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Customer has a dimmer that quit working, wouldn't turn on the lights at all like the circuit was dead. Pulled the dimmer, there was power to it, found they installed all CFL's on an old dimmer. I installed a CFL friendly dimmer and all dimmable cfl's and it worked fine. As I was putting the plate back on I noticed the TV had a slight buzzing (it was off). I checked the connections on the dimmer (it fed the outlet the tv was on) and everything was tight. Was it the dimmer? I have installed a lot of these and never had anything like this before.
 

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Customer has a dimmer that quit working, wouldn't turn on the lights at all like the circuit was dead. Pulled the dimmer, there was power to it, found they installed all CFL's on an old dimmer. I installed a CFL friendly dimmer and all dimmable cfl's and it worked fine. As I was putting the plate back on I noticed the TV had a slight buzzing (it was off). I checked the connections on the dimmer (it fed the outlet the tv was on) and everything was tight. Was it the dimmer? I have installed a lot of these and never had anything like this before.
Does the power pass through the box or is the TV on a dimmer?

Another grounded electronic device can cause tv speakers to buzz when the tv is on...but I've never seen one buzz while off.
 

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My recollection is CFLs are pretty good sized inductive loads, and dimmer switches put out spiky harmonics of 60Hz. The combination of the two puts harmonics voltage spikes back up the line. Just plug the TV into a power conditioner.
 

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Capra Aegagrus
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CFL theory for geeks:

http://www.eetimes.com/document.asp?doc_id=1272528

No modern TV is ever completely off unless it's actually unplugged. I encountered such buzzing a time or three during my electronics career (pre-CFL). It was usually due to crappy filtering on a relatively high-current device attached to the circuit.

Sometimes replacing that device cleared it up, sometimes moving it (or the radio/TV) to a different circuit worked, or using a line conditioner did the trick. Sometimes the client just opted to live with it.
 

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Well, I got that backwards - they're capacitive loads due to the electronics. The article states the lamps themselves are resistive, but the actual waveforms show some slight current lag.
 

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All I know is my battery charger causes my radios to go staticy if it's in the same house. Can't listen to music and charge batteries at the same time...
 
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CFL theory for geeks:

http://www.eetimes.com/document.asp?doc_id=1272528

No modern TV is ever completely off unless it's actually unplugged. I encountered such buzzing a time or three during my electronics career (pre-CFL). It was usually due to crappy filtering on a relatively high-current device attached to the circuit.

Sometimes replacing that device cleared it up, sometimes moving it (or the radio/TV) to a different circuit worked, or using a line conditioner did the trick. Sometimes the client just opted to live with it.
Have you come across a tv that doesn't cut the power to the amp when in standby?
 

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Capra Aegagrus
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Have you come across a tv that doesn't cut the power to the amp when in standby?
Yep, though not in the way you're thinking.

Semiconductor switching, especially years ago, isn't 100% leakproof (though for most practical purposes it can be considered to be). Also, capacitors can remain energized for quite a long time after source Vcc has been removed. If there isn't circuitry to clamp down the input signal line, random noise can still wind up getting processed even with the unit unplugged. :thumbsup:
 

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Yep, though not in the way you're thinking.

Semiconductor switching, especially years ago, isn't 100% leakproof (though for most practical purposes it can be considered to be). Also, capacitors can remain energized for quite a long time after source Vcc has been removed. If there isn't circuitry to clamp down the input signal line, random noise can still wind up getting processed even with the unit unplugged. :thumbsup:
Don't they still use a mechanical relay off the main ps board then IC switches after that?
 

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Capra Aegagrus
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I haven't looked at the guts of a TV for at least 20 years, but I doubt it. Relays cost more and are less dependable.
 

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All these TVs that turn on with remote controls are always on. The old days of an actual switch that kills the power (On/Off/Volume) are long gone. I don't believe I've ever seen a TV that used an electromechanical relay anywhere in the circuitry - as already pointed out there's no real benefit, they're big, expensive, and unreliable.
 

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All these TVs that turn on with remote controls are always on. The old days of an actual switch that kills the power (On/Off/Volume) are long gone. I don't believe I've ever seen a TV that used an electromechanical relay anywhere in the circuitry - as already pointed out there's no real benefit, they're big, expensive, and unreliable.
Turn on a big plasma and tell me where the loud click comes from.
 

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My Samsung flat screen makes a click noise....sounds like a relay to me.., and I have seen it on the main power board. . ..I had to replace some poorly made capacitors in my power source circuit board and there is one in the power circuit area ......just saying,,,,:blink:


What I don't understand is how can a buzz noise come through a Tv when it's amplifier,...and some other main circuits are shut off.....


I just don't get that......:blink:

I run my VFD's on my machines ,when the motor is running,and it is a very high pitched , slight noise that comes through the motors on some of my machines,,,,,and some I don't hear a thing,,,,,but that is a frequency modulation between the windings - totally different scenario .....

But buzzing through a tv when it's off......:blink:



B,
 

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Thanks for the diagram. I also found a Samsung board shot with the relay, so there are no doubt relays out there. I couldn't find an actual *free* schematic to see why the design choice.

Maybe it's an energystar thing - even 50 inch plasmas are below 400W, so it could be handled without relays.

Thanks for pointing it out!
 

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What I don't understand is how can a buzz noise come through a Tv when it's amplifier,...and some other main circuits are shut off.....
Because the buzz comes from the standby power supply magnetics that is always on or perhaps that particular set never powers down its main power supply. Being a switching power supply it draws very little line current when no current is drawn from it. The harmonics from the dimmer are apparently causing a transformer to buzz for some reason.
 
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