SERVICE MANUAL
15
SERVICE DAT
1.TV signal processor TDA935X/6X/8X PS-N3 series
1.1 GENERAL DESCRIPTION
The various versions of the TDA935X/6X/8X/9X PS-N3 series combine the functions of a video processor together with
a -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
9 0 a n d 110picture tubes.
The ICs have supply voltages of 8 V and 3.3 V and they are mounted in an SDIP-64 envelope.
The features are given in the following feature list.
1.2 FEATURES TV processor
Available in TDA935X/6X/8X PS versions
·
Multi-standard vision IF circuit with alignment-free PLL demodulator
·
Internal (switchable) time-constant for the IF-AGC circuit
·
The mono intercarrier sound circuit has 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.
·
The FM-PLL demodulator can be set to centre frequencies of 4.74/5.74 MHz so that a second sound channel can be
demodulated. In such an application it is necessary that an external band pass filter is inserted.
·
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) and blue- and black stretching. All features are available for CVBS, Y/C
and
YPBPR
signals.
·
Tint control for external RGB/YP
B
P
R
signals
·
Integrated chroma band-pass filter with switchable centre frequency
·
Only one reference (12 MHz) crystal required for the -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/YP
B
P
R
input with fast blanking for external RGB/YUV sources. The synchronisation circuit can be
connected to the incoming Y signal. The Text/OSD signals are internally supplied from the -Controller/Teletext decoder.
·
RGB control circuit with ‘Continuous 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.
·
2 levels of contrast reduction of main picture possible during OSD/Text insertion (
‘
halftone’)
·
OSD/Text gain reduction control
·
Adjustable ‘wide blanking’ of the RGB outputs
·
Horizontal synchronization with two control loops and alignment-free horizontal oscillator
·
Vertical count-down circuit
·
Vertical driver optimized for DC-coupled vertical output stages