Replacing LCD CCFL backlight

Hmmm... Did you look at the inverter output with a scope before you decided that it was the CCFL lamp? It could easily be the inverter. However, as the fading took several years, it's most likely the CCFL lamps. Still, I would measure the inverter output.

This one?

Looks clear enough to me, but the English sucks. Basically, don't touch, tweak, bend, or even move the row and column driver contacts.

You can go to almost any PC repair shop or eecycling center, and get a dead LCD panel with which to practice. I wish I had because I managed to destroy a perfectly good laptop LCD the first time I tried to fix one.

I'd like to add one item. Please either keep your greasy hands off the CCFL lamp, or clean it with alcohol just before installing it.

Yep. The white tape is what holds the row can column driver board contacts to the panel. Take it off and you're sure to get vertical or horizontal black lines or intermittant black lines.

Yep, that's correct. You don't need to do anything with the area around the row and column driver board. The lamp is on the other end.

Yep. However, you don't need to remove the entire frame. It comes off in sections. Leave the one near the row and column driver boad alone.

You shouldn't do anything to move the board that's under the tape. If some of the tape slops over onto some other piece of removable frame metal, just cut it with an xacto knife and remove the frame. You can always get some more tape and pile it on top of the cut line.

It should pull out neatly *WITH THE REFLECTOR*. In other words, don't try to extract the lamp. Pull the reflector out and the lamp will follow. Note the the reflector is attached with double sided tape and will require seperation with a knife or tiny screwdriver.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

NoSp wrote in news: snipped-for-privacy@news.broadpark.no:

That 'white tape' appears to contain multiple conductors and possibly active elements that drive the LCD. Any damage to the 'white tape' could cause parts of the screen to be 'dead'.

I doubt that your assumption is correct.

I can't tell from the pictures whether that silver band across the 'bottom' of the screen is removable or not.

Good luck.

--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an 
infinite set.

bz+spr@ch100-5.chem.lsu.edu   remove ch100-5 to avoid spam trap

NoSp wrote:

Here is my story: A few weeks ago the backlight on my wife's Dell 700m laptop would go out after a minute or so. Research indicated that replacing the tube might solve this (and this info turned out to be correct). Since I have worked in microelectronics for 30+ years I thought I would try it. I had an old display that I took apart for practice and that one was very simple. The tube just slid out the side; no skills necessary! The laptop display was very different. Nothing went according to plan and everything was just too small , too fragile, and too precise. Yes I read those same instructions but they are too generic. And dealing with a 10 inch tube that is only 2mm in diameter is scary; I recommend you order at least two! Anyhow, after much frustration I managed to successfully replace the tube and it now lights up properly. There were only two problems. Somehow I managed to crack the corner of the display making it useless. See this photo:

Even ignoring this, the bottom of the display is no longer of uniform brightness. We probably could have lived with this but be forewarned that the same thing could happen to you. This repair may be best left to the experts. I will never try this again on a laptop. Fortunately newer laptops now are beginning to use LED backlights....like the one my wife had to buy to replace her 700m. The CCFL should be obsolete in about 3-5 years.

Good luck!

To prevent such a crack do you think such displays need a temporary scaffold somehow attached to them while doing such work? I'm assuming the damage was done just by holding between thumb and finger at the corners.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

You just have to be careful not to flex them. I've replaced a number of backlight tubes and have yet to crack a panel, I just lay a towel down on the table and set the display face down on that.

Greetings..

Regarding: "Since I have worked in microelectronics for 30+ years I thought I would try it." "And dealing with a 10 inch tube that is only 2mm in diameter is scary; I recommend you order at least two!" . . "...This repair may be best left to the experts. I will never try this again on a laptop."

There's a moral to that story..

Cheers, Mr. Mentor

"John Vallelunga" wrote in message news:48323f09$0$34483$ snipped-for-privacy@news.sonic.net... | NoSp wrote: | > My laptop's display backlight has been fading since I bought it a few | > years ago, so I think it's about time I exchange the CCFL backlight | > with a new one. The LCD in question is a Samsung LTN152W6-L01. | >

| > I've been trying to follow the instructions at sites such as | > lcdparts.net, but there aren't any instructions for my particular LCD. | > I've never disassembled an LCD before, so I'm a little worried that | > I'll do something wrong. | > Here are a couple of photos I've taken of my LCD: | >

| >

| > | >

| > There's a warning at the top saying I shouldn't touch the white tape. | > Does this mean the white tape shouldn't be *removed*? | > I've read somewhere that if you apply pressure unevenly to the LCD | > panel you'll get lines and other abnomalities in the display (I assume | > the white tape has been applied for even pressure all across the LCD | > panel). | >

| > The problem is that it seems (at least according to what I've read | > online) that I need to remove the metal frame around the LCD panel in | > order to expose the CCFL backlight -is this correct? | > Unfortunately the white tape extends beyond the metal frame, so if I | > shouldn't remove it what do I do? | >

