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Old 08-17-2018, 12:27 AM
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You got me to look at the schematic.

The 4 stage IF doesn't necessarily eliminate the need for a first video amp in terms of video voltage, at least not in terms of luma amplitude. In sets with a first video amp, the first amp is used as a cathode follower for luma to drive the delay line, so there is no voltage gain, just a low impedance output to drive a defined resistance into the delay line. It's hard to know, however, if the final IF output transformer in the Admiral is actually providing a lower impedance than in other maker's designs (supplying more current, not voltage), thereby replacing the impedance matching effect of a cathode follower stage. To answer this speculation, you need to know the turns ratio of the last IF transformer that drives the detector and also calculate how much load the detector and its following circuitry represents.

The luma circuitry in this set also contains some mutually coupled coils that look like video phase correction. Very interesting.
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