CCFL Backlight Replacement
Replacing an LCD or Laptop CCFL backlight tube/lamp/bulb.
(Or, what to do when your Laptop or LCD screen/laptop screen goes dark, black, red, orange, or any other annoying color.)
!UPDATE! 9/23/2004: I have actually replaced my own bulb some time ago! A while after posting this, I found a source for CCFL lamps--Mouser Electronics, based out of Texas. With a catalog the size of a small metro phonebook, they have everything. Soooo. Couple of things: Make /sure/ that you measure your old bulb precisely. Anticipate that the new bulb will have flared tips at both ends. Be gentle when bending the leads, and make certain you form them properly if the old leads were shaped strangely. These little guys are cheaper than expected--less than $20 including shipping for a bulb. That's about it. Email me if you have more questions, or concerns. Good luck!
Some number of years ago, my father gave me his old work laptop. It was a home-style laptop. A Compaq Presario 1681. Compaqs, I have since determined, are not going to be a sort of computer I will ever purchase myself. This system, I should say now, has had numerous issues. But anyways. After using this system extensively, in a manner which was not prescribe by the surgeon general (long nights hacking beauticious MUSHcode(Opens in a new window), and leaving it on as a -server- under linux), it began to develop issues. First was the screen going floppy on me, which was annoying and mechanical. I'm not good at mechanical, and to this day, it is still floppy. It has no tension in one of the feet which clamp onto the skeleton of the laptop body. I guess the gear-teeth got stripped, from what I can tell. Other issues developed, which next included the screen itself--the subject of this text.
What happened was an annoying thing. The laptop's LCD screen turned orange-red. Not completely. I mean, you could still -read- everything just fine. Just that everything had an orange hue. Not only is this annoying, but it is most likely unhealthy for you. (Your eyes are not used to staring at one hue for hours at a time, I imagine.) I dealt with it by attaching an external monitor. And then the system began overheating more and more, and finally melted its own solder, on the DC jack. Hence, she died, and was shelved for some number of years.
For most computers in this situation, with most owners, this would mean the end of a potentially useful life. A computer without a use is landfill. But then, a few weeks ago (as of this writing, 10/4/2003), around the beginning of September, I was rummaging through my garage, looking for a stereo y-adapter (which I never did find) for hooking various sound sources together. And then I found the old laptop. Dusty, stuffed haphazardly in a box of miscellanous other computer-related things. And so I get brave. I pulled her out, as well as her AC adapters, and began messing about with it in my room. Obviously, the power had long drained out of her batteries, and since the AC adapters didn't work (her solder melted. Remember?), I was left with one choice.
Okay. Well. I should regress, and note now. I had two choices. I could have shipped her off for repairs; but I'm cheap, and I know I'll get charged anally. So that left me with fixing it myself. This in and of itself consisted of prying her apart, and carefully removing each and every part of her chassis to get to the motherboard, which itself was nigh impossible to remove. (I'll do disassembly instructions, some day, maybe.) Finally, with that removed, I worked at resoldering the DC jack properly. That finish, reassembly was a breeze, and she charged to a full 100% within the hour. I was very pleased. Finally, she booted up, and I was greeted with an orange-on-darker-orange version of 'COMPAQ' as her BIOS snappily shifted bits and bytes about. And then she bit me. She had no functional bootloaded; but that didn't matter right now. I would later reinstall Windows 95, and then upgrade to 98. But that was some time later. What struck me, as I stared at a blank screen, with a single underscore in the corner, was how orange everything was. And then I felt inspired to fix that, before doing anything else to her.
It was at this point that I briefly installed Linux and such, so that I could open an image editor (the Gimp), to throw some color bars on the screen. I took out my prismacolors, and drew identical bars on a sheet of white paper, held it up to the screen, and took a digital picture. (available at the link below) Just for proof. And comparison. Then I got to the real work. Turning her off, pulling her battery, and making to to have discharged anything nasty in my body, I began prying the LCD screen off. I first detached it from the body itself. (her feet brackets were removed by their screws, and any cables/sheet-cables were removed from the main system) I then proceeded to remove the front bezel-panel from the LCD (there were four screws, covered by rubber feet), to give access to the LCD panel and circuitry proper.
