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[QUOTE=Yamamaya42;3247041
A telltale sign of messed up IF is getting good BW but crappy or no color, why it does this is complicated, but it has to do with how they took the normal BW video standard and crammed color info into it and still had it compatible with older non color sets.
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It depends on what the actual IF response is on the malfunctioning TV. Generally (but see the service data first) the video carrier and color carrier are at or near the 50% amplitude point on the response curve; the 45.75MHz video carrier is there to compensate for how the unwanted sideband is filtered out at the transmitter, and the 42.17MHz chroma subcarrier point is placed there to minimize interference in the picture from the chroma information. The chroma bandpass circuits compensate for this falling response and have to be aligned with a special setup, basically the video carrier modulated by a frequency sweep at the chroma frequency range. If either or both of those carriers is significantly out of place, there are going to be problems with the picture.
Picture problems related to alignment usually end up as ghosting that changes with the fine tuning adjustment, weak or no color, excessive hue shift with fine tuning, or interference patterns in the picture, either from the sound carrier or 920kHz beat from the chroma carrier. These adjustments have to be done with test equipment, they cannot be done visually.
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Erich Loepke
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