Changhong Electric PF2939, Руководство по обслуживанию, Страница: 9 / 47

SERVICE MANUAL
SERVICE DATA
Technical Data of Key ICs
OM8373PS (N201)
UOC
1. General Description
The various versions of the
OM8373 PS/
N
3/A
series combine the functions of a video
processor together with a
μ -Controller and
US Closed Caption decoder. 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 an S-DIP 64
envelope.
The features are given in the following feature
list.
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 positive/negative overshoot
ratio), black stretching and Dynamic Skin
Tone Control
• Integrated chroma band-pass filter with
switchable centre frequency
• Only one reference (12 MHz) crystal
required for the
μ
-Controller, Teletext- and
the colour decoder
• PAL/NTSC colour 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 colour 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
• Horizontal and vertical geometry processing
• Horizontal and vertical zoom function for 16 :
9 applications
• Horizontal parallelogram and bow correction
for large screen picture tubes
• Low-power start-up of the horizontal drive
circuit
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