Screen doesn't lighted up, though it's working

I have a T43 laptop, I am facing strange problem since last week.When I turn on the power the screen starts but it doesn't light up properly, I can see the Window XP logo and once it boots I can see the desktop, but it's too dark to read or use it.When I tap the lid close button number of times then some times the screen starts working otherwise it stays dark.When I manually press down the button the screen goes absolutely blank or lets dead and once i release it, then it turns on but its too dark.Today I had to fiddle with button for 30 mins, then suddenly, it lightened up.

What could be the reason for such problem?what is the remedy?

 

sounds like the backlight bulb is bad/going bad. if so, you'll need to replace the bulb.

 

Is there really a backlight bulb?

I haven't seen one and I've certainly been in the top of my t61p.

Renee

 

yes. liquid crystal has no luminescence property of its own.

 

Well thats true. What does LED mean? Or are they really LEDs?
Renee

 

Well, the displays you see in now that are advertised as LED are not actually LED displays. They're LCD, but backlit with LED's rather than with a CCFL(Cold Cathode Florescent). This has some advantage to creating a more evenly lit display as well as achieving better blackness levels because the LED's can be independently adjusted in their brightness. With a CCFL, you can't control brightness levels in specific areas of the screen.

There are true LED displays, called "OLED displays", but they're still uncommon, very expensive, and no one has put one in a laptop yet to my knowledge.

 

What would be the connection with lid close button then?I just pressed and released it some times, and the screen lite?
expected cost of the bulb?

 

Not sure...my knowledge is just theoretical. Simple vibrations through old bulbs or faulty connections can cause intermittent problems like you describe.

Not sure about the bulb cost...or even if you can buy just the bulb. It may be hard-fitted into the screen in which case you'd have to get a new display. Someone with more practical tech knowledge on these computers will have to answer that one.

 

I have attached the pic of the button switch I am talking about, its on top left side corner just next to silver screen mount.
Source of pic-Flikr, it's just a reference pic, not mine though.

 

Since fiddling with the button seems to turn on the backlight, it maybe a case of faulty button rather than the backlight going bad(it could still be a possibility). The button basically turns your LCD on/off when you close the lid on the laptop. I would start with checking the button and then work your way to the backlight.

 

Went out for food, closed the lid partialy, again the same problem:-((
One thing more I forgot to mention, the LCD color is quite reddish orange once it lightens up.after few second it turns into white.

 

The fact that the screen is just dark, but not blank, leads me to think it's not the button. The button should just be a simple one or two pole switch and if it was malfunctioning then you would have a completely blank screen or a flickering screen, but not a dark screen.

Could be wrong, but that's my thought...

 

I just can't resist this. The screen doesn't lighted up? So the screen won't light up in the past?

Ok, I got that out. Another thing it could be is a bad wire or connection somewhere. I used to have a Dell Latitude XPi and the backlight would flicker from time to time. Turns out there was just a bad solder joint on what I believe was the inverter board for the screen. I redid all of the solder joints on the chip that had the broken joint and the screen was good as new.....aside from the big orange spot in the upper right corner of the screen which was the result of the computer hitting the pavement after my backpack strap broke.

 

Agreed. should I change the screen or CCFL?

 

your CCFL tube is coming to the last leg... so you will have to replace the LCD.

 

It's not related to the button, As I thought earlier,Restarted the laptop, without even closing the lid,again there was not display.So the culprit is not the lid button, might be something else.

Will it do. If i swap the CCFL and Inverter or I have to replace the full panel?

 

The fact that it turns on after some fiddling with the button leads me to guess that some connection may just be loose - that happened on my old Averatec, but I have yet to narrow down which wire is actually loose.

 

when a back-light is going out it usually starts with the light changing to a reddish color, what you need to do is change the back-light bulb or CCFL because yours is dead or about to die.

 

CCFL light bulb can be changed but it is bit more trickier, and would require an clean environment and a steady hand.... there are lot of tutorials on this at forum.thinkpads.com if you are interested in this method. The ccfl tube for LCD are around 20 USD on ebay.

 

back to square one. swapped the Inverter and LCD flex cable, again the problem is there.though I am writing from the same machine, I have to press the lid close button, then it starts working randomly. I am using the machine since past 24 hrs continuously,it's fine, but on a restart, same problem shall be there.

 

Just last week I had my backlight go out on my T42. I found the link below to be a very helpful source of information; I was comforted to know I was not alone with my misery:

http://www.pluralsight.com/community/blogs/aaron/archive/2006/01/19/18114.aspx

Here's the biggest nugget there I latched on to:

The backlight is a small cold cathode, basically like the fluorescent lights you find in office buildings, only much smaller and thinner.

As these bulbs begin to wear down, they tend to flicker a lot and hold only for a bit before burning out. As well, once they crack they are done.

Now the good news. All you need is a soldering iron, and you can replace your cathode for under $10! It sounds wild, but they make these internals look a lot more sophisticated than they actually are. ​

I have opted to pay the $45 on ebay for a replacement screen/lid instead of messing with installing a new CCFL bulb. It's current on its way.