Jump to content


 


Register a free account to unlock additional features at BleepingComputer.com
Welcome to BleepingComputer, a free community where people like yourself come together to discuss and learn how to use their computers. Using the site is easy and fun. As a guest, you can browse and view the various discussions in the forums, but can not create a new topic or reply to an existing one unless you are logged in. Other benefits of registering an account are subscribing to topics and forums, creating a blog, and having no ads shown anywhere on the site.


Click here to Register a free account now! or read our Welcome Guide to learn how to use this site.

Photo

Backlight/Screen power inverter Troubleshooting


  • Please log in to reply
8 replies to this topic

#1 davidherman

davidherman

  • Members
  • 11 posts
  • OFFLINE
  •  
  • Local time:09:01 PM

Posted 10 October 2009 - 05:47 PM

I have a 4+yr old Dell Latitude D810 laptop and this morning I stepped away from my computer for a little while and came back to a dark screen (much sooner than it should have turned off). I moved the mouse to wake it up, thinking it had just turned off for some reason, but it wouldn't come back on.

When I restarted the computer, the screen showed up normally for a minute or two, but then just blinked off again. As near as I could tell there was no image on the screen at this point, but it was difficult to tell. I hooked it up to an external CRT and everything displays fine, so its definitely something specific to the screen. From what I deduced online it's either a problem with the backlight, screen power inverter, or a combo of the two. I have no way to test voltages or anything like that, or swap parts to see whats working, as some suggestions Ive seen online. Basically my question is how can I determine the specific fault and or what I need to replace, and how do I replace it?

When turning the screen on (on bootup or when I switch the video output), it will always light up for a short length of time, but then will lose all brightness; now I can tell that the screen still displays the image, theres just no brightness (I was able to use my desklamp to navigate, albeit barely. for a while earlier today). Also, when it does turn on, the screen takes a few seconds to lose a somewhat reddish hue before looking normal, until it loses all brightness of course... That coloration isn't really any different from how it behaved recently (I can't remember far enough back to know if it is a symptom) but some sites listed it as a symptom...

Ive looked and seen inverters and backlights for pretty cheap, but I don't know how simple a replacement procedure it is (I have no means to solder, if that would be necessary). I don't want to replace the whole LCD screen as that would be like 10x more expensive, if I can avoid it...

The screen is a 15.4" WSXGA+ (I believe) if that makes a difference.

Any help would be greatly appreciated.

BC AdBot (Login to Remove)

 


#2 garmanma

garmanma

    Computer Masochist


  • Staff Emeritus
  • 27,809 posts
  • OFFLINE
  •  
  • Location:Cleveland, Ohio
  • Local time:09:01 PM

Posted 10 October 2009 - 08:13 PM

I have no means to solder, if that would be necessary

Most of the times it is
Mark
Posted Image
why won't my laptop work?

Having grandkids is God's way of giving you a 2nd chance because you were too busy working your butt off the 1st time around
Do not send me PMs with problems that should be posted in the forums. Keep it in the forums, so everyone benefits
Become a BleepingComputer fan: Facebook and Twitter

#3 Platypus

Platypus

  • Moderator
  • 13,673 posts
  • OFFLINE
  •  
  • Gender:Male
  • Location:Australia
  • Local time:11:01 AM

Posted 11 October 2009 - 06:56 AM

when it does turn on, the screen takes a few seconds to lose a somewhat reddish hue before looking normal

That does suggest a CCFL lamp may not be operating correctly. In the course of my work I had to write off a 17" Mitsubishi monitor about 6 weeks ago for this cause (the lamp running poorly causes the inverter to shut off). I did have the advantage of being able to temporarily substitute a good panel to prove the cause, but it was fairly clear the lamp was unhappy.

In a laptop, the lamp can probably be replaced, but I don't work on laptops myself.

Edited by Platypus, 11 October 2009 - 06:59 AM.

Top 5 things that never get done:

1.


#4 garmanma

garmanma

    Computer Masochist


  • Staff Emeritus
  • 27,809 posts
  • OFFLINE
  •  
  • Location:Cleveland, Ohio
  • Local time:09:01 PM

Posted 11 October 2009 - 11:15 AM

I've done two, one solder and one not
The lamp is relatively inexpensive. Buy two JIC
You are fortunate that Dell offers excellent directions
http://support.dell.com/support/edocs/syst...10/sm/index.htm
Mark
Posted Image
why won't my laptop work?

