Philips 7629, Service Manual

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The S8/T8 is divided into 2 basic systems, i.e., mono and stereo sound. While the audio
processing for the mono sound is done in the audio block of the UOC, an external audio
processing IC 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 memory IC mounted on the main panel.
The microcomputer communicates with the memory IC, the customer keyboard, remote
receiver, tuner, signal processor IC and the audio output IC via the I
2
C bus. The
memory IC retains the settings for favorite stations, customer-preferred settings, and
service / factory data.
The on-screen graphics and closed caption decoding are done within the
microprocessor, and then sent to the signal processor IC to be added to the main
signal.
The chassis utilizes a Switching Mode Power Supply (SMPS) for the main voltage
source. The chassis has a ‘hot’ ground reference on the primary side and a cold ground
reference on the secondary side of the power supply and the rest of the chassis.
Audio Signal Processing
Refer to Block diagram Audio
Stereo
In stereo sets, the signal goes via the SAW filter (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 decoder or an
external source.