# Hum



## Bugbitten (Feb 12, 2008)

The hum is back.

I've had issues with the cable bax as of late (moto Moxi). If finally quit updating the program guide.

Newwave (bought local Charter) send out the repair guy. He removes the isolator http://www.axiomaudio.com/groundisolator.html and all is well with the box, but now I have the hum again. He says the isolator was blocking the cable box connection to the IP address. I could see that it was not getting the IP and now is.

I have used the isolator for _*years*_ without issue.

Removing the cable connection OR unplugging the cables box power cable removes the hum. The cable box is a 2 prong plug.

Help!

Bug


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## woofersus (May 6, 2008)

Is the sub using a cheater plug?


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## Bugbitten (Feb 12, 2008)

woofersus said:


> Is the sub using a cheater plug?


Yes, and unplugging the sub from power and /or sub cable as no effect.


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## Bugbitten (Feb 12, 2008)

Everything is plugged in a special 20 amp circuit just for HT.


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## knightgambit (Sep 30, 2009)

I just acquired hum in my system and it turns out I needed to go to a 2 prong for the LCD I put in. Everything else was already 2 prong, so somehow that was causing the loop / hum.

:no clue:


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## dane (Aug 30, 2007)

Bugbitten said:


> Removing the cable connection OR unplugging the cables box power cable removes the hum. The cable box is a 2 prong plug.


What comes out of the cable box downstream to your equipment? Another RG6, or A/V component cables, or something else?

It's still related to the grounding of the input coax cable, by the sounds of it. But your box needs bi-directional communications. *Could* be that in years past the signal strength coming into your house was enough to "overcome" (well not really, but I don't want to get all complicated here) the ground isolator that you had in place, and now the signal coming into the house isn't as strong as it used to be... this is all just conjecture of course on my part.

Regardless, if you have coax coming out of your box, try putting the isolator on the cable from your box to your equipment. If you have A/V cables coming from your box, then it may work to get A/V ground isolators for those cables. I know they have them for audio RCA cables, but I'm not sure that they support full video bandwidth or just audio bandwidth. You could always try just your audio cables first and see if that removes or at least reduces the hum, but I suspect it would still come through the video cable shield wires even after you blocked it from your audio cable shielding..

hope that helps,
..dane


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## dane (Aug 30, 2007)

knightgambit said:


> I just acquired hum in my system and it turns out I needed to go to a 2 prong for the LCD I put in. Everything else was already 2 prong, so somehow that was causing the loop / hum.
> 
> :no clue:


even whatever your CATV coax plugs into is 2prong, you still have the outer shroud / shield of the actual coax cable that is of a different ground potential than your electrical outlets that can cause big problems (even if the difference may be small).. so a 3-vs-2 prong change in that location may not make a difference..

..dane


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