Module Circuits Test; The Audio Power Amplifier - THOMSON MT31AS Service Manual

5.4. Module Circuits Test

5.4.1. The audio power amplifier

The IC adopts RICHTEK's RT9108 chip using 28PIN project. The small sound signals enter IC
after separated. The signals are outputted after power amplifier.
connected to speakers LC net. The settings of AMP IC's peripheries include Gain Control, Power
restrict, Mute control and Abnormal feedback. Mute control is realized by software and
hardware control. Software mute maps to Main IC's I/O port. Hardware mute is work in AC
cut-off. AMP's PIN SD will be pulled to low level to mute when power is cut-off for 60ms. C127
will be charged when power is on. And it will discharge though Q101's E. Because B is power
down, Q101 will break-over. C137 will discharge to Q102's B and MUTE will be dragged to low.
Then power off mute is realized.
The sketch map of control bus
Service manual of MT31AS
Power signals are