I had a power surge at my home this weekend due to lightning. I was not home at the time, so I do not know exactly how close the lightning was. I did have to reset some circuit breakers. I can't find any evidence of a lightning strike on my house, or the trees or ground anywhere around my house. It knocked out my main TV, video player, and cable box (the coax cable is still working). I have a secondary TV hooked up to cable, and it no longer receives the cable signal. The TV is not damaged, because it works when I hook it up to a different cable outlet. I replaced the splitter box, but that did not help. That seems to mean, that the coax cable itself is "fried". It seems impossible, to me, that the coax cable would be "fried" and the TV would still be OK. I am confused. Is coax cable easy to "fry" if there is a power surge? Thanks for any input.
Coax Cable Question
- Thread starter Wingman
- Start date
- Status
TV coax cable is pretty weak stuff- it has a foam core, and its not good for very high voltage. A small arc- not enough to pierce the outer jacket, can still create an RF short circuit between the center conductor and shield.
I agree its hard to imagine the TV surviving but the cable dying... but lighting does some very strange stuff. If you've ruled out everything but the cable, its probably the cable!
I agree its hard to imagine the TV surviving but the cable dying... but lighting does some very strange stuff. If you've ruled out everything but the cable, its probably the cable!
Originally Posted By: 440Magnum
TV coax cable is pretty weak stuff- it has a foam core, and its not good for very high voltage. A small arc- not enough to pierce the outer jacket, can still create an RF short circuit between the center conductor and shield.
I agree its hard to imagine the TV surviving but the cable dying... but lighting does some very strange stuff. If you've ruled out everything but the cable, its probably the cable!
Exactly this happened to me at my old house. A short was caused between the metal cable at the core and the grounding sheath which surrounds it. It caused the cable to stop working. TV was fine. Took days to figure it out, and it was a total pain to find and replace because it ran through several walls. Bummer, sorry man. But this does happen.
TV coax cable is pretty weak stuff- it has a foam core, and its not good for very high voltage. A small arc- not enough to pierce the outer jacket, can still create an RF short circuit between the center conductor and shield.
I agree its hard to imagine the TV surviving but the cable dying... but lighting does some very strange stuff. If you've ruled out everything but the cable, its probably the cable!
Exactly this happened to me at my old house. A short was caused between the metal cable at the core and the grounding sheath which surrounds it. It caused the cable to stop working. TV was fine. Took days to figure it out, and it was a total pain to find and replace because it ran through several walls. Bummer, sorry man. But this does happen.
Can you see if the lightning surge protector on the building was fried? - IIRC COMICAST has one on the feed from the pole to the house with a GND tie in on the house. Do you havbe any channels FCC mandate analogue or digital local news channels for EBS? I get nothing unscrambled with a straight cable these days - but I don't have a ATSC capable digi tuner built in to my ancient Panasonic Superflat.
The strength or weakness of the coax is pretty much irrelevant. You need to make sure you have proper grounding where the cables enter the house. Sounds like the lightning energy came in through the coax and damaged the cable box, leaving through the AC panel ground which was probably what tripped your breakers.
I don't know about your location, but lots of the cable installs I've seen are really [censored] about grounding, some of them downright scarey. Some don't have it at all, others have little tinker-toy 4' ground rods, and some aren't bonded to the AC panel ground.
All grounds *must* be bonded to the AC panel ground. Find that, and make sure your cable entrance ground has a wire going to it with a good mechanical connection (ie, not soldered, or attached with a rusty hose clamp).
Don't stop with your cable TV ground though--you also should verify your telephone box and any other external services are bonded to the AC ground as well. Today lightning energy got into your house via your cable, but tomorrow it could be through the phone line, and next week it could be through that external AM/FM radio antenna you might have on your roof (probably not, but you get my point).
If you feel like you're in over your head, or just don't feel confident to do it yourself, it's *always* worth it to pay a licensed electrician for an hour or two of their time.
Mike
I don't know about your location, but lots of the cable installs I've seen are really [censored] about grounding, some of them downright scarey. Some don't have it at all, others have little tinker-toy 4' ground rods, and some aren't bonded to the AC panel ground.
