Circuit Descriptions, Abbreviation List, and IC Data Sheets
9.
9.
Circuit Descriptions, Abbreviation List, and IC Data Sheets
Index of this chapter:
9.1 Introduction
9.2 The various circuits
9.3 Abbreviation List
9.4 IC Data Sheets
9.1
Introduction
The SK4.0A CA is a CRT TV for the year 2007, based on the
3P61 platform. In this chapter, only a general description of the
various circuits is given. For more detailed information, see the
circuit diagrams in this manual.
9.2
The various circuits
9.2.1
Tuner
The function of the tuner is to select the channel to be received
and suppress the interference of neighboring channels, to
amplify the high frequency signal, to improve the receiving
sensitivity and SNR, and to generate a PIF signal through
frequency conversion.
9.2.2
IF Channel
The IF Channel mainly ensures the sensitivity and selectivity of
the complete TV set. The IF AMP integrated in the UOCIII is
made up of a three-stage dual-differential amplifier with a gain
value above 70dB, a SNR of 55dB and a bandwidth of 7 MHz.
The video demodulation circuit is made from the built-in PLL
Sync Detector. The spectrum of the demodulation carrier is
unitary and it is not affected by the content of the video signal.
The tuner features stable receptivity while the signal output
from the video detector features high fidelity. The built-in PLL
circuit of the UOCIII generates a 38.0 MHz or 38.9 MHz
demodulation reference signal for the sync detector to
demodulate the video signal; this is called "PLL sync
demodulation".
9.2.3
Sound Channel
An external ceramic filter is used to select the second SIF
signal for the sound channel of UOCIII from the signal output of
the video detector. The audio signal is obtained after limiting
amplification and demodulation by the intermediate frequency
detector for the SIF signal, and then the audio signal is output
to the audio amplifier TFA9842., which drives the speakers to
provide the sound. The intermediate frequency detector and
volume-control attenuator that are built in the UOCIII are set
and adjusted via the CPU.
9.2.4
CRT Drive Circuit
In the driver circuit, both the voltage and current of the R/G/B
signal are amplified, after which the CRT drive circuit
modulates the cathode beam current of the CRT. The R/G/B
signal input into the driver circuit is of negative polarity.
9.2.5
Power Supply Circuit
The function of the power supply circuit is to supply various
stabilized operating voltages and to provide protections against
excessive voltages and currents.
9.3
Abbreviation List
2CS
2 Carrier Sound
A2
Commonly known as 2 Carrier Sound
(2CS) system
AC
Alternating Current
ACI
Automatic Channel Installation:
algorithm that installs TV channels
directly from a cable network by
means of a predefined TXT page
ADC
Analogue to Digital Converter
AFC
Automatic Frequency Control: control
signal used to tune to the correct
frequency
AGC
Automatic Gain Control: algorithm that
controls the video input of the feature
box
AM
Amplitude Modulation
ANC
Automatic Noise Reduction; One of
the algorithms of Auto TV
AP
Asia Pacific
AR
Aspect Ratio: 4 by 3 or 16 by 9
AV
Audio Video
AVL
Automatic Volume Level control
B/G
Monochrome TV system. Sound
carrier distance is 5.5 MHz
BCL
Beam Current Limiter
CBA
Circuit Board Assembly (or PWB)
CFR
Carbon Film Resistor
ComPair
Computer aided rePair
CRT
Cathode Ray Tube (or picture tube)
CVBS
Composite Video Blanking and
Synchronisation
CVI
Component Video Input
D/K
Monochrome TV system. Sound
carrier distance is 6.5 MHz. D= VHF-
band, K= UHF-band
DAC
Digital to Analogue Converter
DC
Direct Current
DC-filament
Filament supply voltage
DFU
Directions For Use: owner's manual
DPL
Dolby Pro Logic
DRAM
Dynamic RAM; dynamically refreshed
RAM
DVD
Digital Versatile Disc
EEPROM
Electrically Erasable and
Programmable Read Only Memory
EHT
Extreme High Tension; the voltage
between the cathode and the shadow
mask that accelerates the electrons
towards the screen (around 25 kV)
EMI
Electro Magnetic Interference;
Leakage of high-frequency radiation
from a transmission medium
EU
EUrope
EW
East West, related to horizontal
deflection of the set
EW-DRIVE
East -West correction drive signal.
EXT
EXTernal (source), entering the set by
SCART or by cinches (jacks)
FBL
Fast Blanking: DC signal
accompanying RGB signals
FE
Front End; Tuner and RF part together
Field
Each interlaced broadcast FRAME is
composed of two Fields, each Field
consists of either Odd or Even lines
Filament
Filament of CRT
FM
Field Memory / Frequency Modulation
Frame
A complete TV picture comprising all
lines (625/525)
FTV
Flat TeleVision
