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I'm not sure exactly what kind of "noise" or "distortion" you may be experiencing, so I'll make a couple of guesses about what the problem may be.
If your local analog signals had been weak, and your picture with the converter box is prone to very high contrast or "tears up", you may be able to fix this by backing up on the AGC control on your set (presuming it has one). When only weak analog stations were feeding the set, signal overload was never a problem. With your converter box, a strong analog signal (capable of overload) is fed to your tuner, whether the DTV signal the box is receiving is across the street or from the deep fringe.
As far as audio noise, this is very common, if your box is not delivering fully-modulated audio to the set. Most CECB's have a volume control inside the box (allowing the user to change volume by remote control, even if the set does not have remote). If the volume setting (inside the CECB) is not at maximum, you are turning up the volume on the set to compensate, which reveals the noise your set's audio chain always had. A problem that is just as serious, and not as well known, is that many CECB's have two "audio modes", one for when the user is using RF input (ch3/ch4), another for when the user is using audio inputs (red/whi RCA cables). When set on "A/V out", the volume level (even on ch3/ch4 FM carrier) is far below what it would be using the "RF out" audio mode, so make sure the audio mode is set to "RF out".
That being said, I still notice that video intercarrier buzz (which, IMO, seems to have plagued all old sets, even when I was little and those sets were new) seems to be worse with CECB's than it had been with analog OTA signals, and worse with some CECB's than with others (I wonder if CECBs have a whiter max white than analog signals did?). It was a problem with my Emerson 1224, but recently replacing the 5AN8 and 5T8 tubes (in the audio IF, discriminator, first audio circuits) has made the situation much better.
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02-21-2010, 01:40 PM
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