Grounding issues..... :(

[filtor1 10+ year member]

I give up, so here is my post. I have a little issue with my HT sub. Here is what I have; Yamaha RXV2400; Yamaha 5dsc DVD(I forget the model); 5 Boston Acoustic CR85's; 1 Titanic 15" subwoofer(the kit that PE sells); and what I think the problem is, my Dish network reciever.

Here is the background. I bought all the equipment about the same time. Hooked it up in my Apartment in Tampa and everything was fine. The cable guy(TimeWarner) stopped by to hook up the cable and there was a teriible 60Hz tone coming from the sub. I tried adjusting the gain on the amp, but that didn't help. So I unplugged the coax cable form the cable box and the noise went away. Plug it back in and there it is, back again. So that was my solution for a while, but that got annoying.

We moved. I hooked everything up again. No issues. The Dish Network guy comes and hooks up the sat. box and majically, the noise comes back. Now I am pissed. I have tried using different outlets for the plate amp. I bought a ground loop isolator from PE and that eliminated the issue, but eliminated a number of channels. I am just about at my wits end and still haven't come up with a reliable solution.

Any help will be appreciated. I have been told that it relates to the improper grounding of the sat/cable systems. Apparently it is common to place a 55hz grounding plug at the end of the ground on the dish/cable junction box as a cheap alternative to finding a proper place to ground. Are these things related?

//content.invisioncic.com/y282845/emoticons/blackeye.gif.66a1670f5aaf7f406e783a63e3387dc5.gif

Thanks in advance, Chris

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[joetama 5,000+ posts]

Try hooking the Ground of the Coax to the "power" ground and see if it goes way. If it does then it is definatly a grounding issues. If this is the case get a coax isolator that is made for sat signals... This should fix your problem...

 

[thylantyr 10+ year member]

For debugging ground problems, try one of these on all pieces of equipment.

http://www.adorama.com/images/Product/ZZAC32.JPG

 

[filtor1 10+ year member]

Try hooking the Ground of the Coax to the "power" ground and see if it goes way. If it does then it is definatly a grounding issues. If this is the case get a coax isolator that is made for sat signals... This should fix your problem...

I will try grounding the coax in the morning.

The ground loop isolator I bought is an inline coax GLI. Are there different kinds for cable and sat?

 

[filtor1 10+ year member]

For debugging ground problems, try one of these on all pieces of equipment.http://www.adorama.com/images/Product/ZZAC32.JPG

All of my plugs and wall sockets are 3 pronged. How will this help in the trouble shooting process?

Possibly by using the ground strap on the top to test?

 

[Rich B 5,000+ posts]

All of my plugs and wall sockets are 3 pronged. How will this help in the trouble shooting process?

Have you tried a cheater plug?

Thats one of those AC adapter plugs that has 3 prongs input, with 2 prongs output.

That would lift the ground on your sub.

Old trick in home audio.

 

[filtor1 10+ year member]

Have you tried a cheater plug?
Thats one of those AC adapter plugs that has 3 prongs input, with 2 prongs output.

That would lift the ground on your sub.

Old trick in home audio.

I thought it was bad to remove the ground, or am I missing something?

 

[ballstothewall 10+ year member]

If you don't have a cheater plug, you can pull it outa the socket with a pair of pliers pretty **** easy too.

 

[joetama 5,000+ posts]

I thought it was bad to remove the ground, or am I missing something?

It is and don't do it... People that will tell you to do it understand nothing about grounding. It is OK to trouble shoot but long term it's stupid to remove ground for your safety and you equipment's safety. They didn’t just randomly designing electrical outlets with a ground plug because it looked pretty...

 

[thylantyr 10+ year member]

I thought it was bad to remove the ground, or am I missing something?

Lifting the ground will allow you to debug ground loops. If you lifted the ground using the plug and it fixed the problem, then you now for sure it's a

ground loop. Identify the problem first, then try to fix it.

When a manufacturers builds a product with a metal chassis and it has high voltage wiring inside, they have to connect the ground wire to the chassis

which in turn connects to your AC outlet ground. If by any chance in your life,

that device you bought had a failure, maybe a hot wire came loose and touched the metal chassis, an ungrounded chassis would cause high voltage on the metal and you can get shocked. If the chassis is grounded, you get an electrical short that trips the breaker or blows a fuse so you don't get shocked if you touch it.

Power tools originally came in metal chassis with 3 prong cords. Now, they are 'double insulated' and don't use the grounding method.

There are other appliances in your home that may have plastic chassis and

there is no chance of electrical shock, hence no ground. I've seen toasters with

metal chassis, and no ground plug.

Most homes in the US built 40+ years ago may only have a few outlets with

3 prongs.

There is no real danger bypassing the ground, just don't make a habit of it. Certain items I won't

bypass ground like any machine what works with water that is plugged in to AC, otherwise

audio gear is no big deal really. I've been shocked by 120VAC, no big deal. The bigger demon is 220VAC- 440VAC.

There are some tricks to ground isolate equipment which providing ground protection. Lets say you

wanted to make a DIY preamp or amp, you can installed a simple bridge rectifier to the chassis to

provide ground loop insolation but in the even that voltage > 1.4v hits your chassis, current conducts to

provide protection. You can also modd existing gear using this trick.

 

[filtor1 10+ year member]

Thanks for all the help.

thylantyr, would you mind elaborating on what a simple bridge rectifier is/does?

Lifting the ground will allow you to debug ground loops. If you lifted the ground using the plug and it fixed the problem, then you now for sure it's a ground loop. Identify the problem first, then try to fix it.

