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Screen became black all of a sudden (PHOTOS INCLUDED)

samsung np sa 31

Hi guys, I'm new here and really hope I can get some help :)

I was using my laptop normally, I turned it off, by pressing the power button and then closing the lid if I remember correctly since I was in a hurry.

After coming back to the device, the screen just wouldn't turn on! It just stayed black.

I tried everything. Messed around with the BIOS, reconnected the LCD cable, repositioned the RAM sticks and tried to run it with only one of the sticks, removed the CMOS battery and then placed it back, tried to clear static via power button, and much more, INCLUDING buying a whole new screen! The same problem still persists.

The laptop is fully working when connected to an external display via VGA cable, you can see everything on the screen when you flash with a flashlight on it (same for the original LCD and the brand new one I bought).

I have no idea what's wrong. I fully disassembled the laptop and I will add imaged of the motherboard, to me, nothing seems out of place and no fuses are burnt (the heat sink was removed for the sake of the photo), but maybe you guys will know what to look for and I'm just missing something.

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Thank you !!!

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Hi @prodwood

I can't find the schematic for a Bremen - M motherboard but I'm hoping that this image from a Bremen - L motherboard may be useful as long as the LVDS wiring and circuitry are the same that is.

Looking at the image there is always backlight power supplied to the LCD display on the LVDS connector pins 1-3 and the backlights are turned on and off in the LCD display by a signal voltage applied on the BKLTON lead which is on pin 4

With the laptop turned on etc check if there is voltage on pins 1-3.

If not then there's a problem with the LED power circuit i.e. Q504 and Q505. I can't see a Q504 on your board but there's a Q505 visible near the LVDS connector.

If there is voltage on pins 1-3 check the backlight on circuit around U3 (which I also can't see) but check if the voltage changes on pin 4 if you toggle the keyboard display function button to alter the display between the laptop and the external display.

Note: the above is only relevant if the two motherboards are configured the same as far as the display backlighting power and control are concerned, but unless the schematic can be found for a Bremen - M motherboard you have to start somewhere ;-)

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@jayeff

I appreciate the comment man. I found the correct schematic diagram. Please kindly check it out.

Link: https://drive.google.com/file/d/1Ck3IUzf...

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@prodwood

Good find.

Not too much difference. Same configuration just different component designations

Still LVDS connector pins 1-3 for the backlight voltage leads

Q506 and Q509 for the backlight voltage supply

U5 for the backlight on/off circuit and BKLTON lead still on LVDS connector pin 4

See p.30 of the schematic you linked.

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@jayeff

Thank you for your time, it's truly much appreciated. Please let me know if taking a clearer, closer photo of the part on the motherboard that's relevant to this issue could help with diagnosing the issue. Maybe there's a visible fuse that causes the issue (?). I'm still a little unsure if that's even a hardware issue since the issue arose out of the blue with no outside shocks or failure signs.

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@prodwood

There's no fuse shown in the circuit on p.30 but this doesn't mean that that isn't one further back in the supply as the LED power circuit has another power supply rail feeding the power transistors Q506 and Q509 i.e. P3.3V

Maybe better to check what is on the LVDS connector first e.g. voltage on pins 1-3 yes/no and if no check Q506 and Q509 if yes check voltage on pin 4 and U5.

That way you know where to look further.

It may be software but since you did a power refresh and I'm assuming that you also tried to get into BIOS with a laptop display (you can't with external monitor) and it also didn't work, it's looking like a hardware problem

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@jayeff Yes, I did try getting into BIOS. Also, if it was a software issue the Samsung logo would still show up on boot, right? I will buy a voltage meter and test it.

Would I need to turn on the laptop without the screen and test the connections on the cable or on the pins that are on the screen? I'm a little confused. I will add an image.

https://pasteboard.co/SxqGEZE4pbLb.jpg

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