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Old 09-16-2009, 06:18 PM   #1
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TV interference when devices are turned on or off in the home - ideas?


I am experiencing electrical TV interference, evidenced by a brief moment of pixelation and/or drop or pop in audio (for DTV), or a brief static bar (analog).

I have a home theater PC setup (using Windows Media Center to record live tv, both COX analog and over-the-air HD) with the following components:
  • My home theater PC (HP quad core, 7GB RAM)
  • TV (Sony 34in widescreen tube TV).
  • Sony home theater sound system (800w ??).
  • Xbox 360

I have noticed interference on the TV when lights, air conditioner, ceiling or bathroom fans are turned on or off (not just in the living room, but ANYWHERE in the house). I am told the outlet near the TV is 15amp, and that even with all my stuff hooked to it it shouldn't be overloading it.

I have tried to isolate the cause of the interference with the following methodology, but still cannot determine the cause:
  1. Antenna reception/interference? Nope. I have a digital antenna in my attic, and first thought this was the culprit. However, I then noticed the analog cable from COX has the same interference on low number channels, even with the antenna unplugged.
  2. Electromagnetic interference/Radio frequency interference? Nope. I have tried ferrite beads/coils, and EMI chokes on my cables. I have also tried surge protectors with EMI noise reduction (70dB), and CleanPower technology. The result: no improvement.
  3. Circuit overload: I think not. If my A/V equipment were overloading the circuit that would explain interference when I turn on or off lights/fans in the same circuit. But why then does it happen when I turn on or off a fan in any part of the house?

Other potential causes, yet to be determined:
  • Grounding? Undetermined. But the surge protectors with indicators of proper grounding have never shown that there is a problem.
  • Bad fuse/circuit breaker? Undetermined. Is it possible to have a circuit breaker go bad without me knowing? and without it tripping? (they all look on to me in the panel box, none half-way). Any other wiring related things I can check myself? faulty neutrals, etc??

I believe a power conditioner/voltage regulator/uninterruptible power supply device at the A/v outlet may help, but I fear that it is only masking a deeper problem with the house wiring or circuitry.

Any ideas? PLEASE HELP!

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Old 09-16-2009, 09:08 PM   #2
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TV interference when devices are turned on or off in the home - ideas?


How often is the interference occuring?

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Old 09-16-2009, 09:43 PM   #3
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TV interference when devices are turned on or off in the home - ideas?


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How often is the interference occuring?
It isn't constant. I believe it to only be linked to the turning on or off of devices in the house. I would estimate it happens maybe 5-10 times in an hour long program. And again, the interference is just a brief (maybe half-second) pixelation of DTV and a half-second drop in audio.
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Old 09-16-2009, 10:13 PM   #4
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TV interference when devices are turned on or off in the home - ideas?


Fluorescent lighting is the likely culprit in my opinion.

You may need to run a separate 15 amp individual circuit to correct the problem.

Also, and this may be a quick fix, but try to figure out if the home theatre circuit is on the same phase in your electrical panel as the other things you think are causing the distortion are. If this is the case call an electrician and have him relocate the circuit breaker to the other phase.

Again, this is just a guess.

Good luck.
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Old 09-17-2009, 05:17 PM   #5
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TV interference when devices are turned on or off in the home - ideas?


nope. i tuned off every circuit in the house. Then I plugged the A/V system into a dedicated 20amp outlet (for the disposal) by way of a 10' extension cord. same result. also, the interference happens when turning on or off any light switch or fan in the house - so this isn't a circuit specific problem, or an outlet overload problem.
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Old 09-18-2009, 11:04 AM   #6
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TV interference when devices are turned on or off in the home - ideas?


If you have a computer UPS or you can borrow one, try running the AV system off of the UPS battery backup. (On and unplugged.) Then see if turning on the light switches still causes the problem.

Basically the AV system would be running on its own power and not connected to the house power. So if it stops, then the interference is in the wiring. If it does not stop, then the interference is "in the air".

