Laptop black screen on startup.

[MistretuAndrei]

Hello. My dad has an old laptop that didn't work for some time and i want to try to repair it. The laptop is an Asus k50af. The problem with the laptop is that when you press the power button, the button goes green, but the screen doesn't show anything, it's just black.
I've already tryed:
Switch between ram sticks and removing one of them.
Connect the laptop to a monitor by VGA cable. Still nothing
Get out the CPU and see if it has any pins broke.
If anyone could help me try to troubleshoot this problem i will really apreaciate it.
I wanted to see if maybe the GPU has a problem, but to be honest i don't really know where the GPU is located in the laptop.
I want to say aswell that i can hear the harddisk working, but the CPU fan doesn't turn on, the harddisk is the only thing that i hear working in the laptop.

 

[lga1156_ftw]

Have you tried FN+ (whatever key changes output to your vga) when you plugged in external monitor?

if you get picture its either lcd cable or lcd panel or connectors between / circuit.

 

[lga1156_ftw]

Probably its rs780m (northbridge) chip or ati gpu chip on the mainboard. Do not reflow southbridge (sb700)

Test with mild reflow around 150celcius to see if its problem inside the chip (this wont melt solder)
If works after that do higher temp reflow, its only temporary you need new motherboard if this is the issue. Reflow might work from 1 day up to a year but it WILL fail.

 

[MistretuAndrei]

I've already texted the FN thing, and can you explain I more detail what reflow is?

 

[lga1156_ftw]

Try cmos reset, remove cmos coin battery and wait 5min, put it back, test.

You can also try to boot the motherboard "barebone", meaning remove everything from it, put the motherboard to non conductove table like wood, remove cmos battery, remove power button connector even, then put external VGA connection to your TV. After that plugin power cable it should boot without pressing power button when cmos battery is removed. still green / black screen on vga?

"reflow" isnt really any kind of fix, there is issues inside the video chip or northbridge and heat expansion can "reconnect" broken connection inside it.
It maybe not work after it, or works for awhile. Sometimes even longer like months, usually up to a year is max.

I feel ashamed of even linking this crap but here you go, remove processor and tapes unlike this guy. Do not use too high temperature, your not melting solder under chip (that needs 225c+) , if you dont get any picture after 150c reflow both northbridge and ati radeon chip then you can try 200c but this will probably kill the board. :

View: https://www.youtube.com/watch?v=w37QV0EZXQI