Latitude E6420 LCD Backlight Syncing Issue cause a blown LCD

Ah ok, just wondering about number 1 because someone else posted a question and it turned out that the image on his corporate given E6420 was likely missing a driver for the switchable graphics.

It's very odd for sure, especially if your other two aren't experiencing this issue. I think I tried closing and opening mine with the issue and it didn't work. Take that for what you will.

I noticed the two different choices in terms of software: I assumed that the Dell Enhancement Feature Pack (or whatever it was called) in the first attached pic was the lightweight version of the Dell System Manager in the 2nd pic. I chose the latter for the extra features. I wonder if there's a difference between the new software and the old software.

Sounds like a AC adapter/power subsystem issue as well. I'd just explain that the screen flickers but only when plugged in. That's very strange behavior. Keep us updated!

 

When you say Dell System Manager, are you referring to the Dell ControlPoint System Manager?(APP_WIN_R312259.EXE)--- NM I just tested and figured it

I just uninstalled the "enhanced crap" and installed this version again. Still, the brightness bar does not follow the setting of the LCD like it did in the preinstalled windows 7. Are there some weird LCD drivers i might have to install?

My OEM Drive(with preinstalled windows 7 Pro) - Works perfectly
My new SSD with re-install of windows 7 Pro using the supplied dell disk - fail. On a fresh install of windows, no drivers installed, i can dim the screen to a a complete off, which is bad i think. Can anybody else confirm they can do this? I have a gut feeling that the windows is is the problem since it somehow can't sync up with the dimming levels, or there is some stupid dell driver i overlooked.

Again, this is a nvidia/intel video card setup with the 1600x900 display.

 

I can confirm this. I've installed udpated intel and nvidia drivers (to non-dell, just generic ones from intel and nvidia site respectively) and it caused similar situation.
It concerns i7 setup with Optimus and WXGA++

My theory is: drivers request a backlight level which is out-of spec for hardware. It works for some time and causes extensive heat/wear of the electronics in the LCD itself (DC-DC converter) and/or (need confirmation, but I'm 99% sure) the MB.

Why do I think its the cause?
-one LCD with blown IC
-two LCDs are not working (- not meaning that these are broken - 10.1" working for 20-30 hours, guess it was causing lower load on MB, the AUO replacement worked for 3-5 mins causing higher load and finishing off the components)

Long version of the story:
At first the dimming feature and the lowest brightness step was disabling my lcd backlight. I thought this was not that bad, didnt care so much. The second to lowest brightness point was very dark too, I found this attractive for use in the night. After some hours of such usage screen started to flicker, I reverted the drivers to dell ones, which seemed to fix the problem. I went to sleep. Next day, during morning mail check backlight went dead completely. It wont even blink. I've tracked the issue to LTN-KT140 display panel, which had fuse F2 and chip IC7 blown (the ic is located under plastic foil and gray tape - photo (hi-res!! http://dl.dropbox.com/u/992174/102.JPG ).
I've attached another LCD from (Acer Aspire One KAV60, 10,1" - 1024x600 40pin, LED backlight by chimei) and it worked flawlessly for some time. (not that it was usable and well looking.

I've ordered LCD replacement from AUO - B140RW03 V.1 (Dell PN: 0WJ139). I connected it, tested for 3 mins and was fine. I assembled the lid carrefully and tested again: it started flickering. I turned it off fast, then installed the Acer display to see if it worked. The display was dim as never and flickered. I heard a buzzing noise comming from right front of the laptop. After few secs buzzing increased its pitch and display went dead. Now none of 3 LCDs I got works and I have MB disassembled.
I'm pretty sure its MB fault now. I used to fix such isses by myself, but this one is tough.

 

Ooch. Damn that stinks you ruined a few LCDs. But THANK you for confirming this issue, and a light hit me when you said this happened when you installed the general intel/nvidia drivers. This led me to the solution, that be be said for all the users out there.

The solution: Install the Dell Intel Drivers. The stock windows drivers,or latest drivers from Intel directly don't correctly regulate the LCD brightness(Thus blowing up the LCD backlight). After I installed the Dell Intel version, the windows apps(the bar moves when i press +/-), and the fn hot keys are all now in sync.

