26 November 2014

HDMI monitor blinking (flickering)

I have a dual monitor setup at home, one is connected via HDMI and another one through DVI. A couple days back I noticed that the HDMI monitor was blinking very often, it used to go blank for a couple of seconds but the DVI one just worked fine. According to few forum posts the issue was related to graphics driver but in my case the problem was occurring on both Windows 7 as well as ArchLinux so I ruled out the driver issues, my Arch installation uses open source drivers.

Somewhere it was also mentioned that it might have something to do with "ground loop", you can read more about it on Wikipedia. Then I realized I had recently changed the power cords for the HDMI monitor, and the power cord which was in use did not have an earthing pin (3rd big pin in a plug), it looked like this:

When I replaced the 2-pin plug power chord with a 3-pin plug one (the one with the earthing pin) the blinking problem disappeared. So I guess it was related to earthing but not necessarily to ground loop.