SITRONICS 25F83, Руководство по обслуживанию

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SERVICE MANUAL
SERVICE DATA
1. Technical Data of Key ICs
1.1 Microcontroller and Small Signal Processor TDA935X/6X/8X
(1) General Description
The various versions of the TDA935X/6X/8X PS/N2 series combine the functions of a TV
signal processor together with a
μ
-Controller and US Closed Caption decoder. Most
versions have a Teletext decoder on board. The Teletext decoder has an internal RAM
memory for 1 or 10 page text.
The ICs are intended to be used in economy television receivers with 90° and 110° picture
tubes.
The ICs have supply voltages of 8V and 3.3V and they are mounted in S-DIP envelope with
64 pins.
The features are given in the following feature list. The differences between the various ICs
are given in the table 7 on page 20.
(2) Features
TV-signal processor
·
Multi-standard vision IF circuit with alignment-free PLL demodulator
·
Internal (switchable) time-constant for the IF-AGC circuit
·
A choice can be made between versions with mono intercarrier sound FM demodulator and
versions with QSS IF amplifier.
·
The mono intercarrier sound versions have a selective FM-PLL demodulator which can be
switched to the different FM sound frequencies (4.5/5.5/6.0/6.5 MHz).
The quality of this system is such that the external band-pass filters can be omitted.
·
Source selection between “internal” CVBS and external CVBS or Y/C signals
·
Integrated chrominance trap circuit
·
Integrated luminance delay line with adjustable delay time
·
Picture improvement features with peaking (with variable centre frequency and
positive/negative overshoot ratio) and black stretching
·
Integrated chroma band-pass filter with switchable centre frequency
·
Only one reference (12 MHz) crystal required for the µ-Controller, Teletext and the color
decoder
·
PAL/NTSC or multi-standard color decoder with automatic search system
·
Internal base-band delay line
·
RGB control circuit with “Continuous Cathode Calibration”, white point and black level offset
adjustment so that the color temperature of the dark and the light parts of the screen can
be chosen independently.
·
Linear RGB or YUV input with fast blanking for external RGB/YUV sources. The Text/OSD
signals are internally supplied from the µ-Controller/Teletext decoder
·
Contrast reduction possibility during mixed-mode of OSD and Text signals
·
Horizontal synchronization with two control loops and alignment-free horizontal oscillator
·
Vertical count-down circuit
·
Vertical driver optimized for DC-coupled vertical output stages
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