Sparks while connecting coax cable - AVS Forum
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post #1 of 29 Old 01-07-2010, 04:17 PM - Thread Starter
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I was trying to setup my home AV system as follows and came across a problem:

1. I attached a splitter to the incoming coax from Internet service provider.

2. To one of the splitter out, I ran a cable to my cable modem.

3. I screwed in another coax cable to the second splitter out and was TRYING to screw in its other end into the coax jack on my USB TV tuner dongle when there was sparking and the dongle died. It also tripped my fuse. The dongle was inserted into the PC but I had not plugged in the PC to the AC outlet...in fact, there was no AC cord if I remember correctly.

Why would this short occur?

Some more information:
Initially we had only subscribed to Internet service from the provider (Brighthouse) i.e. no cable TV service. However, one day the Internet service went down and the tech came to fix it. He said that he wasn't sure how to fix the REAL problem, but said that he removed the filter and that boosted the Internet signal and AS A CONSEQUENCE we were also getting free basic cable. I was just trying to see if the guy was right by splitting the signal and connecting it to the USB TV tuner.
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post #2 of 29 Old 01-07-2010, 05:19 PM
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Is the modem working okay?

A spark when you touched the cable to the device sounds like there was a DC voltage either from the cable or from the dongle.

Did you notice a spark when connecting the cable modem?
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post #3 of 29 Old 01-07-2010, 07:23 PM - Thread Starter
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Hi!

No, there was no spark while connecting the cable modem and it is working fine. I guess the circuit tripped and so protected everything?

Why would there be DC voltage? What should I do fix this? Is it because the coax cables are not of good quality?
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post #4 of 29 Old 01-08-2010, 05:29 AM
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Is the cable modem working okay?
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post #5 of 29 Old 01-08-2010, 07:35 AM - Thread Starter
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Yes...the cable modem is working okay.
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post #6 of 29 Old 01-08-2010, 09:46 AM
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To recap you have a splitter one leg feeds the modem no issues no sparks.
The other leg was fed to your PC through a usb tuner adapter when you connected it you saw a spark and it tripped a fuse.
You also stated that the PC was not plugged into an A/C outlet.
Are you talking about the house fuse or something else?
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post #7 of 29 Old 01-08-2010, 12:00 PM - Thread Starter
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RCbridge: You summed it up correctly.

I am talking about the house fuse.
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post #8 of 29 Old 01-08-2010, 09:58 PM - Thread Starter
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bump....

any ideas anyone?
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post #9 of 29 Old 01-09-2010, 06:21 AM
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Why not get a multimeter and test each coax and each RF output/input from every device and check for AC/DC voltages? That way you should be able to trace where the power source originates.
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post #10 of 29 Old 01-09-2010, 08:00 AM - Thread Starter
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Thanks for the idea Ratman...

I do have a multimeter but have absolutely no idea how to use it ...or what I should be expecting when I test the things that you want me to test. Do you have a link handy that explains how to use a multimeter? I will also Google it.

Thank you.
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post #11 of 29 Old 01-09-2010, 08:36 AM
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If you blew the house fuse (AC Power), you ought to call in an electrician. And, you might want to get the Cable guy there at the same time.

Ken English, Sr. Engineer, KSL-TV.
"The postings on this site are my own and don't necessarily represent the Company positions, strategies or opinions."
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post #12 of 29 Old 01-09-2010, 08:52 AM
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Quote:
Originally Posted by snortingdonkey View Post

I do have a multimeter but have absolutely no idea how to use it ...

There should be two voltage test settings, one for DC one for AC. There should be two probes, one black, one red.

Set to measure DCVoltage. Black probe to outside of coax connector, red probe to to center pin/conductor. Same for ACVoltage.

There should be no AC voltage at all.
If there is a DC voltage, I would assume if it measures higher than ~18 VDC, that may be a problem also. Don't take my suggestion as gospel as I am not an electrician, but it should give you some indication as to where "power" is being introduced on the cable.

Obvious question not asked:
Is the incoming cable (from cableo) grounded properly?
Is the splitter also grounded?
Where are they grounded? (ground rod, water pipe)
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post #13 of 29 Old 01-09-2010, 09:26 AM - Thread Starter
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Quote:
Originally Posted by Ratman View Post


Obvious question not asked:
Is the incoming cable (from cableo) grounded properly?
Is the splitter also grounded?
Where are they grounded? (ground rod, water pipe)


#1 - I don't know if the incoming cable is grounded...I will try to check and see if I understand...should I be checking at the pole or where it comes into the cable box attached to the outside of my house?