For anyone who has never seen the inside of one, they are rather simple. Mine, being for a laptop, also had a microphone mounted inside, but other than that and its cable, the guts were the LCD screen itself (surrounded by a hard metal bezel), the cable attached to it, the inverter board (I'll explain later) and the cables to it. It's a very neat package.
Anyways. After that was done, I dismantled the LCD screen after removing it from the screen body itself, and finally got to the backlight tube. (This was a very hard thing to get to.) Finally, I removed the tube from the reflector, attached it to the inverter board, attached the board to the laptop, and turned it on with only those two things connected. Sure enough. I had an orange backlight tube. At this point, I should explain that this is wrong. This backlight tube should, ideally, be pure white, without variance (though each manufacturer will design their LCD screen to varying definitions of 'pure white,' thereby lending any screen with a replaced CCFL tube a slight color variance) so that your screen colors (produced by the liquid-crystal color pixels) are represented naturally.
Now, having determined that the source of the problem is most likely the tube itself (which are usually rated for around 20,000 hours or so of operation), and not the inverter board (which output variable voltage; a voltage drop should not change the color of the tube. only the brightness), it's time to find a new tube. This, however, I will warn you, is not easy. In three days of researching that very thing, and nothing else, I found nothing useful. I found one or two merchants online that would, naturally, take your LCD and replace it for you at a figure of $99 or so. If you aren't comfortable doing this operation yourself, I'd suggest finding such a place, and paying the $99. (Try my links section below.) It really isn't worth damaging a $300 LCD panel over a thing that is 250mm long by 3mm in diameter. ;P But me, I want to replace it myself. And nobody in known existance seems to sell them, by themselves.
I made the next logical step, and tried the local stores in town. Most notably were Radio Shack (who is an authorized HP repair center, btw; they handle the Compaq laptops, too. But not in-house, which is what I need.), who wasn't able to sell me or order the lamp by itself. The store manager wasn't even nice about it. So I'm not returning there ever again. The second place I went was a local electronics supply store that is housed in a warehouse, called Norvac Electronics. If you're ever in need of electronics supplies, and you live in the Northwest in an area with one of these, go there. They certainly had more than I expected them to have. In fact, they even had CCFL lamps.
Don't think it was that easy, though. Their lamps were too big. How? Too big around, in diameter. The lamp reflector housing was too small for the lamps they sold, so I walked out empty-handed. (excluding my laptop; they were nice enough to let me dismantle it in-store for explanation and to try to see if it would work.) I was at a loss. Nowhere else in town had them, and I couldn't find them online. I could find vague references to cost, but none of them would work. It sounded like it would be a cheap operation. Something like $8-30 for a single tube. That's all I needed. I just needed to find a place that had them.
So a month passes, and I took the computer apart and made it into a simple box with an external monitor, so that I could at least use it without wasting the hours of life for the LCD screen itself. Or the inverter, or anything else like that. It's sitting on a speaker right now, hooked up to everything, without its top cover, with its components exposed. WHEE. I pulled up google a few hours ago, and typed in my search string.
Lo and behold, something comes up. JKL Lamps Corporation(Opens in a new window). ("If it lights, and you need it, we have it!") This is a company that produces and distributes miniature lamps (of the old visible filament style), laptop ccfls, various other ccfls, UV ccfls, and inverters for above. And what do you know, they have a product listing with pictures right on their page. With pdf catalogs. And links to their ditributors, which allow online ordering. I am shocked, and very pleased. Plus here's the greatest part: The prices for the tubes are $15 for the most expensive type they have , with $10.29 being the cheapest (and for most of them, I should say) each. Now, the only problem is that they list them by specification, and I don't have the specifications for my current lamp. But I know who will.
