[](/unresolved)
Hey all,
Thanks for taking the time to look at my problem today. I am working on a Dell Laptop, model 15R-5521 for a friend of mine. It was in on repair after a spill knocked it out entirely. I replaced the motherboard in it and that has more or less "fixed it" but its still not 100%.
THE SYMPTOMS:
When you power on the laptop, most times (but not always) rather than getting a Dell splash screen during POST, I get these weird lines, usually horizontal but sometimes also vertical, that fade out as the boot sequence goes up, eventually reaching total blackness. In the black space there isnt anything going on in the background. This happens and you can sorta tell that the computer has booted up in the background, and eventually shuts its screen off.
As soon as you plug in an HDMI monitor though, the laptops screen comes on perfectly fine and will remain on until the screen is told to shut off, either from inactivity or closing the physical lid, at which point it will most likely need a monitor plugged into bring back the display on the laptop.
Its almost as if the motherboard is getting confused in determining whether to send display out via HDMI or via the header to the LCD, and it isnt until a real HDMI device is plugged in that it realizes "Oh wait. Okay. Lid is open, screen is physically, I should send video signal to the lid screen first."
I almost wonder if the lines I see are what one might see on an LCD that is not backlit, say, while the lid is closed and an HDMI monitor is plugged in. Almost as if what I am seeing on the screen is a "frame" of electronic digital noise that is loaded or leftover in the frame "buffer" of the display, until it gets proper data sent to it. It reminds me of similar side-effects on hobby grade 16x2 LCD panels that I use with Arduino that will show garbled characters if you have messy electrical lines until you send it new, good data.
In the attached picture, I show four steps of a single sequence, wherein the computer has evidently booted up, is on the login screen and is waiting for my password, but I let the screen fall asleep, and then pressed a key to wake it back up. Some notes: the specs in the black area on the 4th image are just dust on the screen, not display artifacts. Additionally, the higher brightness towards the top of the nearly all black screen of the 4th image seems to be a byproduct of the backlight/polarizing lens in the display plus my phones camera. Otherwise, you can see a natural progression from glitched lines down to black over the course of maybe 10, 15 seconds.
Also worth noting is that, sometimes, especially before I had the hard drive in and before I switched it from UEFI to Legacy boot (which seemed to be the means to get the BIOS to recognize the hard drive from the old laptops motherboard), it would boot just fine to the Dell screen.
Thanks in advance for help. Its late at night and I am a little frustrated/near my wits end with it but I am gonna try and be responsive to what help you all can offer me so that we can figure this out together.
