LCD backlight replacements/repairs

Hi all,

I just found a company that supplies the cold cathod tube for the backlight found in the LCD of notebooks, LCD monitors and naturally, HPCs ...

http://www.jkllamps.com/laptop.cfm

There are two links below to two retailers for orders less than 100. You need, however, to find the right size for your unit. The specs are voltage (usually 12v EDIT: I think for the inverter input. The cathode itself is *VERY* high-voltage), length and diameter.

I'm trying to see if I can fit a LED based light tube into my current HPC. or maybe even rig it to take two, if the LED unit draws less power!

EDIT: links from that site ...

http://iantha.vectorstar.net/ccfl.html
http://reed-electronics.com/ecnmag/index.asp?layout=articlePrint&articleID=CA414994
http://www.mouser.com/?Ne=400&handler=data.listcategory&N=401
http://digi-key.com/

EDIT: HIGH-VOLTAGE WARNING!!!!!!!! EXTREME CARE NEEDED!!!

Edited by Snappy! 2005-06-03 2:04 PM

Interesting!

I'd be really interested on how you get on here. Trouble for us Jornada owners is that the LCD assembly is sealed up pretty tight, even the digitiser membrane / glass sheet is lock in place on the 680/690/700 (It isn't on the 300).

As you're fortunate enough to have a Clio, this coudl be an interesting experiment

Moved to Hardware Support - I'd class it as on-topic

Actually, I got the whole assembly opened and somehow when I put the whole thing back last night, I thought it looked brighter than it looked earlier! ... not sure if its just my own psychological effect or what ...

What I found about the DSTN LCD that is in my unit ...

1) Touch screen layer (outer)
2) glass/Acrylic plastic layer
3) DSTN LCD layer
4) Plastic reflective/magnifying layer 1
5) Plastic reflective/magnifying layer 2
6) Diffuser plastic layer
7) Acrylic light pipe layer
8) White reflector layer (inner)

The CCFL shines light onto L7 white shines the light onto layer 8 and 6. Layer 8 reflects back the light outwards towards layer 6. Layer 6 diffuses the light for a uniform feel. Layer 4 and 5 looks slightly different. But flipping them over causes the screen to be totally dimmed.

Layer 4&5 is reflective on one side ... frankly, I have no idea how they all work together ... but I think I might have put 4&5 in the wrong (or right) order, and resulted in a slightly brighter screen!

layer 1&2 is mostly clear plastic ... BUT ... it has a blur look on L1 ... which is what gives that washout look in outdoor sun ... it diffuses too much light on the surface.

oh well ...

http://www.jcdsystems.net/ccfl.html
http://www.mp3car.com/vbulletin/showthread.php?t=48909&page=2&pp=100

Looks like there are lots of modders for backlights! ... ok ok, that's just one, but I'm sure there are more out there.

Look at the pictures in the forum ... looks like a winner ... once they get the thermal fixed.

F-a-n-t-a-s-t-i-c

I just wish I knew anything about electronics to be brave enough to do that. I know diddly squat.

Sounds interesting, just one question that is a bit OT. My laptop is a IPC TopNote H (you may have seen some pics of the bluey/green monster), the only problem is that the backlight can become very annoying. Why? It flickers then turns off. When you move the screen, 'lo and behold, it comes back on, until it filckers and turns off again. Does anyone know why?

The backlight is most likely using a CCFL (Cold Cathod Flourescent lamp (or CCFT - T for tube)). Like all flourescent tube, it has a life span and towards the end, it flickers and sputters ... then dies out. So my guess is that your CCFL is dying ... time to replace it. Its only $12~$20!

Or it could be a loose or fractured cable. Which would be nasty to isolate.

An update ...

Here's the correct names for the layers ...

1) Touch screen layer (outer)
2) glass/Acrylic plastic layer
3) DSTN LCD layer
4) Plastic polarizer film 1
5) Plastic polarizer film 2
6) Diffuser film
7) Acrylic Diffusion light guide
8) White reflector film (inner)

I've found that layer 1 can be *enhanced* by

1) Spraying anti-glare coating www.glarebuster.com OR
2) Add a layer 0 of anti-reflection/glare film

Checking with glarebuster if the spray will not damage the plastic LCDs esp the touchscreen!

Layer 4 ~ 7 can be enhanced by

1) Replacing layer 7 with LED array or CCFL array
2) replacing 4~6 with a reflective or *TRANSFLECTIVE* film layer!!

Am waiting for the suppliers to reply to me on Monday ... stay tuned!

The specs from their web sites show that these films work with existing STN, DSTN LCDs ... so ...

EDIT: Further, I'm thinking if one of those mirror-like film will work nice for layer 4 or layer 6. Those type that looks like one sided mirror. These have varying ratings, ie, amount of reflectiveness and also, amount of light *transmissiveness* from inside

By putting such a layer in either layer 4 or 6, light from outside (ie ambient light) will be reflected back out while the light form the backlight will be transmitted out ... anyone wanna try out with me?

Edited by Snappy! 2005-06-04 3:43 PM

Yes, but now is the question, Is it sunlight readable?

you mean my mod (to be done) or the one from previous links?

http://tabletpcbuzz.com/forum/topic.asp?TOPIC_ID=18021&SearchTerms=open,lcd

Here are some folks who found the same site I did.

Wessex_nut ... apparently, with the backlight mod, the video screen is sun light viewable ... though since its mounted in a car ... it may not be direct sunlight in some cases.

From their threads and some sites, it seems like if you can get your display to go beyond 1000nits (whatever that means!), it will be sunlight viewable. The problem is that many LCDs have a *blur* surface that is meant to remove reflections ... but in the process, causes glare, which is the main issue today.

My old old Sony SL10 is a 16-level gray scale Palm4.1 PDA. It is green-backlight, and is totally sunlight readable although the LCD surface is glass-smooth, meaning there is reflection, but *no* glare.

So, besides 1) increasing backlight 2) Modding/adding a transflective polarizer, we'll need to add an anti-glare film. Some sites offer anti-glare + anti-reflection films, but I find reflection ok. ... ok, maybe I just like seeing my own face on the screen! ... but when the screen is turned on, reflection mostly goes away, its the glare that gives the wash-out look.

So I'll probably try adding an anti-glare layer or something.

This site has transmissive polarizer ...
http://www.3dlens.com/enter.html

oh i liked the pics on the above link about the m200's. the modified one compared to the nonmodified one looks like the my 728 and my 720 compared to each other especially the pics with the blue windows background! and actually the 728's screen is more readable in direct sunlight though still not comfortable.. but in a car it's OK.. i don't think it's been modified by the previous owner though

hmmm ... the 728 is more readable? ... hmmm ... now I really understand why the Palm T3 screen was called a transflective screen! It is totally readable!

okay, i didn't say "totally"

hehe ... actually all I wanted to say was that the T3 is called transflective with a reason, in comparison with the transmissive DSTN screen that I'm seeing on the HPCs.

Strangely, I never once used DSTN screen back when it was used in notebooks. ok, I must say I used my uncle's notebook back in the early mid-90s ... I think that might have been a CSTN or STN and not a DSTN!

By the time I got to work in my second job and was assigned a notebook, it was already TFT in its full glory! Strange how so much things transpired in the last 10 yrs!