The manufacturer of my inverter board. Dissecting it from my LCD screen once more, I gaze over it carefully for a long time. (I can't tell if there is a capacitor in it or not, though I assume if there is it is discharged) Markings on the back indicate 'Delta,' and so I pull a google on Delta Electronics. Instantly, I come up with a Taiwanese company that produces a number of electronics components. And after some searching, I find the inverters. I know who made it, for sure. And after peering over their parts listing, I peer at the part no. on my board, and search for that. No luck. It doesn't appear to be manufactured anymore. (This laptop is old. '97, at best.) I sent an e-mail tonight to their US technical support rep, requesting specifications on this very board. I'll have to wait until next week for a response, though. However, I did find a similar part-numbered component on their site, and so I may base my tube decision on that if I receive no response, or no help. (Really, I can make a best guess anyways. There aren't many choices for the length I need.) So once I get the specifications, I'll be able to order the lamp from one of JKL's distributors, get it, and simply install it. That's it. From reading the instructions on several other websites about replacing them, I may or may not have to resolder the leads to the lamp to the inverter board connector. No biggie there, though. Once that's done, I should have a perfectly functional laptop LCD screen again.
Assuming, of course, that the inverter board isn't bad. But then, at least I know who manufactures them now.
Anatomy of an LCD Screen (for laptops)
A laptop LCD screen is comprised of several basic elements. As a whole, you have your LCD screen itself, a backlight bulb, and an inverter. (Not counting the controller boards and such for controlling your video.) LCD screens will always vary. Configurations are wide and broad. In general, though, they will always have the above.
LCD The LCD screen itself is what presents the image. With no power to the monitor, you have a black screen, which looks really slick. It is comprised of several layers of various elements, housed in a metal bezel. Either on the sides, or the top/bottom of the screen, a reflector is mounted with the backlight. The elements of the LCD screen include (from back to front, visually), the mirror/reflector of the backlight. Usually a very high-reflective metal, or similar setup; sometimes, the mirror may be the only source of light, and there will be no secondary light source. This is why some LCD screens do not work in the dark. On top of the mirror is a polarization filter (to only allow light to pass in one direction), and then a sheet of glass (or some transparent polymer). Next is one of the most important components. Essentially, there are two sheets of transparent electrodes, with liquid crystal sandwiched between them. These many, many electrodes will change the orientation of the crystals, to allow/disallow light to pass through them. (Because of this orientation, this is also why LCD screens will appear to be in odd colors, or darker, when viewed at non-standard angles. The properly orientated crystals will now be under the wrong colors, or orientated in such a way so as not to allow the light to shine any way but directly forward.) On top of the outer layer of transparent electrodes is another sheet of glass or polymer, with a polarized filter on it. You may or may not have another layer on top of this, for simple protection purposes. The rear sheet of glass, before the mirror, will be made with various different methods. Either it will be constructed in such a way so as to diffuse the light evenly from the rear over the entire pane with methods I don't entirely understand myself, or it will just be opaque on one side (generally, the side opposite the mirror), hence diffusing naturally.
Now, you can get gray shades by making the crystals only change orientation partially. (Hence allowing x% of the light to go through; otherwise it's 0% or 100%.) You can get color by adding more filter layers. (IE, the three primaries used,arranged each as a pixel, with each color affected by a electrode.) An interesting note is that you can use a magnifying glass to view the spaces between where the electrodes operate. They appear black. Also, the layout of the color pixels is RGB; Red-Green-Blue. The same theory applies to regular CRTs; only they use an electron gun and I don't really know what else. Anyways. The only other parts of your screen are the various controller boards, which vary by manufacturer. These control which pixels do what. Yay.
