Pioneer VSX-4000 Service Manual page 49

e Signal waveform
ball
re ar
u I
Tee
® ® tal io Center
Color
—_—- Emitter potential of Q107
Black and white
Sharp side
(MAX)
Center
{Original signal)
Soft side
(MEN)
Sharp side
Soft side
Volume
position
MB@ SPLIT SCREEN CIRCUIT
A partial of the video signal which has been passed through
the CLAMP circuit (See Fig. (A) ) is input to the synchro-
nizing separation circuit. In the synchronizing separation
circuit, at first, color signal component is eliminated by
passing through the low-pass filter (fc=600kHz) (See
Fig. (© ), and then, only the synchronizing pulse of the
video signal is fetched with the synchronizing separation
circuit (Q117 to Q119) (See Fig. ®).
This pulse is input to the inverter (IC105-1/6) and its
output is differentiated. The differentiated waveform
becomes origin of the reset signal of IC107 and trigger
signal (See Figs. G) and @) ).
Moreover, from the waveforms shown in Figs. @ , @ and
those of shown in Figs. D), ® are generated by D102 and
D103. After that, the signal of which waveform regulated
by two inverters of IC105-5/6 and 6/6 is input to termnal 4
of IC107. This signal becomes the reset signal of IC107
(See Fig. ®) ). Furthermore, the signal of which waveform is
regulated by one inverter of 1C105-2/6 is input to ter-
minal 2 of IC107 and it becomes the trigger signal(See Fig.
( ) of IC107.
On terminals 6 and 7 of IC107, the waveform length
(time length) is varied with the volume VR101 (split screen
volume) and with the time constants of the current mirror
transistor of Q101 and capacitor of C139 which is equiva-
lent to Q101. By this waveform variation, the vertical
line position of the split screen on the picture screen is
shifted.
By the signal input to terminals 2, 4, 6, and 7, the wave-
form shown in Fig. ™) is output from terminal 3 (See the
Block Diagram of IC107). The waveform shown in Fig.
(@) which is output from terminal 3 of C107 is inversed
by the inverter of 1C105-4/6 (See Fig. ©) ) and one is
reinverted by the inverter of IC105-3/6 and then, input to
terminal 7 of IC102 (See Fig. () ). The other is input to
terminal 5 of IC102 after smoothening its waveform rising
edge with D101, R174, and C133 (See Fig. Q)). In order
to make the rising edge of the waveform smooth as shown
in Fig. Q) , the operation time of terminal 5 of IC102 is
delayed. Thus making time difference (the time when both
waveforms of (P) and @) become OFF) and generating
the waveform of Fig. P , to appear the vertical line of split
screen on the TV screen (See Fig. S)).
By switching this control signal, between one synchro-
nizing signal and another, the picture to which enhancer is
applied and that to which enhancer is not applied can
simultaneously be seen apparently at the left and right sides
of the vertical line of the split screen on the TV screen.