Latitude E6500 Blank Screen

Hi Josh,

Yes please let me know how your MB replacement goes. I've been travelling and unable to get back to my wounded machine. I'd appreciate knowing how it turns out for you. 

Cheers,

Doug

Doug,

i worked on swapping the motherboards this afternoon and while the used mb booted up, the screened kicked off like it has before.  With my original mb I could usually unplug the screen cable and plug it back in again to get it working.  That didn't work with this nw mb.  I tried the new inverter I had bought previously, and also tried the used screen cable and neither made any difference.  I'm baffled at what the problem is.  I've sent the screen back, they tested it and said it was good.  The ebay seller said the mb was pulled from a working laptop.  He was going to talk with his techs in the morning and get back with me.

im at a loss since I don't know what other components are left to be replaced, unless one of the spare components I have is also bad, but the chances of trying all the different combinations and it still not working is probably slim.  I'll take a closer look at my original mb to look for leaky or bulged capacitors.

I checked the original motherboard and it looks fine, so I'm not sure what to think.  I'll probably try and put the original mb back in since I could get the screen to come up by playing wito the screen connector.

Hi Josh,

That is very disappointing to read, certainly even more disappointing for you. I was convinced that the MB was the culprit. Although it still may be in my case I'm now very reluctant to even bother trying to swap mine. Not sure what to suggest now, what else could it even possibly be? It appears that you've tried the most likely candidates. 

I plan on sharing your experience with our IT guys and will get back to you with any suggestions that they may have. 

Thank you for keeping me up to date.If I do attempt to swap mine I'll let you know the outcome. 

Regards,

Doug

Doug,

The ebay seller is sending me another motherboard to try, so hopefully I have better luck with it.  I'll keep ya posted on how it goes.

Josh

Hi Josh,

That is very interesting Josh! The likelihood that my laptop suffered the same fate as yours is high and your research and resulting reports have been extremely informative. It appears that my IT guys were incorrect, at least in your case, in suggesting that it was a motherboard issue. Your latest submission clearly points to a problem with the screen assembly itself, which is consistent with my experience. That is to say, my laptop works just fine when another external monitor is attached. 

I look forward to reading your next dispatch!

Cheers,

Doug

Hey guys!  Just wanted to chime in and say that you are not alone!

I have been down basically the same exact paths you guys have been down.  I've replaced my screen, inverter, and cable... but to no avail.  Screen sometimes works for anywhere between 3-40 seconds (longer times on battery, very short times on AC power).  Screen flickers, and before turning black it usually goes up to a really bright intensity.

I've been able to keep the screen on if I keep pressing the Fn+BrightnessDimmer button repeatedly... it's almost as if the system is constantly trying to adjust my brightness for me (via the ambient light sensor, although it's disabled) and if I battle this crazy adjustment it's doing, I can win.  Of course, then I'm not using my computer, I'm pressing buttons non-stop.

I can't help but think it is motherboard related, because it seems that the sellers keep saying that the screens are working, and the only difference is what hardware is connected to the screen.

You know I've had the very same hunch about the ambient light sensor and the circuitry associated with it.  There are times where I've noticed the lighted keyboard functions properly and other times it doesn't appear to light up.  I too have the ambient light sensor disabled, but still think it may have something do with playing into the issues.

I've swapped the entire motherboard with two different motherboards and had the same problem, so I don't believe the motherboard is the issue.  I'm not sure if the ambient light sensor is at the top or bottom of the laptop screen.  I know the camera assembly is up there, but there's also some other items up there.  But there's also another circuit board at the bottom of the laptop screen that might be it as well.

I am expecting an entire screen assembly, which hopefully if it works I can try and determine which component is the culprit.

Josh

Greetings Josh et al,

One of my colleagues, and someone with much better computer skills than myself, saw this post on a Dell  forum - 

Hi Josh,

I noticed something today. When I turned on my laptop the screen was working again. My battery was about 20% no external monitor or power cord was connected. The screen worked even in Windows, although it was a bit dim. The moment I attached the power cord the screen brightness went up for a few seconds and then off.

This makes me think again that it has something to do with the ccfl and/or inverter. It seems that the board cannot supply the full power and shuts itself down for safety.

I might try a new ccfl or test the ccfl tube with a separate inverter board. Now I have to figure out where and which size of ccfl I must order.

I'll keep you posted.

Jorrit

This colleague of mine then emailed me the following- 

When I saw this, I unplugged the power cord.  The computer booted, screen showing the BIOS posting like it should.  I put it into the diagnostics and the computer did its thing.  When it finished, I rebooted, still on battery, and it was working just fine.  Got the Windows prompt, all worked beautifully.  I went in to the Power Management and noticed that the screen was set to full brightness on both the battery and AC profiles.  I dropped both just a bit, to maybe 80%.  Since then, the computer has never flickered, and has rebooted 8-10 times.  I installed updates, let it go to sleep and woke it back up, purposely hard crashed it (battery out, pulled the plug), interrupted the boot up….. I can’t get it to fail.  Without knowing the issue, I’d never suspect a thing was wrong.

It appears that we may have found the problem with my old E6500. Who would have guessed that it could have been that easy? My colleague will continue to put the laptop through a number of tests, hard crashes, reboots etc. so we'll see if our success is fleeting. I'll keep you posted.

D

The above worked for me for a while, but wasn't a complete fix.  So it may do the same for you. 

I'll keep ya posted on my progress.

Josh

Interesting, sorry to hear that you've already tried that. We're putting it back to work so we'll know soon what happens. I'll keep you posted. 

D

Hi,

I fixed this problem by replacing the screen (with ccfl) and the inverter at the same time. It's a risk to replace only one of the two because if the inverter is defective it can damage the ccfls and vice versa.

My screen is still working since I replaced it.

I hope this helps. 

Jorrit

I necro this old thread because it has been informative and my E6500 case is related.

I disconnected the AC adapter and did all of the following on battery.

Holding the D key during power-on, the LCD displays white, off, red, off, and stays off.  I think white means all pixels are on so the LCD is OK.

Holding the Fn key during power-on, sometimes the screen comes on long enough to show the Dell logo and part of the progress bar before the screen turns off.  Diagnostics proceed invisibly.

Doing a normal power-on, the screen displays nothing or just displays white for an instant, but Windows boots and responds to ping.  Furthermore, now I can press Fn + Down Arrow to set the display brightness to minimum.

After that, holding the Fn key during power-on, diagnostics displays are dim but visible.  Even the full colour screen diagnostic is correct.

In BIOS set up, I can use the mouse to slide the slider.  The screen starts flickering, alternating between nearly minimal (as set by the slider) and maybe full brightness (which it should not be doing).  And if I leave it that way for a few seconds, the screen turns off.

So I have a feeling this could be a short in the cable, and if the short causes some kind of power drain other than improperly fully brightening the screen then some protective circuit turns off the screen to prevent further damage.

But I also have a feeling that it's not a short in the cable.  I have a feeling the defect is somewhere else, but I can't guess where.  If it were a short in the cable then the brightness would misbehave even when the BIOS slider is set to minimum.

Any ideas?

The problem is somewhere in the display assembly.  I swapped display assemblies with a different E6500 and the problem followed the display assembly.

When the display brightness is set in the BIOS, the setting is stored in the system board.  When I swapped display assemblies, the settings did not get swapped.

Somehow the display assembly takes turns obeying and not obeying the setting communicated from the system board.  When not obeying, it turns brightness up to full, draws too much power, and some protective circuit shuts it off.

But which part of the display assembly?