The signals from Pin N201 (47) go through the sound intermediate frequency wave trap Z235
(D/K system) or Z236 (B/G system) and the emitter follower V212 so that the video complete
TV signals are got out and sent to TV/AV electronic switch circuit through Pin (43). One part
of the output signals go into the video signal processing circuit, the other go in the color
signal processing circuit via C/VIDEO electronic switch.
The video signals into the video signal processing circuit are amplified by 6dB gain. Then one
part of the signals are sent to the scanning unit and horizontal and vertical signals are output
through Pin (32) and (24) after horizontal and vertical oscillation.
The other part of the signals is output via Pin (35) to Pin (39) after being followed and
resistance voltage divided for 6dB attenuation by V251. The video signals are input into
carrier wave trap circuit and the color signals are removed. Then they enter the Y/VIDEO
switchover circuit to be sent to the video unit.
C/VIDEO electronic switch outputs video complete TV signals or the color signals to the
band-pass/high-pass filter circuit. The color signals are got out and sent to the chrominance
unit. The R-Y, B-Y and G-Y signals output from chrominance unit are sent to the matrix unit
together with Y signal output from the video unit to generate R, G and B primary color signals,
which are then output via Pin (18) (19) and (20) into the final circuit CRT board to the picture
tube circuit.
Tuning reverse code PWM signals are output from super central microprocessor D901 via Pin
(2). With reverse phase amplification and integrator processing by V975, PWM signals
become D.C. tuning voltage and are added to the tuning voltage input terminal (TU) of the
tuner A101. The control signals are output from Pin (9) (10) of D901 into N101 wave band
switchover. The wave band switchover is as follows:
N101
La7910 Band Switch Truth Table
Input Output
Working
band
3 4 1 2 7 8
VL L L L L H L
VH H L L H L L
U L L H L L L
CATV
H H L L L H
(3)
External audio and video signal processing
The video input signals are sent into the TV/AV electronic switch via N201 Pin (41) through
XS212 VIDEO IN after being coupled by C252.
The audio input signals are sent into TV/AV electronic switch via N201 Pin (55) through
XS212 AUDIO IN after being coupled by C207. The picture and sound signal processing is
carried out by N201 (TB1238N).
(4)
Sound signal processing