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Old 07-11-2012, 08:59 PM   #31
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Improper Grounding causing Sub woofer noise


One picture is really enough, since they are all of the same panel, and show nothing for what really needs to be looked at, which is fixing the improper grounding of both your telephone & catv wiring. Your actual grounding is in the panel to the left, which you can not get into, because the Power company would have to pull the meter, and then only a licensed electrician should be the only one in that side.

What is basically happening, is that due to possible poor grounding on that electrical circuit, or multiple circuits inside the house, or to earth ground, the tv equipment, or anything that connects to the catv, or even the home electrical system, is using the catv as its earth ground.

You really need to have a licensed electrician along with the POCO check out both the outside electrical, and the inside. Forget what the idiots from the catv company told you, and forget about using that band-aid that ktkelly talked about, because they are only meant for certain purposes. And fixing a home or structure's poor grounding, along with catv & telco poor grounding is not one of them.

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Old 07-11-2012, 11:21 PM   #32
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Improper Grounding causing Sub woofer noise


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Originally Posted by gregzoll View Post
One picture is really enough, since they are all of the same panel, and show nothing for what really needs to be looked at, which is fixing the improper grounding of both your telephone & catv wiring. Your actual grounding is in the panel to the left, which you can not get into, because the Power company would have to pull the meter, and then only a licensed electrician should be the only one in that side.

What is basically happening, is that due to possible poor grounding on that electrical circuit, or multiple circuits inside the house, or to earth ground, the tv equipment, or anything that connects to the catv, or even the home electrical system, is using the catv as its earth ground.

You really need to have a licensed electrician along with the POCO check out both the outside electrical, and the inside. Forget what the idiots from the catv company told you, and forget about using that band-aid that ktkelly talked about, because they are only meant for certain purposes. And fixing a home or structure's poor grounding, along with catv & telco poor grounding is not one of them.
Hrm yeah I was hoping to leave the expensive professional as a last resort :P
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Old 07-12-2012, 07:07 AM   #33
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Improper Grounding causing Sub woofer noise


Find the ground rod, and run a solid piece of #8 from it, to a common ground block, so that you can connect the one wire for Telco, and the one wire for CATV. Then see if the hum is still there, or goes away. If still there, then you have a job on your hand, checking all of the grounds in the house. If they are attached by screws, not backstabbed, the last place is at the panel. You can contact your PoCo to pull the meter and inspect that side of the panel, to make sure everything is solid.

Still have the issue of hum, then yes, call a licensed electrician.
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Old 07-12-2012, 07:30 AM   #34
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Improper Grounding causing Sub woofer noise


Is there a ground rod anywhere? If not, you should install one. (Code requires achieving a 25 or fewer ohm resistance with the earth or two eight foot ground rods whichever comes first.)

In the panel the neutral bus bars (as I saw them) are bonded to the panel itself (frame; can). Grounding relies on the panel metal to get to the grounding electrode conductor coming out from the sealed portion of the assembly to the left and going to ground rod(s) and/or water pipe.

For good measure I would take a length of #6 copper wire, connect one end to one of the neutral bus bars in the open panel as shown, and connect the other end to the aforementioned (probably also #6) grounding electrode conductor. This new wire (now also a GEC) or a clamped on branch can also be run to a grounding block mentioned previously.

Since you did not need to open up the sealed part of the assembly, you don't need to have the power company come.
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Last edited by AllanJ; 07-12-2012 at 07:39 AM.
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Old 07-12-2012, 07:37 AM   #35
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Improper Grounding causing Sub woofer noise


Allan, he has what appears two #6 in the ground block, and looks like a Neutral bond to the right. My only question about the left side, is where does the ground go from there. I would like to see them fix the two sloppy ungrounded connections for catv & telco first, and then see what happens. That right there, may be the fix, and may not have to go any further.
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Old 07-13-2012, 05:10 AM   #36
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Improper Grounding causing Sub woofer noise


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Allan, he has what appears two #6 in the ground block, and looks like a Neutral bond to the right. My only question about the left side, is where does the ground go from there.
The left side is the meter housing, the grounded conductor (neutral) is bonded to the frame of the can, we would have MORE than a sub woofer buzz if there was a neutral issue... The GEC would not land in that part of the housing because they put the lugs in the disconnect side for this purpose, The picture just doesn't show enough if a ground rod exist for the electrical system or not... BUT... the structure could have other grounding electrodes to meet this criteria...



