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#1
05-31-2005, 08:06 AM
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26jc20 restored
well i'm pretty much done with the restoration of Zenith's re-entry model into the color market circa 1962 just as I remember the color looks typical zenith, with their sheet-beam demodulators, the picture quality other than the color is excellent. will post some img's
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#2
05-31-2005, 11:48 AM
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Pardon my ignorance, but what are sheet-beam demodulators? Looking forward to the pix.
Anthony
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#3
05-31-2005, 12:33 PM
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The sheet beam tubes have a common control grid and cathode and 2 plates and 2 beam deflection grids...you put the chroma signal from the band pass amplifier into the common grid, and then the 3.58 mhz reference signal at different phase angles into the beam deflection grids. (sometimes the chroma signal is introduced at different phases into the beam grids and the 3.58 signal applied to the common grid).
The color difference signals are then taken off of the plates of the tube...I think there is enough amplification in the tube that these signals can go right to the crt grids without another amplifier stage between.
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#4
05-31-2005, 03:57 PM
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Thanks for the edumakaytion Chad. I take your previous comments to mean this results in a less than stellar picture?
Anthony
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#5
05-31-2005, 04:39 PM
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The Zenith sets I have using the sheet beam tubes seem to have good color quality to me...they seem to have fewer color related problems than the RCA sets.
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#6
06-01-2005, 04:27 PM
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The sheet beam tubes are almost ideal balanced multipliers - very linear, which leads to using them for single-sideband transmitters. Complaints about the color in sets using sheet beams could be due to other things, e.g., too-narrow-band chroma, white point/tracking of CRT not proper, color matrix not designed to your taste, or just these demods showing every mistake in the transmission.
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Linear Mode
