Tv/Av Switching Circuits - Sanyo AVM-2550S Training Manual

The VB7C chassis (AVM-2780G) provides for the input of Auxiliary Video and
Audio signals.
When the AV1 or AV2 mode is selected from the remote control, pin 8 of the
CPU will go High. The High from pin 8 is coupled to the base of Q216. The
High coupled to the base of Q216 will switch Q216 On and ground the base
of Q343, the Band Pass Switch. The Low at the base of Q343 will switch
Q343 Off, cutting off L341 and C343 from the Band Pass Filter. This will
flatten the response curve of the Band Pass Filter to compensate for the
differences in the frequency characteristics of the AV video signal and the TV
video signal. This compensation will help to maintain a constant chroma
signal (3.58 MHz) gain.
The selection of the TV Audio, AV1 Audio or AV2 Audio signal is controlled by
the MTS Processor IC3401 through the CPU IC801. All of the TV, AV1 and
AV2 audio inputs are applied to an audio switch within IC3401 which is
controlled by the BUS interface.
MODE TV
CPU (4) L
CPU (5) ––
CPU (8) L
CPU (12) H
CPU (6) ––
CPU (7) L
CPU TV/AV Switching Signal

TV/AV SWITCHING CIRCUITS

AV1
S-VIDEO COMPOSITE
VIDEO
H L
L L
H H
L H
L L
H H
The selection of the AV1 S-Video, AV1 Composite Video, or AV2 Video signal
is controlled by the CPU and the mechanical switch of AV1 S-Video input jack
K1051.
When the AV1 is selected, pin 5 of the CPU will be Low. When the AV2 is
selected, pin 5 of the CPU will go High.
When the AV1 S-Video is connected during AV1 mode, pin 10 of IC1001 and
pin 12 of the CPU will be forced Low. With the Low at pin 12, the CPU will
regard the S-Video as connected and output the High signal from pin 4.
The selection of the TV Video or AV Video signal in the Signal Processor
IC101 is controlled by the CPU IC801. Both of the TV and AV video signals
are applied to an input switch within IC101 which is controlled by the BUS
interface. Either of the video signals is applied to the Comb Filter IC301 and
coupled to the Main S1/V1/V2 Switch IC1081.
Note: • Using the AV1 S-Video Input jack overrides the AV1 Composite
Video Input jack during the AV1 mode.
MODE
IC1001 (9)
IC1001 (10)
AV2
IC1001 (11)
IC1002 (9)
L
IC1002 (10)
H
IC1002 (11)
H
IC1081 (9)
H
IC1081 (10)
H
IC1081 (11)
H
TV/AV Mode Switching Signal
– 24 –
AV1
TV S-VIDEO COMPOSITE
VIDEO
–– L
H L
H H
–– L
–– L
L H
L H
L H
–– L
AV2
L H
H H
H H
L H
L H
H H
L L
L L
L H