Philips - MX3950D, Service Manual

Page: 69 / 128

BRIEF INTRODUCTION OF THE AV BOARD
The AV Board consists of the following features :
a. IC 7130 (TDA7468D)
IC 7130 provides the source selection (TUNER, TV/AV Digital in, DVD/CD & AUX) and basic sound processing - bass, treble, volume
& mute controls for the Front L/R loudspeakers.
Note: Although provided for, the AUX source (pin 3 and 26) are never selected & instead and additional IC 7422 (HEF4052BT) is used
to include a TV in from the Scart connector socket.
Sound features are controlled by the microprocessor IC on the Front Board via I 2 C Bus.
Undesirable noise during source switching are muted off via the software of the microprocessor IC on the Front Board.
b. IC 7422 (HEF4052BT)
This IC allows the additon of another TV source via the SCART connector socket. The output MUX_L/MUX_R will go to pin 4 and 25
of IC 7130.
c. Line out mute
Line out mute is done via the transistors 7100, 7132, 7133 and 7150 during Power up/down, Source and sound switching (MUTE-LO,
active low) and Disc & Digital in modes (MUTE_AV, active high).
d. Headphone amplifier / pre-amplifier
IC 7230 (NJM4556AM) is used as headphone amplifer and pre-amplification for the Front L/R signal to the Amplifier board. The transistors
matrix 7200, 7231, 7232, 7233 and 7250 allows the heaphone out to be muted when inserting the headphone
e. IC 7304 and 7330 (TDA7468D)
IC 7304 and 7330 provides creation of matrix sound (via Line-L/R from IC 7130) during non-DVD source and sound processing - bass,
treble, volume & mute controls for the Center/Subwoofer and Surround L/R loudspeakers respectively.
Sound features are controlled by the microprocessor IC on the Front Board via I
2
C Bus.
Undesirable noise during source switching are muted off via the software of the microprocessor IC on the Front Board.
f. IC 7352 (74HC4051D)
This multiplexer output (MUX_DET) informs the microprocess IC on the Front Board on the type of connection & condition the set is in.
g. IC 7402 (M62320FP)
The IC serves as I 2 C Expander to provide for additional control lines required.
AV BOARD
TABLE OF CONTENTS
Brief Introduction of the AV Board ........................................... 9 -1
Variation Table .......................................................................... 9 -1
Chip & Discrete layouts - Chip side view ................................. 9 -2
Component & Chip layouts - Component side view ................ 9 -3
Inputs, Source Sel. & Vol cont. L/R Circuit ............................... 9 -4
HP amp / Pre-amp., Supply & Interconnection Circuit ............ 9 -5
Volume cont. Surr L/R, Cen & SW & Multiplexer Circuit .......... 9 -6
Digital in/out, S-video, Scart, & I
2
C Expander Circuit .............. 9 -7
Electrical parts list .................................................................... 9 -8
9-1 9-1