Thinkpad LCD problem

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oshilig

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Jan 4, 2005
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I've got an IBM Thinkpad T21 whose display just went out almost completely. If I look very closely, or shine a flashlight on it I can see everything is there, but it is as if the brightness has been turned way way down. It works fine with an external monitor.

For the past couple months it has been starting up with a pink hue that gradually faded. Then a couple days ago it took to flickering, (I posted another question on this). Then today out completely. When I use the hot keys to turn off the monitor and then turn it back on, it'll show up fine for a second or two, and then wink out again. Also on start-up, it'll show normal (almost normal, with flicker) and then wink out but boot up normally.

After some googling and tech forum-ing I have narrowed it down to either a bad backlight, or a bad inverter. Any ideas on how to figure out which one?

Also, I am currently living in Eritrea, (a small country in east Africa) which was one of the last countries in the world to get online. Tech services are poor at best here so I will be trying the fix on my own. Any advice on how to replace these items would be most appreciated.

Thanks!
 
Joined
Aug 2, 2004
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When you said, "either a bad backlight, or a bad inverter".

Were you refering to an external inverter or circuitry internal to the PC? I guess I'm asking are you using an inverter to run this PC off of an external DC source?

Chances are from your description of the symptoms it is the Backlight. This is solidified by the fact that it will drive an external Monitor just fine.

I have had an experience with my laptop where the backlight problem was caused by a pinched cable that runs through the hinge to the LCD. Rerouting, rewrapping the cable, and flexing it got the problem to go away.
 

dustyjay

Jay
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Jan 23, 2003
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Thinkpads use an internal inverter. It sounds like the backlite to me as well. It is not aq cheap fix either if the laptop is out of warranty. probably 3 or 4 hundred or more if you go to IBM for the repair.
 

oshilig

Thread Starter
Joined
Jan 4, 2005
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thanks winbob and dustyjay, it is indeed an internal inverter, but I'm a bit confused on the diagnosis. What's the relationshiop between the inverter and the backlight, and is there anyway to tell which one is the problem. The IBM online tech guy help thought it was the inverter.

As for the price of the repair, that's bad news, and confirms the idea that I'll be trying this on my own if I can figure out what exactly is the problem.
 

dustyjay

Jay
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Jan 23, 2003
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go to the access ibm site and download the maintanance(sp) manual. IBM calls the parts FRU's the manual is free to download and it will tell you how to change the parts. As for obtaining the parts you may have a bit more trouble there. Never ordered laptop parts before.
 
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Aug 17, 2003
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The inverter changes the voltage from the laptop battery supply to the (several hundred) volts, current limited, required by the backlight. It also handles the start-up for the backlight which may be a few milliseconds of even higher voltage.

If you know what voltage is meant to be applied to the backlight, and can find the appropriate connections to measure you could determine if the inverter was running.
 

dustyjay

Jay
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Jan 23, 2003
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12,661
yeah tht is what it is hehehe! Thanks winbob. I knew they had to have a good name to go with the acronym
 
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