Philips PTV800, Service Manual

Page: 112 / 567

Audio Switching
Baseband Audio from Tuner 1 and Tuner 2 are fed to IC105, the Audio Switch, on Pins 2, 1,
13, and 12
. (Figure 8) Switching for IC105 Pins 10 and 11 is done by the Microcomputer IC300
on Pin 39. Selected Baseband audio exits the IC on Pin 15 and is fed to the Stereo Decoder
IC120 on Pin 29. Decoded Left and Right Audio exits IC120 on Pins 15 and 38 where it is fed
to IC1 on Pins 31 and 32. IC1 outputs selected audio from the Stereo Decoder, Aux 1, Aux 2,
SVHS 1, or SVHS 2 on Pins 39 and 38. Selected audio from IC1 is fed to IC120 on Pins 12
and 41. Left and Right outputs from IC120 on Pins 6 and 47 are fed to a 25 watt amplifier.
IC107 selects between Left and Right Audio Out or baseband audio on Pin 4 of IC120 for the
variable audio output.