Audio Signal Processing - Philips 27PS60S321 Technical Service Data

SPMS
Figure:
The S8/T8 is divided into 2 basic systems, i.e.mono and stereo sound. While the audio
processing for the mono soundis done in the audio block of the UOC, an external audio
processingIC is used for stereo sets.
The tuning system features 181 channels with on-screen display.The main tuning system uses
a tuner, a microcomputer, and a memoryIC mounted on the main panel.
The microcomputer communicates with the memory IC, the customerkeyboard, remote
receiver, tuner, signal processor IC and the audiooutput IC via the I
retains the settings for favorite stations, customer-preferredsettings, and service / factory data.
The on-screen graphics and closed caption decoding aredone within the microprocessor, and
then sent to the signal processorIC to be added to the main signal.
The chassis utilizes a Switching Mode Power Supply (SMPS) forthe main voltage source. The
chassis has a 'hot' ground referenceon the primary side and a cold ground reference on the
secondaryside of the power supply and the rest of the chassis.

Audio Signal Processing

Block diagram Audio
Stereo
In stereo sets, the signal goes via the SAWfilter (position 1002), to the audio demodulator part
of the UOCIC 7200. The audio output on pin 48 goes to the stereo decoder 7831or 7861. The
switch inside this IC selects either the internal decoderor an external source.
There are two stereo decoders used:
1. a BTSC DBXstereo/SAP decoder (MSP34X5 at position 7831) for the highestspecified
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 (VolumeMute) from the microprocessor. The
audiosignal from 7901 is then sent to the speaker / headphone outputpanel.
Mono
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Cbus. The memory IC