PROBLEM: Black screen of death on a Lenovo y580 (or probably most of the ideapad Y series since they all use similar bios software) after changing the setting for which video source gets priority (default is "SG").
SOLUTION: Rather than using the vast array of options that rarely work for anyone like heating up your video card by blocking the fan on a pillow for 20 minutes at a time until it "decides" to start working again - after much research I found the solution for setting the modified slv7 lenovo y580 bios back to its defaults in the event that you inadvertently disable your video.
First, press power and immediately hold F2 until your laptop starts beeping, then release. If there is no sound hold it about 45 seconds.
Second, press the following button sequence for 100 extra lives:
left arrow (1x)
down arrow (4x)
At that point the system should automatically shut down and restart. If it does not, the settings may not have been changed correctly but go ahead and manually restart to find out. If you come back to a black screen again try the process over until you're certain that the cause is something other than your bios settings.
This will save you hours upon hours researching CMOS bypass surgeries, blind usb jump drive bios flash procedures, and all those tedious and time consuming processes. I even started questioning whether my keyboard on my laptop worked at one point it got so screwy.
I will add this, if you can use an external monitor and get a signal, do that. Use Fn+F4 to switch to an external signal and that will make your life much easier. Barring that, the above is the easiest solution I was able to track down.
This has come up fairly often, and I've read every post I can find trying to fix it but with no positive results so far.
I've got a lenovo y580, running a modified svl7 bios. I accidentally changed the video setting that was set to "SG" to some other setting, unsure what. Now I can't get a response from the laptop other than from the power button which simply lights up, but no other indications of life show any more. Early on there was a point at which I pressed some button combo and heard loud beeps, but that has not recurred. I've tried the typical blind default reset method (left, 4x down, 4x enter) which didn't help. I cannot access the computer remotely when it's been powered on which makes me believe that it is not moving past the bios to windows. (no ping response or net view access) I have been unsuccessful in getting an external display to work on the HDMI or VGA ports (though I am going to try VGA again to be sure).
Most of the advice I've found says to unplug everything from the system (wifi adapter, HDD, SSD, Optical,etc.), insert a usb stick with various ROM/BIN files conforming to a particular name variant depending on your model, and to hold Fn+B continuously just after inserting power cord w/o battery installed and hit the power button. The 1 time I've tried this, I had copies of the bios w/ extentions .bi .bin .rom .fd with prefixes QIWY3207 or just QIWY3 (which was the suggestion from Andy's phoenix tool that was part of the instructions).
If anyone sees a mistake I've made along the way, another method to try, or just knows the key pattern to reset the modified svl7 y580 bios to default I would really appreciate the help. I'm looking forward to buying another laptop about as much as choking down a bag of cement.