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HP Laptop Screen Dead?


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#1 cmk45

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Posted 08 February 2011 - 12:22 PM

Hi all. I have a HP DV7-1451nr laptop with a screen that appears dead. This unit has an ATI Radeon GPU, so I don't think that it's the same issue that other models with the overheat/desolder NVidia GPU are having, plus my symptoms seem to be different. I never got any strange lines, colors, or anything else on the screen before the problem cropped up. Here are the current symptoms:

1. Screen is completely black, with no backlight, and I cannot see anything displayed on the screen if I shine a bright flashlight on it.
2. The external monitor HDMI port works perfectly if I connect it to my TV. In fact, that's how I'm typing this now.

Here's what lead to this point...

Intermittently for the last month or so, the screen would occasionally be dead upon startup or after hibernation. Usually it would come to life within a few minutes after I messed around with it (open/close screen, unplug, remove battery, hold down power button for 30 seconds, reboot). I suspect that getting it to work again was more related to my handling of the unit than anything else, as just the other day it was initially dead, and cycling the screen open/close three times brought it back to life. Now I can't get it to come back at all.

I'm guessing that I have either a bad screen, damaged wire, or bad connector somewhere? If so, what's the best way to go about diagnosing the issue? If I were to buy a replacement screen will it come with the associated cables/inverter/bulbs that may be damaged and will that likely solve the problem? I'm willing to do just that if I can just get this thing working again.

Since I can't see anything when I shine a flashlight on the screen, that indicates that it's not likely just a bulb issue, right?

I'm not a computer expert, but know my way around, and I'm confident that I can take apart/replace whatever needs done. I just need some help identifying the problem further.

I'm about to start some exploratory work to see if I can see anything that is damaged, but I'm afraid that the problem won't necessarily be visible.

Please let me know if there is other info that might help figure this out.

Edited by cmk45, 08 February 2011 - 12:40 PM.


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#2 killerx525

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Posted 08 February 2011 - 04:16 PM

So when you hook up a external monitor, is the laptop screen still blank?

>Michael 
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#3 ThunderZ

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Posted 08 February 2011 - 04:29 PM

I'm guessing that I have either a bad screen, damaged wire, or bad connector somewhere? If so, what's the best way to go about diagnosing the issue? If I were to buy a replacement screen will it come with the associated cables/inverter/bulbs that may be damaged and will that likely solve the problem? I'm willing to do just that if I can just get this thing working again.



Really the only way I know of to check for loose, broken, damaged connections is to visually inspect and redo each.

Actually there is one thing being left out of the trouble shooting equation. The power inverter. SAMPLE PICTURE ONLY.

#4 cmk45

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Posted 09 February 2011 - 03:24 PM

Yes, when an external monitor is attached to either the HDMI or VGA outputs, the external displays function normally, but the laptop screen remains dead.

I am aware that the inverter may also be involved. The inverter only provides power to the bulb, correct?

My biggest question right now is this... Doesn't the fact that that I see no image at all when shining a light on the screen indicate that it's likely related to the lcd screen being bad or the video cable that provides the signal to the screen being bad?

I opened up the bezel yesterday, reseated the video cable to the screen, visually checked things, and gently probed around the wires where they enter the laptop to see if I could get a bad wire to make contact. Nothing that I did changed anything.

I'm about ready to order a replacement lcd and see if that fixes it, but I'd like to get an answer to the questions above first.

#5 cmk45

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Posted 09 February 2011 - 03:28 PM

Found this, which seems to confirm my understanding that the inverter powers the backlight only, and that if the inverter or backlight were bad, I'd still be able to see a dark image on the screen. To me, this means that it's either a video cable issue or an lcd issue.

TYPICAL INVERTER FAILURE SYMPTOMS

Usually inverters fail in one of the following ways:

1. When you turn on the laptop, the screen lights up for a short period of time and then goes dark. You still can see an image but it is very dark, almost invisible and definitely not usable. When you restart the laptop, the screen lights up and then goes dark again. The laptop works fine with an external monitor.
2. Your laptop turns on but the screen remains dark all the time. You still can see a very dim image outline. The laptop works fine with an external monitor.
3. The laptop screen works fine for hours or even days, but sometimes it goes very dark as it mentioned above. When you restart the laptop, the screen works fine again.

Inverter failure symptoms are very similar to backlight lamp failure symptoms and in most cases you cannot tell which one is causing the problem until you replace either the inverter board or the backlight lamp. From my personal experience, inverter boards fail more often than backlight lamps. If you have to guess, replace the inverter first.






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