Need suggestions please! Electrical noise in my system and it's driving me crazy!

nutty
1,212 posts 09-03-2017 1:29pm

I also recently eliminated a hum by disconnecting my CATV from my system. After
re-grounding it, removing the ground and trying power conditioners, I could not eliminate it until I unhooked the coax from the system.

By re-grounding it I assume you are referring to the CATV coax cable grounding block. Please explain in detail how you re-grounded it.

Sometimes even though the grounding block is well grounded to the main grounding system of the electrical service a difference of potential, voltage, may still exist between the shield of the coax cable and the wall receptacle outlet safety equipment ground where the audio/video equipment is located, and plugged into.

"Well grounded"? The least resistive path, best conductivity path, possible?
The connection made at the grounding block must clean and tight. Both the wire and the inside of the lug of the grounding block must clean and free of any corrosion. Corrosion can add series resistance. The best place for the other end of the ground wire to be connected is as close as possible to the electrical service main disconnecting means equipment. Sometimes that may be on the outside of the house or on the inside the house, on an outside wall. NEC code requires that the ground rod/s, for the earth connection of the electrical service, be driven outside the house in close proximity to the main service panel. So whether the main electrical service panel is outside or inside you should see a bare copper, #6awg minimum (maybe #4) wire that exits the metal enclose and goes down into the ground where it connects to the ground rod/s. Connect the ground wire from the CATV grounding block to this bare ground wire where ever it is convenient above earth grade. At least a foot or so if possible. To make the connection to the bare ground wire use what is called a split bolt.
Example: http://www.elecdirect.com/split-bolts-grounding-products/split-bolt-connectors/copper-alloy-2-conduc...
This one has a max conductor size for #6 copper. If your bare ground wire is #4 go to the size for #4 copper.
Note: Clean the bare copper wire with sand paper first to a new shiny copper color.

You’re not done yet.... Every "F" connector from the CATV grounding block to the one that finally screws on the CATV cable box must be free of corrosion and tightened wrench tight. (Snug) Everyone of them. Again, to eliminate any series resistance in the coax cable shield conductor from one end to the other.

After all that you still experience ground loop hum.

That can be due to the continuity, conductivity, integrity, of the in wall receptacle outlet branch circuit wiring safety equipment grounding conductor, wire.
If the branch circuit is a standard 15 amp convenience outlet branch circuit every outlet box the branch circuits passes through the wires were cut and then connected together again in "some fashion" to feed the next outlet. Every equipment grounding wire connection could be adding just a little series resistance to the equipment grounding conductor. Not a problem if the wall receptacle outlet for your audio/video system is closest to the feed end, but if it’s closer to the end of the run that could be a problem.

The only way to find out for sure is to open up every single outlet box and inspect the wiring connections. Not only receptacle outlet boxes but there may be ceiling lights on the same branch circuit.

Or you could buy one of these,
http://www.jensen-transformers.com/product/vrd-1ff/

Jim

nutty
1,213 posts                                                                  09-03-2017 5:10pm

jea48,
By re-grounding- I removed the old grounding connectors, (both phone and CATV) at the grounding rod and at the exterior (outside) cable junction box. I Cleaned the stake with a wire wheel, (to remove rust or oxidation) and reinstalled new 12 awg solid ground wire and connectors.

I still had the (((hum))). With the system on and the volumn at a reasonable level, I disconnected the coax from the cable box and the (((hum))) disappeared.

This was my particular situation. I hope it helps.

nutty,

Thank you for your response.

The ground rod you speak of. Did you notice any other ground wires that were connected to it? Like a larger #6 bare or stranded copper wire?
Just a guess the ground rod was originally installed for the phone and later when CATV was installed the CATV installer used the same ground rod.

Unless the ground rod is fairly close to where the main electrical service of the house is located I doubt the ground rod for the phone or CATV is connected by at least a #6 copper ground wire to the main grounding system of the electrical service.

Many people think, including communication provider companies installers, a separate isolated ground rod is all that is needed to effectively ground their systems to mother earth. It is not though. Electrical safety codes require the systems shall be bonded, connected, to the main grounding system of the electrical service. The main reason all ground rods need to be tied, connected, together is for lightning. You also want all electrical systems grounding connected to one common ground.

https://www.youtube.com/watch?v=QPWmULYgONA

nutty
1,214 posts                                                                      09-03-2017 8:02pm

jea48,
The main rod was installed when the house was built. It was installed as the main ground for the home. However as you suspected, it is within a few feet of the main service panel and the Phone and CATV service is all there as well. The main rod is grounded with a large solid wire, 8 or possibly 6 awg. I ran new leads for the phone, CATV within the exterior boxes as well as hard wiring it directly to the main rod. The results were the same. The (((hum))) was present until I removed the coax from the system.

jea48,
By re-grounding- I removed the old grounding connectors, (both phone and CATV) at the grounding rod and at the exterior (outside) cable junction box. I Cleaned the stake with a wire wheel, (to remove rust or oxidation) and reinstalled new 12 awg solid ground wire and connectors.

I still had the (((hum))). With the system on and the volumn at a reasonable level, I disconnected the coax from the cable box and the (((hum))) disappeared.

nutty,

But did you clean the connection on the ground rod, the ground rod clamp, and the solid #6awg copper ground wire for the electrical service? If not how do you know the connection was not corroded? You want the best possible connection you can get/make to the #6 copper ground wire. The other end of the #6 wire is terminated on the neutral/ground bar in the main electrical service panel. The neutral/ground bar is where all the equipment grounding conductors, wires, are connected/terminated.
(Assuming the main disconnect breaker for the electrical service is mounted in the electrical panel)

What you want, need, is zero resistance, (as close to zero as possible), continuity, between the safety equipment "U" shaped ground contact, (of the wall receptacle your audio video/equipment is plugged into), and the CATV coax cable shield/"F" connector that connects to the CATV receiver box.

Instead of connecting the ground wires, for the phone line and CATV coax cable, to the ground rod you should have connected them to the #6 ground wire for the electrical service.
You could use one of these to connect the two wires to the #6 wire. Install it above grade so it can be inspected. Clean the area on the #6 wire with sand paper where you will be installing the ground termination device.
http://www.gordonelectricsupply.com/index~text~5979096~path~product~part~5979096~ds~dept~process~sea...

If you are still living at the same house I would recommend you re-terminate the phone and CATV ground wires. Pick up an Intersystem Bonding Termination as shown in the link above.
You could also use a couple of split bolts instead. See my earlier post for a link.
Though the Intersystem Bonding Termination meets NEC code.

Jim

Edit to my post above.

When I spoke about cleaning the connection of the electrical service’s #6 copper ground wire at the ground rod I should have mentioned with extreme caution. There could be a lethal difference of potential, voltage, between the disconnected ground wire (the Grounding Electrode Conductor) and the ground rod (Electrode) as well from the #6 ground wire to the soil you are contacting with your knees or any other part of your body contacting the earth. Especially if the soil and or grass is moist/wet.

Jim