need to take or send it to a laptop repair shop. Thanks.