Changhong Electric 34T18, Service Manual, Page: 19 / 61

SERVICE MANUAL
17
SERVICE DATA
1. Technical Data of Key ICs
1.1 Microcontroller and Small Signal Processor TDA959X
(1) General Description
The various versions of the TDA959X H/PS-N1 series combine the functions of a video
processor together with a m-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. Some versions can generate a ‘Mixed-down’ I-signal for the demodulation of DVB
signals. The ICs are intended to be used in economy television receivers with 110 picture
tubes.
The ICs have supply voltages of 8 V and 3.3 V and they are mounted in an SDIP-64 or QFP
80 envelope.
The features are given in the following feature list. The differences between the various ICs
are given in the table.
(2) Features
TV-signal processor
Available in all versions
● Multi-standard vision IF circuit with alignment-free PLL demodulator
● Internal (switchable) time-constant for the IF-AGC circuit
● Integrated chrominance trap circuit Integrated luminance delay line with adjustable delay
time
● Picture improvement features with peaking (with switchable centre frequency, depeaking,
variable positive/negative overshoot ratio and video dependent coring), dynamic skin tone
control and blue- and black stretching
● Scan Velocity Modulation output
● Integrated chroma band-pass filter with switchable centre frequency
● Only one reference (12 MHz) crystal required for the m-Controller, Teletext- and the colour
decoder
● Multi-standard colour decoder with automatic search system
● Internal base-band delay line
● Indication of the Signal-to-Noise ratio of the incoming CVBS signal
● A linear RGB/YUV/YPBPR input with fast blanking for external RGB/YUV sources. The
synchronization circuit can be connected to the incoming Y signal. The Text/OSD signals are
internally supplied from the m-Controller/Teletext decoder.
● RGB Cathode Calibration’, white point and black level off-set adjustment so that the colour
temperature of the dark and the light parts of the screen can be chosen independently.
● Contrast reduction possibility during mixed-mode of OSD and Text signals
● Adjustable ‘wide blanking’ of the RGB outputs
● Horizontal synchronization with two control loops and alignment-free horizontal oscillator