New Ground Loop - What Could Have Caused?


I never before had a ground loop in my BR system. Everything, amp, pre, tuner, including Verizon FIOS box and TV, is plugged into a PS Audio Juice Bar, which is plugged into an Audience AR1P plugged into the wall.

Upon returning from vacation, I now find I have a very nasty ground loop I so far have been unable to cure.

What would cause a ground loop when there had never been one before? Thx.

Neal
nglazer
Check your cables and connections. Unhook your video coax cable connected to your system and see what happens.
including Verizon FIOS box and TV,

If it is indeed a ground loop hum problem I would start with isolating the CATV coax cable from the Verizon FIOS box. Disconnect the coax from the box, check for hum.

If the hum is gone buy a ground isolator and install it between the incoming CATV coax and CATV box.

http://www.jensen-transformers.com/datashts/vrd1ff_manual.pdf
If the above doesn't help, check to see if there were any storms in your are that could have caused damage to your equipment (if left plugged in) or something else from a nearby lightning strike. Also ask neighbors if they had anything strange happen (electrical) while gone. This would be a possibility if disconnecting the cable doesn't eliminate the hum.
It was the Verizon FIOS box. Once I disconnected IC's running from FIOS box to pre, problem solved. No music statons through stereo, though.

Not sure what happened. I had no problems for years. There may have been storms and the units were plugged in while I was away.

Gremlins in the wires!

Thanks, folks.

Neal
It was the Verizon FIOS box. Once I disconnected IC's running from FIOS box to pre, problem solved. No music stations through stereo, though.

Not sure what happened. I had no problems for years. There may have been storms and the units were plugged in while I was away.

Gremlins in the wires!

Thanks, folks.

Neal
Nglazer,

Somewhere outside your house there should be a grounding block for the Verizon FIOS incoming cable before it enters your house.

The ground wire that connects to the ground block is supposed to connect to the main grounding electrode system of your main electrical service.... You might want to check and make sure that is how it was done.

The ground block should not be connected to a dedicated ground rod that does not tie back the main grounding electrode system. Not only can a dedicated ground rod cause ground loop hum problems especially when the soil is dry but it also can add an alternative path for lightning.
Bad news for your audio equipment and TV.

If the grounding block is properly connected to the main grounding electrode system and was working just fine until you came back from vacation then the ground wire connection at the grounding block could be loose or corroded causing resistance at the connection. A difference of potential, voltage, then may exist from the Verizon FIOS cable and the equipment ground of the electrical system of your house.

If there is a difference of potential and a closed current path is provided then you will have a ground loop and the dreaded hum.

Best thing to do is buy a ground isolator for the Verizon FIOS incoming cable line.....
It was the Verizon FIOS box. Once I disconnected IC's running from FIOS box to pre, problem solved. No music stations through stereo, though.
08-29-11: Nglazer
Nglazer,

Is it? Or is it actually caused by a difference of potential between the shield signal ground of the FIOS cable and the equipment ground of the 120V AC grounded system.

Did you disconnect the FIOS cable from the box, with the ics still connected from the box to the preamp, and check for the hum? If you did and the hum was still present then the hum could be blamed on the box.

I did read your response on AA..... I don't believe the problem is the Verizon FIOS box.
Jim
Whoa. Nothing ever is simple, is it. I will first try Jim's FIOS box suggestion, because it is easier and I know what to do. Jim's other suggestion probably is beyond my technical competence, but I know where the FIOS cable connects to the house.

Thanks again. I would like to go back to where I was.

Neal
Neal- A cheapo way to experiment w a ground iso xfrmr is to put two of those 75 - 300 ohm (aka F to twin lead) converters back to back into the FIOS cable run. Incoming cable to F input to 300 out to 300 in to F output to cable out. If it substantially reduces or eliminates the hum, you can pay RS a ten spot for one, or buy a more expensive one from Jensen or find a used Mondial MAGIC.
Jim's comments are right on, IMO, as usual. Good suggestion by Michael (Swampwalker) as well.

Given that the problem appeared out of the blue, after everything had been fine for a long while, my bet is that the root cause is the possibility Jim suggested of corrosion/poor connections at the ground block outside. If so, the fix could be as simple as tightening a screw or nut on it.

Dealing with a ground block doesn't require much technical expertise. It's just a pair of back-to-back coax connectors connected between the cable from the pole and the cable that goes into your house, with a ground wire clamped onto the block via a bolt or screw.

Regards,
-- Al
You fellows are very smart. I can't even begin to explain it technically. Following the "ground loop" , I started losing the FIOS signal sporadically, then entirely. I checked all the connections and noticed a splitter outside running up to my bedroom was burning hot, and the insulation on the coax cable had melted!

When I told Verizon I had a safety as well as signal problem, they showed up within 2 hour. When the technician opened the box attached to the outside of the house where the cable comes in and disconnected the coax cable, he got a nasty shock. Somehow current was running through the coax and he became the ground! He simultaneously blew out the circuit to which all my stereo and TV equipment is connected, requiring finding an electrician on Friday before Labor Day after a hurricane!Miraculously, I did, and he attributed all the problems to malfeasance in the original FIOS installation. Something about a ground wire missing.

In any case, all is fixed, I got 2 new FIOS boxes out of the deal, the audio output on these is MUCH better than the older boxes, the is no hum through the speakers, and I have even greater respect for you fellows (and women) who understand electricity. I resolved to get a primer on electricity so I understand what is going on, at least on a basic level.

Thanks again.

Neal
This sounds like the neutral wire that is also tied to the ground was no longer making a good connection. The bad connection could have been in your main breaker panel, meter box, or utility line feeding it. Without this connection, your outlets could have 240 volts coming from some of your 120 volt outlets, down to zero volts from the other outlets, do to a bad neutral connection. A lot of the time, anything that draws a low amount of watts, will usually get the higher voltage, and burn out. That neutral wire keeps one phase (hot) line at 120 volts, and also the the other phase (hot) line at a 120 volts, each half of the 240 volt line. It's good to hear everything is fixed, and no major loss.
good to hear that you got it fixed, Neal. Is it safe to assume that ATT is picking up the cost of the electrician?
It's Verizon, Swampwalker, and that is a battle not yet joined!

regards,

Neal
Nglazer,

I ran across this.....
http://www.electrical-forensics.com/Open-Neutral/Open-Neutral.html