Last night I was using my late 2012 MBP (higher res screen, dual intel/amd graphics), and the screen suddenly went black. I left it go for a minute - no change. I open and closed the lid - it suspended just fine, but opening the lid back up gave me nothing. So, I killed the power.
Turning it back on, the screen now had thin green lines overlayed over the apple logo boot screen. This stays for a moment - until the loading scroll bar reaches about 1/3 to 1/2 of the way across - and then the screen goes grey.
The same thing happens if I try to launch recovery, internet recovery, or diagnostics whatever. Bios shows ok (except the overlayed green lines), and then a grey screen. If I hold option, it will show me disk selection (I triple boot osx/linux/windows). But in all cases, the screen goes grey when I try to select something.
The only thing I was able to get to run was internet based diagnostics. I ran extended tests, and no problems were detected (yeah, right).
I've also tried resetting NVRAM, but it doesn't seem to work properly. Usually it boots, goes bong, reboots, and then loads. Instead, it booted, went bong, and then the screen went grey. It never restarted itself.
At the moment I am pretty sure it's either an issue with the the display cable if I'm lucky, or the dedicated graphics adapter or the motherboard (intel graphics are on-die on the processor) if I'm not. I have NOT tried hooking it up via dongle to an external display to see if the issue exists there as well, I'll try that this evening.
Has anyone else experienced this issue? Any other possibilities I could look into? I'm assuming that a repair at the apple store will be prohibitively expensive.