#2 - The splitter is something that I introduced, is inside the house and I haven't done anything other than simply screw in the coax cables....so no ground wire.

Apparently, the multimeters are not working...I had inherited them from someone and never tried them. I am stepping out to get a new one.

More later once I check all the stuff you guys have told me to.

Thanks all.
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post #14 of 29 Old 01-09-2010, 09:27 AM - Thread Starter
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Quote:
Originally Posted by kenglish View Post

If you blew the house fuse (AC Power), you ought to call in an electrician. And, you might want to get the Cable guy there at the same time.

Hi!

Yes, I was thinking of doing that...I will give it a go with the multitesters before I call them.
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post #15 of 29 Old 01-09-2010, 10:58 AM
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Quote:
Originally Posted by snortingdonkey View Post

#1 - ...should I be checking at the pole or where it comes into the cable box attached to the outside of my house?

Typically the incoming coax cable has a ground block where the cable enters your home. The ground should have (usually) a green wire that should (optimally) be connected to an earth ground (used for utilities).

Quote:
Apparently, the multimeters are not working...

Maybe they need new batteries?
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post #16 of 29 Old 01-09-2010, 01:47 PM
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If you are getting voltage between the outer shell of the coax 9from the Cable company) and something grounded in your house, and it's enough to trip a breaker/fuse, it sounds like:
1. The cable is not grounded to your house's ground properly.
2. The house ground/neutral is no where near ground potential, so the current is trying to make it back to the power pole's ground wires.
3. Some jerk has stolen the ground wire off the side of the power pole, and your Cable TV line is acting as the ground for the outside lines now.

Ken English, Sr. Engineer, KSL-TV.
"The postings on this site are my own and don't necessarily represent the Company positions, strategies or opinions."
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post #17 of 29 Old 01-10-2010, 01:39 PM - Thread Starter
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OK..so bought new multimeter (the old ones were definitely kaput)...checked for AC and DC voltage and found that there was NONE. Also went out verified that the cable box outside the house was grounded...all connections seem pretty tight. Also, I bought outlet testers and the outlets are supposedly all good.

I removed all the A/V equipment and began to add one by one. Each time I would test that the USB dongle (I bought a new one too - Happauge 850) was not sparking by inserting it into the USB port of an old laptop that I did not care if it died. But it was fine.

So finally, I tried to insert it into the USB jack on my HTPC, which is a Gateway SX 2000. As soon as I brought the USB dongle (to which the coax was attached) close to the USB port on the Gateway...SPARKS!! The USB port on the computer is all black. Haven't checked if my PC is fried or not....it is still booting...The USB dongle still seems to be alive because when I insert it into the USB port of the old laptop, it recognizes a new device.

Could it be that the Gateway PC is the problem? This is the same machine that had also sparked and died when I tried to connect it to an HDMI switch (see my other thread about this issue --> http://www.avsforum.com/avs-vb/showt...757&highlight=). The funny part is that the Gateway was already connected to the HDMI switch a few months ago and was working fine. But then I had to move it to another room and this issue with HDMI sparking occurred when I was moving it back.

Could it be that the circuit in that room is getting overloaded? Will it do this? I have the following off of two outlets...all devices are plugged into surge protectors and UPS...

SONY GRAND WEGA 51"
DISH Satellite receiver
Pioneer CD changer
Harmon Kardon receiver
Magnavox DVD player
Windows Home Server (come to think of it ...this is a new introduction)
Cable modem
Dlink router
Terk transmitter
HAVA Platinum device
SimpleShare NAS device

Prior to starting what I wrote above, I hooked up the PC to another TV in another room using an HDMI cable and there was no sparking.

Am at a loss now.


UPDATE: I just was pulling the coax cable to unscrew it from the splitter when its loose end struck another piece of metal component behind the DISH satellite receiver...and guess what? SPARKS!!
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post #18 of 29 Old 01-10-2010, 07:25 PM - Thread Starter
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Cable guy coming to check on Tuesday AM.

I just checked and the Gateway is working normally. One of the USB port is all black but it is still working.

