Mitsubishi Electric HITACHI VS-50111 Troubleshooting Manual page 53

Sound Processing Circuitry
Figure 2 shows the Sound Processing and Audio Out-
put circuitry. In the V20 chassis, sound processing in-
cludes:
• Detecting the Sound I.F. signal from the Main
Tuner
• MCS Decoding of the resulting Composite
Stereo signal.
• Audio Control circuitry to adjust Volume,
Treble, Bass etc.
The 4.5 mHz Sound I.F. output from the Main Tuner
is directed to pin 50 of IC3A01. The internal cir-
cuitry in IC3A01 Detects the Sound I.F. signal and
performs MCS Decoding, output TV right and left
signals. The TV right and left signal are directed to the
AV Switch circuitry on PCB-TERMINAL.
The selected signals from the AV Switch circuit are di-
rected back to IC3A01 at pin 44 and 45. The signals
pass through internal Audio Control circuitry, allowing
user adjustment to be made. The Output of the Audio
Control circuitry at pins 21 and 22 takes two paths:
1) To the Monitor Switch circuitry on PCB-
TERMINAL, serving as the variable monitor
output source.
2) To IC3E01, the Audio Output IC on PCB-
MAIN.
8-3
V20 Chassis Technical Training
and Troubleshooting Guide