Having grandkids is God's way of giving you a 2nd chance because you were too busy working your butt off the 1st time around
Do not send me PMs with problems that should be posted in the forums. Keep it in the forums, so everyone benefits
Become a BleepingComputer fan: Facebook and Twitter

#5 davidherman

davidherman
  • Topic Starter

  • Members
  • 11 posts
  • OFFLINE
  •  
  • Local time:09:01 PM

Posted 11 October 2009 - 12:42 PM

I've done two, one solder and one not
The lamp is relatively inexpensive. Buy two JIC
You are fortunate that Dell offers excellent directions
http://support.dell.com/support/edocs/syst...10/sm/index.htm


Is JIC a brand of lamps?

I followed Dell's directions, but I cant get the final 4 or so screws out that hold the LCD panel itself to the fram (screen is removed from the computer base and the bezel is off). Any suggestions on how to safely loosen screws around the screen? I'm afraid the screws, screwdrivers, and my fingers will all be stripped before I can get them out... I just cant get any more torque out of a screwdriver that is small enough to work on these screws; the shaft is just too skinny...

#6 garmanma

garmanma

    Computer Masochist


  • Staff Emeritus
  • 27,809 posts
  • OFFLINE
  •  
  • Location:Cleveland, Ohio
  • Local time:09:01 PM

Posted 11 October 2009 - 02:35 PM

JIC = Just In Case
As you have discovered, a quality screwdriver is a must investment
You will notice some blue material on the screw threads. This is a thread locking compound
You can carefully use heat to loosen the screws
I'll heat it up the stubborn ones with my soldering iron.
I would suggest trying a hair blowdryer

Edited by garmanma, 11 October 2009 - 02:37 PM.

Mark
Posted Image
why won't my laptop work?

Having grandkids is God's way of giving you a 2nd chance because you were too busy working your butt off the 1st time around
Do not send me PMs with problems that should be posted in the forums. Keep it in the forums, so everyone benefits
Become a BleepingComputer fan: Facebook and Twitter

#7 davidherman

davidherman
  • Topic Starter

  • Members
  • 11 posts
  • OFFLINE
  •  
  • Local time:09:01 PM

Posted 11 October 2009 - 03:07 PM

Ok a quick trip to Lowe's fixed my screw/driver problem, and I have the panel completely out.

How do I tell if the inverter or the backlight (or both) is the issue? It looks like the inverter would be easily removed, but everything else is covered by white tape and a label that warns not to touch the white tape because it's a sensitive area...

#8 davidherman

davidherman
  • Topic Starter

  • Members
  • 11 posts
  • OFFLINE
  •  
  • Local time:09:01 PM

Posted 11 October 2009 - 04:19 PM

Posted Image

I don't know it this is useful, but I tried selectively plugging and unplugging the inverter cables to see what would be different. When plugging the main display cable (D) in to the laptop base, the screen flashes on for half a second or so and goes dark (image is still visible, just not backlit). The same thing happens, when I unplug and replug the connector between the inverter and display cable ( C). But when I unplug and replug the (what I assume is) connector between the inverter and backlight (B ), backlight is unaffected (it stays off rather than flashing on like before). And of course unplugging (A) only affects the image, since that just connects the video to the LCD itself.

I don't know if this helps, but since I got different responses from the connectors, I thought I would post it...

Edited by davidherman, 11 October 2009 - 04:20 PM.


#9 DavisMcCarn

DavisMcCarn

  • Members
  • 731 posts
  • OFFLINE
  •  
  • Gender:Male
  • Local time:09:01 PM

Posted 14 October 2009 - 07:22 PM

Most of the time, it is the inverter.
Changing the CCFL bulb itself is very difficult! It is located in a U shaped channel along the bottom of the display and is like a long piece of spaghetti made of glass.
The inverter; though, is easy and is two plugs. Here, $7-10 with shipping: http://shop.ebay.com/?_from=R40&_trksi...-All-Categories
Or, here is the whole upper case with inverter and LCD (WSXGA+) for $95: http://cgi.ebay.com/Dell-Precision-M70-Lat...=item58838712b9
Computer dinosaur, servicing PC's since 1976




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users