
| The tuner unit
converts the incoming sound sound and vision carriers to their IF frequencies.
For more information on how this is done, read the page on AM radios. The oscillator is protected against frequency drift,due to temperature changes, by the Automatic Frequency Control (AFC). The IF amplifier has a bandwidth wide enough to pass both sound (33.5 MHz) and vision (39.5 MHz) IF signals and their sidebands. The video signal is demodulated and amplified and is used to control the brightness at each particular point on the screen. The sync pulses are separated from the composite video signal by the sync separator. These pulses are used to control the frequencies of the timebases, ensuring that they run at the same speed as, and in phase with, those in the studio cameras. The timebases
provide sawtooth waveforms which scan the face of the CRT, while the video
signal controls the brightness at each point on the screen.
The line timebase
also supplies the Extra High Tension (EHT) voltage for the CRT final anode.
Due to a mixing
process between the sound and vision carriers, the sound signal appears
as a 6 MHz FM signal at the video output stage.
A power supply
supplies DC voltages to all stages.
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