US Cable Support → Comcast HSI > Hot/Voltage @ Comcast Demarc/ground block

Hot/Voltage @ Comcast Demarc/ground block

Wasn't sure which Comcast forum to ask this in, so I picked this one:

What could make the Coax "hot"/electrified from the drop side?

I was placing a 75 olm Coax terminator on the "out" side of the ground block where the Comcast drop then connects to the coax that feeds the splitter/wiring inside the house.

This one sparked and melted the terminator cap & made that "burn" smell. I have never come across a "hot" demarc ground block before.

Voltage tester picked up no juice on the ground block or on the connectors, so it had to be down the "stinger" only

Sounds like a bad tap faceplate, either the wrong part was installed or it's shorted.

There's up to 120v on the main trunk to power the line amplifiers and line extenders up on the poles.

The tap plate is supposed to be capacitive-coupled, to block that voltage from being on the drop to the premises.

It sounds like that's the voltage you are seeing at the ground block.

I would call and tell them you have a potentially dangerous situation there.
Whatever you do, don't try to connect anything to the drop before they fix it.
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ROCK 'TIL SUNSET

you cant have 120 on the lines, 60 or 90(89).

ive never seen a tap go bad where it pass voltage unless its an old tap from back during the @home days
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I'm better than you!

could be a bad ground at the pole causing the POCOs lines to ground out through the coax.

you said it melted the terminator, so that was with the ground from your house hooked up?

and then you discod the drop from the ground block? (dangerous) and tested it with a volt meter, or a non contact voltage detector?
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I'm better than you!

I use Comcast at work and Cox at home and have phone service with both. The Cox line has a "Warning - 90 Volts DC" on the coax as it enters the phone box. They block the power from exiting the phone box on the coax. It then feeds the rest of the house. The installer had to move a jumper in the tap box on the pole to apply the 90 VDC phone power. If you don't have Comcast phone, maybe the jumper is placed incorrectly.

comcast doesnt power their phone equipment over coax.
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I'm better than you!

120V eh I don't know what system you work in but it has to be under 90V or it requires a low voltage electrician license and comcast at least does not pay for you to get those so they keep it at like 89.9V [so does phone and it is for the same reason, yes the standard is that old]. Power runs 220/110VAC, but coax and telco do not.

The most likely scenario is he lives in an old DTS system and someone did not pull the shunts at the tap, but his description of melting a terminator sounds like something else, I have never melted a metal terminator in my life, I have seen melted rubber grommets on them, but it took WEEKS to do this, he makes it sound like in 10 seconds it went poof in front of him. Almost make me wonder if he's at something else and doe snot realize its not a Comcast drop he is playing with. But again anything could be happening, some meth head stole part of the ground wire at the pole and now cable and/or phone and power are all sharing a common path to ground over their plant the next pole, etc...

So yeah call the company and report your think you have dangerous voltage on their drop and then BE THERE FOR THE APPOINTMENT.

No, the drop side is still connected to the ground block. The ground block is tied to a meter box ground clamp, but the meter box door was loose/not sure if making a good ground connection.

I only disconnected the house/customer side of the demarc/ground block.

The metal of the terminator did not melt, but there is plastic insulation inside the cap, and that is what melted, but the thing definately sparked & make an audible pop/sizzle

I tested the ground block with the drop attached with a non-contact voltage tester -- I did not remove the drop from the ground block

Call it in right away, tell them it's a life safety issue, need a tech supervisor ASAP.

It could be a problem with the ground/neutral in the electrical box, but nobody should be touching COAX until it is solved.

110/220 only in Europe not in the US 120/240.

Follow up: Saw a Comcast tech in the same neighborhood, explained what I saw to him - he said he'd check it out, and then explained that in the early telephony days they had a little piece @ the tap, about the size of a paperclip, that put voltage on the drop, and that this was probably a remnant of that.

He even got an old tap off his truck and showed me where one one of those things would connect to the drop, but the one he had all the "paperclips" were already pulled off

Re: Hot/Voltage @ Comcast Demarc/ground block

That would be to power the voice port. Its essentially a fuse. the taps that had them worked just fine, but the fuse should have been pulled when the voice port was removed. The main problem with them systems is when people got disconnected the shunt wasnt pulled. Years later when voice ports are not even used people tend to forget that the drops had to be reconnected only to that port. End result 60 volts get passed to the drop. Not the end of the world and much better than having a neutral problem with power. You actually probably solved your problem before he even showed up as you more than likely blew the fuse when you put the terminater on the line. This system with the shunt blown is exactly as a system without the fuse. Not that im recommending it, but if thats what it is a fix is just simply to short the coax out and blow the fuse. At that point the tap becomes a normal tap. While comcast never used voice ports, they purchased plenty of cable companies that did. In fact voice ports were as common back in the day as modems are today.

Im not going to kid you. Comcast gets power where comcast can get it. I can show you places where comcast is spliced into underground house drops to power the amps. Them areas are certainly not 60 volts. They are in fact 120 volts. You are in west chester. I can give addresses in lower merion. In fact very close and in fact both comcast. nuff said tho. The only thing i will say is about ten years ago comcast of montgomery county took over Lower Merion. The guy that knew power in Lower Merion ended up in your area. As the construction contractor i did what i was paid to do.