All grounds *must* be bonded to the AC panel ground. Find that, and make sure your cable entrance ground has a wire going to it with a good mechanical connection (ie, not soldered, or attached with a rusty hose clamp).
Don't stop with your cable TV ground though--you also should verify your telephone box and any other external services are bonded to the AC ground as well. Today lightning energy got into your house via your cable, but tomorrow it could be through the phone line, and next week it could be through that external AM/FM radio antenna you might have on your roof (probably not, but you get my point).
If you feel like you're in over your head, or just don't feel confident to do it yourself, it's *always* worth it to pay a licensed electrician for an hour or two of their time.
Mike
Lightning can do some very bizarre things.
In another life, I was a cable TV service tech and over the years saw every possible scenario. I remember one house that was not directly struck, but a tree in the back yard was. It took out TVs, air conditioners, his refrigerator, and a couple of cable set-top boxes. There were even electrical wall outlets that were literally blown apart...the wiring was still there but the outlet and cover plate were shattered. None of the coax in the home was damaged, but the underground drop was burnt through in the middle between the pedestal and the house.
In another life, I was a cable TV service tech and over the years saw every possible scenario. I remember one house that was not directly struck, but a tree in the back yard was. It took out TVs, air conditioners, his refrigerator, and a couple of cable set-top boxes. There were even electrical wall outlets that were literally blown apart...the wiring was still there but the outlet and cover plate were shattered. None of the coax in the home was damaged, but the underground drop was burnt through in the middle between the pedestal and the house.
Make sure its properly grounded with a grounding block.
The highest voltage I've ever seen pushed down Coax is on DirecTV's SWM LnB which uses a 29v or ~31v DC power inserter.
And that would only be down one Section.
This doesn't mean you can't have neutral issues
Like this poor dude did, luckily it was caught before anything bad happened.
http://www.dslreports.com/forum/r29133406-Connectivity-Coax-cable-on-street-box-keeps-MELTING
The highest voltage I've ever seen pushed down Coax is on DirecTV's SWM LnB which uses a 29v or ~31v DC power inserter.
And that would only be down one Section.
This doesn't mean you can't have neutral issues
Like this poor dude did, luckily it was caught before anything bad happened.
http://www.dslreports.com/forum/r29133406-Connectivity-Coax-cable-on-street-box-keeps-MELTING
Since you guys were so good at answering the original question, let me ask one more. I have six digital "Atomic" clocks (clocks that receive the time via satellite signal). They are battery powered, and hung on various walls throughout the house. As a result of this electrical event, three of the clocks were "knocked" offline. Two recovered on their own, and the other recovered after I reset it. How can a battery powered clock be affected???
If your cable tv isn't working, call your cable provider before an electrician. This is usually something they will look at and fix for free. Especially since it isn't anything you did, lightning is out of your control. If coax needs replaced they will generally replace it. It could also be a blown CPE amp or splitter from the surge. Call them before you pay out of pocket for an electrician.
Originally Posted By: Wingman
Since you guys were so good at answering the original question, let me ask one more. I have six digital "Atomic" clocks (clocks that receive the time via satellite signal). They are battery powered, and hung on various walls throughout the house. As a result of this electrical event, three of the clocks were "knocked" offline. Two recovered on their own, and the other recovered after I reset it. How can a battery powered clock be affected???
EMI pulse. All electrical sparks produce radio waves. Lightning, being a very large spark, produces strong radio waves (Electro Magnetic Interference pulse). Think about the crashing of static on AM radios when a lightning storm is near, if you're old enough.
The electromagnetic wave, as it passes through conductors induces voltages, just like a radio antenna. The circuit boards inside your "Atomic" clocks have conductive traces attached to sensitive electronics. As the electromagnetic wave passed through the clock, it induced all sorts of weird voltages in the circuit and caused the microprocessor to lock-up. Simple, eh?
Since you guys were so good at answering the original question, let me ask one more. I have six digital "Atomic" clocks (clocks that receive the time via satellite signal). They are battery powered, and hung on various walls throughout the house. As a result of this electrical event, three of the clocks were "knocked" offline. Two recovered on their own, and the other recovered after I reset it. How can a battery powered clock be affected???
EMI pulse. All electrical sparks produce radio waves. Lightning, being a very large spark, produces strong radio waves (Electro Magnetic Interference pulse). Think about the crashing of static on AM radios when a lightning storm is near, if you're old enough.
