...electrical problems are due to voltage?

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  #1  
Old 04-25-05, 12:52 PM
Deity
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...electrical problems are due to voltage?

Hi,

To make a very long story much shorter than I could make it:

I've been told by cable technicians that all the ingress, noise/lines and loss of digital picture and sound all of my sets are having is due to the fact that my 30 year old house has voltage problems. I feel it is the cable company's problem and not mine, based on past experience, but the truth of the matter is, I don't know where to start to even verify it. This is what I've done so far:

I got a multimeter to measure voltage, but I'm not sure where to put the plugs or what I'm supposed to see afterwards. An example of this is that I put the black prong in the... ground of an outlet. Then I put the red prong in one of the slots. There was no voltage reading no matter how I moved it around. To prove it was a bad outlet, I plugged a calculator in it; it worked! Another outlet, the left slot gave me 120 volts and the other virtually nothing. Is this what it's is supposed to be, one slot hot and the other neutral?

In case anyone is curious to what the cable tech shows me, he puts the red prong on the cable connector coming off of my tv and the black prong either in the outlet's ground hole or touching the cable converter. It reads between 20-58 volts.

This is my first post here and while I think it's in the right sub-forum, please feel free to move it if it isn't.

"It's not that I don't want to learn, but that I don't know the right words in which to ask a question."
 

Last edited by Deity; 04-25-05 at 12:53 PM. Reason: misspellings
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  #2  
Old 04-25-05, 01:15 PM
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First off a house built in 1975 would hopefully have a decent grounding system. At the very least have well grounded recptacles.

If he is going from ground to the cable wire it is either voltage on the cable line, or a bad cable ground which is not bonded to the houses grounding system. Grounds from two separate areas have to potential for voltage between them. This is why eveything in a homes grounding system must be bonded together, to eliminate this potential.

Did they confirm a good ground on the incoming cable line?
Is it bonded to the houses grounding system?
 
  #3  
Old 04-25-05, 01:41 PM
Deity
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I've been told that the ground is good, but then we've been dealing with this for over three months. They have redone the ground, twice, to the electrical box outside by the cable "tap". The last time I talked to the tech, he said that they would have to look at doing another ground.

I am embarassingly ignorant when it comes to electrical issues, and while I have taken to looking some things up, I'm still in the dark when it comes to understanding the whole grounding thing. I thought grounding to the box woudl be a bad idea, but I read it's not.

After I escalated the issue with a supervisor, more effort has been put into solving the problem, including taking readings at numerous outlets; readings are all over the place. Two different techs seemed to be getting different readings. That's one reason I thought it was time to learn how to use a multimeter so I could at least quell my suspicions that one tech may not be measuring correctly.

I don't have answers to your other questions. How do you know if the cable is grounded well? Or grounded with the house's system?

IF... everything they say is true, and there is all this excess voltage, shouldn't we be seeing other indication, other than degraded picture quality?
 
  #4  
Old 04-25-05, 01:43 PM
WFO
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Looking at your wall receptacle with the ground (round hole) at the bottom, you'll notice that the slot to the left is slightly larger than the one on the right. The left (larger) one is the neutral and the other is the hot leg. Ideally, you should read;

ground to neutral=zero (see exception)
ground to hot=120
neutral to hot=120

Your voltage could easily vary between 115 to 125, so don't get frantic if you don't get exactly 120.
Exception to ground to neutral....the neutral (technically the GROUNDED conductor) is a current carrying return path for the load. The round holed ground (tehnically the GROUNDING conductor), is normally a non-current carrying wire that serves as a means of providing a ground to the appliance as a safety feature. If the neutral GROUNDED conductor is carrying current at the time you measure it, you could see a slight voltage between it and the GROUNDING conductor.
This ties into what Speedy Petey was saying. Both the neutral and ground need to be properly bonded together at the service entrance. Multiple bonds, multiple grounds, or even poor (or no) grounds can lead to considerable problems with digital equipment (to say nothing of being dangerous).
 
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Old 04-25-05, 01:55 PM
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Quick follow up. Do you ever see lights in part of the house get bright while others dim when a 120 volt load (like a microwave oven) is turned on?

