T42 display goes dark

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chchandler · #1 Post by **chchandler** » Wed Apr 22, 2009 10:45 am

I have a T42 model 2373-3UU with SXGA display that I bought off a corporate lease about a year ago. It runs Ubuntu Linux, but can dual-boot into XP if needed. A few months ago I began to see a pink tinge on-screen when it started. Then, recently, the screen would go dark. The images were still there, but the screen lamp would shut off. Fn-F3 would re-start the lamp, and reducing the lamp brightness worked to keep it on for a while. Over time, though, the period between re-starts got shorter and shorter and the brightness possible for any meaningful work period got less and less.

So, I researched the HMM and found the part listed as 11P8346. I found one on-line and a local shop to do the swap. I hesitated to do it myself since I have never worked on a laptop before. This was a mistake... The tech left me a note saying "The display provided is not an exact match and shorts out the laptop. The part needed is LTN141P4-L02 (Samsung)." The tech was kind enough to put the original lcd back, and it worked the same. With the brightness all the way down it will stay lit for a few minutes, then I have to use Fn-F3 to restart the lamp.

So, I was able to exchange the 11P8346 for a Samsung LTN141P4-L02. I also found a new shop. The first one was a mom & pop type, and I didn't see any new computers there. The university IT folks recommended another shop, which looked much more capable. They swapped in the second new lcd and reported it left the laptop dead. They showed me that with the battery removed the HDD will spin for a second and the power LED will light, but nothing else. With the battery installed not even the power LED will light and pushing the power button does nothing. Their best guess is a bad system board.

So, right now I have it all at home and tonight will take a deep breath and dive in. First task will be to swap back the original lcd and se if I can get it to boot again. If so I'll try the Samsung and see if it will work while it's un-buttoned. I read of some lcd replacement failures due to badly-routed cables so that is worth a check.

I need some advice! So far I have spent $200 and have a non-working laptop. I can spend more but can't afford to throw good money after bad. Can anyone point out where the problem is likely to be?

I suppose it could be the inverter. That would be great, although it would mean I have wasted $200 so far.

If it's the system board (maybe the flexing GPU issue) wouldn't that lead to a display that was blank? This issue is with the lamp turning off, as if it over-heats.

I see new system boards available. I also see re-work services that seem, in at least one case, to be better than new. Any experiences with them? How can I tell if that is where the problem lies?

Any help appreciated...

Chuck

sjthinkpader · #2 Post by **sjthinkpader** » Wed Apr 22, 2009 12:58 pm

If you installed the wrong panel, it may blow a fuse on the motherboard. But 11P8346 IDTech panel is pin compatible with e Samsung 11P8348 panel and should work for T4x 14 inch SXGA+ applications.

It is rare that multiple points of failure happen at the same time. I would be very suspicious at the repair shop when that happens.

With the old panel in place, you can try booting with an external monitor.

chchandler · #3 Post by **chchandler** » Wed Apr 22, 2009 6:06 pm

OK, here's the latest. I open up the T42. Not as bad as I had feared, the HMM is a big help. I undo all the wires that might be crimped, apply power and try to start - a quick HDD whir, then nothing.

So, I take the new lcd out. It is labeled 141P2/L02. Not quite the same...

In goes the old lcd. It is labelled 141P4(U2)/L02. T42 boots right up, though no light on the lcd. Right now it's been running, found my wifi and all seems normal except for the dark display.

I have ordered a new inverter, despite my fear of sending good money after bad... it was not expensive and it is worth the try.

I will later try an external display and report how that works.

chchandler · #4 Post by **chchandler** » Wed Apr 22, 2009 7:15 pm

Final update for the night... until I either get the new inverter to try out or until I think of something else to investigate or someone posts an idea to try...

I attached an external monitor and it works just fine.

I am leaning away from a system board or GPU issue and more towards an inverter or CCFL issue. Still wish I understood why two new lcd's failed... at least one of which should have been the right one.

Chuck

chchandler · #5 Post by **chchandler** » Sun Apr 26, 2009 3:36 pm

Haven't updated this thread in a bit.

I replaced the inverter, no change. I can get the lcd to light, at the lowest intensity level, long enough to get work done but it then goes off again. I've got a near-new panel, but it won't work in my laptop... possibly the wrong panel. I've e-mailed the shop with a picture of the label off the panel that came with the laptop, we'll see if I can work an exchange.

I also researched the lcd lamp. It's a $10 part! Removing it and replacing it will not be kid stuff, but I think I can handle it so I ordered a new CCFL and we shall see if I can ruin a non-working lcd panel or if I can get it all good as new for short $$.

FWIW, the fragile lamp connections need a fairly deft touch with a soldering iron, but I've been a ham radio operator for 25 years and have burned my fingers enough times to handle one pretty well

sjthinkpader · #6 Post by **sjthinkpader** » Sun Apr 26, 2009 5:14 pm

Per your description, yes, replacing CCF would be my next step too. Beside getting the CCF in the panel, make sure the BEF (brightness enhancement films) are flat.

chchandler · #7 Post by **chchandler** » Mon Apr 27, 2009 7:02 am

sjthinkpader wrote:...make sure the BEF (brightness enhancement films) are flat.

What are the BEF's? Are they a part of the lcd sandwich? I guess they are flat right now, but when I remove the CCFL housing (or replace it) they may get wrinkled?

Any help appreciated!

sjthinkpader · #8 Post by **sjthinkpader** » Mon Apr 27, 2009 8:43 am

Yes, BEFs are part of the LCD sandwich.

#9 Post by **Johan** » Mon Apr 27, 2009 12:35 pm

chchandler wrote:What are the BEF's? Are they a part of the lcd sandwich? I guess they are flat right now, but when I remove the CCFL housing (or replace it) they may get wrinkled?

... there is a (brief) discussion about BEF's and a couple of illustrative links in this and the following post. Especially, see the links at left at the 3M site, e.g. the LCD Optics 101. Does not seem as BEF's are for "average Joe" to play with...

Johan

poshgeordie · #10 Post by **poshgeordie** » Mon Apr 27, 2009 1:25 pm

sjthinkpader wrote:Yes, BEFs are part of the LCD sandwich.

I love a nice "Be-f" sandwich especially with a bit of mustard on....

T42 display goes dark

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