Entertainment Center: TVs, Stereos, VCRs and DVDs - ground loop hum and antenna grounding

I think I have a ground loop hum problem and also think I know the cause.

I wanted to connect all my audio signals (TV, VCR, computer) to the AUX input of my audio amp, using a three-way switching box (3 RCA inputs - 1 RCA output).

It seems that whenever both my TV and computer are connected to the switching box (or just to the audio amp directly) there is 60 Hz hum.

I solved a previous, related problem thusly: when I connected an FM signal (split from the VHF signal) to the tuner/amp and then connected the computer audio signal to the AUX input, there was 60 Hz hum.

I solved the problem by installing an in-line switch on the FM signal, so I could break that signal whenever I wanted computer audio and wasn't listening to the radio.

Today, I found out that if I disconnected the coax from the back of the TV, the 60 Hz hum quit.

Now, this is going to perhaps sound very stupid, but aren't rooftop antennas supposed to be grounded? I don't think mine is.

We do, however have a top of the line Panamax surge protection system that serves all the appliances mentioned above.

If I ground the rooftop antenna, will my 60 Hz hum disappear?

:confused:

The problem is in your electrical source and you will find that that
the "neutral" (or grounded leg) is not grounded.

This takes a person with some knowledge of electrical boxes.
But, often, an electrician will wire a system without a ground on
the neutral wire (white wire). The system will work okay but the
system will never find "Ground". If you check, the neutral wire will show about 30-40 volts AC. Since the ground is "hot", it will
give you the hum you describe.

Been there! Done that! Have the T-Shirt!


Smokey ;)

Smokey,

Believe it or not, I found the source of the problem. Now, all I have to do is find the cause of the source, lol.

Using the process of elimination, I began un-plugging things, one by one.

I unplugged the Panamax surge unit in the bedroom, which has our second TV, and of course, both the power and coax pass through this unit.

The hum stopped.

I then plugged the Panamax unit into ANOTHER wall outlet in the bedroom (there are 3) and again, there was no audio hum in the living room.

I took some readings from the "suspected" wall outlet and found the following:

Reading between the neutral terminal and the TV coax ground, I read 1.5 ohms. This SHOULD read less than an ohm.

I also read 9 VAC!!!!!!!

Where the heck am I picking up 9 VAC on a neutral terminal?

Anyway, I fixed the problem by simply changing outlets in the bedroom.

Now....all I have to do is figure out where 9VAC are coming from on a neutral terminal......?????????

Dick:confused:

Same answer. Your neutral line on your AC is ungrounded. You
need to talk to an electrical person to check your household
electricity. When the neutral on your electrical service is
properly grounded, all these problems will go away.

Smokey ;)