I am plugging my TV into a grounded outlet. When I plug an HDMI cable into the back of the TV and measure the voltage coming out of the other end of the cable (should be 0 shouldn't it?) it reads 380 volts…
I'm talking to my landlord about this but this is absolutely not normal is it? If so, what could be causing this? It happens with other outlets as well.
UPDATE
PAST INFO:
When the first Comcast guy came and tried to install the X1 box, he got a little shock while trying to connect the two. He told me that the outlet I was plugging them into was reversed wired. The landlord fixed this and I confirmed that he did with a plug in tester. After this, Comcast came back and tried to install it again, same sparking issue.
I had two TVs with this problem
- TV #1 (3 pronged) was in my bedroom and was plugged in, and hooked up to a Comcast Digital Receiver with an HDMI cord. Worked perfectly. When I moved it into my living room and tried it with the Comcast X1 HD box, it created sparks when I tried to connect the two with an HDMI. The Comcast technician verified that no foreign voltage was coming out of the box or the HDMI from the box. He also replaced the box and the box's power supply. So this happened with two comcast boxes Could it be the Comcast box?
- TV #2 (3 pronged) was always located in the living room and created sparks after I plugged in the Comcast X1 box (both of the boxes).
NEW INFO: The two TVs that had high voltage coming from the HDMI cord that was plugged into the back of them had one thing in common. The power cords for those TVs had a ground on them (3 prong). My landlord brought his TV over and tested it and it worked. His TV has 2 prongs. I just bought a new TV and had an electrician come and we tested it, it worked. My new TV has 2 prongs. Could the three prongs be a problem with something?
My landlord used a Digital Volt Meter and had it set to the vAC option when it read 300+.
Best Answer
You mention that there were sparks and a concern about your ground, I'd check for an incorrectly wired outlet as a precaution. The initial check is a simple outlet tester. These have 3 lights and quickly identify a hot ground or swapped neutral/hot, along with other common issues.
What they can't identify is if there's voltage on both the neutral and ground, for that, you'll need a known good ground and a simple voltage tester. For a known good ground, you can find some plumbing lines that are grounded, or perhaps the ground rods that the panel connects to, but a really easy way is to plug a long extension cord into a friendly neighbor's house and use the ground pin (in your case, the bedroom is probably a good ground). Check if there's voltage between the known good ground and your ground, or your neutral.
Since you're seeing actual sparks, I'm going to rule out phantom voltage from running an hdmi near electrical wires. And since the problem happened after you moved the TV, either the TV was damaged in the move, or it's another device that you added to the mix. Start with the outlet to be safe, but if that's not the problem, you likely had a faulty device. Given the reading of over 300V, I'm guessing that it was a faulty device. A hot/ground short would usually trip a breaker (unless it's not really grounded) and only read 120V.