CUC 7305Schaltungsbeschreibung / Circuit Description
3.8 RGB Signal Path3.10 Line Oscillator
For contrast control of the RGB signals, IC850-(23) generates aWith this IC concept, the line frequency is generated completely inside
variable control voltage for the contrast controlling amplifier atthe line oscillator. The IC is not connected to external components so
IC150-(25). Because too high a beam current may cause damage tothat it is not necessary to adjust the free running horizontal and the free
the picture tube, the beam current is limited by this IC. The internal peakrunning vertical frequency.
beam current limiting function is carried out in the peak white limiting
3.11 j1 Phase Control
stage. If the RGB signal exceeds 2.6V, the internal peak white limiting
pp
The j1 phase control stage is for controlling the frequency. This stage
function starts working and reduces the contrast. The external peak
adjusts the frequency of the line oscillator to that of the line synchro-
beam current limiting threshold is 2Vpp approximately.nising pulse. For this, the frequency of the line synchronising pulse is
The average beam current limiting function reduces the setting voltages
compared with the line oscillator frequency.
at IC150-(25) for the contrast.
A j1 phase control stage defines the time constant of the control
After the brightness amplifier, the RGB signals leave the IC150 and are
voltage which is fed out at IC150-(40). The control voltage shifts the line
passed on to the cathode amplifiers on the CRT base panel.
oscillator until the frequencies are equal.
3.9 Generation of the Horizontal and Vertical Sync Signals
3.12 j2 Phase Control
The TV signal processor IC150-(13), -(15) is connected to the CCVS
The j2 phase control stage is for controlling the phase position of the
signal from the IF and from the EURO-AV socket. Following an internal
line drive pulse. This determines the phase off-set between the line
colour trap where the colour information is filtered off the CCVS signal,
synchronising pulses and the actual position of the electron beam.
the resulting Y-signal now divides into two paths. In one path the signal
Dependent on the circuit components and the beam current, the delay
is passed on for further processing, and in the other, the signal is
time between the external signal, the trigger signal and the actual
applied to the sync separator.
reaction of the line output stage is different. These differences are
The sync separator produces the horizontal and the vertical synchro-
compensated for by the j2 control.
nising pulses from the Y-signal. The horizontal synchronising signal is
To identify the position of the electron beam the line flyback pulse from
passed on to the j1 phase control, the vertical synchronising pulse is
the line output transformer is applied to IC150-(38). From the oscillator
used to start the line counter for vertical synchronisation.
signal and the line flyback pulse the j2 controlling stage produces a
control voltage at IC150-(39) which is filtered by CC166.
34Farbdemodulation
Colour Demodulation
3,58
MHz
35Farb-OszillatorH/2
Colour OscillatorPAL-Schalter
4,434,43PAL Switch
MHzMHz
33
Burst
PLL
TDA4662
TDA4665 (OIRT/FR)
30
Delay
Chroma-Signal29(R-Y)R
+
(R-Y)
Farbkontrast vom26RGB
Prozessor
Matrix
Colour Contrast
from Processor31G
Delay28(B-Y)
+
(B-Y)
LuminanzsignalYB
Luminance Signal
RGB internRGB AusgangsverstÅ rker
Internal RGBRGB Output Amplifier
20
19
18RGB zur
Bildrohrplatte
RGB to the
CRT panel
Spitzenwei§
RGB von ScartBegrenzung
oder VideotextPeak White
RGB from ScartLimiting
or Videotext
22
23212517
24
RGB externDataKontrastHelligkeit
External RGBContrastBrightness
GRUNDIG Service2 - 13 |
ACEC
