Quote:
Originally Posted by Penthode
There a number of variables at play here! Yes the alignment may be out. But the oscillator may not be at 93MHz. Maybe Chris tuned to an image or harmonic? How certain are we the oscillator is correct?
Certainly the fine tuning test will show if we are in the ballpark. If the video carrier is not on the slope at 50%, the picture will be smearyand awful anyway.
I see impatience here. Too often I see the knowledge we have gathered taken for granted.
If the alternative is to feed the video amplifier, fine. But will no contrast control in this set to set level and assuming the output composite analog video polarity of say a DVD player is negative sync you may not need to invert video. Is Chris up to devising a way to interface the video and manage signal level?
It seems simpler to me to resolve the relative simple problem the set has rather than introduce another problem. Maybe the best way is to let somebody else work on it.
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I went back and reread all the posts. What strikes me odd is the Leader test pattern gets a signal through to the output of the second video amp, enough to drive the CRT well with a high contrast test pattern, however Chris has said his over the air box gets little to no legible picture. We have not been shown what the signal from the over the air box looks like, but he hints it has a poor picture on other TV's as well. I would assume the RF output has something wrong with it or it's signal is much weaker than the Leader. Is the over the air box outputting on the same rf channel as the Leader, or are we comparing reception on two different channels on the 721 tuner? Given the digital signal source, a properly working converter box should not produce a weak or snowy rf signal - they more less lock in or not. So without a decent rf modulated video source it's very difficult to observe the fine tuning detail you're looking for. I would prefer to see a signal from a known good DVD player feeding an rf modulator outputting on Ch 3 or 4.