Question Mysterious lack of anything on monitors after power outage


Aug 24, 2013
My two monitor Linux desktop computer was running fine this morning. Then the power went out due to thunderstorms. I have a hefty UPS, enough to keep it going for maybe an hour. I continue on for several minutes, taking no special action in case it's a brief outage. Nope. I save all important data, close certain applications, and as the outage continued, did a proper power down, with "sync" (if that actually does anything these days), exit the windows manager and "shutdown now".

Also, being a bit paranoid when it comes to expensive essential tools, I unplug the UPS from the power outlet. Monitors, speaker system, USB gadgets and anything else are all plugged into the same UPS, and it was no longer plugged into any external source of power. The network cable goes to another room, to a router, and that gets its power from a power strip. That was plugged into the same outlet as the UPS, but I took that out too. Everything plugged into the computer, or plugged into something plugged into the computer, was electrically isolated from the outside power. Computer totally off. The UPS was still running an LED lamp, about 6 watts. I wait.

Outage was maybe eight hours.

I plug the UPS back in, boot up, and see blank screens. Not even a brief BIOS logo. I hear a single short beep, which for a Gigabyte motherboard means "booting up fine". A couple LEDS on the keyboard blink. All is normal except both monitors are blank. I make sure both monitors are plugged in, HDMI cables in the graphics card. From the start of the outage to the end when I tried booting up, I did not touch anything but the keyboard and the power cable to the UPS. I switched one HDMI cable. Swapped cables between the two monitors. I'm using a GTX 1050 card. I try plugging into the motherboard's video - there's DVI and HDMI. Still blank.

I know it's not the MB or hard drive because I can, after a minute, type in my user name and password, hear disk activity (an advantage of spinning disk drives over SSDs), and type in commands like "ls" and "ls images/" and "pacman -Qs x" and hear disk activity of more or less the expected durations. "startx" makes a lot of disk activity, like normal.

I can imagine one cable going bad, or one monitor, even if nothing physical happened to it. But both? And trying both the fancy graphics card and the onboard graphics?

Does anyone have any further diagnostics tests to try? Ideas on what's wrong?