LCD TV Hums when Connected to Computer

January 16, 2011 10:28:06 AM

I have a 42 Sylvania LCD TV that quite a while ago I started watching movies on via the computer. It connects to the computer through the HMDI port and also has a DVR cable box and another DVD player attached to other inputs.

With everything disconnected and just my hdmi attached to use it as a monitor [full1080p] to avoid other possible grounding issues I have tested it and it Hums.

Now usually these hums are grounding issues, I do not think so and here is why.

When I first turn on the TV and extend the desktop to the LCD TV. It does not make a sound. I can use the internet etc anything, basically use it as a giant 42 inch monitor. But as soon as I turn on anything that utilizes sound, it starts humming and loud. Loud enough that unless Im watching a movie at normal Volume or higher it is real annoying. If I wanted to watch something late night on low volume, no way.

What causes the hum to start:
IF the HDMI TV is set as default sound device , When I activate any program that uses the sound card for any reason, HUM comes. SO basically once I turn on VLC to play a movie or click on a link or web page that wants to make a noise, anything. even system sounds or even sounds that play through the computer speakers when the TV is the default sound device. I can run 2 different sound sources at the same time like play a game on the computer speaker while a movie is running through the TV sound. I dont know why but some things let me do that some things dont. From what I have read that's not supposed to be able to happen either. Different issue...not the important one now.

I can mute the TV. Hum goes away until i unmute

Adjusting the level of volume on the TV or the computer has no effect on the Hum what so ever.

To stop the hum I can turn off the tv and turn it back on, no hum.

If the default sound is the Computer speakers, then no hum for any reason, its only when the computer wants the tv to make sounds.

This isnt too bad because if I jsut buy a real nice sound setup and run it all from the computer sound or spdif then it never hums, I just havent bought a nice sound system yet. I would like it just just not happen, but...

Anyone have a clue what this may be? I am positive it is not a software issues, it doesnt matter what the program is it hums. I have no other LCD tvs to test this with either. And it does not hum on its own. I know some TV's do. If it does its so minimal I have never noticed.

i7 950
asus sabertooth x58
6gb corsair @ 1600hmz
Sapphire HD6970 [card doesnt matter though, my HD4890's did it and so did an old Nvidia 8600GT

Thanks in advance!

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leon2006

TV Expert

January 18, 2011 9:35:48 PM

On your TV select audio source to digital (or HDMI) some HDTV don't automatically select to correct audio input.

On your Video CARD for HD6970/HD4890: If you are using DVI port.. For it to work you need ATI Provided DVI to HDMI converter. Other 3rd party converter don't work. No audio comes out. I get audio and video from my 4890's and i use ATI provided ATI/HDMI converter. I check out several converter was able to make it run on the one that came with my video card.

ATI/HDMI converter is free. Just call your video card vendor and after 3 days it will be in your mail.

Try using a different HDMI cable. I don't think it is cable related but you can never tell until you try it.

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leon2006

TV Expert

January 18, 2011 9:37:28 PM

If you have another HDMI input on your HDTV try it as well. If you have another HDMI source (i.e. PS3 or Blue Ray/DVD player) that use HDMI try it as well check if you can get the audio to work

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etdavenport

January 26, 2011 12:04:10 AM

it does it on all sources, HDMI or regular monitor. and it does it on either sound devices not just the HDMI. with cables made no difference.

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kwd

October 13, 2011 5:19:13 PM

I had a similar problem--only worse. Not only hum but dying components in my two PCs and their associated components.

All connected computer equipment should be connected to the same 110 volt socket to prevent eddy currents, hum and damage because of the possibility that the hot and neutral wires could be reversed between different sockets. Even if you make sure of this, like I did, there can still be problems.

I had bought a voltage regulator and surge suppressor combo for each of my two tower computers. Both voltage regulator units were plugged into the same wall socket which I had tested to make sure it was grounded and the polarity was correct and then into their individual UPSs--so I thought everything was fine.

After installing the new voltage regulators, over the next 1 1/2 years I had over $1000 worth of component failure. 3 Power supplies, 2 network cards, USB components, 2 high dollar UPS units and 3 mother boards as well as other minor failures. I could not figure out what was wrong and I have years of experience as an electronic tech.

I was having problems with some kitchen appliances shocking me (mildly) when I was grounded and touched them so I decided to buy a polarity and ground fault tester and fix it before I got electrocuted... <grin>

After fixing the kitchen problem (reversed polarity with no 3rd wire ground) I decided to use the tester to check my computer's AC connection. The wall socket was perfect. While standing there I wondered if the 3rd wire ground actually worked all the way through the voltage regulator and UPS. and decided to test the connection on every component, from the computer through to the wall socket, for both computers.

The first computer's connections were perfect all the way through but when I plugged it in to the second computer the polarity was reversed. OOOPS NOT GOOD. I traced it back to the voltage regulator. The input to the voltage regulator was correct but the output of the voltage regulator had reverse polarity.

I took the voltage regulator apart and discovered that the factory had wired it wrong. I rewired it correctly and have not had any problems with hum or dying hardware since.

So... My advice is to never assume that any AC powered component is wired correctly (especially if it is made in China) and test everything before you connect it to your "system".

Theoretically this polarity problem should not cause equipment damage--but that depends on all equipment being wired correctly including your house and earth ground rod--which is not something you can depend on. In the case of a dual computer set up where they are cross connected with USB cables and network cables through modems, and routers as well as monitor, keyboard and mouse switches the possible paths for eddy currents increases dramatically and almost anything could happen.

Keith

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