Power surge over HDMI


Old 12-21-17, 07:55 AM
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Power surge over HDMI

I recently had a power surge and everything connected via HDMI was affected. I had a 4x2 HDMI switching matrix, this is how everything was connected.

Stupidly, what was the culprit either was not on a surge protector, was on a cheapie power strip or plugged into a UPS on the surge protect side.

Until I determine what the root case is, should I go with a GFCI, good surge protector, or simply make sure everything is plugged into the ups surge protector?

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Old 12-21-17, 08:02 AM
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A surge protector is a good idea, but they are not a magic bullet. Also there is not much difference internally between middle price models and high-end, so no need to spend too much.

Another course of action is to evaluate your electrical service for proper grounding, good single-point grounding of all other telecom and utilities, and possibly installing a panel-mounted surge protector in your electrical panel. The electrical service should have solid earth grounding, achieved by one or more methods like grounding to metal water service piping, a pair of ground rods or the foundation rebar. All of your other utilities and telecom services should also ground to this same point (single-point grounding) to prevent one signal from having a difference ground level than the others. This is usually achieved by having a grounding block near the electrical meter that all other services bond to via ground wires. Finally, you or an electrician can install a central protector in your electrical panel. These are much more effective than the power strip or UPS models.
Old 12-21-17, 09:26 AM
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With high value electronics, you need to go beyond NEC if you expect protection. Two ground rods may keep you alive in the house, and keep the wiring intact, but can still provide many thousands of volts in unwelcome places.

I can't pretend to detail design you a system from afar, but there are some things that do help every situation.
1. Provide many paths to dirt for a lightning strike. UFER, multiple ground rods, and low Z bonding.
2. Provide coordinated surge protection. At service, at receptable, and at the PCB's.
3. Use optical com in high risk situations.
4. Isolate the high value A/V stuff, using UPS, common grounding, co-located, etc

WHat you show in the pix was the result of a high energy surge. I'm supposing a direct lightning strike to the building or wires going to the building?
Old 12-21-17, 09:53 AM
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As telecom guy said, from the marks, that was definitely more than just a power surge.

Decent surge protectors along the whole system should have at least reduced the surge, though can only do so much for large surges/lightning. What many people miss is surge protecting and bonding the CATV or telephone connections. Lightning will find interesting paths into electrical equipment.

But again, there's only so much you can do to protect against large surges in a residential environment (without spending lots and lots of $$)
Old 12-23-17, 05:24 AM
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With damage like that, it looks like
A) lightning strike, (which, if near enough, can still fry everything due to inductance)
B) cable tv line that touches one branch of a tree which has worn away the rubber insulation and is touching the braided metal,
another branch of the tree touches the local ~15-50 kV supply line, and during downpour or windstorm you get a voltage.spike.
Old 12-23-17, 06:27 AM
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For coax, HDMI, etc. cables coming into the house from exterior mounted equipment or from equipment owned by a cable TV company or other third party, I suggest grounding the shield or plug shell of the cable end. The idea is to not have the interior of the equipment the cable plugs into be the first contact with ground.

For coax cables the plug shell or jack shell is usually well enough exposed for a not too thin wire to be wrapped tightly around. This wire is in turn connected to a (suggest 14 gauge bare) separate equipment grounding conductor whose far end is connected to a known ground. It is better if this EGC daisy chains to or has branch wires (taps) connected to each piece of electronic equipment nearby. Unused jack shells can be used for these connections, or a screw penetrating to the equipment chassis can be used.

In the picture, what was at the other end of the cable that was plugged into the jack nearest the black smudge?
Old 12-23-17, 12:08 PM
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I DO NOT recommend adding random "ground" wires to equipment that does not expressly have a connection marked for a ground wire.

Power surge is a very misused term. It has no real definition. It can mean many different things. The most accurate definition of a power surge is an increase in voltage.

I severely doubt a surge suppressor would have saved your here.

I've been servicing A/V equipment for most of my life and I have seen many problems.
In your case there were two HDMI ports affected. That means there were probably two units also damaged. Your switcher uses a wall wart for power so the chassis of the switcher wasn't grounded from the power line.

I'm guessing one of the units was a TV and if the other was your cable box... a probable cause could have been a lightning related incident. Lightning could have followed the cable line in. Another problem that I've seen happen is one that is harder to prove. A direct short from the AC line to a units chassis. This usually happens in a TV. The high voltage switch supply shorts to the chassis.

I just wanted you be aware so that you can check for hazardous voltages. Check everything using an AC voltmeter from the equipment chassis or some other metal on it to a know good ground.
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