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XPS 15 9550 screen went black but external monitor works

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I have a Dell XPS 9550 running Windows 10. Yesterday all of a sudden the LCD monitor went totally black, and now it won't turn on at all (not even the backlight), but an external HDMI monitor works fine. I've tried all the usual: powering it off and on, running diagnostics, booting into safe mode, booting into the BIOS, etc, and nothing I've tried will make the LCD monitor working again.

Additional notes:

* I can run the display test on startup by pressing "D" and it runs fine -- I see red, green, blue etc -- and the monitor itself seems to be working fine. So it's not an issue with the LCD monitor hardware.

* Even when I boot into the BIOS (either via F12 on startup or via rebooting into the UEFI from Windows) it doesn't turn on the backlight or show on the LCD screen. But I can use the BIOS fine via the external HDMI monitor. So it's not a Windows or driver issue, as the BIOS (well before Windows boots) has the same issue.

* I've tried disabling the Intel and the Nvidia graphics cards in turn, but neither operation helped (and see above point where it doesn't seem like a driver issue).

* The touch aspect of the LCD screen still works.

* I've tried updating to the previous version of the BIOS (1.8.0) and it updates to that version but doesn't fix the problem or change anything.

* My laptop is not under warranty so I want to try to fix it myself.

Any ideas of what to try next? Maybe the red/green/blue diagnostic test uses lower-level hardware to drive it than normal, which is why the "D" test works but nothing else?

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Re: XPS 15 9550 screen went black but external monitor works

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I didn’t even know about the “D” test, but based on the description of how it’s invoked, I’m thinking that test might run a routine embedded into the display electronics thenselves, in which case if even the BIOS interface doesn’t appear, it’s probably an issue with the display ribbon cable from the motherboard to the display — although some sort of USB channel would seem to still be working if it gets the diagnostic command triggered by you pressing the “D” key. I assume the display diagnostics that are part of the longer Dell system diagnostics routine you can boot into don’t work? If you want to look at the Owner’s/Service Manual for that system on support.dell.com, you could try releasing and reseating the display cable in the system, but be warned that those cables are very fragile, so be careful, otherwise you could end up breaking something that wasn’t already broken.

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Re: XPS 15 9550 screen went black but external monitor works

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Re: XPS 15 9550 screen went black but external monitor works

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I didn’t even know about the “D” test, but based on the description of how it’s invoked, I’m thinking that test might run a routine embedded into the display electronics thenselves, in which case if even the BIOS interface doesn’t appear, it’s probably an issue with the display ribbon cable from the motherboard to the display — although some sort of USB channel would seem to still be working if it gets the diagnostic command triggered by you pressing the “D” key. I assume the display diagnostics that are part of the longer Dell system diagnostics routine you can boot into don’t work? If you want to look at the Owner’s/Service Manual for that system on support.dell.com, you could try releasing and reseating the display cable in the system, but be warned that those cables are very fragile, so be careful, otherwise you could end up breaking something that wasn’t already broken.

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Re: XPS 15 9550 screen went black but external monitor works

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Re: XPS 15 9550 screen went black but external monitor works

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Thanks for that, @danderso8. I'll try to take it apart, re-set the cable and the battery and report back here.

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Re: XPS 15 9550 screen went black but external monitor works

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Here's how I got one laptop back up and running.

For some reason internal display stopped showing anything after initial DELL logo when powering laptop up on 14.6.2019. The laptop was connected with HDMI to external monitor. This original external monitor didn't show up image either. With another HDMI external screen was working.

Steps to fix:
1. Took battery out and hold power button for 60 seconds.
2. Updated everything with Dell Command Update and checked that BIOS is up-to-date (this needs to be done separately as I've noticed that Dell Command Update doesn't always show the latest BIOS).
3. Disabled Dell PremierColor from auto startup. This had some kind of memory leak as 4 GB memory was in use (after 5 mins PC powered on) and it was raising. This shouldn't use almost any resources.
4. Changed resolution with Intel Graphics control. This was actually the thing which brought image to internal screen. So there was some kind of glitch in Intel's graphic configuration. Tho I must say that the Intel graphic drivers were updated with Command Update also.

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