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

+1 on the drop isolator recommended by @jea48

I don’t have the Jensen, but I do have an Extreme. When I traced a hum to my cable line, the cable company (Cablevision, Long Island) installed an Extreme drop isolator http://www.extreme-broadband.com/hardware.html and the hum was completely gone.

Edit: My cable company provided the part and installed it free. Also, I was told there is no degradation of the picture/sound quality, nor did I detect any degradation. I think this is one of those "can't hurt and can only help" kind of parts.

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.

N

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

Coaxial ground isolators are fabulous ideas, I always use one just in case, but easy to test. Just disconnect any and all incoming coaxial leads.

http://amzn.to/2wzJ3Cq

There are also specific one's for satellite antennas, which need power injection. Also, cable/satellite antennas should be bonded to the house ground, a step installers conveniently skip.