Can a current be induced in an HDMI cable that runs parallel to a 120v AC cable for 15 feet?

Question

I just went to go unplug an HDMI cable and got shocked from the end of it! The only possible causes of this that I can think of are that the receiving or sending end of the long (50ft) HDMI cable is introducing a live current into the line, or that an electrical current is being induced in the HDMI cable because it runs side by side (parallel) to a 120v AC extension cable for 15 feet.

Should I be concerned? What are the first steps I should take to diagnose this?

For reference, there was a Sony PS3 connected to one side, and an HDMI Splitter to the other end (http://smile.amazon.com/dp/B00B46XUQU)

If you need any clarification, please don't hesitate to ask!

Answer 1

The coupling could result from a Y-capacitor in the HDMI switch power supply. A Y-capacitor is placed between L-GND and N-GND and often used to filter out common-mode noise and to establish a common ground reference (with respect to "earth").
If the outlet / plug does not provide proper grounding (only N and L connected) and you touch GND on the HDMI cable, there might be a small current between flowing from L-GND-YOU-EARTH. Y-capacitors are tested to applicable standards to qualify them as safe. They never fail as "short" and there are typically only a few uA flowing, but it is enough to feel a tickle.

Answer 2

It's not likely that a 120v power cord induced a significant voltage in the HDMI cable. Voltage induced by wire A in a wire B is proportional to the amount of current flowing in wire A and is transferred by the magnetic field. However your power cord has both hot and neutral lines, and they carry (nearly) the same amount of current in opposite directions. This means the magnetic field is cancelled out, except for minute variances between the current in the lines.

What's more likely is that device on the other end is badly designed so that it's not grounded, not properly isolated from the HDMI plug or broken/damaged.

Since you are unplugging the cable, is it safe to assume that it's still connected at the other end? Was it the PS3 or another device?

Answer 3

If it is 50 feet long and you are using devices fed from different circuit breakers or from a circuit supply a lot of power to other devices, it is more likely that "ground" is not the same at the two ends of the cable. A current carrying wire can not be at ground potential and inside buildings the neutral wire can vary in voltage from place to place depending on loads. I have seen as much as 40 volt difference in large buildings. It can be quite dangerous to run long extension cords and cables that connect to power sources on different circuits. This is why there have been standards for ages that say doorbells are run from low voltage isolation transformers.

Check with a voltmeter to see the difference between the neutral side of the outlet (I'm talking U.S.A. here) which is the wide slot and earth ground which is the round hole - and should not be carrying any current. It is there in case of a short so the circuit breaker will blow, instead of you or a fire. If it is old and there is no ground plug, the screw that holds the plate might be grounded.

Of more interest is exactly how did you get the shock? What else were you touching? What is the floor material and did you have shows on?

Answer 4

It didn't harm you so that is good but, does it suggest a darker and more serious problem that could be classed as potentially life threatening?

My belief is that the power source that caused the "tingle" is a switched mode power supply and a little bit of AC current is leaching thru the EMI reduction capacitors. If it is this it is quite common and not dangerous but it ought to be a small wake up call for you to double check this by seeing if touching either of the wall wart's dc wires can produce a similar effect. If it does then I'm fairly convinced that all is well.