Backlight The backlight is just a fluorescent lamp. Basically. The technical name for it, generally, is the Cold Cathode Fluorescent Lamp, or CCFL. It is this lamp which brightens your screen in the dark. (There is another kind found in older PDAs and watches, called Electroluminescant; but that relies on a different method.) The lamp(s) will be mounted on the top and bottom of your screen, or on the sides. If you only have one, chances are it will be on top. With most screens, the CCFL will be part of the LCD screen itself; in others, it will be removable easily with only a screw. The lamp(s) will be as long as the screen is wide, or tall. Occasionally, two lamps will be placed side-by-side. The lamps themselves are comprised of the glass, filled with whatever gasses the manufacturer filled it with. There is no filament inside, meaning they will last a lot longer than typical 'hot' neon fluorescent lamps. At either end will be a lead wire. If there are two tubes, they will be daisy-chained. Otherwise, one wire will loop back towards where the first terminates. These two wires are then mounted into a plug which attaches to the inverter board. These lamps, it is worth mentioning now, are extremely high voltage. The highest I've found was 1,820V@5mA(Start)-810V@5mA. Be careful. Not only here, but with the LCD itself, as it can contain high voltages as well. The backlight will be mounted inside a metal reflector, which is then attached to the inside of the LCD. Basically, the reflector bounces any light from the CCFL that doesn't go directly into the LCD, back into the LCD. It is highly reflective; hence, you should wear gloves or something similar if you are going to mess with it. And that's it. The light, being extremely bright as compared to your standard fluorescent lamp. (~32,000Cd./m2) They are very fragile, being ~3mm in diameter.
Inverter Board The last part of your LCD panel screen is the inverter board for your CCFL. Here(Opens in a new window) is a basic diagram for a DC/AC inverter. One thing to note, from what I understand, is that these inverters are not like your typical DC/ACs that may be found for 12VDC-120VAC for running household electronics in a car or somesuch. These produce an output waveform that is nearly a square wave. This is simple, and doesn't require much to do, but for most electronics equipment, an advanced version producing a pure sine wave is required. The inverter itself just takes input 12VDC, runs it though some hoops and a transformer, and outputs your 120VAC. Understand, though, that as your output (V) increases, your output (W/A) decreases. That is given a basic inverter, of course, which doesn't deal with the things that a ccfl lamp requires. Like, for example, dimming. And nearly 2,000VAC@5mA, from a 10-20VDC input. What this means is that instead of just having your input DC+ and ground, there are extra pinouts. For an inverter board similar to mine, it has two 18.0V ± 10% inputs and two grounds. That provides the main power. Power to the inverter board itself is provided by a 5V On/0V Off input. Dimming is controlled with the BL-Adj pin, at 1.0V ~ 5.0V. And of course, the high voltage DC output pin, and the return pin. Boards may vary, but for CCFL controlling, these things are generally common.
Replacing the CCFL is a task that may be difficult, depending on your brand of LCD screen. Basically, you'll want to remove the external plastic cover to your monitor, to gain access to the LCD screen itself. Remove the two leadwires from the inverter board. (Which should have a small transformer on it, two output wires, and somewhere around six input wires that go to some power source; whether it be the computer, or the main power source of the screen.) If you are able, at this point, to simply pull the CCFL/reflector out, do so carefully, being careful not to snag the wires on anything. If you aren't able to do this yet, you'll need to disassemble the LCD panel itself by removing, first, the metal bezel, and gaining access to the metal reflector that houses your CCFL tube. The reflector will usually have small rubber/silicone mounts that will keep the tube firmly in place. The next step is to replace the tube in the reflector. If your new tube has a new connector already, then all you need to do is place this new tube into the reflector. Otherwise, carefully desolder the old connector from the old tube, and solder it to the new tube. You may need to cut (with a razor or exact-o) the silicone/rubber off of the old tube, and replace it on the new tube. As soon as your solder is sufficiently cool, replace the silicone/rubber, and place it back into the reflector, and assemble as need be. Please ensure that you know what you are doing with your CCFL tube. You need to get one with exacting specifications to your old one.
If you don't know the specs to your old tube, you'll need to contact the manufacturer of the inverter board. Look on it for a manufacturer name and a part number. (IE, Delta, with a D symbol in a triangle.) Contact the manufacturer, and ask them for the output AC start and lamp voltage, and current ratings for your board. Then make your purchase of CCFL tube appropriately. If you can't find the manufacturer of your inverter board, you should contact first the manufacturer of your screen/laptop, then the manufacturer of the LCD panel itself. (Which should normally be etched, or on a sticker; as well as a part number. They may be able to help you with the specifications also.) If you are not able to locate the manufacturer of the inverter board, please remove it, take a digital picture of both the front and back of it, and contact me. I may be able to help.
