Ac 3 Ic Functions; Interface Switching - Loewe Q2500B Serviceanleitung

Technology of Q 2500 colour TV set
The interrupt causes I 2 to load new software
from the memory. Due to the block pre-
selection from the the I2C bus expander, the
DSP now loads the software for Dolby Pro
Logic.
The DSP processes the I
ing to the appropriate instructions. The over-
whelming number of sound parameters to be
set also occur in the DSP.
The DSP feeds the digital sound bus data
back to the converter I 2, where the digi-
tal/analogue conversion takes place. The 6
sound output channels of I 2 reach W 301 via
the operational amplifier and the loudspeaker
matrix – consisting of I 6/9/14.
- pin 1 LFE/SUB (deep sound channel)
- pin 2 RS (Surround right)
- pin 3 LS (Surround left)
- pin 4 R (Front right)
- pin 5 L (Front left)
- pin 6 LC (Center left)
- pin 7 RC (Center right)
- pin 8 C (Center channel)

5.3.3 AC 3 IC functions

CS 4925-01 (I 1)
Multi Channel Digital Audio Decoder.
Processes according to the operating
-
mode, - Circle Surround, Dolby Pro
Logic Dolby, Digital 5.1 - digital Sound-
bus-data.
- Implements all sound settings, such as
height and depth settings.
CS 4226 (I 2)
DAC
- Converts SPDIF signals into I
for I 1 .
2
- Converts the I S bus data processed by I
1 into analogue signals for the loud-
speaker matrix.
Document Q 2500
2
S bus data accord-
2
S bus data
6

Interface switching

Interface switching is via Q 2500 on the signal
board. Switching of the various on and off sig-
nals is implemented essentially by six ICs; two
TEA 6415, two CD 4053 for the video signals,
a TEA 6422 and a TEA 6420 for the audio
signal switching. Control is directly from I²C
bus system 3 via SDA 6000. An exception is
CD 4053 I 1631 and I 1771.
I 1631 switches between the RGB lines of the
AV3 socket and the RGB signals of the DVB
decoder. I 1631 is controlled from a free
switch output in MSP, which itself is activated
by the CCU via the I2C bus. If the output on
pin 78 of the MSP is switched to H level, then
L level is felt on pins 9/10/11 of I 1631 via in-
verter Q 1637. With L level on, its control input
I1631 switches to AV3 operation, at H level
the RGB signals from the DVB decoder are
switched through to the signal processing.
I 1771 is used for chroma signal switching if a
Digital Link Plus SVHS video recorder is con-
nected.
During SVHS operation a chroma signal is
expected from SVHS Digital Link Plus video
recorders on pin 7 of the AV socket. For VHS
video recorders it is pin 15.
If the device control detects a SVHS Digital
Link Plus VCR, the chroma signal is switched
to pin 7 of the AV1 or AV2 socket on overplay
and during a DVB recording. I 1771 is
switched from two switch outputs on pin
115/116 I 2311. This in turn is controlled by
the CCU.
As the two TEA 6415 must be addressed dif-
ferently for picture signal switching, pin 7 of I
1116 is earthed and I 1181 is at the operating
voltage.
The exact signal flow for the video and audio
signals can be obtained from the appropriate
flow diagrams.
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