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Re: Replacing LCD CCFL backlight

I'm the original poster and have a problem after having replaced the old CCFL with a new one :-( The display lights up like it should, but displays vertical lines (from the top of the display down towards the keyboard. I can't remember if it came in different colors or just brighter white than the backlit background. I connected the computer to a TV, and it displays fine there, so the graphic circuitry and the computer itself must be OK.

I've been extremely careful with the LCD ribbon connectors, so I don't think that's it, but of course I can't be 100% sure about that. I have however tried carefully poking a plastic tool on top of the ribbon cables (the end attached to its PCB), flexing the very slightly to see if it made any difference, but there was no difference at all. This is when the LCD is mounted in its frame (e.g. the Samsung LCD is assembled, while the computer's rear display panel is absent, giving me access to the rear of the LCD, exposing its PCB etc.). I don't know how the ribbon cables are attached to the LCD itself as I haven't flipped it around.

I've also checked to see if the data cables (from the computer to the display are attached properly -they both are: a wide ribbon cable and a small white Molex or whatever connector (perhaps that one is for the CCFL inverter, I don't know). I don't know if this makes a difference or not, but I haven't attached the aluminum tape as I first wanted to check if everything looks OK (dust etc.) before re-assembling it properly. Would interference (because of the lacking shielding) cause these problems?

The computer is a Apple Mac Powerbook G4. Any ideas anyone?

Reply to
NoSp
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NoSp wrote in news:4846cbd6$ snipped-for-privacy@news.broadpark.no:

It is likely that some of the connections along the top [or bottom] of the LCD have been disrupted.

Likely you need a complete new screen.

....

Possible but not likely. You will know when you put on the tape. Let us know if that fixes it.

Look for a junker with a good screen.

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bz    	73 de N5BZ k

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

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

Bad news :-( And this after taking the utmost care in handling the LCD. It's apparent that Samsung don't want people replacing their CCFLs, but buy a completely new screen instead.

I've tried that now, but it didn't help. I have however made some progress as wiggling the screen around gives a very distorted, but correct desktop picture. It flickers, and is "stretched" in the vertical direction -sort of like a low resolution 80s computer using a TV.

So it does seem like a contact problem, but the question is where. There's no positive sign that it is the ribbon connectors on the LCD as I've carefully poked them to see, but then again that's from the top of the screen (where the circuit board is placed), and the connections to the LCD panel are further down. Perhaps if I carefully removed the "frame" with all the layers (reflector etc.) leaving me only with the LCD panel itself, I could connect it to the computer internal display cable and see if it makes a difference. I would be able to see something on the screen with a light shining through, even though the layers of reflectors etc. and the backlight would be missing, wouldn't I?

Regarding the connections to the LCD panel itself. They seem to be "sandwiched" in between glass, and look quite firm to me. I assume they're fastened with epoxy or something around where they go inside the LCD panel as opposed to just being loose?

Another thing: there are 3 thin "flexible PCBs" so to speak along the left hand side of the LCD panel (viewing the LCD from the display side). They don't see to contain any components, and extend further beyond the width of the metal frame which surrounds the display. Are these grounding planes or something?

Yeah, I've already put out ads. In case someone here is reading: it's a 15.2" screen (1440x960 pixels). The particular model in my computer is a Samsung LTN152W6-L01, but for all I know computer manufacturers like Apple might be using different brands/models within the same resolution.

Reply to
NoSp

Using google I found a number of hits for companies selling this panel. The cheapest in the hits I looked at, is this one:

formatting link

Reply to
JW

Thanks. I also found out that Moniserv/LCDparts does LCD repairs

formatting link
which might be worth looking into, once I figure out where the problem lies.

It seems like some sort of contact problem as wiggling the display around changes it from showing just a bunch of vertical lines and the actual computer desktop (although quite distorted). Apart from the LCD display itself it could be the connector/cable that goes from the computer to the LCD panel.

So what I've done now is very carefully remove the LCD panel itself (the glass only), connected the cable from the computer and having a light from behind so I can see what's going on. So far I only get the vertical lines, and there's absolutely no changing in that no matter what I do. (the reason I took the LCD panel out of its frame/assembly is because I wanted to access the areas where the ribbon cables enter the LCD panel, so as to carefully wiggle them to see if it made any difference -it doesn't!). That's probably good news because it probably means that the ribbon cables aren't damaged, but why is there no desktop display no matter what I do? At least, when I had the LCD assembled I could wiggle it until I saw the desktop on the screen.

This brings me to my next question... There are 3 thin, flexible PCB type things sticking out on the left hand side of the display. Here's a photo I've taken of the topmost one (there are two more like it):

formatting link

What's the purpose of these? Are they some sort of ground connections? I'm asking because I find it strange that the display doesn't change now that I don't have it in its frame along with the filters/reflector etc. as it did when I had those parts available, and everything was assembled.

Reply to
NoSp

NoSp wrote in news:4849161a$ snipped-for-privacy@news.broadpark.no:

formatting link

In brief, signals come in along the edges, all across the top and side of the screen. If any of the connections are damaged, entire rows or columns can stop responding.

--
bz    	73 de N5BZ k

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

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

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