HELP!! GOT A ZAP! 90Volts between my cable and PC!! RESOLVED

[DAVE440]

Don't know if this belongs in capture cards or General.

Just got my cable back after hurricane wilma and went to hook up the
cable to pc again and got a zap. Got a little one bout a month earlier
while connecting the tv to the cable outlet.

I just used my digital voltmeter and measured 90v A/C between
the cable outer shield and my PC case/motherboard ground. I also measured 90volts between the cable center conductor and the PC case/motherboard ground.

The TV is working fine and the PC capture card probably will too if I plug the cable in...but why is there 90volts here? Is this a ground loop? If so...its a pretty big one. Usually those are only a few volts.

Devices connected as follows....
1. Coax Cable from the Cable signal at the wall to Signal Splitter IN
2. Coax Cable from Splitter OUT to VCR1 IN
3 Coax Cable from VCR1 OUT to VCR2 IN
4. Coax Cable from VCR2 OUT TV ANTENNA IN
5. Coax Cable from Splitter OUT to PC Capture card.

-VCRs and TV do NOT use grounded plugs. Just 2 prong.
-The PC DOES use a grounded plug.
-The Cable shield most likely goes to house or earth ground at the box

Is there a problem with my cable or Is this a ground loop between the cable signal and the Computer ground since the PC Power suppy uses a grounded plug to AC?

The capture card was working on the cable signal before....but since I got a zap hooking it back up and decided to check it out....and now know there is 90v there....I dont want to damage anything on the PC....not to mention 90v is a might dangerous when connecting the cables.

Whats going on here?

Thanks
Dave

[Dragonsf]

Have you measured the voltage at the splitter input against common ground?

[Nelson37]

I only know enough about electricity to know it's dangerous.

But, I do know that a strong static spark can be enough to damage a PC's electronic components. If you got a noticable zap from the cable, twice, I would NOT plug it into the PC.

I think TV cable does carry a slight voltage, but I don't think its anywhere 90V.

[redwudz]

A couple things to check. Look where your cable TV comes into the building. There will be a ground block and a ground wire that goes to a stake in the dirt. Make sure those connections to ground are secure.

Also where your AC power enters the building. Usually at the exterior fuse or breaker box, there should be the same setup, with a ground lead going to a stake in the dirt. Check to make sure that connection is secure.

Your local power company is probably busy, but call them to check to see if you are getting safe power from their line. If their ground fails between your building and the pole and your ground stake is not connected securely, you can get power on the ground lead.

Usually this blows out appliances, so it's something you want to be careful with.

Power on the shield and the center conductor of the cable is a bad sign. That usually indicates that a ground has failed.

[edDV]

Call the cable company and get them there tomorrow to fix it. They may be liable for damages as well.

[DAVE440]

I put the Digital Voltmeter on the coax connector out of the wall and read 86-90 vac between the center pin and shield.

Also got that same voltage between the center pin and wall outlet (earth ground).

I called the cable company and 3 service agents and 20 mins later I was advised it sounds like the ground block had lifted... (hello...big surprise) and they have scheduled an appointment. They guy was like....DON'T TOUCH ANY MORE WIRES!!...Haha.... guess they dont wanna get sued!

I looked outside and the ground wire is still solidly attached via a copper clamp to my AC Power Meter box galv. pipe but the galv. is a bit powerdery under it so its possible the ground connection has high resistance.

Have to wait and see what the outcome is here. Might have to re-schedule since they want to come out fri. ... I might be out shopping for bargains.
You can never have enough PC Accessories! :P

As for Damage due to the 90v on the cable. Big Screen TV seems ok.

Fortunately no damage to the PC either but am getting physical memory dumps and on a more frequent basis....even with the cable tv coax removed now and wire antenna in place. I seriously doubt that its related. If the TV card was damaged by a spike...I think that would be it. Then again....maybe that voltage leak hurt the RAM or a motherboard chip that is faulting intermittently now but everything checks out and I have no way to confirm this so I cant find the source of the memory dumps. Got a post going on that problem in the Capture forum since I suspect its the capture card causing the issue as there are no other PCI cards in here.

If anyone has ideas on the memory dump problem please DON'T respond in this thread...since I already have another post running. It's here.
https://www.videohelp.com/forum/viewtopic.php?t=285317


Thanks for the suggestions and HAPPY THANKSGIVING TO EVERYONE!
Dave

[redwudz]

A year or two ago my dad called me and said his cable TV quit. I went outside to check the cable and a piece of it about 6 inches long, just below the ground block was vaporized and burnt into the wall. Seems a 2000VAC line up the street broke a crossarm and the live wire fell on the cable. Blew out a couple of TVs in the neighborhood, but his was saved by having a good ground connection. 8)

It pays to check those ground connections occasionally. A little corrosion is no big deal, but that's for the cable or power company to judge.

Your problem shouldn't have done any damage. A computer power supply is fairly well protected from a voltage like you measured. Does make you a little nervous unplugging cables for a while, though.

Hopefully they will get it quickly fixed and all your devices will be OK.

[DAVE440]

Nervous....? Not me....

You should see me workin the cables with rubber gloves...HAHA!!

Did one more test few mins ago.

Since the outside cable box has a ground wire clamped to the mains meter pipe...the cable coax shield SHOULD be grounded to the same AC house ground. I put the voltmeter from the coax shield at the wall to the AC ground ...set to resistance...and it didn't give me a reading....even at 2000000000 ohm setting. Definitely bad cable to house ground!

No voltage measured from outer cable shield to house ground...with AV devices disconnected......

BUT once u plug the cable into a VCR or TV the power internally runs thru the center pin thru device circuitry and eventually to shield. With a cable connected...There IS voltage from the shield to AC ground on all equipment. I'm surprised the TV or VCRs didnt fry!

Theres no reason for 90volts to be on an RF signal line so grounding aside....somethings wacky with their gear.

Let u know what they find.

[DAVE440]

Update: RESOLVED - Sorry for the 2 year delay....hah!

Was just about to post another topic and looked through my old ones. Realized I never posted my resolution to this. If you have Cable phone and cable tv service READ THIS.

Comcast came out and after several service calls one of the techs finally figured out that during repairs after hurricane wilma another tech had accidentally connected my line to the wrong output port on the distribution box. The port it was connected to feeds Comcast phone signals to houses that have comcast phone service. There IS 90v on the Comcast phone line feeds, however houses that have Comcast phone svc and comcast cable tv also have a special filter installed that blocks the 90volts from entering tv sets and video equipment. Since I don't have Comcast phone service (and never did) ...there is no such voltage filter on my tvs or video equipment and thats why there was 90 volts entering my equipment. After checking my 2 vcrs and all tvs to make sure they were ok...I discovered this tech oversight had KO'd one of my VCRs. After the tech connected my cable feed to the proper port up on the pole, I showed him my damaged vcr and he advised his supervisor. It took me 4 follow up calls and 3 months as they lost the claim paperwork...but they did make good on it finally.

** If you have Cable tv and Cable phone service BE SURE you have the proper filter installed on your tv and video equipment to block the voltage from the phone service...or you may end up with damaged video equipment.**