 

Ooch. Damn that stinks you ruined a few LCDs. But THANK you for confirming this issue, and a light hit me when you said this happened when you installed the general intel/nvidia drivers. This led me to the solution, that i think should be a sticky for all E65420 users.

The solution: Install the Dell Intel Drivers. The stock windows drivers,or latest drivers from Intel directly don't correctly regulate the LCD brightness(Thus blowing up the LCD backlight). After I installed the Dell Intel version, the windows apps(the bar moves when i press +/-), and the fn hot keys are all now in sync with the screen.

For the NVidia drivers, i experimented, and it doesn't seem to matter where you get that one from. I went with the drivers directly from Nvidia, since those are the latest.

 

Ouch, sounds like that's something that's definetly sticky-able, especially since Windows Update loves to push the Intel driver to you if you're not right on top of installing. I'd recommend installing as much as you can disconnected from the internet.

Glad to hear you guys figured it out and it'll be the first thing I do when I reinstall windows on my E6420 once it's back.

 

Wow holy crap. I did a screen swap to a better screen. I had the same issue and it killed my newer screen. Everything worked fine until I left it on over night and dead screen...I think it may have updated during that time? In any event, I ordered a 2nd of lcd type #2 and it would work in the bootup screen but it died on windows. Completely dead as I tested these lcd's in another laptop to verify.

I'm back on the stock E6420 panel and it's working fine but damn that is some scary stuff.

Which Intel drivers are we avoiding? The one for the integrated graphics?

 

I've had luck installing all the drivers. Because optimus routes even nvidia traffic through the intel IGP, im pretty sure a intel driver is required for proper functioning.

The key is installing the drivers in the right order. I'll provide a link to the post around here that has the correct driver order for our machines.

Here's the link: http://forum.notebookreview.com/showthread.php?p=8126791

My advice would be to grab a old usb key that's lying around and devote it to driver installation. Store the drivers and software on that key in the numbered order from the list.

I also now reboot after each driver/system software install during the clean install process. Yes it's overly paranoid but it was something i wasn't doing before and i had the out of sync backlight issues. I'll add that, at least for me, sticking with the dell provided intel IGP driver didn't prevent my issue but since it did fix someone else's upstream it's not a bad idea to do so just to be safe.

 

I just killed my LCD backlight the same way - after installing the proper Intel drivers from the Intel website...

Here is my case:

I have my DELL Latitude E6420 for almost a year. It came with Free DOS, I installed WIN 7 x64 myself and it worked fine until I installed a new SSD yesterday and made a clean WIN 7 x64 install. I got all the Intel drivers from the Intel website. The difference in my system from the other posters here is that I only have the Intel HD3000 video in my system - no Nvidia card. Screen is again 1600x900.

Everything was working fine for about 24hrs after installing all the drivers and software. Setting the backlight to minimum wasn't turning it off, but my only issue was the backlight bar wasn't moving at all. Trying to fix this I reinstalled the Dell Feature Enhancement Pack and this time when trying to set the backlight to minimum it did turn off and I was unable to turn it back on using the keyboard....

I didn't know what to do, so I switched my laptop off and the back on - the backlight switched on during POST, but then switched back off when booting Win7. Again i switched my Laptop off and back on and this time I was missing the backlight even during the POST.

I found this thread in Google immediately and tried the Windows Mobility Center to turn my backlight back on, but unfortunately it didn't work. I also tried to switch it back on in BIOS (using my Phone's flash to see the screen), but this didn't work either, so I guess my backlight is now dead...

Tomorrow I'm going to bring the laptop to the service for repair.

 

I am experiencing the exact same issue described in this thread but on Windows 8 Release Preview. Backlight is shot. My mobile display is essentially useless now, good thing I get complete care on all of our laptops.

Also using the drivers from nVidia/Intel instead of dell.

I have had nothing but problems with the display and video drivers for the e6420 in the ~1 year that I've owned it. What a terrible turn of the worse, the E6x10 were solid machines, I have about a hundred of those in the field and zero issues like this garbage.