What can happen if there is a poor neutral bond is that the voltages from the center tapped transformer on the pole don't have a good "midpoint" reference anymore. Think of a 240 volt winding with a center point grounded. Each end of the winding to the center point will be 120 volts. But if the center point is poorly bonded, it can essentilally "float" back and forth between the two ends. So instead of getting 120 from each end to ground, you might get 100 and 140, or even worse depending on the load and the quality of the ground.

Hence the lights. Turn on a large 120 volt load like a microwave oven or an iron (not a 240 volt AC or heater). It's very common to see a slight dimming of a light from the voltage drop of the load, but you shouldn't see any lights get brighter (as would happen as the midpoint "foats").
 
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Old 04-25-05, 02:04 PM
Deity
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So its safe to stick both prongs into the slits? LOL, I was afraid to do that...

You lost me with the, "Both the neutral and ground need to be properly bonded together at the service entrance." Are you referrign to all outlets needing to be properly grounded or something else? (We need an emoticon with a little plane flying over it's head for me sometimes...)
 
  #7  
Old 04-25-05, 02:08 PM
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If what you are reading reveals that you have 120V on the neutral leg, you have reverse polarity, it needs to be corrected.

With the cable disconnected from your TV, read from both the crimped part of the connecter and from center spline of the coax to a proved ground.

You may also drive an entirely separate ground rod for the cable.
 
  #8  
Old 04-25-05, 02:13 PM
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Because you are unfamiliar with electicity, I think you need to have an electrcian look at your service to insure the proper bonding exists.
 
  #9  
Old 04-25-05, 03:20 PM
Deity
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Okay, a multi-post answer:

It appears, from the two outlets I just tested, we do not have reverse polarity. Until posting here, I thought the slit on the left (neutral) was hot. The outlet in the kitchen that I tested the other day, and again just now, I could get no reading from the bottom socket, but a calculator works in it?

I have not noticed lights dimming or brightening when using devices like microwave or vacuum cleaner.

What is a proven ground, other than that of an outlet, and how do you know? Is a screw in the chassis of a converter grounded or does it depend on the maker? What about the chassis itself?

Is a ground rod for the cable just a metal rod, like that used to reinforce concrete and hammered into the ground or does it need to be connected to something?

Before posting here, all I knew to tell the electrician was how the cable guy showed me I had voltage problems. I didn't even know the term "bonding". I will definately let him do the work with it.

To be perfectly frank, electricty rather scares me.
 
  #10  
Old 04-25-05, 06:39 PM
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Originally Posted by Deity
Okay, a multi-post answer:
It was an after thought. I was concerned that you would remove the dead front panel on your service and we'ed have to call the "SOILENT GREEN" van.


[/QUOTE]It appears, from the two outlets I just tested, we do not have reverse polarity. Until posting here, I thought the slit on the left (neutral) was hot. The outlet in the kitchen that I tested the other day, and again just now, I could get no reading from the bottom socket, but a calculator works in it?[/QUOTE]

It could be worn.

[/QUOTE]What is a proven ground, other than that of an outlet, and how do you know?[/QUOTE]

When you read from the right slot to the ground hole and the meter reads 120V. That proves the local ground. I could go into a lenghty desertation about meggers, which would be moot.

[/QUOTE]Is a screw in the chassis of a converter grounded or does it depend on the maker? What about the chassis itself?[/QUOTE]

If they are internaly bonded and not plastic. With it plugged in and has a three prong cord, measure from thr hot outlet to the chassis.

[/QUOTE]Is a ground rod for the cable just a metal rod, like that used to reinforce concrete and hammered into the ground or does it need to be connected to something?[/QUOTE]

The rebar buried in concrete where the service grounding is connected, is called a UFER ground. The driven rod is copper clad and is connected to the service through an armored cable and a specific series of clamps and bonding connecters.

The cable grounding carries much lower standards, yet is still connected from the driven ground to the terminal on the splitter which connects mechanicaly to the crimpped connecter on the coax.

[/QUOTE]I will definately let him do the work with it.[/QUOTE]

Recognizing you limits, is a plus.

[/QUOTE]To be perfectly frank, electricty rather scares me.[/QUOTE]

Its one of those intangibles, and is unforgiving.
 
  #11  
Old 04-26-05, 10:06 AM
Deity
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Thanks for all the replies. I will post back here when I get some answers.
 
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