| > The second photo shows the metal bracket removed. It's the only one I | > could remove without removing the white tape as well, and the | > backlight is found underneath. Is there a neat way to remove the CCFL | > without removing the whole frame? | Here is my story: | A few weeks ago the backlight on my wife's Dell 700m laptop would go out | after a minute or so. Research indicated that replacing the tube might | solve this (and this info turned out to be correct). Since I have | worked in microelectronics for 30+ years I thought I would try it. | I had an old display that I took apart for practice and that one was | very simple. The tube just slid out the side; no skills necessary! The | laptop display was very different. Nothing went according to plan and | everything was just too small , too fragile, and too precise. Yes I | read those same instructions but they are too generic. And dealing with | a 10 inch tube that is only 2mm in diameter is scary; I recommend you | order at least two! | Anyhow, after much frustration I managed to successfully replace the | tube and it now lights up properly. There were only two problems. | Somehow I managed to crack the corner of the display making it useless. | See this photo:

| Even ignoring this, the bottom of the display is no longer of uniform | brightness. We probably could have lived with this but be forewarned | that the same thing could happen to you. This repair may be best left | to the experts. I will never try this again on a laptop. Fortunately | newer laptops now are beginning to use LED backlights....like the one my | wife had to buy to replace her 700m. The CCFL should be obsolete in | about 3-5 years. | | Good luck!

You can remove the white tape, but you have to be very careful not to damage the LCD driver chips and ribbon cables under the tape. These are the cables that are glued to the LCD glass itself. If one of these connections is damaged, the LCD will be useless.

Some LCDs have back lights that are meant to be replaced and just slide out, but most are not designed to be replaced. It can be done, but it's difficult. Be sure to work in a clean dust free area since any dust that gets under the LCD will be visible. Andy Cuffe

snipped-for-privacy@gmail.com

I see. So the white tape (which at some sections extends over the metal frame) doesn't actually have any functionality at all, performance-wise, but is there just to keep things in place and as an extra protection?

I guess I can cut through the tape with a sharp knife, so I can remove the metal frame from the LCD panel. The white tape at the top covers over the edges so I can't really see what's underneath, but this is where there are some thin, flat ribbon cables which go to the actual LCD? What would be the best way to go about removing the white tape so as to be able to unclip the metal frame from it?

By "dust free" I assume you're not referring to a so-called "Clean room", which I currently don't have access to ;-) From what I understand the LCD panel consists of several layers, which when the metal frame is removed won't keep them in place any longer, right? So at that stage I assume it's important to keep the stack of layers horizontal on the table I'm working at. If I don't shift the layers around I shouldn't risk getting any dust in between them either, should I?

Sorry about all the questions, but hopefully I'll understand enough to get it right the first time. Thanks.

Might be some info at the following url's:

right?

Generally I warm such tape with a hot air gun set on the lowest setting, but I've not ever explored such area of a laptop screen.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

I've found out that I need a 328mm/2mm diameter CCFL tube, but all I can find online are 324mm and 325mm types. Would it make a difference?

What's a good place to order them from?

3mm is quite a small difference, you'll probably be ok with 325mm, I'd try it and see what happens.

I would go with the smaller one only because things get very cramped while working in those very tight spaces and its nice to have the extra room. The difference in brightness is negligible. I would go with Moniserve....I received mine in only one day's time! They ship it in a triangular tube.

You can either cut it, or peel it off. Just be careful not to cut the ribbon cables. When you reassemble it, use some scotch tape to reattach it.

No clean room is needed, but if you're like me, a few dark specs of dust in the display would drive me nuts. There's nothing worse than putting it back together only to have to take it apart again to clean it. You shouldn't have to separate the layers to get to the tube. I can usually replace the tube by only taking apart the side with the tube. Of course this will depend on the design of the LCD. Andy Cuffe

snipped-for-privacy@gmail.com

I finally managed to work it out, thanks to the following web page

some guessing and a lot of patience. I had to remove 2 groups of layers (with 2 sheets each) consisting of various kinds of plastic -transparent, shiny, white etc. to get to the CCFL, but I left the glassy LCD section alone. I haven't even removed it, but only slightly lifted up from the metal frame. I put a soft piece of cloth between, so I can easily put it together again, but don't dare move it around etc.

Does the LCD itself come in one piece, or can it fall apart into several different "sheets" if you mess with it?

In any case I took the utmost care with the ribbon cables, so I think it should be OK.

The manufacturers sure make it hard for people to replace CCFLs -I'm sure they could design it much better if they wanted, but they probably just want to sell new LCDs instead. Talk about unnecessary environmental waste and production.

You're right. I checked up several websites where it says that 2-8mm shorter makes no difference. Longer might of course as they won't fit, so I'll go with the 324/325mm type.

Yes, that's actually

isn't it? At least I get redirected there if I go to moniserv and click on spare parts. I'll probably order two tubes just in case one breaks, and for the next time I need to replace the tube.

The LCD is all glued together, so there's no danger apart from cracking it, or pulling off the ribbon cables.

Andy Cuffe

snipped-for-privacy@gmail.com

Well, I ordered and paid for the item 4 days ago but the item hasn't been sent yet. They haven't replied to any of my emails before I placed my order nor an email I sent after ordering. Things seem pretty quiet in other words. Not a good sign.

Is it a long time since you order/received from them?