Technicolor - Thomson ICC19, Principles And Maintenance

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INTRODUCTION
Time base commands are produced by the IV001 video processor:
STV2161 for the 50-Hz chassis.
STV2162 for the 1006Hz chassis.
Apart from the difference in frequency, the difference between these two
circuits is in the internal oscillator, which is used constantly in the STV2161,
but only for start-up in the STV2162 (an external 27-MHz signal then takes
over).
In Standby Mode, only the I2C interface of IV001 is powered. This allows the
microcontroller to manage start-up by freeing the transistor regulating control
TV002 (Pin 24), which then supplies the main power supply voltage to the
VCC1 circuit.
PRODUCTION OF H-DRIVE COMMAND IN STV2161
A VCO (sawtooth signal generator) operates at 2 MHz. It calls on a reference
current supplied by Resistor RV003 (Pin 23). Its free frequency can be
adjusted in 125-Hz steps in the 15,500-15,750 Hz range according to
operating mode.
The video signal is applied to the synchronisation separation stage by Pin 16
(SYNC-IN).
The resulting signal is brought to the first phase detector which generates an
error voltage on filter RV206, CV206, CV207 (Pin 21).
A HORIZONTAL-LOGIC stage then divides the frequency from the
automatically controlled VCO to apply it to the second phase detector.
The second phase detector also receives the HFLY line return (Pin 33). This
is where the horizontal phase adjustment takes effect; this also takes place
via Operating Mode.
A signal shaping stage increases the H-DRIVE signal on the open-collector
output (Pin 38). On start-up, this signal appears with a duration of 5 µs typ.
(low level), and then widens to 38 µs as the charging of CV246 progresses
(related to the soft start, Pin 17).
NOTES :
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