Ibm thinkpad t42 screen problem?

[mnplus1556]

hello. ok so i recently bout a friends old laptop. it's a ibm thinkpad t42 type 2373.

so if i have the screen problem. i can plug it into an external monitor and it works fine. otherwise the built in lcd will display the image but the back light stays off. in attempt to fix this i bought a new lcd inverter. now it stays on for a max of 10 seconds. the only ways that it will go on is if i push the button to make it think i closed the lid. after i release the button the back light goes on for a few seconds. i have opened the laptop. the connection seems to be fine. the lights on the inverter stay on. i've heard that buying a new ribbon cable could fix it....is that true?? is there a bios update or something? has anyone else had this problem? how do i fix it???


thanks!!

[Harryc]

It's either the LCD cable or the CCFL (backlight). The chances of it being a bad CCFL are greater than it being a bad cable. The easiest solution to a bad CCFL is to replace the LCD panel.

[mnplus1556]

ok. so i put a voltage meter up to where the backlight plugs into the inverter. it hangs at like 1.5 volts. so i pushed the button down, and held it for like 4 seconds. when i let go there was a huge increase of voltage. then it went back down to 1.5 volts seconds after.

does that sound like the cable or the backlight is faulty??

and thank you, i appreciate the help.

[RealBlackStuff]

Be very careful if you are going to measure a CCFL! It's nearly 1400V (that's fourteenhundred !).

[mnplus1556]

ok check out my vid.

http://www.youtube.com/watch?v=-24-TYR8gus

thanks.

[RealBlackStuff]

On your video, it looks like you hook up the LCD's CCFL to an external inverter, and it then works?
Maybe the 'new' IBM inverter you got is (also) faulty?

[wearetheborg]

On your video, it looks like you hook up the LCD's CCFL to an external inverter, and it then works?
Maybe the 'new' IBM inverter you got is (also) faulty?

On the video, the LCD seemed quite "white" --- is that an indication that the backlight is OK ?

[Harryc]

Here's my take on this problem. As CCFL's get older it takes more power to fire them up. Once they get to a certain point, a conventional inverter will not provide enough power to turn the CCFL on. So, by using a desktop inverter of unknown output, and assuming that power output is higher than the inverter in a Thinkpad, that might explain why the desktop inverter will light the CCFL, even though it is old and worn out. So, my opinion is that the CCFL itself can't be ruled out just because it lights with the desktop inverter. CCFLs themselver are fairly cheap, and can be used for problem determination. See this link and read the comments that follow the removal procedure for some ideas on using a CCFL for problem determination.
http://www.laptoprepair101.com/laptop/2 ... -comments/