Screen goes black but PC is still running.

Oct 14, 2018
I've got this build for about a month or two now, and everything has been working just fine, until today my screen has started going black at random times when playing a game.

My specs:
Gigabyte G1.Sniper B6
Intel i5-4460
2x8GB DDR3 1600Mhz
be quiet! System Power 7 400W

The first time this happened it wasn't actually an entirely black screen, there was a horizontal white line and some colored dots above it. I've got an old monitor so I thought it might've finally been time to say goodbye.
I couldn't do anything but force shutdown my pc.
However when booting up it showed me the screen to enter my BIOS, and that did work, but launching into Windows showed me that same black screen with a white line and some colored dots.
After 1 or 2 more reboots I managed to get back into Windows, and everything seemed to work like it used to.

Until after an hour of gaming, when my screen went entirely black. I heard a Windows error sound, and I could still hear everything else what was going on like my music, game sounds and discord. All the fans were still running at the normal speed, but I couldn't do nor see anything. (in Discord I use Push-To-Talk, my friends couldn't hear me speaking anymore after my screen turned black)

At first I thought it might have been my GPU overheating, but I tried to play a game again while watching the temperatures, and my GPU was only at around 70C, CPU at around 45C. (Both loads 100%).

Did some stress test with FurMark, GPU temp went up to about 80C but nothing happened there.
I'm not overclocking anything.
Most of the parts I got second hand, but everything was cleaned thoroughly and I also recently cleaned it myself, so I'm guessing dust can't really be the issue here either.
Oct 14, 2018

I did a little research, and I thought it might be the PSU indeed, but shouldn't my pc shut down completely if it doesn't get enough power from the PSU?

However, what I got from the calculators is indeed what you said, that I might need more than 400W. It says my rig would use about 360W-370W, recommended is about 415W-420W.


Not necessarily. PSU's provide different voltages to different components. So an output failure on one voltage could cause power loss on one computer component and take down the entire system. But other components (e.g. fans) could continue spinning happily along and LED's light up, etc...

Here are a couple of suggested links to read:

You can find many more with just a google or two.

If you decided to do some PSU testing on your own be very sure to read and follow the safety warnings and cautions.

You can damage the system and it is all too easy to get shocked and hurt or worse.

Get someone knowledgeable to help you if you are at all uncomfortable about doing any testing on your own.

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