Frankly, the only thing I'd like to do with this PC now is to connect it to my TV using HDMI and not have it fry...(HDMI switch from IOGear on its way...should get it next week).
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post #19 of 29 Old 01-11-2010, 05:34 AM
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Odd.
If there are sparks, there's voltage. Hopefully you'll have a competent cable tech.

As kenglish suggested in post #11, I'd try to get an electrician to work with the cable tech.
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post #20 of 29 Old 01-11-2010, 07:37 AM - Thread Starter
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As listed above, there are many devices off the two outlets in that room. If one of them is NOT grounded properly, could this cause the sparks? Is there a way that that I can check every device to see if its ground properly? (I am thinking there is with my multimeter).
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post #21 of 29 Old 01-11-2010, 08:02 AM
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Well... I'd start with checking for a voltage between the cable/USB and the PC since that is the apparent symptom.

If you take the PC to another room and connect the cable/USB, is there a problem? If so... it's the PC and/or cable feed. If not... the it's the power outlet, the UPS, the power strip and or one of the other external devices.

Unfortunately, it's tough to pinpoint your issue sitting in my home.

But! You do have a potentially serious problem. If you want to diagnose yourself, the all I can suggest is to remove/disconnect ALL external components (UPS, surge, AV, etc.) Start with two and introduce one device at a time.

I'm sure a competent electrician could diagnose quicker though. It's worth the $$ as opposed to frying equipment, burning down your home or... electrocution.
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post #22 of 29 Old 01-11-2010, 04:48 PM
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Quote:


UPDATE: I just was pulling the coax cable to unscrew it from the splitter when its loose end struck another piece of metal component behind the DISH satellite receiver...and guess what? SPARKS!!

Clarification please
Satelllite systems do use voltage amplifiers
Is this coax from the Dish

Why are we here, because we're here, Roll the Bones
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post #23 of 29 Old 01-11-2010, 08:50 PM - Thread Starter
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Quote:
Originally Posted by Home2stay View Post

Clarification please
Satelllite systems do use voltage amplifiers
Is this coax from the Dish

Hi!

No, the coax is from Brighthouse for the broadband Internet service.
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post #24 of 29 Old 01-12-2010, 11:20 AM - Thread Starter
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So the cable guy came and checked and apparently everything checks out OK. The guy said that their cable does carry some current...90V (I think).

It seems that this issue with cable/HDMI sparking is because the circuit is overloaded. :-/
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post #25 of 29 Old 01-12-2010, 11:46 AM
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Overload should not cause "sparks". You really should consider a licenced electrician.

I just read your edit...

Yeah 90v is used to power amps from the headend to distribution points, but that volatge should not be "presented" to the home. 90VDC will give anyone a good jolt! Don't test this with Grandma.
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post #26 of 29 Old 01-12-2010, 01:08 PM - Thread Starter
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Quote:
Originally Posted by Ratman View Post

Overload should not cause "sparks". You really should consider a licenced electrician.

Hi!

Yes, a licensed electrician is coming on Friday.
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post #27 of 29 Old 01-12-2010, 01:17 PM - Thread Starter
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Quote:
Originally Posted by Ratman View Post

Well... I'd start with checking for a voltage between the cable/USB and the PC since that is the apparent symptom.

If you take the PC to another room and connect the cable/USB, is there a problem? If so... it's the PC and/or cable feed. If not... the it's the power outlet, the UPS, the power strip and or one of the other external devices.
...


I did try this...not with the cable + USB TV dongle, but with an HDMI cable and another TV in another room.

As I had written in my other thread (see post #17), I was trying to plug in an HDMI cable whose one end was already attached to an HDMI switch into the PC and it caused a spark and fried the motherboard.

After replacing the mobo, I took the computer to another room and attached it directly to another TV using an HDMI cable...no problems there.
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post #28 of 29 Old 01-12-2010, 02:49 PM
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Which is why I think you are in over your head and don't understand how to properly troubleshoot your electrical issues.

I'm glad you have (hopefully) a licenced eletrician coming to diagnose.
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post #29 of 29 Old 01-15-2010, 12:57 PM - Thread Starter
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The electrician just left...and kenglish gets the prize!

We have an old house and someone down the road had jumped the connectors of the three pronged outlet to make believe that it was grounded. In fact, the coax was acting as the ground.
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