When a manufacturers builds a product with a metal chassis and it has high voltage wiring inside, they have to connect the ground wire to the chassis

which in turn connects to your AC outlet ground. If by any chance in your life,

that device you bought had a failure, maybe a hot wire came loose and touched the metal chassis, an ungrounded chassis would cause high voltage on the metal and you can get shocked. If the chassis is grounded, you get an electrical short that trips the breaker or blows a fuse so you don't get shocked if you touch it.

Power tools originally came in metal chassis with 3 prong cords. Now, they are 'double insulated' and don't use the grounding method.

There are other appliances in your home that may have plastic chassis and

there is no chance of electrical shock, hence no ground. I've seen toasters with

metal chassis, and no ground plug.

Most homes in the US built 40+ years ago may only have a few outlets with

3 prongs.

There is no real danger bypassing the ground, just don't make a habit of it. Certain items I won't

bypass ground like any machine what works with water that is plugged in to AC, otherwise

audio gear is no big deal really. I've been shocked by 120VAC, no big deal. The bigger demon is 220VAC- 440VAC.

There are some tricks to ground isolate equipment which providing ground protection. Lets say you

wanted to make a DIY preamp or amp, you can installed a simple bridge rectifier to the chassis to

provide ground loop insolation but in the even that voltage > 1.4v hits your chassis, current conducts to

provide protection. You can also modd existing gear using this trick.

 

[thylantyr 10+ year member]

Thanks for all the help.
thylantyr, would you mind elaborating on what a simple bridge rectifier is/does?

Here is the wiring for a common piece of electronics.

http://sound.westhost.com/psw-f2.png

IEC mains socket, node 'E' is earth ground. The 3rd prong on AC home voltage.

Notice the socket is node 'E' is connected to the metal chassis.

Same thing in schematic form.

http://sound.westhost.com/psw-f1.png

Notice they imply that center tapped T1 is grounded, the same ground as

AC input ground. This can create a ground loop as T1 output ground is also

connected to your AC mains all the time. If you disconnect the T1 ground

from chassis ground, you should have no issues, but if there is an electrical

'hot' short to chassis, there is no short circuit to protect the user from shock.

A clever approach to solve both issues, ground isolation and have protection is this.

http://sound.westhost.com/p27-f3.gif

You install a bridge rectifier, one resistor, one cap. One side is earth/chassis connected, the other side goes to the electronics power supply ground.

Simplified, it looks like this;

http://sound.westhost.com/p04_fig1.gif

Two diodes.

The reason the bridge rectifier is used is because;

1. It's common and cheap, and easy to install.

Here's a beefy one;

http://www.herbach.com/Merchant2/graphics/00000001/g4-015.jpg

Medium sized;

http://www.herbach.com/Merchant2/graphics/00000001/g4-004.jpg

They come in different voltage and current ratings. To protect against short

circuit, the rectifier or diodes will need to have a high current rating so

when a short circuit happens, this gives the breaker or fuse time enough

to trip or blow, but you don't want your diodes to blow prematurely, hence

use high current diodes, maybe 30A rated.

I'm not sure if the resistor is really needed as it makes a low impedance path

from electronic ground.

How this works? referencing this pic;

http://sound.westhost.com/p04_fig1.gif

If the power supply high voltage touches the chassis, current passes through

D1 to it's ground return path, thus creating a short circuit and blowing the

5A fuse.

If there is no fault, the only path from electronics ground to earth {chassis ground} is through the 10 ohm resistor, essentially isolation both from

each other, albiet 10 ohms isn't much isolation, but if you have hum issues

still using this method, then I'd remove the resistor entirely and try it without.

 

[filtor1 10+ year member]

Wow. Thanks for all of the explanations. I am going to try and ground the coax first as it seems to be the easiest solution. If that doesn't work, bridge rectifier it is. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif I just hope I can actually figure it out.

 

[joetama 5,000+ posts]

Lifting the ground will allow you to debug ground loops. If you lifted the ground using the plug and it fixed the problem, then you now for sure it's a

ground loop. Identify the problem first, then try to fix it.

Ok that I agree with; just make sure you find a way to fix it if it IS the ground.

If by any chance in your life,

that device you bought had a failure, maybe a hot wire came loose and touched the metal chassis, an ungrounded chassis would cause high voltage on the metal and you can get shocked.

Ok, I might be a rather unlucky person or something, but at the Ripe Old Age of 20 I have NEVER seen a hot come loose and ground, however I have seen power supplies, outputs, and filters fail which cause a direct connection to ground that if not wired properly could have had the potential to kill or injure someone.

There is no real danger bypassing the ground, just don't make a habit of it.

Totally not true. The ground is a safety fail safe designed for electrical signal path. The ground IS a REAL DANGER and improperly grounded equipment may have a much shorter life.

Certain items I won't bypass ground like any machine what works with water that is plugged in to AC, otherwise audio gear is no big deal really. I've been shocked by 120VAC, no big deal. The bigger demon is 220VAC- 440VAC.

This is one of the dumbest things I have ever heard. VOLTAGE DOES NOT KILL YOU! CURRENT DOES!!! 120 Volts AC has the ability to KILL YOU because of its ability to move current, it is a BIG DEAL!!! It honestly proves you have NO real concept about safety/grounding/or electric in general!

You can also modd existing gear using this trick.

 

Do not MODD your equipment! Unless you know EXACTLY what you are going to do and don't give a **** about your warranty or the rest of your system!

Electricity is NOT something to take lightly, it is NOT something to play with, and it most defiantly is something you ALWAYS treat with RESPECT!

 

[thylantyr 10+ year member]

Wow. Thanks for all of the explanations. I am going to try and ground the coax first as it seems to be the easiest solution. If that doesn't work, bridge rectifier it is. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif I just hope I can actually figure it out.

You have to see if there is a ground loop first using the adapter plug to identify

if that is the problem. Then determine your next path.