Technicolor - Thomson ICC19, Принципы и обслуживание

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AUTOMATIC CUTOFF CONTROL
Automatic cutoff control is performed for Lines 21 through 24 and 334 through
337. To compensate for the tube leakage current, the RGB outputs are erased
during Lines 21 and 334. The leakage current measurement determines a
compensation current within IV001 that creates a voltage of 1.5 V at the
terminals of RV092 (Pin 43 of IV001). This compensation current is memorised
for an entire frame, and is taken into account for the automatic control of the
tube cutoffs. This compensation current is added to the RGB gun cutoff
measurement currents.
During Lines 22 and 335, the blue channel is in operation. The blue gun
measurement current added to the compensation current produces a voltage
at the terminals of RV092. This voltage is compared to an internal 3-V
reference, and then determines the black level of the blue signal.
During Lines 23 and 336, the green channel is in operation. Its automatic
control is identical to that of the blue channel.
During Lines 24 and 337, the red channel is in operation. Its automatic control
is identical to that of the blue channel.
Transistor TB18 and its associated components limit the cutoff measurement
voltage to approximately 4.2 V.
NOTES :
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