I recently bought a new laptop, and was finally ready to wrap up the long-delayed transition from my aging desktop PC. I wanted to connect my 19″ Samsung monitor as an external display, so I plugged it in, set up the resolution and refresh, etc., and immediately noticed some serious horizontal flickering. I suspected the video card, so I began to fiddle with the display settings in Windows 7’s control panel (which is rather nice, and very reminiscent of Ubuntu, actually). But nothing I did made any difference, so I started Googling.
As it turns out, this problem affects laptops generally, and is due to something called a “ground loop”. Basically, the flickering is a visual symptom of signal noise traveling along the ground circuit. The solution? Well, reducing the signal noise in the ground circuit isn’t easy, but removing the monitor from the circuit is – the fastest fix is to unplug your monitor and tear off the ground prong from the plug with a pair of pliers. I did this, and it almost completely stopped the flickering – to the point that it isn’t discernible under normal conditions.
The post I have to thank for this advice: Ground loop causing flickering in external LCD.