Panasonic BT-M1950Y Service Manual page 95

5. Pulse cross circuit
The same type circuits are used for the Y and color difference signals. The pulse cross circuit for the Y signal system is
described below.
The Y signal through amplifier and buffer circuits 0305, 0301 and 0302 goes in one line directly to IC304 pin 12 and in
another line to 0303. The burst gate pulse is applied to 0303 gate and the gate opens only during this period to
determine the pedestal DC level (sampling hold). The signal goes to IC301 pin 3, where it is compared with the 5 V
reference voltage of R311 and C304, and provides feedback to 0302 base. The DC voltage is supplied to IC301 pin 6
and IC304 pin 13. The signals at pins 12 and 13 are switched by the H blanking delay signal produced by IC506. When
the Pulse Cross switch is on, the output signal indicated in Fig. 5-2 is obtained from pin 14.
!Pulse Cross switch on
I
IC304 12PIN
IC304 13PIN
__fl_
T
BGP
-,5v
__L_GND
Fig. 5-1 Pulse cross circuit
H BLK DL
.JLJL
IC304
1(304 _11_P_IN ____
~n~
_________ n ________ _
IC304 14PIN
Fig. 5-2 Pulse cross circuit timing
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