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Old 08-13-2019, 11:09 PM
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Anyone know much about how DISH equipment works?


First off, I'm not asking for repair advice. The repair has already been made, but the tech said some things that don't make much sense to me.

The dish antenna is attached to the roof and coax cables descend down the wall to what appears to be a splitter. Cables then come out of the splitter and go to the various TVs throughout the house. The problem: our entire system stopped working. The tech says that our dogs chewed through the cables and, in so doing, ruined the LNB and the Hopper3, which is brains of the whole system. The tech replaced those two pieces of equipment, replaced the damaged coax cables, and rerouted the new cables out of reach of the dogs. I am not actually at home -- I work more than 500 miles from my house. I haven't actually seen the damage or the repair. Nevertheless, repairs were made and everything is back in order.

Here is what I don't understand. The dogs chewed through cables (presumably). Damaging the cables would interfere with the signal between the LNB and the DVR. But, how could chewing the cable damage those components? Sure, it would make them not work properly, but I don't see how they could actually require replacing the DVR and the LNB. Furthermore, the tech remarked to my son "You're lucky to still have dogs." He said that those cables carry a lot of electricity. I've never heard of a coax cable carrying enough power to hurt anyone. My dogs are chihuahuas and dachshunds. They're not the biggest dogs, but they're substantial, healthy dogs. How could a coax hurt the dog (with electricity)?

When we first encountered the problem, I called tech support. They worked their magic and determined that the Hopper3 DVR was working correctly and that it was communicating properly with the LNB. The guy on the phone said that something must have moved the dish -- wind, a bird crashing into it, etc. Or, the dish wasn't properly tightened when installed. He was certain that all the equipment was functioning properly and that the dish was simply not seeing the satellites. This does not jibe at all with the tech saying that dogs chewed through the cables. In fact, during this outage, the DVR continued to allow us to play recorded programs (including on my AppleTV using the DishAnywhere app 500 miles away). The DVR also allowed my wife to view Netflix using its app.

Anyone in the know have any thoughts about this tech that came out today?
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Last edited by Drum God; 08-13-2019 at 11:13 PM. Reason: Fixed typo.
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Old 08-13-2019, 11:23 PM
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That tech is an idiot. The only usual household cables with enough juice to fry a critter is the mains. And MAYBE the speaker cables if you have a massive amp that is on at the time of chewing.
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Old 08-13-2019, 11:25 PM
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I don't know about DISH, but I do know that Directv systems do send power from the DVR receiver to the LNB, as the LNB needs power in order to process multiple channels and send them over a single cable as discrete signals (maybe it's called multiplex? My older DRV had two tuners, and required a separate cable for each channel). I'd image DISH works similarly. As for the amount of electricity, it is about 24 volts or less, and probably not much amperage.
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Old 08-13-2019, 11:26 PM
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First, some low-hanging fruit.

Co-ax cables do not carry high voltages; they carry low voltage RF signals.

Did the repair also include repositioning the dish?

ETA: Thanks Dag Otto

Last edited by Leaffan; 08-13-2019 at 11:28 PM.
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Old 08-13-2019, 11:31 PM
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Originally Posted by Leaffan View Post
First, some low-hanging fruit.

Co-ax cables do not carry high voltages; they carry low voltage RF signals.

Did the repair also include repositioning the dish?

ETA: Thanks Dag Otto
I wasn't there, so I didn't witness the repair. I don't know if he did anything to the dish itself. But supposing the dog chewed through the cable and his saliva somehow shorted between the outer net and the center conductor, I don't see how that could fry another piece of equipment. It certainly would sever the connection between the DVR and the LNB, but I can't see how they would have been damaged. All power is inserted inside the house away from where the dogs can access it.
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Old 08-13-2019, 11:40 PM
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Dag Otto is correct, the LNB is powered from DVR. Given that information, I can certainly now see how these components got fried shorting the inner wire to the braided ground.

I think you're at their mercy now.
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Old 08-13-2019, 11:46 PM
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Originally Posted by Leaffan View Post
Dag Otto is correct, the LNB is powered from DVR. Given that information, I can certainly now see how these components got fried shorting the inner wire to the braided ground.

I think you're at their mercy now.
Power through coax? Like 120vac?
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Old 08-13-2019, 11:51 PM
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Power through coax? Like 120vac?
No, low voltage DC, like 3 - 14 Volt kinda range, from what I can see.
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Old 08-13-2019, 11:55 PM
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No, low voltage DC, like 3 - 14 Volt kinda range, from what I can see.
Ah, ok. That still won't fry a critter tho. That's putting your tongue on a 9v battery.

But yeah, *maybe* it could fry a chip.
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Old 08-14-2019, 08:17 AM
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The CoAx has an inner conductor and an outer braid that are separated by insulation. There's also one or more foil shielding wraps over the braid and under the outer jacket. There may also be another shielding braid over the foils. If they chewed the cable between the splitter and the LNB it's likely the power supply in the splitter was damaged.

Coax
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Old 08-14-2019, 08:55 AM
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Co-ax cables do not carry high voltages; they carry low voltage RF signals.
Coax in home satellite systems like OP's doesn't carry high voltage but coax used in transmitting can and does.
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Old 08-14-2019, 10:10 AM
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Originally Posted by jnglmassiv View Post
Coax in home satellite systems like OP's doesn't carry high voltage but coax used in transmitting can and does.
That's true of course. And the voltage varies along the length of the cable run.

