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EN 34
9.
L03.2L AA
9. Circuit Descriptions, List of Abbreviations, and IC Data Sheets
Index of this chapter:
9.1 Introduction
9.2 Source Selection
9.3 Audio
9.4 Video
9.5 Synchronization
9.6 Deflection
9.7 Power Supply
9.8 Control
9.9 Abbreviation List
Notes:
•
Only new circuits (compared to the L01.2 chassis) are
described in this chapter. For the other circuit descriptions,
see the manual of the L01.2L AA.
•
Figures can deviate slightly from the actual situation, due
to different set executions.
•
For a good understanding of the following circuit
descriptions, please use the block diagram in chapter 6,
and/or the electrical diagrams in chapter 7. Where
necessary, you will find a separate drawing for clarification.
9.1
Introduction
The "L03"' chassis is a global TV chassis, and is used for TV
sets with screen sizes from 14 inch to 21 inch, in Super Flat and
Real Flat executions. In comparison to its predecessor (the
"L01"), this chassis is further simplified: it contains economized
executions of the power supply, the video processing
(microprocessor), and the audio processing.
Due to a cost down action this chassis has some more
simplified circuitry like the audio processing and some parts are
fully omitted like top-control.
The standard architecture consists of a Main panel (called
"family board") and a Picture Tube panel. The Main panel
consists primarily of conventional components with some
surface mounted devices in the audio and video processing
part.
The functions for video processing, microprocessor (µP), and
CC/Teletext (TXT) decoder are combined in one IC (TDA937x),
the so-called Ultimate One Chip (UOC). This chip is mounted
on the component side of the main panel.
The L03 can be divided into two basic systems, i.e. mono and
stereo sound. While the audio processing for the mono sound
is done in the audio block of the UOC, external audio
processing ICs are used for stereo sets.
The tuning system features 181 channels with on-screen
display. The main tuning system uses a tuner, a
microcomputer, and a memory IC mounted on the main panel.
The microcomputer communicates with the memory IC, the
customer keyboard, remote receiver, tuner, signal processor IC
and the audio output IC via the I
the settings for favorite stations, customer-preferred settings,
and service / factory data.
The on-screen graphics and closed caption decoding are done
within the microprocessor where they are added to the main
signal.
The chassis uses a Switching Mode Power Supply (SMPS) for
the main voltage source. The chassis has a 'hot' ground
reference on the primary side and a cold ground reference on
the secondary side of the power supply and the rest of the
chassis.
Circuit Descriptions, List of Abbreviations, and IC Data Sheets
2
C bus. The memory IC retains
9.2
Source Selection
The Source Select is divided mainly into two types, the "Mono
Source Select" and the "Stereo Source Select".
•
The Mono Source Select, both audio and video, will be
done entirely by the UOC and will only be able to select one
external audio source.
•
As for the Stereo Source Select, the Panasonic IC, which
is for BTSC decoding also, has 2 audio source inputs used
for source selection, whereas the UOC will take care of the
video selection.
9.2.1
Switching Function for Stereo I/O
Audio / Video Source Selection
The video source selection is done by the UOC. The video
setting for LATAM / NAFTA is rather straightforward: a so-
called "WYSIWYG" (what you see on the screen, is what you
get from the video ouput).
There is only a front input available, therefore the source
selection is basically limited to the UOC.
9.2.2
Switching Function for Mono I/O
For the Mono configuration, only one input pin is available for
the UOC.
Video Source Selection
The video switching is similar to the section above.
Audio Source Selection
The audio input (L1_IN) is connected to pin 35 of the UOC.
9.3
Audio
This chassis is targeted for the NAFTA market with Mono,
Stereo, or SAP sound system.
For the "basic" Mono and Stereo sets, sound processing
includes Volume control and AVL.
For stereo sets, IC TDA9853H is the BTSC audio signal
decoder and audio processing..
9.3.1
Processing
This chassis uses the Intercarrier demodulation concept (one
SAW filter for both video and audio). The base band (full
bandwidth) BTSC audio signal from the UOC is fed to pin 14 of
the stereo decoder. The Pilot detection and SAP detection
registers indicate the type of transmitted audio signal such as
Mono, Stereo, and/or SAP. Based on this indication, the
software controls will help to output the appropriate audio
signal at pins 21 and 22. The controls are done by the I
connected to pins 18 and 19.
Internal or External audio (pins 2, 3, 23, and 24) can also be
selected by the source selection register. For the selected
audio source, the AGC function can be applied. The output is a
fixed level output. The volume control function is available via
the power amplifier (AN7522/23).
9.3.2
Amplifier
The output is fed to the audio amplifier (IC7901 for stereo sets
or IC7902 for mono sets). This is a BTL amplifier (Bridge Tied
Load), which is actually a class AB amplifier with four
transistors for each channel. The advantage of BTL over the
standard Class AB amplifier is that it requires a lower supply
voltage to deliver a higher output.
2
C bus
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