Main Board; Brief Introduction Of The Main Board - Philips FWM35/21 Service Manual

6-1

MAIN BOARD

TABLE OF CONTENTS
Brief of Introduction of Main Board .................................. 6-1
Internal IC Diagram ......................................................... 6-2
PCB Layout Top View /21 ................................................ 6-3
PCB Layout Bottom View /21 .......................................... 6-4
Circuit Diagram - Amp Part .............................................. 6-5
PCB Layout Top View /22 ................................................ 6-6
PCB Layout Bottom View /22 .......................................... 6-7
Electrical Parts list ........................................................... 6-8

BRIEF INTRODUCTION OF THE MAIN BOARD

The Main Board consists of the following features :
a. TDA7468D
TDA7468D (IC704) provides the basic sound processing - loudness, bass, treble, volume & mute controls and source selection - TUNER,
TAPE, CD & AUX including Mic mixing for the set.
Sound features such as ALC, DBB, DSC and IS are controlled by the microprocessor IC on the Front Board via I
Undesirable noise during source switching are muted off by via the software of the microprocessor IC on the Front Board.
b. TDA8947J
The TDA8947J contains a unique protection circuit that is solely based on multiple temperature measurements inside
the chip. This gives maximum output power for all supply voltages and load conditions with no unnecessary audio holes .
Almost any supply voltage and load impedance combination can be made as long as thermal boundar y conditions
external heatsink and ambient temperature) allow it.
(number of channels used,
c. MIC MIXING
Simple Mic mixing is provided by pin 2 of TDA7468D. During Mic mixed a 1nF capacitor is connected across this pin to ground instead
of a chip connector(0R).
d. HEADPHONE AMPLIFIER
Headphone amplifier NJM4556AM is provided after the Sound processor to drive 32 ohm to 1kohm headphone.
Remark: 1) For ECO6 Tuner Part built in Main Board, refer to Chapter 7A & Chapter 7B.
2) For Ver 22, whole Main Board Ass'y can be ordered with 12nc: 9940 000 01506.
6-1
2 C Bus.