Last edited by GaryM; 08-14-2019 at 10:10 AM.
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Old 08-14-2019, 10:40 AM
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Thank you all for the discussion. It sounds like the dogs could have damaged the DVR and LNB if they chewed through the cable that carries power up to the dish. However, that electricity is not enough to have harmed the dogs. My son told me this morning that he did see cables that were chewed. Of course, that damage may have come in the TWO WEEKS between the time I called for service and the time the tech actually arrived.
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Old 08-14-2019, 06:29 PM
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I'm just amazed that the Hopper isn't able to withstand even a dead short on the coax. Sounds like another case of the old electronics joke about how a $300 picture tube will protect a ten cent fuse by blowing first.

Never mind dogs - it's not exactly rare to have a single stray bit of the shield braid or foil touch the center wire at a connector.

Also weird that the cable damage apparently cooked the LNB. Guess I'll keep paying for that "Dish Protect" as it's cheaper than fragile satellite hardware!
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Old 08-14-2019, 06:55 PM
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No, low voltage DC, like 3 - 14 Volt kinda range, from what I can see.
A long time ago I fried ECL chips with 12 volt power supplies when I connected power as the data sheet said, the data sheet being wrong. You don't need high voltage to fry silicon.
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Old 08-14-2019, 07:27 PM
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A long time ago I fried ECL chips with 12 volt power supplies when I connected power as the data sheet said, the data sheet being wrong. You don't need high voltage to fry silicon.
For about 7 years of my career I was involved in semiconductor qualification, manufacturing, test, and failure analysis. I've seen quite a number of blown I/Os due to electrical over-stress.

Last edited by Leaffan; 08-14-2019 at 07:28 PM.
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Old 08-14-2019, 07:48 PM
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For about 7 years of my career I was involved in semiconductor qualification, manufacturing, test, and failure analysis. I've seen quite a number of blown I/Os due to electrical over-stress.
Remember the "good old days" of 7400-series TTL chips? Those rascals had an insanely tight Vcc tolerance. Five volts, plus or minus, well, pretty much nothing - 5.5v would kill them.
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Old 08-14-2019, 09:43 PM
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Remember the "good old days" of 7400-series TTL chips? Those rascals had an insanely tight Vcc tolerance. Five volts, plus or minus, well, pretty much nothing - 5.5v would kill them.
That depends a lot on the specific logic family you're using. The 74LS series stuff (still popular today) is a lot more tolerant of aberrant input voltages. Still anything above ~8-10v or so will probably fry it after a little while.
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Old 08-15-2019, 11:15 AM
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If you're using a chip or any component that is so sensitive to fluctuations, wouldn't you install a component ahead of it to regulate the voltage?
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Old 08-15-2019, 12:15 PM
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If you're using a chip or any component that is so sensitive to fluctuations, wouldn't you install a component ahead of it to regulate the voltage?
Yes, they are called (wait for it...) Voltage Regulators.

Almost all circuits use one or more of them, but sometimes one is tempted to use a battery, and skip the regulator. This can work, but its iffy. Also, some circuits are “mixed signal” and have ICs of one supply voltage connected to ICs of a different supply voltage. This can result in failures unless some care is taken in the design.

Also, voltage regulators can fail, and apply too much voltage to the circuit.
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Old 08-15-2019, 12:36 PM
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If you're using a chip or any component that is so sensitive to fluctuations, wouldn't you install a component ahead of it to regulate the voltage?
Yep. It is bad neglectful design to have a box be unprotected from shorting on a coax cable that runs out to an environment where it is commonly cut/stripped/trimmed/kinked/stepped-on/chewed-on, etc. Overvoltage from a lighting strik or something more severe? Sure, maybe. But self-shorting? Fuhgeddaboutit, the engineer should be demoted to the 9-volt battery tongue-testing QA division.
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Old 08-15-2019, 01:28 PM
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Fellow I knew related the story - he was helping his friend , they were in the garage when the dog in the back yard started barking, then the phone rang. Funny thing is, not long after - same thing. The dog barked then the phone rang. By the third time, he went out to see. The guy had put the dog's chain in a loop over the telephone wire across the back yard so the dog could run back and forth. Over time the insulation wore off, every time the phone rang the dog got a 48V buzz to ground through his collar. His friend said..."If you ever tell anyone about that I'll kill you." But, he's still alive.

The key test of "were you ripped off?" Did the repair guy leave you the dead components? I don't know enough to say whether the situation could have fried those pieces. I could imagine a very convoluted short during a chew cycle, where the voltage is fed backwards into the components - voltage to ground and ground to voltage; that might do it.

Last edited by md2000; 08-15-2019 at 01:28 PM.
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Old 08-15-2019, 03:28 PM
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Fellow I knew related the story - he was helping his friend , they were in the garage when the dog in the back yard started barking, then the phone rang. Funny thing is, not long after - same thing. The dog barked then the phone rang. By the third time, he went out to see. The guy had put the dog's chain in a loop over the telephone wire across the back yard so the dog could run back and forth. Over time the insulation wore off, every time the phone rang the dog got a 48V buzz to ground through his collar. His friend said..."If you ever tell anyone about that I'll kill you." But, he's still alive.
Now that's a great story!
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Old 08-15-2019, 04:19 PM
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In fact, during this outage, the DVR continued to allow us to play recorded programs (including on my AppleTV using the DishAnywhere app 500 miles away). The DVR also allowed my wife to view Netflix using its app.

Anyone in the know have any thoughts about this tech that came out today?
Other people have covered electrical current on the coax cable. In my old setup there was a power supply that plugged into the wall that sent power over the coax cable up to the LNB.

The Netflix and DishAnywhere are going to depend on your DVR's internet connection, not on it's satellite connection. If the satellite connection is messed up, for whatever reason, then you should be able to still watch recorded shows. As long as your DVR has internet, then you should also be able to use the streaming services which stream to or from the DVR over the internet. Some streaming and on demand things may come over the satellite, but those are most likely limited to pay-per-view type programming, and would not work if the satellite signal was down.
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