Replace LCD cable or replace LCD screen

stepheng273

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Apr 15, 2013
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Recently my laptop screen started flickering. I don't know what might have caused it. I've had this laptop for about 3 years now and it worked perfectly up until now. The bottom half of the screen sometimes flickers and image of what's on the top half of the screen. I'm confused as to whether I should replace the LCD cable or the LCD screen. I've tried changing the refresh rate, re installing the graphics drivers, and moving and lightly applying pressure to some parts of the screen to see if there is a change. Nothing changes. It starts this behavior as soon as the LCD comes on during the boot up. The backlight is fine and I haven't noticed any discoloration. Plugged it into an external monitor via VGA and it displays just fine.
 

poweruser_24

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Feb 24, 2012
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Laptop screens used to be manufactured in two pieces, and would periodically do what you are describing. Been a while since I've seen a split screen though (always fun explaining to customers why only half their screen works).

Sometimes it was the connection needed reseating, which you need to open the laptop to get to. Other times the gfx device/DAC going bad (there is a separate buffer for the external device - which is why you can run them both at once), which as it is soldered to the MB (most of the time) means repair/replace (it can sometimes be the solder, but finding it and resoldering is difficult without the right gear).
 

poweruser_24

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Feb 24, 2012
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Cool... or not...

If no longer under warranty, I would try opening up the lap top (you usually start with the keyboard - although it does depend on brand/model - most keyboards are designed to pop out easily as they are the most replaced item), and try and get to the connectors from the lcd to the motherboard (this is usually a ribbon cable or tied cable near the back of the laptop). IFixit usually has good teardown processes.


If reseating this doesn't resolve, you could go through the effort of getting to the LCD end of the same cable, and trying there too.

Failing that, it is more than likely a RAMDAC is failing/loose. If your laptop has a removable video card (possible, some do), then you may be able to get a replacement. Normally it will need to be the same as what you already have - not an upgrade. Most laptop components are custom fits, but there are some interchangable pieces between particular models.

edit:
Wow just realised that it is really bizzare because it is not a full mirror of the top half. You sill have the correct background and the taskbar. Perhaps it could be some accessibility tool or some dodgy application.

 

stepheng273

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It starts this behavior as soon as I see the HP logo at the boot screen. Its not a graphics card problem because I can hook it up to an external monitor and still play games like need for speed and sims 3. Made sure all the cables were all the way in (on both the mother board and the back of the display) and none of that worked. I know its either problem with the lcd cable or the lcd display itself.
 

poweruser_24

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Feb 24, 2012
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Sounds like a hardware type problem, whether that is card/cable etc if it is happening during the bootup too.

Each display output has a separate RAMDAC, one for each port. So the external display has a separate RAMDAC to the internal display. If they didn't then you couldn't use both displays at the same time which every laptop since the early 1990's has supported. So it could be the graphics card.

Unlikely to be the LCD itself. The buffers are generally on the graphics hardware, and not built into the LCD panel. The panel generally is all about signalling and lighting.

If it was a problem with the cables, you wouldn't be getting such specific cross talk behaviour, or ghosting. It woudl be top half is mirrored on the bottom half. Same for if it was a buffer on the LCD.

You are still getting the full buffer. But in that image, the Calculator Window is being ghosted on top of the correct background/taskbar. This will be from the graphics card or the RAMDAC.

Mind you, you dont have to believe me. I've only been repairing laptops for 16 years. You may have more experience.
 

stepheng273

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Oh ok. I understand now. How should I resolve this problem? And no, it's not that I don't believe you. I greatly appreciate your help even if we can't find the problem.

edit: I forgot to say that there is a vertical light blue line in the middle of the left side of the screen. It's about one pixel wide and it goes all the way from the top of the screen to the bottom.
 

poweruser_24

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Feb 24, 2012
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If your in a warranty, send it in for repair. If not, then sometimes the cost of replacement parts can be more than the notebook is worth, especially with labour on top. Even if you do it yourself, I have had the experience of some customers paying $600+ for an LCD on a laptop worth $900.

Cables are still unlikley culprits, unless there is obvious damage to the cable, which would be in the hinge (i.e. where the cable has to flex).

As you also have another fault, being a vertical line as well as the ghosting then you may have been right with your initial assesment on the LCD (it woudl have been usful info up front). Having two very different faults, especially with a straight line would be unusual for the graphics card/RAMDAC. But ghosts are not normal for LCD faults - usually this only occurs when the LCD is cracked after a drop.

To fix, you need parts to test.
 
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