> I even checked my electricity 'pen' reader on an HDMI at work to see if it was the reader. It's not the pen. It's my wires. Ah… there it is. Stop using those

> I even checked my electricity 'pen' reader on an HDMI at work to see if it was the reader. It's not the pen. It's my wires. Ah… there it is. Stop using those; use an actual multimeter. See, the problem with measuring voltage is that you really need two points of reference: you’re really measuring the voltage potential between two separate points. When you say your HDMI is live, what does that mean? Relative to what? Are you talking about the grounded shielding, or one of other conductors? This individual is waving around a no-contact A/C voltage detector. These can be useful indicators in the right hands, but they’re just estimation devices. They’re prone to false positives and negatives. If you wave one near an HDMI or coax cable, there’s a good chance it’s going to beep and turn red. That being said, if you see your lights getting brighter on the regular (rather than dimmer), your neutral is probably going bad, and that can be quite dangerous. Call your electric company and/or an electrician if you see that. It’s not going to stop your coax and HDMI from showing as live when you wave a death stick near it, though; they are live, at least from the perspective of a no-contact voltage tester.