The electromagnetic wave, as it passes through conductors induces voltages, just like a radio antenna. The circuit boards inside your "Atomic" clocks have conductive traces attached to sensitive electronics. As the electromagnetic wave passed through the clock, it induced all sorts of weird voltages in the circuit and caused the microprocessor to lock-up. Simple, eh?
Nick,
Thanks for the advice. The cable guy (not Larry, I hope) will be here tomorrow.
Rick,
Thanks for giving me some understanding on this event. I really wish I had been here when it happened. Perhaps that would have given me a better understanding of what actually occurred. I still have not found any evidence of a lightning strike anywhere around here.
Thanks for the advice. The cable guy (not Larry, I hope) will be here tomorrow.
Rick,
Thanks for giving me some understanding on this event. I really wish I had been here when it happened. Perhaps that would have given me a better understanding of what actually occurred. I still have not found any evidence of a lightning strike anywhere around here.
Regarding my original question about coax, I have some results. I had three TVs hooked up to coax cables when the electrical event occurred.
TV#1 - TV burned out, coax cable OK.
TV#2 - TV OK, coax burned out.
TV#3 - TV OK, coax OK.
I guess lightning is a fickle thing.
I still have not found where lightning actually struck. Thanks for all who shared their knowledge. I am back up and running except for the dead TV.
TV#1 - TV burned out, coax cable OK.
TV#2 - TV OK, coax burned out.
TV#3 - TV OK, coax OK.
I guess lightning is a fickle thing.
I still have not found where lightning actually struck. Thanks for all who shared their knowledge. I am back up and running except for the dead TV.
Put a spike arrester (SIDACtor - Holland Electronics makes a decent one) right at the coax drop, and then isolators at each device. Don't use cheap consumer grade stuff.
Most cable providers won't give you any of those. The isolators will also stop any ground loop issues. Be aware of attenuation and reverse signal factors if you are running some STBs.
Strange that it reached the TVs, as Comcast out here requires a STB for service, which should take the hit first.
It's possible that the TV got fried on the mains side. That's an entirely different transient protection scheme. A good AC transient implementation starts before the service panel.
Of course, none of this matters much where a DIRECT hit takes place.
Most cable providers won't give you any of those. The isolators will also stop any ground loop issues. Be aware of attenuation and reverse signal factors if you are running some STBs.
Strange that it reached the TVs, as Comcast out here requires a STB for service, which should take the hit first.
It's possible that the TV got fried on the mains side. That's an entirely different transient protection scheme. A good AC transient implementation starts before the service panel.
Of course, none of this matters much where a DIRECT hit takes place.
Originally Posted By: Volvohead
Put a spike arrester (SIDACtor - Holland Electronics makes a decent one) right at the coax drop, and then isolators at each device. Don't use cheap consumer grade stuff.
These?
http://www.techtoolsupply.com/ProductDetails.asp?ProductCode=SA-1F
http://www.techtoolsupply.com/ProductDetails.asp?ProductCode=CISP
Put a spike arrester (SIDACtor - Holland Electronics makes a decent one) right at the coax drop, and then isolators at each device. Don't use cheap consumer grade stuff.
These?
http://www.techtoolsupply.com/ProductDetails.asp?ProductCode=SA-1F
http://www.techtoolsupply.com/ProductDetails.asp?ProductCode=CISP
That spike arrester is a good one, and there are four or five other vendors of basically the same thing. The gas tube ones can degrade over time. These types won't.
The isolator can be kept more simple, though.
You don't want too much insertion loss through the run.
A simple inline barrel type usually suffices.
I usually just drive over to these folks and pick up what I want:
http://www.tonercable.com/
The isolator can be kept more simple, though.
You don't want too much insertion loss through the run.
A simple inline barrel type usually suffices.
I usually just drive over to these folks and pick up what I want:
http://www.tonercable.com/
High voltage will break through at the weakest point. While I don't have any experience with burnt out coax, I'd check the connectors carefully. This is where the insulation between the center conductor and shield is "interrupted". It may have flashed over there and with a bit of luck, cutting back the coax and re-terminating may be what's needed.
- Status
