Dynex LCD tv hum

[lipwak]

Hi,

I have a Dynex DX-24L150A11 LCD HD tv. I bought it last June and I just don't remember but I don't think it had a hum problem until a month or two later. I have the audio outputs connected to an A/B switch that runs to my stereo. I also have 4 VCRs, a DVD recorder, a DirecTV HD DVR, a Linksys router, a cable modem and some other stuff hooked up to a power strip and an extension cord all going to an outlet near them. I have all the video stuff interconnected so I can record and play anything from each source and watch it all on the tv.

A month or two after I bought it, I started to notice the hum enough to write it down. Since then I disconnected everything and hooked them all up again to try to figure out where it was coming from. A month or two ago I figured out it was coming from the tv so I sent it off to be fixed. It only is noticeable from the audio output. The speakers are so small and tiny I doubt they would let you hear it if there is any hum there...

Long story short, they didn't fix it. They said they couldn't hear the hum. They didn't put it on a scope and I'm guessing whatever speaker they used wasn't veru good or that background noise in the work area masked it.

When I got it home, I plugged the audio cables in to the stereo and without hooking anything else up to the tv other than the power cord , I heard the hum. To me that cinched it. All the other sources are plugged into the same outlets and there is no hum. I tried a different outlet. The hum was there.

I then got a 3 prong adapter to remove the ground. That did it. While I can hear some hum when I crank the stereo volume dial up to about 1 o'clock it is MUCH better. (I also tried a different power cord to the tv. It didn't fix it.)

So, my question is, can I conclude that there is something wrong with the tv?

I can live with it and probably will since Best Buy wants me to bring it back 3X before they will exchange it. By then it will be out of warranty. Is there a risk that something else will go wrong since the hum is indicating something is wrong anyway? A short? Or is this just bad design?

One other thing I noted about this tv is that it's audio output is 10db lower than the DVR's. I've asked Dynex about this and they just say that tvs are different. Of the 3 I've had before, this is the only one with hum and much lower output. All my other tvs have been hoooked up to the same stereo setup.

Many thanks for any help. I appreciate it.

Cheers,

John

[Vidd]

Unplug everything from the power strip. Remove all connections to the TV. Connect the DVD player directly to the TV, the DVD player and TV should not be connected to anything else. Have all other device cables pulled and unplugged. Only have the the TV and DVD plugged into the power strip. Play a DVD and listen if you hear a hum. If you do, I would say its a defective TV. If you don't hear the hum, it is a ground loop problem.

The most likely source of a ground loop would be the coax cable of the cable modem.

[lipwak]

Wow. I did as you said. Hooking up the DVD recorder, I have never heard it so quiet! Cranked it to the max and it was beautiful. I didn't do any more testing and will leave it as a ground loop problem that is now fixed. What I do wonder though is why did I hear hum when nothing else was plugged in but the tv (and it wasn't on). That would indicate to me that the tv is causing the problem. Removing the ground has fixed it but it still points to the tv, doesn't it? (The coax cable could be causing it but it doesn't run that close to the power cables. I didn't unplug the modem in this latest test...) I do get a little bit of hum when I turn the tv off and crank the volume to the max but it is nowhere near what is was before. Entirely liveable.