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HP Pavillion dv4 blank screen - what to replace?

Posted on 2010-09-10
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Last Modified: 2012-05-10
Hi Experts,
I have an HP DV4-1114NR (FR931UA#ABA) laptop with nothing on the screen but the VGA externally works fine and it boots up into Vista with no problems. Shining a light I don't even see the faintest image that would indicate the LCD is working. Turning it on I don't even get a quick pulse of light in any way, either. As I said, once Windows would come up, I can't even see anything on the LCD that would show me it's working.  What would I be best off replacing - the LCD, the backlight, or the inverter? From what I read I'd have to see at least something on the screen, albeit dark to suggest the inverter or backlight? I'm also confused as if some replacement LCDs (such as the ones you get on eBay for $100) include a backlight or not... If anyone has suggestions, links for what sounds like the best replacement part, I'd be very appreciative!
By the way, I've also read of crazy ideas suggesting to take the battery out for a while, open the display all the way out, hold in the power button for 30-60 seconds, then plug the AC back in and try it with no results...

Thanks! Scott
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Question by:ConcordNH
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by:thakurdinesh
ID: 33651012
This problem seems to be with LCD itself, not the built in display adapter. Because you can see the plug in external monitor. If you dont even see a small light spike in LCD as you mentioned, 80% chance is PCB associated with the LCD is damaged or LCD itself. I doubt it if you can get that part, so best approach will be to get a new LCD and replace it. If you have tried the things you said above, I belive you can replace the LCD yourself. Instead of spending 100 bux or more for troubleshooting, give it a try ad get new LCD for that amount of money..

If you still have some question, feel free to post it. I will be happy to assist if I can.

Thanks
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by:David-Howard
ID: 33651014
I'm sure the advice you are going to get is sound. That said, if you have a mom and pop repair shop near you, you might give that some consideration and for a few reasons.
1) They can usually troubleshoot the issue quickly, for a low cost and many of them will apply the diagnostic fees directly to the repair part costs. Which brings me to my second point. You can save a lot of time (and more importantly money) by having this professionally diagnosed. This way you aren't ordering and trying to replace parts that you may not need.
Finally, I would suggest that you stay away from places like Best Buy, etc. They are enormously over priced for many things, including service troubleshooting and replacement.
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Author Comment

by:ConcordNH
ID: 33651117
Thanks all for the quick advice! I am the mom & pop repair shop - I do pretty much everything unless it involves soldering and getting more and more laptops to work on, but usually the extent of monitor damage I work on simply requires swapping the entire screen assembly with a used one from eBay so it usually just involves taking out several screws and a cable (at least with the Dells). Being that this is a newer HP unit, I need to isolate the specific problem and just replace that part (ugh).  So it does sound like the LCD - should that include the backlight somewhere in the assembly so I just need to order that one part and replace? Thanks again from a novice when it comes to LCD repairs! :) Scott
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thakurdinesh earned 500 total points
ID: 33651175
If I was you, I would buy the entire assembly instead of buying individual parts, and replace the entire panel, including screen, cable etc. Buying seperate parts may cost less but eventually may end up costing more than the entire screen. Replacing LCS is almost same in all laptops, either dell or HP or sony(Sony will drive you a bit crazy but managable, I did replaced on SZ120P a few weeks back). Before you buy a new set of screen, I will suggest you to disassemble the screen and note down the part numbers and assemble it back. In that way you will be sure about the part number and If there is any lose connection as well. Who knows if it worked after that, dry solder or something...
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by:legendary1
ID: 33651557
When I have cracked LCD's I take them apart I pull the backlights to use for testing. Then when a system comes in I usually have a backlight with an appropriate connector to test wether the inverter has power output or not. This is easier and cheaper than a universal backlight or changing connectors yourself.  The inverter is an easy replacement. The LCD is an easy replacement. I don't like replacing both unless I have to. You have it down to one of those two. You could just change the cheaper one and hope that's it.
And technically the backlight could be out and the LCD fine. I have found that unless you have experience. You shouldn't consider replacing the backlight. You will also learn a good bit about how an LCD works taking the backlights out.

