LCD TV Interference

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bthouse

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St. Louis, MO
I'm troubleshooting why an LCD TV is experiencing interference on the screen. There are several components wired to this TV. The components are split between two cabinets, 1st floor cabinet and basement cabinet. The TV, 1st floor cabinet, and basement cabinet each have their own dedicated
2-wire circuit. The 1st floor cabinet contains the entertainment components. The basement contains surveillance equipment. While viewing the TV through any of the components in cabinet 1, there is interference. When viewing surveillance cameras, no interference. And to make things even more interesting, there are two lights on dimmers within' 20 ft of the TV. If you dim either one of the lights the interference gets worse. The dimmers are not on any of the component or TV circuits. The dimmers are Lutron electronic dimmers. The interference is a white horizontal line that travels up the screen every 15 sec. or so. Anybody got any ideas?
 
grich

grich

Senior Member
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MP89.5, Mason City Subdivision
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Broadcast Engineer
A first guess would be a ground loop between the TV and the 1st floor equipment, but more info is needed:

-What connections are being made to the TV, and from which cabinet (such as composite video on RG-59 from the basement, or an HDMI cable from the 1st floor, etc.)?

-Where is the TV in relation to the cabinets (how many feet of wire)?

gr
 
mdshunk

mdshunk

Senior Member
Location
Right here.
bthouse said:
And to make things even more interesting, there are two lights on dimmers within' 20 ft of the TV.
Click to expand...
Within the first couple sentences, I was going to ask if there are dimmers. Now, I see that there are. Replace them with regular switches as a troubleshooting step, and I think you'll be surprised at the results.
 
StreamlineGT

StreamlineGT

Senior Member
If they are Maestros, just pull the tab out on the bottom instead of replacing them. That should do unless you think the light fixtures themselves are the culprit. It'll be a quick step closer to the cure.
 
StreamlineGT

StreamlineGT

Senior Member
Well gee, that makes me not want to put them in my theater...... But I have Maestro's all over the place, and I don't have a problem with any of my TV's....
 
mdshunk

mdshunk

Senior Member
Location
Right here.
StreamlineGT said:
Well gee, that makes me not want to put them in my theater...... But I have Maestro's all over the place, and I don't have a problem with any of my TV's....
Click to expand...
I don't either, but he said "LCD" TV, which I equate lately to the 99 dollar special at Target. Could also be a wiring issue, up to and including RF ingress on a bad TV cable or component interconnect cable termination.
 
dereckbc

dereckbc

Moderator
Staff member
Location
Plano, TX
You said everything is 2-wire cord connector right. Don't chase ghost aka ground loops, ground is not involved with 2-wire plugs. If it were a ground loop problem it shows up in video as 60-Hz hum bars.
 
wirenut1980

wirenut1980

Senior Member
Location
Plainfield, IN
bthouse said:
How would the dimmers cause the interference without being connected to the TV or the cabinet circuit?
Click to expand...

RFI is through the air, not through conductor connections. Replacing dimmers with a standard switch is a good cheap fast test to see if they are the culprit. I have no idea why it causes problems in some locations and not in others. There is a good link to the FCC page that explains about RFI and even has pictures of TV screens with interference.

http://radiomagonline.com/images/archive/notebook/fcc/fcc_rfi.pdf
 
weressl

weressl

Esteemed Member
Location
Texas by the Gulf, geat crab, great shrimp
bthouse said:
I'm troubleshooting why an LCD TV is experiencing interference on the screen. There are several components wired to this TV. The components are split between two cabinets, 1st floor cabinet and basement cabinet. The TV, 1st floor cabinet, and basement cabinet each have their own dedicated
2-wire circuit. The 1st floor cabinet contains the entertainment components. The basement contains surveillance equipment. While viewing the TV through any of the components in cabinet 1, there is interference. When viewing surveillance cameras, no interference. And to make things even more interesting, there are two lights on dimmers within' 20 ft of the TV. If you dim either one of the lights the interference gets worse. The dimmers are not on any of the component or TV circuits. The dimmers are Lutron electronic dimmers. The interference is a white horizontal line that travels up the screen every 15 sec. or so. Anybody got any ideas?
Click to expand...

As it was pointed out in another post check if the braid on your coax cable is grounded. Each separate run should be grounded at a single point.
 
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