PRECAUTIONS Please be aware that you are working with high voltages here. You should take proper precautions not to do anything stupid, like licking the inverter board. Especially if it's turned on. It may have capacitors. It may have stored charges. So may the LCD panel. It says DANGER: HIGH VOLTAGE, for a reason, you know. I will not be held responsible for anything you do with the information I've provided on this page. If you don't know what you're doing, like I don't, then don't do it. Pay the $99 to have your CCFL tube replaced professionally, or just buy a brand new screen for $300. Because I won't pay for it. Take caution, as these are sensitive electronic devices, with transistors the size of a pinhead, which could EXPLODE VIOLENTLY with a static discharge from your body, thereby ruining the need for your $10.92 CCFL tube you just bought, and necessitating a $150 Inverter board. Or worse. Wear an anti-static device, or continuously discharge your body of static by touching something grounded (a metal water pipe, et cetera, if you're in an older home; damned new plastic pipes). BE CAREFUL with the new and old CCFL tube. THEY ARE MADE OF GLASS AND WILL HURT LIKE A MOTHER BITCH FOO IF IT BREAKS AND IMPALES YOU. Not to mention they'll be broken, then, and useless. THEY ALSO CONTAIN TRACE AMOUNTS OF MERCURY GAS. Which makes it ILLEGAL in most places to just throw it away. Not only are these suckers deadly to you, they are deadly to the environment. Contact your local city folks to find out what to do with hazardous things such as these. Be gentle with the LCD screen as a whole. As I mentioned earlier, they are composed of GLASS LAYERS. Which means, if you push or pull to hard when trying to take it out of its mounts, you MAY BREAK IT. The first laptop I ever used had its glass fracture, and puncture the liquid-crystal element, thereby making the screen warped and defective. This happened on a trip across the country, in a U-Haul. And it was in the cab, with me. I remember it being about $700 to replace, back then. You don't want that to happen. Do not disassemble the LCD screen any more than you have to. Only take it apart enough to remove the CCFL. If you get even a single speck of dust in one of the layers, you will have dead pixels. I guarantee it. Dead pixels can also occur if your CCFL shatters while still in the housing. This sucks.
I don't know everything. I am not a certified technician. I am just a guy that knows how to fix stuff. As a result, I may not have told you everthing. By following any instructions on this page, you take full risk and responsibility for your actions, and discharge any legal right to sue me, or place blame on me for things you did. Mmmkay? kthx.
Tools There will be some tools that will come in handy during all of this. Obviously, a small phillips-head screwdriver, and a set of hex. (My laptop uses a T8 for almost all of the hex-screws. There are maybe three or four phillips in the entire system.) Keep a flathead, preferably a big mutha, on hand for prying things apart, and a small one for maneuvering the locks on cables off. Pliers are handy. Use a long strip of duct tape, doubled around so that you have two tape surfaces, and attach it to your workspace. Put your screws on it, in the order that you took them out. If you want, you can make a diagram of where the screws came from. Keep your parts organized as you take them out, and memorize how you got them out. Do not force things too hard. Tweezers are useful for some small parts, and especially for things that drop in inconvenient spots. One of my tool sets has a pair of teeny-assed pliers, about 2 1/2 inches long and with a total tip area the size of a pen point. These are handy. You'll also have hex bolts keeping things in the air. I use pliers for these, because I don't have a nut that fits them. Tighten these are far as you can when you put them back in. Lastly, keep a razor blade on hand, for cutting tape that may be used internally. Oh, and lest I forget: Bright lights, and a flashlight. And a lot of patience.
If I can find them, I'll post them; but they aren't very exciting, since I was so excited to be able to repair mine finally. ;) I forgot to take good expository ones!
Copyright (c) 2003-2004 Taylor J. Meek All rights reserved. All sources Copyright (c) their respective owners. Compaq, NEC, Presario, JKL, et cetera, are all registered trademarks of their respective owners.