Hopefully that and this site will help you some. It's not specifically about laptops, but the concept is the same.

http://www.inventgeek.com/Projects/BacklightFix/Overview.aspx
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Expert Comment

by:thakurdinesh
ID: 33651650
If you are confident replacing Backlight inverter, you can try it. But you need to be very careful while replacing. Still I will sugest to replace the entire panel. To replace backlight you can find many video tutorials on YouTube.

This is one of them, you can search for some the model you are having problem.
http://www.youtube.com/watch?v=UT2GFVem_9U&feature=related
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Expert Comment

by:thakurdinesh
ID: 33651662
very good video I just came accross with

http://www.youtube.com/watch?v=aRQSk4bhcCU
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by:Grant1842
ID: 33652017
In general if it it the (ccfl) back light it would have started showing sighs of pink over a little time.

If it just quit all the sudden probably the back light.

When you press your power button on your laptop and the LCD screen just stays black.  What is the problem?

Possible problem can be the on-board video chip or Video Card.

Possible problem can be the power inverter.

Possible problem can be the back light of the LCD screen.

Memory

Bad LCD Cable Connections


On-board VIDEO CHIP or Video Card BAD

First let's look at the possibility that your video chip on your motherboard is bad.  You can also have a separate video card instead of on-board video chip.

If you press the power button on your laptop and you just get a blank screen, then you need to do a couple of checks to see just what the problem might be.

1) If the LED lights are on and you hear the fan in the laptop running and hard drive working but there is no video, that usually means the video chip on the motherboard has gone bad.  This can be repaired by re-flowing the video chip. You will have to find a good repair tech that knows what he is doing for this repair.  It might cost in the neighborhood of $150.00 for this repair.

2) Plug a external monitor to the laptop and see if you have any video. If you see video on your external monitor then your video is OK.
NOTE:
When your power inverter is bad or the back light is bad, you can usually see a faint image on the LCD screen.


Power Inverter / Backlight BAD

1) If your video displays on the external monitor then your LCD screen has a problem.  Either your power inverter is bad or your LCD backlight has gone bad.

2) Check that your power inverter plug it seated properly. Without a tester to hook to the inverter or back light (CCFL) there is a general guideline you can use:
If this happen all the sudden that your screen just went black it is most likely it is the inverter.
If your LCD screen has been geting light and dark or colors have been getting off for a while it is your back light (CCFL).

You can actually have the light replaced but it is a tedious process and it is probably better and cheaper to find a new LCD screen on eBay.

Memory
Sometimes memory modules can do this. If you have extra good memory you can swap out and see if it woks. If you have an extra laptop around that usees the same memory you can put the memory modules in question in the extra laptop and use memtest software to test it.
http://www.memtest86.com/

Cable Connections
I have seen loose cables and improperly seated cables do this as well.
Check the connections at the motherboard and back of lcd screen to make sure they are seated properly.


Conclusion
 
If your onboard video chip has gone bad on your motherboard, you can have it repaired at a reasonable cost compared to having to buy a new motherboard.  This repair will have to be done by a good repair technician and that will be cheaper than a new motherboard.  If your video card is bad then you can replace it.

If your inverter or backlight is bad and you have taken apart a laptop before, you can change the power inverter or LCD screen yourself, but only attempt this if you are sure you can take apart the laptop without breaking anything.

If you can take apart your laptop and check the cables you can save your self some money and time.
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Expert Comment

by:nobus
ID: 33652329
here a nice nite for troubleshooting lcd's : http://www.lcdparts.net/howto/troubleshooting/troubleshootingLaptop.aspx      
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Author Closing Comment

by:ConcordNH
ID: 33655451
Thanks, all for your help. Turns out by further taking the unit apart, I saw that the video cable was pulled out enough which was causing the issue. Guessing that each time the display was opened all the way it pulled it out just slightly enough to eventually not make a solid connection...  Glad I didn't purchase anything yet. Thanks again!
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