I also faced this problem yesterday. Horizontal lines over logo, Doesn't boot no matter what i tried
PRAM Reset, SMC Reset, Verbose mode, Safe boot - none worked
My friend had a look and said that he will try to save it.
He tried a process which he called "reflow" the gpu, i think.
Basically the Derived graphics card in my mac has stopped working he claimed and using a box like device he heated it up to the right temperature and this melt the led and made it connect properly and the laptop booted just fine :D
After this, I just started gfx card status and made sure that my laptop will only use my Integrated Intel HD graphics as a precaution and prevented automatic switching. Its been working fine till now
Hope this helps someone else If they have a problem