Help me cure my slight hum problem (1 Viewer)

[Philip Hamm]

Don't forget to go out and get thee an outlet tester. If anything Phil, its good for peace of mind.

I have a hardware store near me with lots of tools (including a non-Radio Shack SPL meter that's tempting). I may be able to get it there.

Kenmore says I have a grounding problem with the electricity in my house. I will need to call an electrician.

 

[Blake R]

Hey Phil before you blow a wad on an electrician you might pull the cover on your load center(service entrance panel) and make certain that all of the branch circuit grounds and neutrals are tightened down at the bus bars. You should also check and make certain that the main grounding and neutral lugs are good and tight. It is also important that ground and neutral be bonded together at the load center. This is required at the service entrance panel only.

A few minutes in the load center with a screw driver could save you a few bucks. If you're just too intimidated by electricity as some understandably are, an electrician may be the only course.

Good luck.

 

[Chu Gai]

Phil, these are some replies I received.

Have an electrician go through your electrical system and check/tighten all the connections. Some of them get loose after a few years, especially aluminum wire.

Check the voltage between neutral and ground at your stereo. It should be a few volts only. It's possible that the neutral line has a bad connection or the 'fridge is dumping current into the earth ground.

Are you sure the hum is really coming from the speakers ?
The fridge may be vibrating the floor and hence ceiling of your HT room.

 

[Philip Hamm]

Chu, thanks

Are you sure the hum is really coming from the speakers ?
The fridge may be vibrating the floor and hence ceiling of your HT room.

The hum is most definitely coming from the speakers, no doubt.

 

[Rick Guynn]

Unless I am mistaken, I think the outlet testers only check for power/polarity/grounding. They will probably not give you info on the Voltage between ground and neutral.

I toss in my agreement with others to go in and make sure all of the lugs are tight. And it is very simple to do yourself, the ground and neutral bus strips aer usually not too terribly close to the 'hot' rails. If it is a newer 'plug-in' breaker type box, you would have to be really trying to screw something up in order to cross anything. As to not being on the same curcuit... you have to remember that all of the ground wiers go back to a common bus, so there could be transmission along those lines.

BTW, did you ever decide what to do with your old processor?

RG

 

[Philip Hamm]

The house is about 10 years old. I'm very hesitant to go into the breaker box at all.

BTW, did you ever decide what to do with your old processor?

No. It's boxed up at the moment. From looking at Ebay and Audiogon and other places it seems that the used market ir pretty nonexistant for these excellent boxes. I'm guessing it would cost me about $150-200 to fix. Then say I sell it for what, $300? Is it worth the trouble? Maybe I'll try to sell it "As is - needs repair" for $50. Would be a great bargain for someone looking for a nice low cost 5.1 preamp. But who's looking for a low cost 5.1 preamp?

 

[Rick_Brown]

Would clamping a ferrite bead on the fridge power cord help? They only cost a few bucks at radio shack and I've read about them in this Forum.

 

[Chu Gai]

the frequencies those attenuate are beyond what Phil's experiencing. Shack's got some VOM's on closeout FYI Phil.

 

[Grant B]

I would try a heavy extension cord for the fridge and try plugging it into different circuits. Does it no matter what line it's on, it's the fridge and an electrician wont do no good.
Only does it on the originial outlet, it could be wired incorrectly.
Good luck it can be a real pain

 

[Chu Gai]

That's a pretty good idea Grant. Let's say it solves his problems because now he's on a different circuit then attention could be focussed strictly on the outlets of the offending circuit. In fact, I think one could then cut the power to the problem area, and work on some of those suggestions themselves.

 

[Philip Hamm]

That's interesting. The Fridge is definitely on a separate outlet than the Home Theater as described above. There is another outlet near the fridge that I can try that will isolate the fridge on a different circuit (the GCFI circuit).

The Ferrite traps did nothing and don't even fit on my HT gear power cords. But I put one on my modem wire just in case they help with data transmission.

Chu, what's a VOM?

Hey I have a Multimeter, can I use that instead of an outlet tester? How?

 

[GeorgeTW]

You have ground interrupts on all your equipment? Did you try reversing their polarity?

Do your signal cables have enough dielectric distance away from power cords(if running parallel)?

Cross signal & power cables at 90 degrees to each other.
This minimizes AC inductance into nearly cables.

If you have excessive length on your AC cords, coil the extra wire in a Figure 8 pattern so that the sine wave cancellation keeps induced voltages to a minimum.

Lastly, you may have ground between components which are not supposed to. Invest in some contact cleaner, and do a once-over on your connections to break up any oxidation between dissimilar metals.

The last and most expensive option is to install isolation transformers between everything (ouch).

 

[Chu Gai]

a vom is a multimeter...i recommend the outlet tester because its fast, doesn't require you to stick probes inside and you can quickly run through your house and identify any problems regarding miswiring. a while back, suttondesigns gave out a bunch of these and from the responses that came back, about 1/4 of the houses had some miswiring. they're about 10 bucks.

 

[Philip Hamm]

I checked the outlets in the living room and kitchen behind the fridge with an outlet tester and everything was reported to be fine.

 

[Philip Hamm]

NEXT QUESTION:

The outlet tester on the back of the package specifically stated that it could not indicate the quality of the ground. Is there any way I can get this information with my multimeter?

 

[GeorgeTW]

IMHO, the quality of the ground is directly related to the integrity of the wire's physical connection. A VOM is not going to be able to show this, only that continuity is present.
There is only one instrument I know of that could give you the quality of your connection, but it is super expensive, and takes practice to interpret. This is a TDR (Time Domain Reflectometer)
It literally sends a pulse down the cable. When that pulse reaches the end of the cable, a part or all of the pulse energy is reflected back to the instrument, measuring the time it takes for the signal to travel down the cable, see the problem, and reflect back. It then displays the reflected signal as information on waveform display. It's a literal picture of the wire, and it can show cuts, abrasions, even places where a cable tie has been scewed down too tight(crushing the wire).

Aside from a TDR, the quality of a ground connection becomes your responsibilty to visually check your outlets, and physically test them to ensure secure contact.

 

[Philip Hamm]

Damn. I wonder what the hell I can do now? I suppose just call an electrician or find an electrician forum online for help. Does anyone know of such a place?

 

[Chu Gai]

I'm not so sure about that George. My take on the quality of the ground has to do with his external ground on the house and of course how the box is tied into that. Ascertaining the quality of that is complicated and can't simply be done using a multimeter. Things I'd be looking for is examining the connections to the external ground (probably one or two deep pipes) and making sure the connections are tight, clean, free of oxidation, and that the ground wire itself has no kinks, sharp bends, and is intact.
Phil, I know this is driving you crazy. Have you taken a stab at getting a long extension cord and seeing if plugging that fridge into a different outlet (that would be on a different circuit) does anything?

 

[GeorgeTW]

Here in Texas, the proper ground for a residence is an 8 foot copper rod driven into the dirt. That is where quality begins. If you live in an apt, condo, or mobile home, then the ground is only as strong as your weakest connection, be it water pipes, breaker-box casing, or copper rod. As I said before, isolation transformers are the only real way to eliminate loops entirely, but they are expensive.

 

[Chu Gai]

that a NEMA spec and if you drive two, you don't even have to test. while it's purpose is for safety, it doesn't address issues that were never in existence back when the specs were formulated which is the issues facing proper grounding of sophisticated electrical components. Consider the following link which would provide adherence to NEMA specs while providing an outstanding earth ground even in dry areas of the country.
http://scott-inc.com/html/ufer.htm
sorry for the off-topic there Phil.