Quote:
Originally Posted by radio nut
Turn it on and the sound is great......give it about an hour and it slowly starts buzzing through the speaker.......
text on the screen is worse.
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I assume that the set is an intercarrier design. What usually happens to create such buzz is the video carrier momentarily disappearing when there is peak white in the video. Peak white corresponds to the lowest RF level in the modulated TV channel, and a misbiased or misaligned video IF stage going into cutoff killing the video carrier when the peak white happens. The video detector creates the 4.5MHz sound carrier by beating the sound carrier against the video carrier, and if that video carrier isn't there, you get no sound carrier into the 4.5MHz sound IF. These sound "holes" end up sounding like the buzz you're hearing.
I have a TV that suffers from this, but I cheated by reducing the amplitude of the video feeding the RF modulator. Leaving more RF amplitude when peak white happens.