General Question

webmasterwilliam's avatar

Why does my TV hum when white letters come on the screen?

Asked by webmasterwilliam (165points) September 11th, 2008

It’s really frustrating and I can’t seem to fix it.

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7 Answers

IchtheosaurusRex's avatar

That’s happening because of overmodulation of the luma signal. This often happens with cable broadcasts, or when you have an amplifier on your antenna. The signal being received at your TV’s front end is too strong for the AGC to adjust, and the buzzing is the result. This can also happen at the point of origin.

You can get an attenuator for your antenna or cable feed to see if that helps. Here is a link:

Plug it in line between your antenna/cable and your TV set.

webmasterwilliam's avatar

Great information. I subscribe to DirectTv, which is going into my DirectTV Plus DVR which is going into my Panasonic SA-HT790V Home Theater sytem and finally to the Philips 27” TV model 27PT643R37A. I tried to look up the specifications for the desired input dBmV, but was unsuccessful. I don’t have any test equipment to determine what value dBmV is currently going to the TV either, unless I can use a regular voltmeter.

Any suggestions?

IchtheosaurusRex's avatar

You would need special equipment for that. A VOM won’t read in the RF range. Where do you have a 75 ohm cable, if anywhere. That’s where you’d need to put the attenuator. I don’t have much experience with satellite systems, but I’d suspect the front end. Maybe DirecTv can send you another satellite receiver.

syz's avatar

“It’s like he’s trying to speak to me, I know it!”

IchtheosaurusRex's avatar


“Technology is not for wimps” – Dilbert

mamabeverley's avatar

I had this problem with my surround sound system. My mom in law would alway turn up the t.v. and not the surround. It sounded like a leaf blower with the “feed back” It would only happen when the t.v. was up and the cable box or surround was down. (I finally hid the remote to the t.v.)

terrygrant's avatar

i agree with IchtheosaurusRex
after a month with this problem i turned the sound on my sony tv DOWN and the sound on my humax pvr UP
problem solved

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