There are two stereo decoders used:
1. a BTSC DBX stereo/SAP decoder (MSP34X5 at position 7831) for the highest
specified sets and
2. a BTSC non-DBX stereo decoder (TDA 9853 at position 7861) for BTSC
Economic.
The output is fed to the to the audio amplifier (AN7522at position 7901). The volume
level is controlled at this IC (pin9) by a control line (Volume Mute) from the
microprocessor. The audio signal from 7901 is then sent to the speaker / headphone
output panel.
Mono
In mono sets, the signal goes via the SAW filter (position 1002), to the audio
demodulator part of the UOC IC 7200.The audio output on pin 48 goes, via the smart
sound circuit (7941for Bass and 7942 for Treble) and buffer 7943, to the audio amplifier
(AN7523 at position 7902).
The volume level is controlled at this IC (pin 9) by a ‘Volume Mute’ control line from the
microprocessor.
The audio signal from IC 7902 is then sent to the speaker / headphone output panel.
Figure:
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