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11-18-2018

RU

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Black screen but GPU, LCD cable and panel are fine [ThinkPad t440p]

2018-11-18, 11:39 AM

Laptop was on when this happened: no beeps, no error messages, no reboots or system shutdowns, no nothing. The screen just went black while the rest of the device continued running. I’ve connected the laptop to an external display and my desktop was there as it was before an image has gone.

 

After some reading, guessing and experimenting I’ve come to the conclusion that motherboard needs replacement. However, before taking any further actions (which include riding 100km to the nearest service center) I’d like to make sure I didn’t miss anything and have no other options left.

 

So, below is the list of versions I’ve rejected and reasons why:

  1. GPU failure or GPU driver issue. Since I get an image from an external device I assume GPU is ok. Just in case, I’ve rolled back GPU drivers for both Nvidia and Intel HD Graphics and nothing good nor bad happened.
  2. Some OS settings thing. I’ve got both Windows 7 and Ubuntu 16.04 installed on the same machine, and the problem begins before any of them starts loading (i.e., screen remains black while POST). Also, both Windows Device Manager and Linux hardinfo see only the external display. Lenovo Solution Center “Snapshot” menu fails to provide any information about current device display.
  3. LCD cable or panel went down. I’ve managed to borrow another ThinkPad t440p for a while. Both LCD cable and panel work fine while connected to another laptop.

Considering observations above, I conclude that system doesn’t “see” the display at all. If I understand everything correctly, the only candidate left is motherboard.

Arguments against:

  • Hardware check via Lenovo Solution Center under Windows hadn’t fire any notifications on motherboard state or anything else.

Arguments for:

  • Hardware Maintenance Manual for my laptop says (p.39, Table 6) that the only action in case of “No beep, power-on indicator on, and a blank LCD during POST” is “Replace the system board”.

  • Since the screen went black in a second, while the laptop was on, and without any mechanical stress or software settings changing, and the only version I have left is printed circuit board related, this might be explained by the capacitor failure.

I’m asking for an opinion of someone more knowledgeable and informed because I’ve never faced any similar issues before and, to be frank, don’t know much about OS and hardware internals.

 

By the way, is there any test I could do to check motherboard for failed capacitors? Any ideas on how this can be done (direct observation)? What other source of a problem can it be? Have I missed anything? Any thoughts would be greatly appreciated.

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Re: Black screen but GPU, LCD cable and panel are fine [ThinkPad t440p]

2018-11-18, 18:46 PM

First, GPU failure is motherboard failure.  The GPU is soldered, not a separate card.  There are separate leads and connections to the LCD and exyernal screen, so one could work while the other is bad.  Occasionally a capacitor could just blow out and be visible, but that is unlikely and if that were the case, there would likely be another failed part that caused the blow out.


Rich


I do not respond to requests for private, one-on-one help. Your questions should be posted in the appropriate forum where they may help others as well.

If a response answers your question, please mark it as the accepted solution.

I am not an employee or agent of Lenovo.
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2 Posts

11-18-2018

RU

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  • Posts: 2
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Re: Black screen but GPU, LCD cable and panel are fine [ThinkPad t440p]

2018-11-19, 4:26 AM

Yup, I've missed the fact that in my laptop motherboard has soldered GPU. Which, as I understand, implies that my assumptions about its GPU's irrelevance to the problem might be wrong and things are too complex for nonprofessional to try to guess. Anyway, it seems I'm riding to a service center.

 

I'll report the results. Thanks.

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