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Discussion Starter · #1 ·
Hi, I have a small problem with my home theatre setup.


My harmon/kardon receiver is creating noise that I see on my TV.


When using DVD, I see absolutely no noise on the TV at all.


But, when using either the cable box or the VCR, I see noise on the TV whenever the reciever is powered on.


The reciever doesn't even need to be connected to anything, just plugging it into the AC outlet and turning it on, creates this noise. I tried unplugging all RCA's from the back, and still get noise.


When the reciever is turned off, I get no noise whatsoever.


It's a really, buggin me! :(
 

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when a cable tv feed is connected to your ht system a grond loop can develop. a grund loop can develop when two or more grounds have a differance of resistance between them.Try using a 2 prong adapter from your cable box to your outlet this may solve the problem. if not tributaries makes a grond guard video isolater that sould to the trick.
 

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CZ,


what kind of noise do you mean? speckles? or dark bars slowly moving up the screen? The bars would be caused by a grounding problem. Try disconnecting your cable connection and just watching a prerecorded video tape, not one recorded off cable. If the bars are gone, it's a cable TV grounding problem. A ground isolator may help, but you also should get the cable company to check the cable grounding at your home.


There have been many discussions on the AVS forum about grounding issues. The search button is your friend.


If you use a two-prong "cheater", it should only be used to verify that you have a ground problem. It should *not* be installed permanently. Doing so can be lethal.


Equipment that uses a 3 prong power cord with a ground pin uses it to ground the case for your safety. Some kinds of power supply failures will result in 110VAC being shorted to the case. That is not good for anyone touching it.


Most consumer grade equipment, including cable decoders, use two prong power cords. Their cases are carefully insulated, not grounded.


I hope this helps a little.
 

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Discussion Starter · #4 ·
The noise comes in the form of bars going up and down the TV screen.


The problem was there even before the cable box ever came.


It does happen with pre-recorded (original) movies.


I found out that there are no sockets in the living room that use all three wires.


In other words, it might be a three pronged socket, but it's fake.


Is this what's causing the problem?


What can I do to fix it, if so? I'm no electrician, but I do have a toolbox. :)
 

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Another common cause of "hum bars" is plugging different equipment into different lines coming from your power distribution panel. This is most easily fixed by plugging them all into a power strip so that all of your A/V equipment is powered from the same wall socket.


Most houses are powered from two of the three power phases used by the power company. Different outlets in the same room may be connected to the different phases. If different equipment is powered by different phases, then their grounds will be at slightly different AC potentials. This will cause a very small AC current in the cables that connect them together. This current causes "hum bars" and, in the worst cases, audible hum, too.


Sometimes hum can be seen or heard when using separate outlets that are on the same phase but different circuits. This can happen when much different amounts of power are being drawn on the different circuits. A slight amount of voltage is lost due to the resistance of the wiring. Since the voltages on the two outlets are slightly different, again current will flow between the equipment plugged into them.


Most of the time TVs, receivers, DVD players, CD players and VCRs draw much less than 100 watts each, the equivalent of a light bulb. Plugging them all into the same outlet should not cause problems. Most home power circuits are rated to carry up to 15 amps. At 110 volts, that translates into about 1600 Watts..


I hope this helps a little.
 

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Discussion Starter · #6 ·
Selden Ball, I tried plugging everything into it's proper slot on my Monster Cable power strip. The same one that is designed to minimize noise.


I then tried removing the reciever and plugging it into a power outlet across the room. This helped a little, but the noise bars are still very much visible.


An interesting note. The bars become less visible when I select the optical or coxial audio output ont he reciever. Huh. mmm.


Anyone have any ideas? :)
 

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It's beginning to seem that there may be a problem in the power supply in the receiver. I'd suggest trying to get a (cheap?) loaner to see if replacing the receiver fixes the problem. If so, hopefully you'll be able to get it repaired under warrantee.
 
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