Noise in my AV setup.

[Lonestar382]

I have an 02 HR Navigator that we have enjoyed for several years. One issue we have had since purchasing the coach is very poor picture quality on our coach. Up front we have a 42" Plasma fed with a coax feed from my AV cabinet. I am running a KVH R6SL that is a little over a year old. The TV is plagued with slow moving gray lines that move upward over the screen. There is also a constant "hum" through the Sony surround sound system. When we unhook from shore power, and run on only the inverter, the picture is clean and there is no noise in the surround sound. It appears to me that the battery charger, or converter is causing noise to interfere with the A/V system. Where can I start trying to correct this problem. It is aggravating to have several thousand dollars of A/V equipment and have such a poor pic. Please help!

Thanks
Corey

[BoonHauler]

Do you have a Solar system?

[wintersun]

Both symptoms are ones associated with a poor ground. I would look for a poor ground connection that is shared by both the TV and sound system.

A hum with a sound system can also be the result of an unshielded wire that is picking up stray signals from power supplies or even a neighbor's equipment. Any long wire has the potential to function like an antenna in this way.

[Lonestar382]

Sorry, yes I did unplug from shore power.

[MrWizard]

Did you unplug Coach shore power
So the charger part of the Xantrex is turned off
This will help determine if the Xantrex is radiating noise, for the coax to carry

[Lonestar382]

Today I unhooked the AV system from the coach power and plugged it into an external source. Still no change in the picture. So I'm assuming the noise is coming from the coaxial cables and not from the power cables. You guys may have been saying that all along and I didn't understand. I have two LED tvs in the coach that aren't drastically bothered by the lines. The only major complaint is the plasma. Should I just plan to swap the plasma for an LED? Should I call Xantrex and ask them for assistance? Would temporarily grounding the inverter/charger to a ground rod help trouble shoot? Thanks again.

[wa8yxm]

Two common causes of that

1: MSW inverters.. The slow moving gray line is a staple of MSW inverters in fact, that is called a HUM line.

2 Ground loops. though USUALLY they do not bother receive only installs. here is the problem

You have multiple TV's. all hooked to one distribution box, the box is grounded to the chassis (12 volt ground) and all the TV's are grounded through the 3rd wire to the same chassis.. This can cause issues.

You can easily test that one. You may also have A/V cables providing still more paths to ground (loops)

One way to test the 3rd wire loop is this.

Ebay Link

Try one or two of those on some of the sub systems and see if it helps. I keep one handy for other jobs anyway.

Ground loops are a major PITA.. There are ground loop breakers you can buy.

[Lonestar382]

I will unplug from shorepower and run direct from an external outlet this afternoon and see what that does. I have a Xantrex 2500 watt inverter with built in charger. I may try directly grounding the charger to a temporary ground rod external of the coach and see if that doesn't help direct me to the source. Thanks so much for the replies!

[MrWizard]

make model # of inverter
good possibility that you have a Combo inverter/charger

shore power pass thru is built into the combo unit
meaning replacing the converter means installing a "replacement" unit that is also a combo unit

try this test
get a long 15amp extension cord, unplug coach from shore power unplug TV and media from internal outlets, plug into the extension cord

if this problem has existed since NEW, then the combo charger is faulty or very likely has a loose ground which allows interference to be on the 120v pass thru

[TucsonJim]

One more area of interest. Do you have an antenna amplifier in your AV circuit? If so, try shutting it off or bypassing it.

[TucsonJim]

Here are some more things I'd try:

1. Disconnect the rig from shore power, and run an extension cord from outside directly to the AV system. If it's clean too, it really starts to point to the converter.

2. If the signal is clean with an extension cord, leave the A/V system running on the extension cord and plug the rig into shore power. This will fire the converter up. If the noise comes back, it once again points to a potential converter noise issue.

3. Even if the converter (or another electrical appliance) might be the issue, you have more checks to make. make sure that you eliminate as many coax connections as you can between the dish, receiver and TV. Directly linking them may point to a connection that is susceptible to RF noise.

4. These are a few tests to help you narrow down the issue. But if you can't find it, you might try a noise filter in the coax line to filter out the extraneous signal.