Chosen Solution
Hi all, after fixing one of the hinges of my Asus Zenbook UX303LA-R4342H, while trying to plug the display cable back into the mainboard, I accidentally let the display cable touch the mainboard. This lead to a small flash of light and it smelled burnt. (I still had the battery pluggged in.) Now the display backlight does not turn on anymore. If I shine a light through the back of the display I can see the Desktop and also with an external monitor everything works fine. What do you think broke? Is it the mainboard, the cable or the display? How can I figure out? Unfortunately, I don’t have any other divices on which I could test the display. I did not see exactly where the cable touched the mainboard - I only saw the spark in the corner of my eyes - but since the cable is relatively stiff and does not have a lot of reach I think it must have touched the mainboard to the left of the connector.
I already tried unplugging the battery and holding the power button for 30s as suggested on some backlight problem questions here, but this did not help. Here is a picture of the mainboard:
And here is the output of the CPU-Z Utility:
Update: I took the mainboard out the check the other side. I guess I found the source of the burnt smell. The burnt part is exactly on the other side of the display connector. There are also these two smaller things further above that also seem to have burned?
What are these broken parts? Is that something I could fix?
Replacing the mainboard fixed my backlight problem.
@lymanox something obviously got shorted out on your backlight circuitry. You would have to to a really good visual inspection of the complete board. Remember that just because the cable does not have a long reach, it may have create a short circuit in a component along a trace. Asus is really stingy with schematics so we will need to know the exact motherboard your Zenbook is using. See if there are any numbers etc. silkscreened right on the board and let us know what those are. We may get lucky….
