Backlight problem on T22

[bowwer@racemail.com]

Hello everyone,


Several weeks ago my t22 booted with a very weak backlight on occasion on startup. I could coax the backlight into full operation for the remainder of a session with a couple fn-f7 presses to change output display, which was a nuisance but manageable.

Then a couple weeks later the fn-f7 trick would only cause the backlight to flash bright for a few seconds, and then go dark once again. Finally, now, the light doesn't come on at all.

My first step was to disassemble the unit as per the hardware guide and check the connections, which I did. Inside the inverter card and cable looked snug but i reconnected them anyway to be sure. Once I put it back together there was no change in the condition of the computer.

One thing I noticed when I took it apart was that the inverter card was from 2004, while the computer was manufactured in 2001. I got the unit used on ebay so it appears someone changed the inverter in the past. Not sure if that is relevant.

Any help on what to change out next? Looks like I will need to buy something, but what? Cable, inverter card, backlight, whole lcd assembly? Suggestions?

Thanks in advance!

[rkawakami]

Welcome to thinkpads.com!

A little more information... Was the backlight (when it worked), pinkish or reddish when first fired up? Did moving the LCD panel back and forth on the hinges make any difference? Do you hear any high-pitched whistle while the laptop is on (coming from the area of the inverter)?

[bowwer@racemail.com]

Welcome to thinkpads.com!

A little more information... Was the backlight (when it worked), pinkish or reddish when first fired up? Did moving the LCD panel back and forth on the hinges make any difference? Do you hear any high-pitched whistle while the laptop is on (coming from the area of the inverter)?

Thanks for the reply and welcome -

- When the backlight worked, it was normal in hue, no discoloration at all.

- Moving the LCD back and forth might have done something, but I don't know because I didn't try it. Sorry! Fn-f7 worked perfectly, and so I didn't try alternative solutions. When it started without an operational backlight, as soon as Windows loaded I pressed Fn-f7 once or twice, and presto, backlight was back on for the remainder of the session.

- No unusual noise is made when the laptop is on, I can still use it with an external monitor without any problems.

Thanks again!

[rkawakami]

From the information given, first check the wires going from the inverter card to the CCFL (backlight) inside the LCD panel. If you can see where they are soldered onto the pins of the CCFL and they look snug, then I would try replacing the inverter card (again). There is also a small chance that the problem exists on the motherboard and/or the wiring (ribbon cable) to the LCD panel. As the backlight is the normal white when first lit, I am tending to believe that the lamp is good and that your problem is that the lamp is losing power. That's the job of the inverter card. As you initially said that the date code on your current inverter is newer than the manufacturing date of the laptop, there still is a chance that the "new" inverter is also defective. It's only about $15 off of eBay. My philosophy is to start with the cheapest possible solution and work my way up. At the top of the list is a complete LCD panel swap. Replacing just the backlight is mostly a job for a masochist (sorry basscleff! ), but it can be done.

I believe that it is possible to test the voltage coming out of the inverter, but you'd better know what you are doing. The information I have seen online says that several hundred volts AC is being sent to the backlight. If you can manage to get a voltmeter attached to the terminals of the backlight (or off the inverter card) and power up the system long enough to measure the voltage, without getting shocked, that should tell you whether or not the inverter is working. If you see plenty of voltage, your backlight is the problem. If you don't see any voltage, it could be the inverter, the ribbon cable to the inverter or the motherboard causing the problem.

EDIT: Strike the previous paragraph. I found out you can't simply hook a voltmeter across the inverter's output pins. It requires a special method/circuit to measure the voltage.

Assuming another inverter card does not cure the problem, then I would go after the ribbon cable. I believe the T22 cable is similar enough to the one I have replaced in a T23, in that the power to the inverter card comes up from the motherboard on that ribbon cable. If THAT doesn't work, then the solution is probably motherboard or LCD panel based and the cost of repair goes up significantly.

As I alluded to earlier, I understand a user on this board has replaced several backlights for other people. His ID is "basscleff". You may want to discuss with him what he thinks might be the problem.

[bowwer@racemail.com]

Sorry for the late, late update to the thread but I got busy and had a late delay of my ordered inverter.

I did want to let everyone know though, that I successfully changed the inverter and fixed my backlight problem, so thanks a lot for the help and anyone else in a similar situation:

Order an inverter and try swapping it first. Cheap and (relatively)easy fix if it is the cause of the problem (as it turned out to be in my case).