If it does stop, try plugging in just certain things to the UPS. Like just TV, just set top box, etc. See if just one of these is getting the interference. (Plug the others into regular AC.)

And don't forget to test other gizmos - like if you have a TV antenna amplifier located elsewhere.

If you track down the problem to being "in the air", then examine your wiring to be sure it is what is recommended - that it is shielded wire.

The general idea of shielded wire is called a Faraday Cage...
http://en.wikipedia.org/wiki/Faraday_cage

Poor quality coax cable can be a cause of noise. Quad shielded RG-6 is the best coax cable. The white coax cables sold in discount stores which does not say anything on the wire are the worst - will let "noise" into the wire.

If a power problem, might want to try a power line conditioner or "online" "true sine wave" UPS.
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Old 09-18-2009, 12:29 PM   #7
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TV interference when devices are turned on or off in the home - ideas?


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Originally Posted by Billy_Bob View Post
If you have a computer UPS or you can borrow one, try running the AV system off of the UPS battery backup. (On and unplugged.) Then see if turning on the light switches still causes the problem.

Basically the AV system would be running on its own power and not connected to the house power. So if it stops, then the interference is in the wiring. If it does not stop, then the interference is "in the air".

If it does stop, try plugging in just certain things to the UPS. Like just TV, just set top box, etc. See if just one of these is getting the interference. (Plug the others into regular AC.)

And don't forget to test other gizmos - like if you have a TV antenna amplifier located elsewhere.

If you track down the problem to being "in the air", then examine your wiring to be sure it is what is recommended - that it is shielded wire.

The general idea of shielded wire is called a Faraday Cage...
http://en.wikipedia.org/wiki/Faraday_cage

Poor quality coax cable can be a cause of noise. Quad shielded RG-6 is the best coax cable. The white coax cables sold in discount stores which does not say anything on the wire are the worst - will let "noise" into the wire.

If a power problem, might want to try a power line conditioner or "online" "true sine wave" UPS.
I am picking up a UPS today to try that very thing out. However, I suspect that the interference is in the air. For example, today my wife was vacumming (12amp vacuum). i had her plug the vacuum in to the same circuit as my A/V TV equipment. There was no interference whatsoever while the vacuum was on, nor was there interference when we switched it on and off.

The coax from my attic digital antenna to the TV I did myself, and it is RG6U quad shield. However, the COX analog is the basic white coax that goes from the side of the house to the TV. I have suspected that the COX coax could be problematic so I have tried disconnecting the COX to the house, but the problem still exists when viewing the digital antenna feed. However, i don't think the interference is the digital feed either, because when i disconnect it and do analog only, the problem still exists.

But i may consider replacing the COX cable altogether and upgrading it to RG6U quad shield anyways, if I thought it would help. Hmmmm.
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Old 09-19-2009, 11:43 AM   #8
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TV interference when devices are turned on or off in the home - ideas?


You're on the right track - disconnecting things and see what happens.

If the white cable disconnected does not solve the problem, then that is not it.

Also check any input cables you have. TV in from another box. Stereo in from something else.

For example I have a subwoofer in my living room and from time to time would get sudden weird noise on it. I replaced the cable from the amp to the subwoofer with a shielded coax cable and that solved the problem.

So that was a case of an "input" (input to the subwoofer) which was picking up external noise "in the air" through an unshielded cable.

BTW a "regular" UPS just passes through the house electricity. But makes its own electricity when on and unplugged. An "online" UPS "makes" the electricity when on. A "true sine wave" ups makes the "best" electricity.

So if a regular UPS, if plugged in, the electricity provided would be the same as plugging directly into an outlet. (Unless it includes a power line conditioner.)

Also might want to check your electrical system grounding. Sometimes there is a cold water pipe ground only, then PVC plastic pipe is added, then there is no longer a good electrical system ground.

Some electronic devices with "polarized" plugs or grounded plugs might use the electric system ground for noise suppression.

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