Does your TV make a buzzing sound? My new Panasonic does, when it's off. - AVS Forum
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post #1 of 8 Old 01-07-2010, 05:35 PM - Thread Starter
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A few weeks ago I joined and posted here to ask for recommendations between a Toshiba or a Panasonic.
I ended up going with the Panasonic L37S1, based on some feedback and also on its technical aspects, my budget and overall preference for that brand. It's a beautiful TV, the image is perfect and it's exactly what I needed.

But here's the strange thing:
When the TV is on, everything is fine.
When the TV is off, firts I hear what I think is a normal "click" sound of the Tv turning off and then, about 90% of the times, comes a slight metallic buzzing sound that comes from the bottom-back of the panel.
It sounds as if a small metallic cricket was there. (Excuse my lack of other technical words, but I'm trying to give you a clear image of what it sounds like)
Most of the time (say, 90%) that buzzing sound stays there until I turn the tv on again. But some other times in the morning after a few hours of the tv off, the sound is gone.
Some other times (maybe 10%) when I turn off the TV, that buzzing sound doesn't show up.

Like I said. This is only when the TV is off. When the TV is on, there's no buzzing sound, even when it's on MUTE or when I turn down the volume.

This sound is very low. The TV is in the living room and I can't hear it from the bedroom, but as soon as you're 10 feet away from it you can hear it. (I'm the kind of guy that can hear the static sound of a CRT tv when it's on and there's no picture showing, so I might be kind of picky about those things. My wife never hears a thing

Do any of you have, or have heard about this kind of issue with LCDs, even if they are from another brand?
Without technical expertise on the matter, I feel that the sound comes from the electric current on the back of the tv, so this may be a normal thing.
My tv says it was produced in October 2009 and I bought it online this past December, btw. Feel free to ask questions in case I didn't provide other details.
I appreciate your feedback. Thanks!!
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post #2 of 8 Old 01-07-2010, 06:42 PM
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your TV is not off it is in standby so that it can be restarted using it's remote.
Your are probably hearing noise created by the TV's power supply generating the minimum power to respond to the remote.
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post #3 of 8 Old 01-08-2010, 10:27 AM - Thread Starter
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Thanks for your reply, walford.
I was thinking it could be related to this you mention.
I called Customer Service at Panasonic and they indicated that I shouldn't hear any sound from the TV when it is off, but I wonder if this even qualify as an abnormal sound. It is my first LCD TV ever, so I wonder if this is part of what comes with this technology, when compared to a classic CRT tv.
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post #4 of 8 Old 01-08-2010, 01:46 PM
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Do you have a dimmer switch on the same circuit?

- Eric
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post #5 of 8 Old 01-08-2010, 02:00 PM
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Quote:
Originally Posted by tripoman View Post

Thanks for your reply, walford.
I was thinking it could be related to this you mention.
I called Customer Service at Panasonic and they indicated that I shouldn't hear any sound from the TV when it is off, but I wonder if this even qualify as an abnormal sound. It is my first LCD TV ever, so I wonder if this is part of what comes with this technology, when compared to a classic CRT tv.

the noise could come from 2-3 places inside the TV's power supply...

...switching transformers' cores not glued properly, or loose coils around these cores

... switching transistors have ferrite beads around their legs to prevent very high frequency switching rubbish infiltrating other areas of the TV (this very high frequency noise can affect other sections of the TV quite badly and is hard to remove, so prevention is the best cure - hence the reason for beads as close as possible to switching transistors) now, the beads have to be glued to the pins to prevent their movement... sometimes there's not enough glue, or the glue hasn't settled properly, so the ferrite beads start making annoying sound the basically oscillate at switching frequency

the switching frequency and current are different in stand-by mode from full ON mode... and you ear is more sensitive to stand-by switching frequency

.. this can be easily fixed if you are savvy with electronics and you worked with high tension (mains) powered-up devices before...

you could try one more thing turn ON the quick start-up (or similar setting that will change the current draw from the power supply in stand-by mode) that may be enough to change the switching current and just enough to prevent things from oscillating or just replace the whole TV

Boky
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post #6 of 8 Old 01-09-2010, 12:45 PM
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post #7 of 8 Old 01-09-2010, 01:14 PM
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As I sated before your TV was in standby not trully "off" If yoiu want it to be truly off then after you set it to "Off" you then unplug it I bet the sound goes away.
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post #8 of 8 Old 01-11-2010, 08:06 PM - Thread Starter
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Thanks to all of you for your answers and guidance on this.

Quote:
Originally Posted by 68rustang View Post

Do you have a dimmer switch on the same circuit?

Do you mean, a dimmer switch for the lights in the room? If so, there are no dimmers in the room or even the apartment where I live. I've read they cause problems with electronics in the same circuit though.

Quote:
Originally Posted by Extreme_Boky View Post

the noise could come from 2-3 places inside the TV's power supply...

...switching transformers' cores not glued properly, or loose coils around these cores

... switching transistors have ferrite beads around their legs to prevent very high frequency switching rubbish infiltrating other areas of the TV (this very high frequency noise can affect other sections of the TV quite badly and is hard to remove, so prevention is the best cure - hence the reason for beads as close as possible to switching transistors) now, the beads have to be glued to the pins to prevent their movement... sometimes there's not enough glue, or the glue hasn't settled properly, so the ferrite beads start making annoying sound the basically oscillate at switching frequency

the switching frequency and current are different in stand-by mode from full ON mode... and you ear is more sensitive to stand-by switching frequency

.. this can be easily fixed if you are savvy with electronics and you worked with high tension (mains) powered-up devices before...

you could try one more thing turn ON the quick start-up (or similar setting that will change the current draw from the power supply in stand-by mode) that may be enough to change the switching current and just enough to prevent things from oscillating or just replace the whole TV

Boky

Thanks a lot Extreme_Boky, this answer goes along with my idea that this is part of the technology and how components are supposed to work inside the TV.
I have thought about replacing the TV but the whole process of doing that (I bought it through amazon so would need to ship it back, I also live in NYC and don't have own car to move my tv to post office, have no help to do that either, etc) and also considering this might be a "natural" sound that could come in the replacement tv I get, makes me think I should just stop being so picky and simply enjoy my TV (which I do, btw)

Quote:
Originally Posted by EliteData View Post

based on your information, i would say your set is within normal operating specifications.
especially if you can hear the 16Khz oscillation on a crt with the high voltage static.
what youre hearing the is switched mode power supply in standby mode.
if this noise bothers you, use a remote controlled a/c switch, such as a cable box with a switched outlet and simply turn the tv off first, then turn off the cable box.

Thanks. Based on what others have commented this should be normal I guess.
I don't have cable box/DVR. I connected the coaxial cable that has always existed in my apartment and get a couple of the cheap cable channels (besides the usual OTA channels). I am not sure if I'll go with Cable TV, since I'm on Netflix, and I am also getting a Roku now.
The other things that are plugged to the TV are the DVD player and the PS2, both of which are off most of the time.

Quote:
Originally Posted by walford View Post

As I sated before your TV was in standby not trully "off" If yoiu want it to be truly off then after you set it to "Off" you then unplug it I bet the sound goes away.

thanks Walford, you've been very helpful.
LOL, yes, the sound goes off if I unplug the TV, but I think I can live with it.
One person that would have done that was my dad. He believed everything would caught fire if left plugged for too long.
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