HDMI Cable Hum

[shadowlight]

Could use some suggestions on how to get rid of hdmi cable ground loop hum.  I have search and all solutions that I found keeps talking about how to get rid of it based on rca/catv environment and not hdmi.  The hum is been around ever since I finished the basement and hooked up the projector.  If I disconnect the project hdmi cable either from the projecto or from the receiver the hum goes away.

The one thing that I have not tried is cheater plug on the projector power.  Will try it to see if the hum goes away.

[richidoo]

Hum in a video system usually originates from the video signal ground, especially cableTV. Cable ground is shared through the neighborhood with lots of temporary connections, corrosion, old equipment, etc. That's why it must be earthed again at your house. Check that your cableTV cable is connected to the copper earthing rod as it enters your house. If that's OK try disconnecting the cableTV wire from the system. If that stops the hum even when projector power cord is grounded, then use this on your cableTV input:
http://www.jensen-transformers.com/datashts/vrd1ff.pdf
It is expensive compared to cheap Chinese brands, but they will break over time and this one will last. It is actually a capacitor, not a transformer.

Since the projector is a high current appliance, I would want to keep a safety earth on it and find another way to kill the loop.

You are correct to suspect electrical earth if the projector only has two wires connected, signal and power. If the cableTV idea doesn't affect a change then check the house wiring connections for all of the outlets on the circuits powering the receiver and the projector. You are looking for a loose ground or neutral on any of the outlets on those circuits. Also double check that the bonding cable from the service panel to the earth rod is good. Shut off those circuits before opening up the outlets.

The outlets should have the wires wrapped around the side screws, not wires stabbed into the back holes of the outlet. Tighten all the screws on every outlet of every circuit in your AV system. If you find some are loose, put it on your honeydoo list to check the whole house eventually.

That oughtta keep you busy for a while...  
Good luck. You have to have a can-do attitude for ground loops, they can be frustrating. But they can always be solved.

[shadowlight]

Rich,

Thanks for the information.  I will recheck the CATV ground.  At one point I did have it unhooked from everything and it still hummed with just the receiver, projector and amp connected.  Would having the outlet tester with GFCI make it easier to track down the issue?

[richidoo]

If the ground connection on the outlet is totally open then that tester will show the problem. But if the ground is weak, like a loose connection but still touching, it may not show the problem. You have to kill the power to that circuit and open up each outlet to inspect the connections. If they are back stabbers move them to the screws. Tighten them down with your full man strength and a big flat screwdriver. Make sure the wire has a full 180+ degree loop tight around the screw. 

I assume you have quality brands of projector and receiver, that each have good signal ground design inside. Assuming that, they should have HDMI connections grounded to chassis. Assuming that, and no other components connected to receiver or projector, just two power cords and one HDMI between them (and speakers) and still humming the only thing left is high resistance between the ground connections of the two outlets being used for receiver and projector.

Understand that ground wires are strung in series between outlets on a circuit branch. So every outlet in the string of a circuit that precedes the outlet being used will contribute to the quality of ground at the used outlet. In other words, if there is a bad ground connection in a wire nut or a back stabber or loose ground screw on an outlet upstream from the project or reciever outlet, then the ground at the Rx outlet will be bad also. That's why you have to test and tighten all of the outlets on a given circuit, especially for appliances whose performance depends on low impedance and quiet ground. The projector outlet may be good, but the outlet preceding it may be bad, and ruining the ground impedance for the projector and causing the hum. This is why dedicated circuits are so beneficial for audio equipment that needs excellent power connections to perform well.  Let me know what you find?

[BobM]

It seems to me that the better HDMI cables all have ferrite on the ends. You can pick up small ferrite collars pretty cheap at Parts Express, I believe. It may be worth a shot.