05 Mar, 2009
How to replace a Dell Latitude notebook backlight and LCD screen
Posted by: Ecomer In: LCD Screen Repair ()
I always pull the battery before I work on any laptop or notebook. The last thing you need is for your Dell to power up while you’re taking it apart. I’m taking apart this Dell Latitude for the sake of illustrating an example, but it’s not something you normally want to undertake without first troubleshooting the screen failure. The first challenge for getting into the Dell and checking connections replacing the screen or backlight is to find the screws. Like all laptops I’ve seen lately, the Latitude has four screws hidden under rubber pads at the corners of the screen.
Some would-be home laptop repair techs give up because they can’t get the rubber pads out. In some instances, as with this Dell, you really need to dig something fairly sharp and stiff into the cavity to get under the plug. I used a jewelers screwdriver in this case. Once you remove the rubber bumpers, you’ll expose a regular Philips head screw. Some laptop manufacturers put a little glue on there to keep the screw from loosening, in this case Dell didn’t, they probably figured it’s hard enough just to get the rubber out. Don’t rush into tearing the screen apart without troubleshooting the video problem first.
Once the screws securing the plastic bezel are removed, you still have to unsnap it from the body of the lid. If you’ve never worked on the particular notebook model before, you don’t know where the plastic latching tabs are, so it’s a bit nerve wracking. You can see the main locking tab holding the screen bezel on this Dell Latitude about halfway down the side of the bezel. The circuitry to the right of the LCD is the inverter that provides the high voltage for the backlight.
Sometimes you can locate hidden tabs with a thin screwdriver, sometimes I just keep a steady force on the bezel and pry. When you locate the sticking point, if should release if you push in on the bezel at that point to free it from the notebook lid. Here I’m lifting the whole bezel off our Dell laptop, exposing the inverter circuit to the right (you can also see it above), which is a standard placement. The only function the bezel serves is as a cover, removing the screws doesn’t free up any of the components.
The LCD screen is secured to the back of the Dell laptop lid with four screws. The light grey metal structure you can see on the front isn’t actually part of the LCD screen, we’ll be removing it later. It houses the backlight and the reflector, keeping the whole assembly together as one unit. This Latitude LCD assembly is a much more modular design than the Toshiba we disassembled in the last page.
Once the screws are removed, I stood the LCD assembly on the keyboard while removing the connectors. The first connector I removed was the simple ribbon cable which delivers the digital video signals (addressing for the LCD matrix) to the Latitude screen. It’s a simple push together connector that I removed by grasping it right at the connector and gently pulling it out.
Here I’m removing the inverter connector. The inverter circuit powers the backlight in our Dell, a CCFL (Cold Cathode Fluorescent Lamp), which requires a high voltage to strike a plasma. CCFL tubes actually have better life expectancy than the inverters, so most techs will try replacing the inverter before fooling around with removing the backlight. I illustrate removing the inverter board from a Toshiba Satellite here. You can find replacements on the aftermarket fairly easily for most models.
Now we get to removing the grey metal structure that secures the actual LCD screen to the backlight assembly. The design used a dozen little metal tabs that are bent into depressions in the white plastic holder, and which are easily opened with a small screwdriver. Dell also saw fit to tape the units together on the top and bottom. I just undid the tape on the top and left it on the bottom as a hinge.The LCD screen from this Dell Latitude utilizes a nice translucent light panel, in addition to the backlight, The purpose of the light panel is to spread the light from the backlight equally behind the LCD for even backlighting.
The CCFL backlight itself is secured over the top of the LCD screen in a channel with a thin strip of copper tape. The tape is reusable, at least it held up through this extraction and replacement. Dell really seems to have a tape thing going on with this Latitude:-) Once the CCFL backlight is exposed, you can pull back the little rubber insulators on the ends and unsolder it. Yup, the tube is actually touch soldered to the inverter leads on either end. Below I show the exposed backlight on a black background. Assembly is simply the opposite of disassembly.
Source from fonerbooks.com.