Circuit Description
GB 65L01.1E 9.
information if a Y/C or CVBS source is present (signal is
high). The presence of an external Y/C source makes
this line ‘high’ while a CVBS source makes the line ‘low’.
– 0 to 2 V: INTERNAL 4:3
– 4.5 to 7 V: EXTERNAL 16:9
– 9.5 to 12 V: EXTERNAL 4:3
• SEL-MAIN-FRNT-RR This is the ‘source select control’
signal from the microprocessor. This control line is under
user control or can be activated by the other two control
lines.
9.7.6 Power Supply Control
The microprocessor part is supplied with 3.3 V and 3.9 V both
derived from the ‘MainAux’ voltage via a 3V3 stabiliser (7560)
and a diode.
Two signals are used to control the power supply:
• Stdby_con This signal is generated by the
microprocessor when over-current takes place at the
‘MainAux’ line. This is done to enable the power supply
into standby burst mode, and to enable this mode during
a protection. This signal is ‘low’ under normal operation
conditions and goes to ‘high’ (3.3 V) under ‘standby’ and
‘fault’ conditions.
• POWER_DOWN This signal is generated by the power
supply. Under normal operating conditions this signal is
‘high’ (3.3 V). During ‘standby’ mode, this signal is a
pulse train of approx. 10 Hz and a ‘high’ duration of 5 ms.
It is used to give information to the UOC about the fault
condition in the Audio amplifier supply circuit. This
information is generated by sensing the current on the
‘MainAux’ line (using voltage drop across R3564 to
trigger TS7562). This signal goes ‘low’ when the DC-
current on the ‘MainAux’ line exceeds 1.6 - 2.0 A. It is
also used to give an early warning to the UOC about a
power failure. Then the information is used to mute the
sound amplifier to prevent a switch off noise and to solve
the switch-off spot.
9.7.7 Tuner IF
Pin 3 of the UOC (SEL-IF-LL’_M-TRAP), is an output pin to
switch the SAW-filter to the appropriate system.
• If UOC pin 3 is ‘low’, the selected system is:
– West Europe: PAL B/G, I, SECAM L/L’
– East Europe: PAL B/G
– Asia Pacific: NTSC M
• If UOC pin 3 is ‘high’, the selected system is:
– West Europe: SECAM L’, L’-NICAM
– East Europe: PAL D/K
– Asia Pacific: PAL B/G, D/K, I
Note: For West Europe, two separate SAW filters (1002 and
1004) are used for video and audio (Quasi Split Sound
demodulation). For East Europe, one SAW filter (1003) is
used for both (Intercarrier demodulation).
9.7.8 Protection Events
Several protection events are controlled by the UOC:
• BC protection, to protect the picture tube from a too high
beam current. The UOC has the capability of measuring
the normal back level current during the vertical flyback.
So if for some reason the CRT circuit is malfunctioning
(i.e. high beam current), the normal black current will be
out of the 75 mA range, and the UOC will trigger the
power supply to shut down. However, this is a high
beam-current situation, the TV screen will be bright white
before the set is shut down.
• I2C protection, to check whether all I
2
C IC's are
functioning.
In case one of these protections is activated, the set will go
into ‘standby’. The ‘on’ and ‘standby’ LEDs are controlled via
the UOC.
9.8 Abbreviation list
2CS 2 Carrier (or Channel) Stereo
ACI Automatic Channel Installation:
algorithm that installs TV sets
directly from 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
AFT Automatic Fine Tuning
AGC Automatic Gain Control: algorithm
that controls the video input of the
featurebox
AM Amplitude Modulation
AP Asia Pacific
AR Aspect Ratio: 4 by 3 or 16 by 9
ATS Automatic Tuning System
AV External Audio Video
AVL Automatic Volume Level
BC-PROT Beam Current Protection
BCL Beam Current Limitation
B/G Monochrome TV system. Sound
carrier distance is 5.5 MHz
BLC-
INFORMATION Black current informationrmation
BTSC Broadcast Television Standard
Committee. Multiplex FM stereo
sound system, originating from the
USA and used e.g. in LATAM and
AP-NTSC countries
B-TXT Blue teletext
CC Closed Caption
ComPair Computer aided rePair
CRT Cathode Ray Tube or picture tube
CSM Customer Service Mode
CTI Colour Transient Improvement:
manipulates steepness of chroma
transients
CVBS Composite Video Blanking and
Synchronisation
DAC Digital to Analogue Converter
DBE Dynamic Bass Enhancement: extra
low frequency amplification
DBX Dynamic Bass Expander
D/K Monochrome TV system. Sound
carrier distance is 6.5 MHz
DFU Direction For Use: description for the
end user
DNR Dynamic Noise Reduction
DSP Digital Signal Processing
DST Dealer Service Tool: special remote
control designed for dealers to enter
e.g. service mode
DVD Digital Versatile Disc
EEPROM Electrically Erasable and
Programmable Read Only Memory
EHT Extra High Tension
EHT-
INFORMATION Extra High Tension
informationrmation
EU Europe
EW East West, related to horizontal
deflection of the set
EXT External (source), entering the set
via SCART or Cinch
FBL Fast Blanking: DC signal
accompanying RGB signals
FILAMENT Filament of CRT
FLASH Flash memory
FM Field Memory
FM Frequency Modulation
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