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?
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.
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.
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.
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.
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.
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.
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!
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.
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.
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.
