Lenovo IdeaPad Y700 15ISK black screen after boot

[openminded]

Hi,

I have a strange issue with a Lenovo IdeaPad Y700-15ISK.
It goes on, shows the logo and as soon as it goes further, the screen goes black.
When I use the Novo button, the screen works fine.
When I then choose for example BIOS, I see the BIOS screen for like 1 second, then the screen goes off. The laptop is still on, it responds to the power button, so it seems it works fine except for the screen.

I connected a screen to the HDMI but get nothing, no signal.

It looked like the GPU ( Nvidia 960M ) so I tried to reflow that up until a short 350 degrees Celcius.
The problem remains the same.

Tried multiple adapters, same issue.

I have a supicion that the computer switches to the dedicated GPU and the issue may be the power to it, but I am not sure.

Has anyone seen this, or does anyone know how to troubleshoot it?
Thanks a lot!

[openminded]

Re: Lenovo IdeaPad Y700 15ISK black screen after boot

I found out a bit more. It looked like the screen is just on for a few secs, even when waiting on the boot menu screen, it will go off in some seconds.
Also found out that when the LCD cable is disconnected, the HDMI port works and the laptop works fine with an external screen.

I found a BIOS option to set video card to internal only, but the problem remains.
It seems to work all ok when LCD cable is not connected.
I hope this helps anyone help me further, thank you.

[openminded]

Re: Lenovo IdeaPad Y700 15ISK black screen after boot

a bit more info from testing:
- external HDMI seems to work ok now, just the internal screen is the issue
- when waking up from sleep, the internal screen 'just works' for a few seconds before it goes off again - it still looks like full off, not just backlight
- I ran a stress test with Furu 3D test on a monitor on HDMI and it worked great. so Nvidia GPU seems to work fine.
- with BIOS set to Internal GPU, the Nvidia GPU does not show up in Device Manager but behaviour os screen etc is the same. When set to with external, it shows as 960M working fine

Is this just some issue with the voltages to the LCD, or the LCD itself?
I have attached the files I found for it.
Any help is still greatly appreciated!

[mcplslg123]

Re: Lenovo IdeaPad Y700 15ISK black screen after boot

Very likely a damaged edp cable. Try replacing the edp cable or post measurements on edp connector pins.

[openminded]

Re: Lenovo IdeaPad Y700 15ISK black screen after boot

Very likely a damaged edp cable. Try replacing the edp cable or post measurements on edp connector pins.

Hi thank you for the response. I have another laptop coming so I can compare parts. It's hard to measure those points but I will find a way.
Do you think it is the cable and some kind of resistance causing it to go off?
I really hope it is the issue, that's fixable .

[openminded]

Re: Lenovo IdeaPad Y700 15ISK black screen after boot

hi, I got the replacement screen and cable. Both seem to be fine, but a strange observation. Taking the fully working laptops screen and put it on the broken one, this time gave just a flickering screen and light stripes - mostly looked like just backlight on.
I verified the cable was put on properly, cleaned it, three times the same effect. When I put the screen from the broken one on the good laptop, it works perfectly fine!
Then when I put back the screen from the broken one to it's housing I get the original behaviour : lenovo logo at boot, then some timebefore the screen gets black.

I think it rules out cable and screen but it is very strange. I will try to measure voltages on the pins, any other ideas are always appreciated.
thank you!