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I would like to see them fix the two sloppy ungrounded connections for catv & telco first, and then see what happens. That right there, may be the fix, and may not have to go any further.
There is nothing wrong with the existing connections as long as they were installed before the paint went on, looks like the cable company already addressed that issue as they removed the paint.
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Old 07-13-2012, 05:47 AM   #37
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Improper Grounding causing Sub woofer noise


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Can you explain how I could make use of a 2 to 3 prong adapter in this situation?
Plug your subwoofer into one of these (temporarily isolating it from ground). See if this solves your problem. If so, then I would expect one of those jenson isolators (or equialent) to work.

Sometimes, bandaids are the pragmatic solution. Still, be sure your electrical system is safe, if you have any doubt.
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Old 07-13-2012, 08:44 AM   #38
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Improper Grounding causing Sub woofer noise


I work in audiovisual, and this is a VERY common problem I encounter out in the field. The most common reason this comes up is because the CATV company has installed a ground rod, and the electrical system also has it's own ground rod, and they are at two different locations. This is called a GROUND LOOP. There will be voltage potentials between the CATV shielding, and the AC power's third prong on the outlets. Most electronic equipment uses 3-prong grounded cords (like your subwoofer), and the metal casing is bonded to this ground. Voltage will flow from the CATV line, through the shielding on your AV signal connections, to any device that's grounded with a 3rd prong, like your sub, and the result is hum.

What you need to do is get the CATV company to ground their lines to the same ground your electrical system is grounded at. CATV companies don't like to admit their equipment is at fault and will try and pass the buck, which seems to be happening here, but they should have their lines grounded to the same rod. In some localities, not using a common ground point is actually a code violation!
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Old 07-13-2012, 08:59 AM   #39
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Improper Grounding causing Sub woofer noise


problem is I don't know where the electrical system is grounded at this point.

I did try using the 2 prong adapter and it definitely removed the hum from the subwoofer.

So I guess that means it is a ground loop?
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Old 07-13-2012, 09:04 AM   #40
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Improper Grounding causing Sub woofer noise


Go outside and use a hand shovel and start digging. Once you find it, where the conduit enters the ground, you just follow it from there, to find the rod.
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Old 07-13-2012, 09:51 AM   #41
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Improper Grounding causing Sub woofer noise


The easiest solution would be just drive two rods outside and tie them into the the panel outside.
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Old 07-13-2012, 10:18 AM   #42
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Improper Grounding causing Sub woofer noise


So when it comes down to it the catv guys are morons :D. Bonding their rod and the house system should solve all issues no? Thanks to av geek for explaining it in an easy to understand way.
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Old 07-13-2012, 11:39 AM   #43
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Improper Grounding causing Sub woofer noise


Could this be an issue?
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Old 07-13-2012, 02:17 PM   #44
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Improper Grounding causing Sub woofer noise


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So when it comes down to it the catv guys are morons :D. Bonding their rod and the house system should solve all issues no? Thanks to av geek for explaining it in an easy to understand way.
In the pictures the catv and phone are bonded to the electrical.
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Old 07-13-2012, 08:10 PM   #45
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Improper Grounding causing Sub woofer noise


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Hrm yeah I was hoping to leave the expensive professional as a last resort :P
Have you performed all of the things in the various replies to this thread yourself yet (short of calling any people: electrician, cable rep, power co. rep)?

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