This is ridiculous.. I've got an Asus U56E that I was replacing the screen in. The screen was cracked, but the backlight still lit up. So, I order a new screen, put it in, and its fixed!.... a few moments later, the screen just goes dark!.. The backlight had cut out.. So I plug in an external monitor via VGA, and it comes up on the monitor and everything is fine.. So I go to inspect what could of just possibly happened. I notice a blown fuse close to the spot where the screen connects to the motherboard, and I also notice a small hole in the tape wrapped around the screen connector cord which looks like it had a torn wire. So I order a new board, and new screen cable (and at this point, there's nothing else to replace? right?) and the problem is still there!... No back light!.. What could it BE!??!?! Iv'e tested BOTH screens in another Asus machine and they work PERFECTLY! .. no problems!.. But if I test them back in the original Asus, I get NOTHING!... How is this possible?!?! I've checked the fuse on the new board, and it's fine!.. This honestly makes no sense... It's almost like something needs to be configured in the Bios somewhere, but there's nothing remotely close besides flashing it... How could this be?!?
I am... very confused. I imagine this is rather frustrating.
So it must be something in the laptop. If the new screen works in other systems and no screen works on the laptop, it can't be anything else. So, what could it be... Did you double-check all the connections? Make sure all the cables are plugged in correctly? Hm....
I don't want to suggest calling ASUS, because I know how useless tech support can be, but I am stumped. It seems like you've covered all the options.
Trust me, this is extremely frustrating. I've worked in a computer repair shop for years, and I've never had something so annoying, and possibly costing us so much)..
I tried calling Asus, the foreign girl said the "bulb" was burnt out.. I had to explain to her that this was a LED LCD, and that it worked fine in another machine.. She was CLUELESS...
I've checked all the connections, and all that.. Tested the magnet on the lid, and it works.. (the screen is dim but I can see it cut off when I shut the lid)..
I've had a fuse blown before, but the fuse is fine on the new board.. So I just don't even know. I never work on the machine with the battery or cord in. I always press the power button a few times as well to make sure it's drained before touching anything.
I think that's an option. That's really the ONLY thing I haven't tried... My co workers say it's "risky" and could mess up the laptop.. but I use to do it all the time... I mean there's a tutorial with pictures for the exact model on Asus's website. But how often does flashing the bio's fix a backlight issue....
I'll have to test it when I wake up, It's 6 in the morning here. How often does a missing screw cause a BACKLIGHT to not work though?.. I mean honestly, there's nothing else to replace. The board, cable, and screen have all been replaced..
I had the same problem replacing a screen on an ASUS U35jc. Turns out the backlight fuse was blown on the motherboard. It was easy to tell because it was completely charred. Probably happened because I didn't disconnect the battery and/or power cord when I hooked up the replacement screen. Anyway I tested this by bridging the blown fuse with a screwdriver and the screen backlight worked. I eventually just soldered the fuse and it's worked ever since. Don't have pictures but the backlight fuse was located right above (north of) the LED display connection on the motherboard. There were actually two fuses in parallel at this location. The blown fuse was located above (north of) the working fuse so that must be the backlight fuse. BTW those fuses were tiny. I don't know the configuration of motherboards for other sizes but I'm pretty sure this applies to any 13.3 inch ASUS U series machine.