CUC 7303 FDescription des circuits / Circuit Description
The required demodulator circuit F130 is connected to Pin 2 and Pin 3.
3. TV Signal Processor TDA8362A
The demodulated signal passes through an amplifier and is then
3.1 Overview:present at Pin 7 of the IC (BB). The IC identifies the synchronising
With this TV design the whole signal processing is carried out in asignal internally and for this reason, feedback of the line flyback pulse
single IC, i.e. the TV Signal Processor TDA 8362A.for gating purposes is not necessary. Corresponding to the synchron-
It accommodates the following stages:ising signal level a control voltage is generated. This control voltage
first acts on the controlled input amplifier of the IF. Via Pin 49 a
IF Signal:
reference threshold U is set. Below this threshold, only the input
RV
- IF amplifier
amplifier of the IF is regulated. If the threshold is exceeded, the control
- Demodulator
voltage U is applied from Pin 47 to the tuner. Pin 47 is an open collector
t
- AFC
output. In uncontrolled condition, the voltage is approximately 5V. With
- AGC
increasing input amplitude the AGC level decreases. The direct
- Coincidence identification
voltage for automatic frequency control (AFC) is generated in the
CCVS Signal:demodulator. Pin 9 feeds out this signal as a current signal. When the
- Signal source switch for the CCVS signalreceived frequency increases the control voltage for AFC decreases.
- Luminance processingThe processor IC850 evaluates the signal and fine tunes the tuner
- Colour demodulationaccordingly. The demodulated signal is examined by the sync detector
- Chrominance processingfor the presence of synchronising signals. If no such signals are
- Colour contrast controlpresent, the IC150-(4) switches to "Low". By this level the processor
IC850-(33) can identify that the coincidence signal is missing and
- RGB matrix
- C-AV inputmutes the sound.
- Signal source switch for RGB signals3.3 CCVS Signal
- Brightness controlThe demodulated CCVS signal leaves IC150-(7), TDA8362A, as a
- Contrast controlbaseband signal together with the sound-IF. In the following path, the
- Black level control (cut-off)sound signal is separated from the CCVS signal. After the transistor
CT921 and the sound trap F923 and F924 the signal path divides.
Sound:
Via the transistor CT110 and IC2807 (optionally) it is fed through to the
- Signal source switch for the sound
videotext decoder IC850-(30) as FBAS signal, and via the transistors
- Sound demodulationSC
CT963, CT962 it is supplied to the Scart socket pin 19.
- Volume control
At the signal source switch IC150-(13), the signal is present as FBAS
Deflection:(CCVS). The second input of the signal source switch Pin 15 is
- Sync separatorconnected to the Scart socket pin 20.
- Line oscillatorAt IC150-(16), the processor IC850-(42), voltage UVQ, transistor CT840
- O1 phase controldecides as to whether the signal from the tuner or the external signal
- O2 phase controlis processed.
- Trigger pulse generation for the line output stage
3.4 External CCVS Signal
- Line counter
At the signal source switch IC150-(15) either an external CCVS signal
- Saw-tooth generation for the vertical deflection
from the Scart socket or the RF-CCVS signal is present. The voltage
- Drive signal for the field output stage
UVQ at IC150-(16) decides which signal shall be passed on, the CCVS
Dependent on the associated circuitry, the IC is also able to processsignal from the Scart socket or else the RF-CCVS signal. IC150-(16)
PAL, NTSC and SECAM signals."Low", the internal signal is selected; IC150-(16) "High", the external
signal is passed on.
3.2 IF
Attention: If the option "Decoder On" has been selected the TV
The IF spectrum of frequencies is fed through a symmetrical path from
expects the signal to come from the Scart socket. However the CCVS
the tuner Pins 11 and 10 via the filter F901 and the Surface Acoustic
signal from the tuner can be measured at output Pin 19 of the Scart
Wave filter F906. The signal formed by the Surface Acoustic Wave filter
socket.
is applied symmetrically to Pins 45 and 46 of the signal processor. The
demodulation of the CCVS signal is carried out in a product demodulator.
Bild-ZF und Demodulation
Vision IF and Demodulation
F130
23
45FBAS- und Ton-
ZF vom Tuner7Ausgang
IF from TunerCCVS and Sound
46Output
U~
47
für denTuner
for the Tuner~
TDA8362A
URV
49
vom Prozessor
from Processor
9
AFC
4
KoinzidenzSync
CoincidenceDetector
GRUNDIG Service2 - 9 |
ACEC
GRUNDIG
