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Topic:
Bad HDMI port and 60 Hz hum
This thread has 4 replies. Displaying all posts.
Post 1 made on Monday September 26, 2022 at 10:11
Chris L
Founding Member
Joined:
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October 2001
355
Clients cable went out, cable company came out to fix it and found a bad HDMI port on the Denon receiver. To get it working they used a different port on the receiver. They also replaced the old cable box with a new Contour box.

I came out to program the remote and noticed the system now has a 60 Hz hum coming through the speakers in zone 2 when listening to cable. Zone 2 is RCA out of the Denon into a Parasound Zone Amp When I disconnect the RG6 cable from the cable box the 60 Hz hum goes away. I doubt its a ground loop since the system has been fine for years.

Is this AC current coming over cable line and could this also have caused the HDMI port to go bad.

Google search showed everything to loose ground in the breaker box, bad CATV amp on the utility pole to your house will catch on fire.
Post 2 made on Monday September 26, 2022 at 10:21
buzz
Super Member
Joined:
Posts:
May 2003
4,366
I'll bet that there was a nearby lightning strike that damaged the cable box and HDMI input. As the cable company fussed with things, the cable ground probably got disconnected. Most of the installers in my area don't see any point in that ground. Even if the ground was not deliberately disconnected, corrosion or accident may have eliminated the ground.
Post 3 made on Monday September 26, 2022 at 10:33
Brad Humphrey
Super Member
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Posts:
February 2004
2,586
If they messed with the connections coming into the house (which includes the grounding block), why would you think it couldn't be a ground loop? If they changed anything with the ground, then it absolutely could be getting a ground loop now.

I would check and see if the cable is still grounded at the DEMARC (point of entry). Check both ends - the ground block where the cable screws in and where the ground wire attaches to the house ground.
If all looks good, temporarily disconnect the ground and use your DMM to measure any voltage difference between the ground block and the ground wire. Remember to reconnect the ground.
Next disconnect the cable line and measure across the center conductor and shield for any DC voltages.

If all that looks good, install a Jensen ISO on the cable box's coax input and see if the noise goes away. If it does, check and see that all the channels still come in and leave the ISO in place if it does.
If the noise is still there, this will require a much deeper dive and time.
Could be a defective cable box, swapping this box with another one in the house could be revealing.
Post 4 made on Monday September 26, 2022 at 14:03
Ernie Gilman
Yes, That Ernie!
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Posts:
December 2001
30,104
Brad has this totally covered, though I would go one step further. He says DEMARC is the point of entry, but the concept is slightly different: the DEMARC is the point of demarcation, where on one side of that point everything is the cable company's (or phone co, etc.) responsibility and on the other side it's all your responsibility.
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
OP | Post 5 made on Monday September 26, 2022 at 21:29
Chris L
Founding Member
Joined:
Posts:
October 2001
355
I will check it out and post what I find.


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