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Here is our setup

  • Outlet in older house that was replaced with a GFI last year. (no issues until recent)

  • The GFI doesn't have a ground wire running up from the basement. Just the white and black wires. (From my understanding this is an acceptable configuration)

  • The outlet reads 119.0v when checked with my multi-meter.

  • The outlet reads less than a volt when the "positive" line and the ground are checked with the multimeter. Same with the "negative" with the ground.

  • A (real) surge protector plugged into the outlet

  • A large tv plugged into the surge protector

  • A cox cable box plugged into the surge protector

  • A coax cable (run by cox) from the outside of the house, split and sent to a modem and the cable box. The coax reads 0v (no leakage at all) when a multimeter is placed on the inner coax wire and the outer shielding. I tried this on both DC and AC settings on multimetter

The problem:

When either a coax cable or HDMI cable is run from the cable box to the TV, an Arc appears. This has already fried one TV.

My theory:

The coax cable is improperly grounded. I just need a way to prove it. The basis for this theory is the coax cable in a separate apartment tests with an AC voltage of 1.5v. The cable technicians are somehow less informed about circuitry than me. This is a hobby for me so I am lost in the sauce. Any Ideas?


So I took the time to diagram what I have observed. This further supports my theory that the cable isn't grounded properly. I'm not 100% sure how coax is supposed to be run from a telephone pole though so I could be incorrect.

Just in case there is confusion, no the neutral is not plugged into the ground. I was just demonstrating that there is only two wires going to the GFI.

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marked as duplicate by Niall C. Sep 15 '14 at 4:03

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

migrated from electronics.stackexchange.com Sep 14 '14 at 21:48

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  • What is the voltage between the coax shield and ground? – Ignacio Vazquez-Abrams Sep 14 '14 at 20:17
  • @IgnacioVazquez-Abrams if you are talking about the one at the cox exterior box, I didn't test it. I didn't want to mess with their stuff in case it was screwed up so they couldn't blame it on me. – Anthony Russell Sep 14 '14 at 20:25