T42 lcd screen randomly goes extremely dim while using

[ncsugurl717]

Hello everyone. I have searched other posts trying to find someone who has had the same problem I have now but couldn't find anything. If you have seen a post concerning my problem please let me know.

Maybe it would help if I actually described what the problem is first......

I will be using my T42 computer by typing, scrolling, clicking, etc and suddenly the screen will "turn off." When it first started happening that is what I thought it was doing....turning completely off but then I realized it was just going very very dim. You can barely see it so I know it is still on just not enough to use the computer. Initially I could just hold down the "Fn" + "3" buttons and that would turn the screen off and then I could hit any button or move the mouse to turn it back on and it would be fine for me to use for awhile. It would stay on for about 30-45 minute increments. After a few days though it got worse. I am having trouble finding a pattern with the screen dimming but I have noticed that it seems not to go dim for awhile after it has been shut down for a few hours (almost like it needs to cool down or something). Then it will start going dim for frequently while I'm using it until all I can do is stop using the computer because after hitting the Fn+3 buttons it will immediately go back off. I also have to move the screen to a different position (as in forward and backward to where it is almost closed or almost completely back at 180 degrees)every time I turn the screen off and back on again in hopes of getting the brightness back for a little while.

I am wondering if there may be a short in the cable behind the screen but I have no clue really. I tried taking the screen apart after reading about someone else doing it on here but after getting the screws out I couldn't get but about 1/3 of the bezel to pop off and I didn't want to break it so I stopped.

Any opinions or advice would be much appreciated.

[richk]

I can tell you what I know, but it won't help you narrow it down much. First, it could be software or hardware. Software is less likely that hardware, but it is free and easy to try. If you still have the recovery partition on your machine, press the access IBM buton at startup, which will let you run diagnostics from the presesktop area. Run some sort of diagnostics that will run in continuous mode and wait to see if the screen goes dim. If it does, it is hardware. First make sure the little switch at the left rear of the keyboard bezel (that depresses when lid is closed) is working. That is also free and easy. It could be the inverter (cheapest & easiest to fix), the bulb (hard to fix without skills and equipment - most people replace the whole panel) It could also be the cable (I think unlikely but possible) or the motherboard. You say that you had trouble getting the LCD bezel off. Do you know there are 11 screws? 3 along the bottom front, 3 on each side and 2 on the top-front

[Robbyrobot]

The backlight going on and off sounds like a flaky inverter, and that is the first thing I would try replacing. As for getting the bezel off, you might note that the bottom edge is not only secured by screws, but also by strips of double-sided tape (not mentioned in the HMM) and you have to gently, firmly but above all slowly pull the bezel away from the panel with your fingernails until the tape joint "gives" to get the bezel off. If you pull too hard or too fast, you'll break the bezel. But you can feel the tape joint slowly releasing the bezel as you continue pulling it gently upwards.

I do wish the HMMs would point this out, but I have yet to see any mention of this in one.

[ncsugurl717]

Thanks for the information from both of you. I am thinking it is the backlight inverter too so that is what I am going to try first. I started searching for a replacement inverter and found a couple on ebay.

I have another question though. On the Lenovo parts website the FRU numbers are different for the XGA, SXGA+ and the UXGA but do all 3 of them use a different inverter for the 15" screen or could an inverter with the FRU number for the XGA work in the SXGA+? In other words, I need the inverter with a FRU number of 93P4161 but have found an inverter that says it can work with all the FRU numbers of 93P4161, 91P7422, 27K9976, 39T0359, 39T0361 and I want to know if this is true?

Thanks again for the previous help and the information on getting the bezel off was helpful too. I understand now why it was being so reluctant.

[Robbyrobot]

In other words, I need the inverter with a FRU number of 93P4161 but have found an inverter that says it can work with all the FRU numbers of 93P4161, 91P7422, 27K9976, 39T0359, 39T0361 and I want to know if this is true?

Although I can't speak from experience on this series, there is presumably a similar situation in the T2x series and in that case the inverter is for all models in the series. I'd check the HMM and see if there are any obvious physical differences. If not, I'd believe the claim you cite above.